Don't pull in locale dependency

See fmtlib/fmt.dev#25

.clang-format

@@ -7,6 +7,7 @@ IndentCaseLabels: false
 AlwaysBreakTemplateDeclarations: false
 DerivePointerAlignment: false
 AllowShortCaseLabelsOnASingleLine: true
+QualifierAlignment: Left
 AlignConsecutiveShortCaseStatements:
   Enabled: true
   AcrossEmptyLines: true

.clang-tidy

@@ -0,0 +1,4 @@
+Checks: modernize-use-trailing-return-type
+CheckOptions:
+  - key: modernize-use-trailing-return-type.TransformLambdas
+    value: none

.github/workflows/cifuzz.yml

@@ -25,7 +25,7 @@ jobs:
         language: c++
 
     - name: Upload crash
-      uses: actions/upload-artifact@50769540e7f4bd5e21e526ee35c689e35e0d6874 # v4.4.0
+      uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
       if: failure() && steps.build.outcome == 'success'
       with:
         name: artifacts

.github/workflows/doc.yml

@@ -7,11 +7,10 @@ permissions:
 
 jobs:
   build:
-    # Use Ubuntu 20.04 because doxygen 1.8.13 from Ubuntu 18.04 is broken.
+    runs-on: ubuntu-22.04
-    runs-on: ubuntu-20.04
 
     steps:
-    - uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+    - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
 
     - name: Add Ubuntu mirrors
       run: |
@@ -25,7 +24,7 @@ jobs:
       run: |
         sudo apt update
         sudo apt install doxygen
-        pip install mkdocs-material==9.5.25 mkdocstrings==0.25.1 mike==2.1.1
+        pip install mkdocs-material==9.5.25 mkdocstrings==0.26.1 mike==2.1.1
         cmake -E make_directory ${{runner.workspace}}/build
         # Workaround https://github.com/actions/checkout/issues/13:
         git config --global user.name "$(git --no-pager log --format=format:'%an' -n 1)"

.github/workflows/lint.yml

@@ -13,16 +13,16 @@ jobs:
   format_code:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+    - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
 
     - name: Install clang-format
       run: |
         wget https://apt.llvm.org/llvm.sh
-        sudo bash ./llvm.sh 17
+        sudo bash ./llvm.sh 21
-        sudo apt install clang-format-17
+        sudo apt install clang-format-21
 
     - name: Run clang-format
       run: |
         find include src -name '*.h' -o -name '*.cc' | \
-          xargs clang-format-17 -i -style=file -fallback-style=none
+          xargs clang-format-21 -i -style=file -fallback-style=none
         git diff --exit-code

.github/workflows/linux.yml

@@ -7,87 +7,143 @@ permissions:
 
 jobs:
   build:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     strategy:
       matrix:
-        cxx: [g++-4.9, g++-10, clang++-9]
+        cxx: [g++-4.9, g++-11, clang++-3.6, clang++-11]
         build_type: [Debug, Release]
         std: [11]
         shared: [""]
         include:
           - cxx: g++-4.9
-            install: sudo apt install g++-4.9
+          - cxx: clang++-3.6
-          - cxx: g++-8
+          - cxx: g++-11
             build_type: Debug
             std: 14
-            install: sudo apt install g++-8
+            install: sudo apt install g++-11
-          - cxx: g++-8
+          - cxx: g++-11
-            build_type: Debug
-            std: 17
-            install: sudo apt install g++-8
-          - cxx: g++-9
-            build_type: Debug
-            std: 17
-          - cxx: g++-10
             build_type: Debug
             std: 17
           - cxx: g++-11
             build_type: Debug
             std: 20
             install: sudo apt install g++-11
-          - cxx: clang++-8
-            build_type: Debug
-            std: 17
-            cxxflags: -stdlib=libc++
-            install: sudo apt install clang-8 libc++-8-dev libc++abi-8-dev
-          - cxx: clang++-9
-            install: sudo apt install clang-9
-          - cxx: clang++-9
-            build_type: Debug
-            fuzz: -DFMT_FUZZ=ON -DFMT_FUZZ_LINKMAIN=ON
-            std: 17
-            install: sudo apt install clang-9
-          - cxx: clang++-11
-            build_type: Debug
-            std: 20
-          - cxx: clang++-11
-            build_type: Debug
-            std: 20
-            cxxflags: -stdlib=libc++
-            install: sudo apt install libc++-11-dev libc++abi-11-dev
           - cxx: g++-13
             build_type: Release
             std: 23
             install: sudo apt install g++-13
             shared: -DBUILD_SHARED_LIBS=ON
+          - cxx: clang++-11
+            build_type: Debug
+            std: 17
+            cxxflags: -stdlib=libc++
+            install: sudo apt install clang-11 libc++-11-dev libc++abi-11-dev
+          - cxx: clang++-11
+            install: sudo apt install clang-11
+          - cxx: clang++-11
+            build_type: Debug
+            fuzz: -DFMT_FUZZ=ON -DFMT_FUZZ_LINKMAIN=ON
+            std: 17
+            install: sudo apt install clang-11
+          - cxx: clang++-14
+            build_type: Debug
+            std: 20
+          - cxx: clang++-14
+            build_type: Debug
+            std: 20
+            cxxflags: -stdlib=libc++
+            install: sudo apt install libc++-14-dev libc++abi-14-dev
 
     steps:
-    - uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+    - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
 
     - name: Set timezone
-      run: sudo timedatectl set-timezone 'Asia/Yekaterinburg'
+      run: sudo timedatectl set-timezone 'Europe/Kyiv'
 
-    - name: Add repositories for older GCC
+    - name: Install GCC 4.9
       run: |
-        # Below repo provides GCC 4.9.
+        sudo apt update
-        sudo apt-add-repository 'deb http://dk.archive.ubuntu.com/ubuntu/ xenial main'
+        sudo apt install libatomic1 libc6-dev libgomp1 libitm1 libmpc3
-        sudo apt-add-repository 'deb http://dk.archive.ubuntu.com/ubuntu/ xenial universe'
+        # https://launchpad.net/ubuntu/xenial/amd64/g++-4.9/4.9.3-13ubuntu2
+        wget --no-verbose \
+          http://launchpadlibrarian.net/230069137/libmpfr4_3.1.3-2_amd64.deb \
+          http://launchpadlibrarian.net/253728424/libasan1_4.9.3-13ubuntu2_amd64.deb \
+          http://launchpadlibrarian.net/445346135/libubsan0_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/445346112/libcilkrts5_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/253728426/libgcc-4.9-dev_4.9.3-13ubuntu2_amd64.deb \
+          http://launchpadlibrarian.net/253728432/libstdc++-4.9-dev_4.9.3-13ubuntu2_amd64.deb \
+          http://launchpadlibrarian.net/253728314/gcc-4.9-base_4.9.3-13ubuntu2_amd64.deb \
+          http://launchpadlibrarian.net/445345919/gcc-5-base_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/253728399/cpp-4.9_4.9.3-13ubuntu2_amd64.deb \
+          http://launchpadlibrarian.net/253728404/gcc-4.9_4.9.3-13ubuntu2_amd64.deb \
+          http://launchpadlibrarian.net/253728401/g++-4.9_4.9.3-13ubuntu2_amd64.deb
+        sudo dpkg -i \
+          libmpfr4_3.1.3-2_amd64.deb \
+          libasan1_4.9.3-13ubuntu2_amd64.deb \
+          libubsan0_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          libcilkrts5_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          libgcc-4.9-dev_4.9.3-13ubuntu2_amd64.deb \
+          libstdc++-4.9-dev_4.9.3-13ubuntu2_amd64.deb \
+          gcc-4.9-base_4.9.3-13ubuntu2_amd64.deb \
+          gcc-5-base_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          cpp-4.9_4.9.3-13ubuntu2_amd64.deb \
+          gcc-4.9_4.9.3-13ubuntu2_amd64.deb \
+          g++-4.9_4.9.3-13ubuntu2_amd64.deb
       if: ${{ matrix.cxx == 'g++-4.9' }}
 
+    - name: Install Clang 3.6
+      run: |
+        sudo apt update
+        sudo apt install libtinfo5
+        # https://code.launchpad.net/ubuntu/xenial/amd64/clang-3.6/1:3.6.2-3ubuntu2
+        wget --no-verbose \
+          http://launchpadlibrarian.net/230019046/libffi6_3.2.1-4_amd64.deb \
+          http://launchpadlibrarian.net/445346109/libasan2_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/445346135/libubsan0_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/445346112/libcilkrts5_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/445346128/libmpx0_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/445346113/libgcc-5-dev_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/445346131/libstdc++-5-dev_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/445346022/libobjc-5-dev_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/254405108/libllvm3.6v5_3.6.2-3ubuntu2_amd64.deb \
+          http://launchpadlibrarian.net/254405097/libclang-common-3.6-dev_3.6.2-3ubuntu2_amd64.deb \
+          http://launchpadlibrarian.net/254405101/libclang1-3.6_3.6.2-3ubuntu2_amd64.deb \
+          http://launchpadlibrarian.net/445345919/gcc-5-base_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          http://launchpadlibrarian.net/254405091/clang-3.6_3.6.2-3ubuntu2_amd64.deb
+        sudo dpkg -i \
+          libffi6_3.2.1-4_amd64.deb \
+          libasan2_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          libubsan0_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          libcilkrts5_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          libmpx0_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          libgcc-5-dev_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          libstdc++-5-dev_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          libobjc-5-dev_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          libllvm3.6v5_3.6.2-3ubuntu2_amd64.deb \
+          libclang-common-3.6-dev_3.6.2-3ubuntu2_amd64.deb \
+          libclang1-3.6_3.6.2-3ubuntu2_amd64.deb \
+          gcc-5-base_5.4.0-6ubuntu1~16.04.12_amd64.deb \
+          clang-3.6_3.6.2-3ubuntu2_amd64.deb
+      if: ${{ matrix.cxx == 'clang++-3.6' }}
+
     - name: Add repositories for newer GCC
       run: |
         sudo apt-add-repository ppa:ubuntu-toolchain-r/test
-      if: ${{ matrix.cxx == 'g++-11' || matrix.cxx == 'g++-13' }}
+      if: ${{ matrix.cxx == 'g++-13' }}
 
     - name: Add Ubuntu mirrors
       run: |
-        # Github Actions caching proxy is at times unreliable
+        # GitHub Actions caching proxy is at times unreliable
-        # see https://github.com/actions/runner-images/issues/7048
+        # see https://github.com/actions/runner-images/issues/7048.
-        printf 'http://azure.archive.ubuntu.com/ubuntu\tpriority:1\n' | sudo tee /etc/apt/mirrors.txt
+        mirrors=/etc/apt/mirrors.txt
-        curl http://mirrors.ubuntu.com/mirrors.txt | sudo tee --append /etc/apt/mirrors.txt
+        printf 'http://azure.archive.ubuntu.com/ubuntu\tpriority:1\n' | \
-        sudo sed -i 's~http://azure.archive.ubuntu.com/ubuntu/~mirror+file:/etc/apt/mirrors.txt~' /etc/apt/sources.list
+          sudo tee $mirrors
+        curl http://mirrors.ubuntu.com/mirrors.txt | sudo tee --append $mirrors
+        sudo sed -i \
+          "s~http://azure.archive.ubuntu.com/ubuntu/~mirror+file:$mirrors~" \
+          /etc/apt/sources.list
 
-    - name: Create Build Environment
+    - name: Create build environment
       run: |
         sudo apt update
         ${{matrix.install}}
@@ -100,10 +156,12 @@ jobs:
         CXX: ${{matrix.cxx}}
         CXXFLAGS: ${{matrix.cxxflags}}
       run: |
-        cmake -DCMAKE_BUILD_TYPE=${{matrix.build_type}} ${{matrix.fuzz}} ${{matrix.shared}} \
+        cmake -DCMAKE_BUILD_TYPE=${{matrix.build_type}} \
-              -DCMAKE_CXX_STANDARD=${{matrix.std}} -DFMT_DOC=OFF \
+              -DCMAKE_CXX_STANDARD=${{matrix.std}} \
-              -DCMAKE_CXX_VISIBILITY_PRESET=hidden -DCMAKE_VISIBILITY_INLINES_HIDDEN=ON \
+              -DCMAKE_CXX_VISIBILITY_PRESET=hidden \
-              -DFMT_PEDANTIC=ON -DFMT_WERROR=ON $GITHUB_WORKSPACE
+              -DCMAKE_VISIBILITY_INLINES_HIDDEN=ON \
+              -DFMT_DOC=OFF -DFMT_PEDANTIC=ON -DFMT_WERROR=ON \
+              ${{matrix.fuzz}} ${{matrix.shared}} $GITHUB_WORKSPACE
 
     - name: Build
       working-directory: ${{runner.workspace}}/build

.github/workflows/macos.yml

@@ -9,13 +9,10 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [macos-13, macos-14]
+        os: [macos-14]
         build_type: [Debug, Release]
-        std: [11, 17, 20]
+        std: [11, 17, 20, 23]
         shared: [""]
-        exclude:
-          - { os: macos-13, std: 11 }
-          - { os: macos-13, std: 17 }
         include:
           - os: macos-14
             std: 23
@@ -25,10 +22,10 @@ jobs:
     runs-on: '${{ matrix.os }}'
 
     steps:
-    - uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+    - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
 
     - name: Set timezone
-      run: sudo systemsetup -settimezone 'Asia/Yekaterinburg'
+      run: sudo systemsetup -settimezone 'Europe/Minsk'
 
     - name: Select Xcode 14.3 (macOS 13)
       run: sudo xcode-select -s "/Applications/Xcode_14.3.app"

.github/workflows/scorecard.yml

@@ -29,12 +29,12 @@ jobs:
 
     steps:
       - name: "Checkout code"
-        uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+        uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
         with:
           persist-credentials: false
 
       - name: "Run analysis"
-        uses: ossf/scorecard-action@62b2cac7ed8198b15735ed49ab1e5cf35480ba46 # v2.4.0
+        uses: ossf/scorecard-action@05b42c624433fc40578a4040d5cf5e36ddca8cde # v2.4.2
         with:
           results_file: results.sarif
           results_format: sarif
@@ -52,7 +52,7 @@ jobs:
       # Upload the results as artifacts (optional). Commenting out will disable uploads of run results in SARIF
       # format to the repository Actions tab.
       - name: "Upload artifact"
-        uses: actions/upload-artifact@50769540e7f4bd5e21e526ee35c689e35e0d6874 # v4.4.0
+        uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
         with:
           name: SARIF file
           path: results.sarif
@@ -60,6 +60,6 @@ jobs:
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: "Upload to code-scanning"
-        uses: github/codeql-action/upload-sarif@662472033e021d55d94146f66f6058822b0b39fd # v3.27.0
+        uses: github/codeql-action/upload-sarif@0499de31b99561a6d14a36a5f662c2a54f91beee # v3.29.5
         with:
           sarif_file: results.sarif

.github/workflows/windows.yml

@@ -10,22 +10,18 @@ jobs:
     runs-on: ${{matrix.os}}
     strategy:
       matrix:
-        # windows-2019 has MSVC 2019 installed;
         # windows-2022 has MSVC 2022 installed:
         # https://github.com/actions/virtual-environments.
-        os: [windows-2019]
+        os: [windows-2022]
         platform: [Win32, x64]
-        toolset: [v141, v142]
+        toolset: [v142]
         standard: [14, 17, 20]
         shared: ["", -DBUILD_SHARED_LIBS=ON]
         build_type: [Debug, Release]
         exclude:
-          - { toolset: v141, standard: 20 }
           - { toolset: v142, standard: 14 }
-          - { platform: Win32, toolset: v141 }
           - { platform: Win32, standard: 14 }
           - { platform: Win32, standard: 20 }
-          - { platform: x64, toolset: v141, shared: -DBUILD_SHARED_LIBS=ON }
           - { platform: x64, standard: 14, shared: -DBUILD_SHARED_LIBS=ON }
           - { platform: x64, standard: 20, shared: -DBUILD_SHARED_LIBS=ON }
         include:
@@ -36,10 +32,10 @@ jobs:
             standard: 20
 
     steps:
-    - uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+    - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
 
     - name: Set timezone
-      run: tzutil /s "Ekaterinburg Standard Time"
+      run: tzutil /s "FLE Standard Time"
 
     - name: Create Build Environment
       run: cmake -E make_directory ${{runner.workspace}}/build
@@ -76,14 +72,14 @@ jobs:
         sys: [ mingw64, ucrt64 ]
     steps:
     - name: Set timezone
-      run: tzutil /s "Ekaterinburg Standard Time"
+      run: tzutil /s "FLE Standard Time"
       shell: cmd
-    - uses: msys2/setup-msys2@c52d1fa9c7492275e60fe763540fb601f5f232a1 # v2.25.0
+    - uses: msys2/setup-msys2@40677d36a502eb2cf0fb808cc9dec31bf6152638 # v2.28.0
       with:
         release: false
         msystem: ${{matrix.sys}}
         pacboy: cc:p cmake:p ninja:p lld:p
-    - uses: actions/checkout@d632683dd7b4114ad314bca15554477dd762a938 # v4.2.0
+    - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
     - name: Configure
       run: cmake -B ../build -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE=Debug
       env: { LDFLAGS: -fuse-ld=lld }

.gitignore

@@ -3,11 +3,14 @@
 *.xcodeproj
 *~
 .vscode/
+.cache/
+.vs/
 /CMakeScripts
 /Testing
 /_CPack_Packages
 /install_manifest.txt
 CMakeCache.txt
+CMakeUserPresets.json
 CMakeFiles
 CPack*.cmake
 CTestTestfile.cmake

CMakeLists.txt

@@ -9,7 +9,9 @@ endif ()
 # or if it is the master project.
 if (NOT DEFINED FMT_MASTER_PROJECT)
   set(FMT_MASTER_PROJECT OFF)
-  if (CMAKE_CURRENT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
+  # NOTE: source vs current_source detection is unreliable
+  # this heuristic is more generally applicable esp w.r.t FetchContent
+  if (NOT DEFINED PROJECT_NAME)
     set(FMT_MASTER_PROJECT ON)
     message(STATUS "CMake version: ${CMAKE_VERSION}")
   endif ()
@@ -27,12 +29,15 @@ endfunction()
 # DEPRECATED! Should be merged into add_module_library.
 function(enable_module target)
   if (MSVC)
-    set(BMI ${CMAKE_CURRENT_BINARY_DIR}/${target}.ifc)
+    if(NOT CMAKE_GENERATOR STREQUAL "Ninja")
-    target_compile_options(${target}
+      set(BMI_DIR "${CMAKE_CURRENT_BINARY_DIR}")
-      PRIVATE /interface /ifcOutput ${BMI}
+      file(TO_NATIVE_PATH "${BMI_DIR}/${target}.ifc" BMI)
-      INTERFACE /reference fmt=${BMI})
+      target_compile_options(${target}
-    set_target_properties(${target} PROPERTIES ADDITIONAL_CLEAN_FILES ${BMI})
+        PRIVATE /interface /ifcOutput ${BMI}
-    set_source_files_properties(${BMI} PROPERTIES GENERATED ON)
+        INTERFACE /reference fmt=${BMI})
+      set_target_properties(${target} PROPERTIES ADDITIONAL_CLEAN_FILES ${BMI})
+      set_source_files_properties(${BMI} PROPERTIES GENERATED ON)
+    endif()
   endif ()
 endfunction()
 
@@ -69,8 +74,6 @@ function(add_module_library name)
     target_compile_options(${name} PUBLIC -fmodules-ts)
   endif ()
 
-  target_compile_definitions(${name} PRIVATE FMT_MODULE)
-
   if (FMT_USE_CMAKE_MODULES)
     target_sources(${name} PUBLIC FILE_SET fmt TYPE CXX_MODULES
                    FILES ${sources})
@@ -160,7 +163,7 @@ option(FMT_WERROR "Halt the compilation with an error on compiler warnings."
 
 # Options that control generation of various targets.
 option(FMT_DOC "Generate the doc target." ${FMT_MASTER_PROJECT})
-option(FMT_INSTALL "Generate the install target." ON)
+option(FMT_INSTALL "Generate the install target." ${FMT_MASTER_PROJECT})
 option(FMT_TEST "Generate the test target." ${FMT_MASTER_PROJECT})
 option(FMT_FUZZ "Generate the fuzz target." OFF)
 option(FMT_CUDA_TEST "Generate the cuda-test target." OFF)
@@ -201,8 +204,7 @@ if (NOT CMAKE_RUNTIME_OUTPUT_DIRECTORY)
   set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/bin)
 endif ()
 
-set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH}
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/support/cmake")
-  "${CMAKE_CURRENT_SOURCE_DIR}/support/cmake")
 
 include(CheckCXXCompilerFlag)
 include(JoinPaths)
@@ -295,6 +297,7 @@ function(add_headers VAR)
 endfunction()
 
 # Define the fmt library, its includes and the needed defines.
+set(FMT_HEADERS)
 add_headers(FMT_HEADERS args.h base.h chrono.h color.h compile.h core.h format.h
                         format-inl.h os.h ostream.h printf.h ranges.h std.h
                         xchar.h)
@@ -427,7 +430,7 @@ if (FMT_INSTALL)
 
   # Install the library and headers.
   install(TARGETS ${INSTALL_TARGETS}
-          COMPONENT core
+          COMPONENT fmt_core
           EXPORT ${targets_export_name}
           LIBRARY DESTINATION ${FMT_LIB_DIR}
           ARCHIVE DESTINATION ${FMT_LIB_DIR}
@@ -443,13 +446,13 @@ if (FMT_INSTALL)
   # Install version, config and target files.
   install(FILES ${project_config} ${version_config}
           DESTINATION ${FMT_CMAKE_DIR}
-          COMPONENT core)
+          COMPONENT fmt_core)
   install(EXPORT ${targets_export_name} DESTINATION ${FMT_CMAKE_DIR}
           NAMESPACE fmt::
-          COMPONENT core)
+          COMPONENT fmt_core)
 
   install(FILES "${pkgconfig}" DESTINATION "${FMT_PKGCONFIG_DIR}"
-          COMPONENT core)
+          COMPONENT fmt_core)
 endif ()
 
 function(add_doc_target)
@@ -486,7 +489,7 @@ function(add_doc_target)
   include(GNUInstallDirs)
   install(DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/doc-html/
           DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/doc/fmt
-          COMPONENT doc OPTIONAL)
+          COMPONENT fmt_doc OPTIONAL)
 endfunction()
 
 if (FMT_DOC)

ChangeLog.md

@@ -1,3 +1,436 @@
+# 12.1.0 - 2025-10-29
+
+- Optimized `buffer::append`, resulting in up to ~16% improvement on spdlog
+  benchmarks (https://github.com/fmtlib/fmt/pull/4541). Thanks @fyrsta7.
+
+- Worked around an ABI incompatibility in `std::locale_ref` between clang and
+  gcc (https://github.com/fmtlib/fmt/issues/4573).
+
+- Made `std::variant` and `std::expected` formatters work with `format_as`
+  (https://github.com/fmtlib/fmt/issues/4574,
+  https://github.com/fmtlib/fmt/pull/4575). Thanks @phprus.
+
+- Made `fmt::join<string_view>` work with C++ modules
+  (https://github.com/fmtlib/fmt/issues/4379,
+  https://github.com/fmtlib/fmt/pull/4577). Thanks @Arghnews.
+
+- Exported `fmt::is_compiled_string` and `operator""_cf` from the module
+  (https://github.com/fmtlib/fmt/pull/4544). Thanks @CrackedMatter.
+
+- Fixed a compatibility issue with C++ modules in clang
+  (https://github.com/fmtlib/fmt/pull/4548). Thanks @tsarn.
+
+- Added support for cv-qualified types to the `std::optional` formatter
+  (https://github.com/fmtlib/fmt/issues/4561,
+  https://github.com/fmtlib/fmt/pull/4562). Thanks @OleksandrKvl.
+
+- Added demangling support (used in exception and `std::type_info` formatters)
+  for libc++ and clang-cl
+  (https://github.com/fmtlib/fmt/issues/4542,
+  https://github.com/fmtlib/fmt/pull/4560,
+  https://github.com/fmtlib/fmt/issues/4568,
+  https://github.com/fmtlib/fmt/pull/4571).
+  Thanks @FatihBAKIR and @rohitsutreja.
+
+- Switched to global `malloc`/`free` to enable allocator customization
+  (https://github.com/fmtlib/fmt/issues/4569,
+  https://github.com/fmtlib/fmt/pull/4570). Thanks @rohitsutreja.
+
+- Made the `FMT_USE_CONSTEVAL` macro configurable by users
+  (https://github.com/fmtlib/fmt/pull/4546). Thanks @SnapperTT.
+
+- Fixed compilation with locales disabled in the header-only mode
+  (https://github.com/fmtlib/fmt/issues/4550).
+
+- Fixed compilation with clang 21 and `-std=c++20`
+  (https://github.com/fmtlib/fmt/issues/4552).
+
+- Fixed a dynamic linking issue with clang-cl
+  (https://github.com/fmtlib/fmt/issues/4576,
+  https://github.com/fmtlib/fmt/pull/4584). Thanks @FatihBAKIR.
+
+- Fixed a warning suppression leakage on gcc
+  (https://github.com/fmtlib/fmt/pull/4588). Thanks @ZedThree.
+
+- Made more internal color APIs `constexpr`
+  (https://github.com/fmtlib/fmt/pull/4581). Thanks @ishani.
+
+- Fixed compatibility with clang as a host compiler for NVCC
+  (https://github.com/fmtlib/fmt/pull/4564). Thanks @valgur.
+
+- Fixed various warnings and lint issues
+  (https://github.com/fmtlib/fmt/issues/4565,
+  https://github.com/fmtlib/fmt/pull/4572,
+  https://github.com/fmtlib/fmt/pull/4557).
+  Thanks @LiangHuDream and @teruyamato0731.
+
+- Improved documentation
+  (https://github.com/fmtlib/fmt/issues/4549,
+  https://github.com/fmtlib/fmt/pull/4551,
+  https://github.com/fmtlib/fmt/issues/4566,
+  https://github.com/fmtlib/fmt/pull/4567,
+  https://github.com/fmtlib/fmt/pull/4578,).
+  Thanks @teruyamato0731, @petersteneteg and @zimmerman-dev.
+
+# 12.0.0 - 2025-09-17
+
+- Optimized the default floating point formatting
+  (https://github.com/fmtlib/fmt/issues/3675,
+  https://github.com/fmtlib/fmt/issues/4516). In particular, formatting a
+  `double` with format string compilation into a stack allocated buffer is
+  more than 60% faster in version 12.0 compared to 11.2 according to
+  [dtoa-benchmark](https://github.com/fmtlib/dtoa-benchmark):
+
+  ```
+  Function  Time (ns)  Speedup
+  fmt11        34.471    1.00x
+  fmt12        21.000    1.64x
+  ```
+
+  <img width="766" height="609" src="https://github.com/user-attachments/assets/d7d768ad-7543-468c-b0bb-449abf73b31b" />
+
+- Added `constexpr` support to `fmt::format`. For example:
+
+  ```c++
+  #include <fmt/compile.h>
+
+  using namespace fmt::literals;
+  std::string s = fmt::format(""_cf, 42);
+  ```
+
+  now works at compile time provided that `std::string` supports `constexpr`
+  (https://github.com/fmtlib/fmt/issues/3403,
+  https://github.com/fmtlib/fmt/pull/4456). Thanks @msvetkin.
+
+- Added `FMT_STATIC_FORMAT` that allows formatting into a string of the exact
+  required size at compile time.
+
+  For example:
+
+  ```c++
+  #include <fmt/compile.h>
+
+  constexpr auto s = FMT_STATIC_FORMAT("{}", 42);
+  ```
+
+  compiles to just
+
+  ```s
+  __ZL1s:
+        .asciiz "42"
+  ```
+
+  It can be accessed as a C string with `s.c_str()` or as a string view with
+  `s.str()`.
+
+- Improved C++20 module support
+  (https://github.com/fmtlib/fmt/pull/4451,
+  https://github.com/fmtlib/fmt/pull/4459,
+  https://github.com/fmtlib/fmt/pull/4476,
+  https://github.com/fmtlib/fmt/pull/4488,
+  https://github.com/fmtlib/fmt/issues/4491,
+  https://github.com/fmtlib/fmt/pull/4495).
+  Thanks @arBmind, @tkhyn, @Mishura4, @anonymouspc and @autoantwort.
+
+- Switched to using estimated display width in precision. For example:
+
+  ```c++
+  fmt::print("|{:.4}|\n|1234|\n", "🐱🐱🐱");
+  ```
+
+  prints
+
+  ![](https://github.com/user-attachments/assets/6c4446b3-13eb-43b9-b74a-b4543540ad6a)
+
+  because `🐱` has an estimated width of 2
+  (https://github.com/fmtlib/fmt/issues/4272,
+  https://github.com/fmtlib/fmt/pull/4443,
+  https://github.com/fmtlib/fmt/pull/4475).
+  Thanks @nikhilreddydev and @localspook.
+
+- Fix interaction between debug presentation, precision, and width for strings
+  (https://github.com/fmtlib/fmt/pull/4478). Thanks @localspook.
+
+- Implemented allocator propagation on `basic_memory_buffer` move
+  (https://github.com/fmtlib/fmt/issues/4487,
+  https://github.com/fmtlib/fmt/pull/4490). Thanks @toprakmurat.
+
+- Fixed an ambiguity between `std::reference_wrapper<T>` and `format_as`
+  formatters (https://github.com/fmtlib/fmt/issues/4424,
+  https://github.com/fmtlib/fmt/pull/4434). Thanks @jeremy-rifkin.
+
+- Removed the following deprecated APIs:
+
+  - `has_formatter`: use `is_formattable` instead,
+  - `basic_format_args::parse_context_type`,
+    `basic_format_args::formatter_type` and similar aliases in context types,
+  - wide stream overload of `fmt::printf`,
+  - wide stream overloads of `fmt::print` that take text styles,
+  - `is_*char` traits,
+  - `fmt::localtime`.
+
+- Deprecated wide overloads of `fmt::fprintf` and `fmt::sprintf`.
+
+- Improved diagnostics for the incorrect usage of `fmt::ptr`
+  (https://github.com/fmtlib/fmt/pull/4453). Thanks @TobiSchluter.
+
+- Made handling of ANSI escape sequences more efficient
+  (https://github.com/fmtlib/fmt/pull/4511,
+  https://github.com/fmtlib/fmt/pull/4528).
+  Thanks @localspook and @Anas-Hamdane.
+
+- Fixed a buffer overflow on all emphasis flags set
+  (https://github.com/fmtlib/fmt/pull/4498). Thanks @dominicpoeschko.
+
+- Fixed an integer overflow for precision close to the max `int` value.
+
+- Fixed compatibility with WASI (https://github.com/fmtlib/fmt/issues/4496,
+  https://github.com/fmtlib/fmt/pull/4497). Thanks @whitequark.
+
+- Fixed `back_insert_iterator` detection, preventing a fallback on slower path
+  that handles arbitrary iterators (https://github.com/fmtlib/fmt/issues/4454).
+
+- Fixed handling of invalid glibc `FILE` buffers
+  (https://github.com/fmtlib/fmt/issues/4469).
+
+- Added `wchar_t` support to the `std::byte` formatter
+  (https://github.com/fmtlib/fmt/issues/4479,
+  https://github.com/fmtlib/fmt/pull/4480). Thanks @phprus.
+
+- Changed component prefix from `fmt-` to `fmt_` for compatibility with
+  NSIS/CPack on Windows, e.g. `fmt-doc` changed to `fmt_doc`
+  (https://github.com/fmtlib/fmt/issues/4441,
+  https://github.com/fmtlib/fmt/pull/4442). Thanks @n-stein.
+
+- Added the `FMT_CUSTOM_ASSERT_FAIL` macro to simplify providing a custom
+  `fmt::assert_fail` implementation (https://github.com/fmtlib/fmt/pull/4505).
+  Thanks @HazardyKnusperkeks.
+
+- Switched to `FMT_THROW` on reporting format errors so that it can be
+  overriden by users when exceptions are disabled
+  (https://github.com/fmtlib/fmt/pull/4521). Thanks @HazardyKnusperkeks.
+
+- Improved master project detection and disabled install targets when using
+  {fmt} as a subproject by default (https://github.com/fmtlib/fmt/pull/4536).
+  Thanks @crueter.
+
+- Made various code improvements
+  (https://github.com/fmtlib/fmt/pull/4445,
+  https://github.com/fmtlib/fmt/pull/4448,
+  https://github.com/fmtlib/fmt/pull/4473,
+  https://github.com/fmtlib/fmt/pull/4522).
+  Thanks @localspook, @tchaikov and @way4sahil.
+
+- Added Conan instructions to the docs
+  (https://github.com/fmtlib/fmt/pull/4537). Thanks @uilianries.
+
+- Removed Bazel files to avoid issues with downstream packaging
+  (https://github.com/fmtlib/fmt/pull/4530). Thanks @mering.
+
+- Added more entries for generated files to `.gitignore`
+  (https://github.com/fmtlib/fmt/pull/4355,
+  https://github.com/fmtlib/fmt/pull/4512).
+  Thanks @dinomight and @localspook.
+
+- Fixed various warnings and compilation issues
+  (https://github.com/fmtlib/fmt/pull/4447,
+  https://github.com/fmtlib/fmt/issues/4470,
+  https://github.com/fmtlib/fmt/pull/4474,
+  https://github.com/fmtlib/fmt/pull/4477,
+  https://github.com/fmtlib/fmt/pull/4471,
+  https://github.com/fmtlib/fmt/pull/4483,
+  https://github.com/fmtlib/fmt/pull/4515,
+  https://github.com/fmtlib/fmt/issues/4533,
+  https://github.com/fmtlib/fmt/pull/4534).
+  Thanks @dodomorandi, @localspook, @remyjette, @Tomek-Stolarczyk, @Mishura4,
+  @mattiasljungstrom and @FatihBAKIR.
+
+# 11.2.0 - 2025-05-03
+
+- Added the `s` specifier for `std::error_code`. It allows formatting an error
+  message as a string. For example:
+
+  ```c++
+  #include <fmt/std.h>
+
+  int main() {
+    auto ec = std::make_error_code(std::errc::no_such_file_or_directory);
+    fmt::print("{:s}\n", ec);
+  }
+  ```
+
+  prints
+
+  ```
+  No such file or directory
+  ```
+  (The actual message is platform-specific.)
+
+- Fixed formatting of `std::chrono::local_time` and `tm`
+  (https://github.com/fmtlib/fmt/issues/3815,
+  https://github.com/fmtlib/fmt/issues/4350).
+  For example ([godbolt](https://www.godbolt.org/z/8o4b1PPn5)):
+
+  ```c++
+  #include <fmt/chrono.h>
+
+  int main() {
+    std::chrono::zoned_time zt(
+      std::chrono::current_zone(),
+      std::chrono::system_clock::now());
+    fmt::print("{}", zt.get_local_time());
+  }
+  ```
+
+  is now formatted consistenly across platforms.
+
+- Added diagnostics for cases when timezone information is not available.
+  For example:
+
+  ```c++
+  fmt::print("{:Z}", std::chrono::local_seconds());
+  ```
+
+  now gives a compile-time error.
+
+- Deprecated `fmt::localtime` in favor of `std::localtime`.
+
+- Fixed compilation with GCC 15 and C++20 modules enabled
+  (https://github.com/fmtlib/fmt/pull/4347). Thanks @tkhyn.
+
+- Fixed handling of named arguments in format specs
+  (https://github.com/fmtlib/fmt/issues/4360,
+  https://github.com/fmtlib/fmt/pull/4361). Thanks @dinomight.
+
+- Added error reporting for duplicate named arguments
+  (https://github.com/fmtlib/fmt/issues/4282,
+  https://github.com/fmtlib/fmt/pull/4367). Thanks @dinomight.
+
+- Fixed formatting of `long` with `FMT_BUILTIN_TYPES=0`
+  (https://github.com/fmtlib/fmt/issues/4375,
+  https://github.com/fmtlib/fmt/issues/4394).
+
+- Optimized `text_style` using bit packing
+  (https://github.com/fmtlib/fmt/pull/4363). Thanks @localspook.
+
+- Added support for incomplete types (https://github.com/fmtlib/fmt/issues/3180,
+  https://github.com/fmtlib/fmt/pull/4383). Thanks @localspook.
+
+- Fixed a flush issue in `fmt::print` when using libstdc++
+  (https://github.com/fmtlib/fmt/issues/4398).
+
+- Fixed `fmt::println` usage with `FMT_ENFORCE_COMPILE_STRING` and legacy
+  compile-time checks (https://github.com/fmtlib/fmt/pull/4407).
+  Thanks @madmaxoft.
+
+- Removed legacy header `fmt/core.h` from docs
+  (https://github.com/fmtlib/fmt/pull/4421,
+  https://github.com/fmtlib/fmt/pull/4422). Thanks @krzysztofkortas.
+
+- Worked around limitations of `__builtin_strlen` during constant evaluation
+  (https://github.com/fmtlib/fmt/issues/4423,
+  https://github.com/fmtlib/fmt/pull/4429). Thanks @BRevzin.
+
+- Worked around a bug in MSVC v141 (https://github.com/fmtlib/fmt/issues/4412,
+  https://github.com/fmtlib/fmt/pull/4413). Thanks @hirohira9119.
+
+- Removed the `fmt_detail` namespace
+  (https://github.com/fmtlib/fmt/issues/4324).
+
+- Removed specializations of `std::is_floating_point` in tests
+  (https://github.com/fmtlib/fmt/issues/4417).
+
+- Fixed a CMake error when setting `CMAKE_MODULE_PATH` in the pedantic mode
+  (https://github.com/fmtlib/fmt/pull/4426). Thanks @rlalik.
+
+- Updated the Bazel config (https://github.com/fmtlib/fmt/pull/4400).
+  Thanks @Vertexwahn.
+
+# 11.1.4 - 2025-02-26
+
+- Fixed ABI compatibility with earlier 11.x versions on Windows
+  (https://github.com/fmtlib/fmt/issues/4359).
+
+- Improved the logic of switching between fixed and exponential format for
+  `float` (https://github.com/fmtlib/fmt/issues/3649).
+
+- Moved `is_compiled_string` to the public API
+  (https://github.com/fmtlib/fmt/issues/4335,
+  https://github.com/fmtlib/fmt/issues/4342). Thanks @SwooshyCueb.
+
+- Simplified implementation of `operator""_cf`
+  (https://github.com/fmtlib/fmt/pull/4349). Thanks @localspook.
+
+- Fixed `__builtin_strlen` detection (https://github.com/fmtlib/fmt/pull/4329).
+  Thanks @localspook.
+
+- Fixed handling of BMI paths with the Ninja generator
+  (https://github.com/fmtlib/fmt/pull/4344). Thanks @tkhyn.
+
+- Fixed gcc 8.3 compile errors (https://github.com/fmtlib/fmt/issues/4331,
+  https://github.com/fmtlib/fmt/pull/4336). Thanks @sergiud.
+
+- Fixed a bogus MSVC warning (https://github.com/fmtlib/fmt/pull/4356).
+  Thanks @dinomight.
+
+# 11.1.3 - 2025-01-25
+
+- Fixed compilation on GCC 9.4 (https://github.com/fmtlib/fmt/issues/4313).
+
+- Worked around an internal compiler error when using C++20 modules with GCC
+  14.2 and earlier (https://github.com/fmtlib/fmt/issues/4295).
+
+- Worked around a bug in GCC 6 (https://github.com/fmtlib/fmt/issues/4318).
+
+- Fixed an issue caused by instantiating `formatter<const T>`
+  (https://github.com/fmtlib/fmt/issues/4303,
+  https://github.com/fmtlib/fmt/pull/4325). Thanks @timsong-cpp.
+
+- Fixed formatting into `std::ostreambuf_iterator` when using format string
+  compilation (https://github.com/fmtlib/fmt/issues/4309,
+  https://github.com/fmtlib/fmt/pull/4312). Thanks @phprus.
+
+- Restored a constraint on the map formatter so that it correctly reports as
+  unformattable when the element is (https://github.com/fmtlib/fmt/pull/4326).
+  Thanks @timsong-cpp.
+
+- Reduced the size of format specs (https://github.com/fmtlib/fmt/issues/4298).
+
+- Readded `args()` to `fmt::format_context`
+  (https://github.com/fmtlib/fmt/issues/4307,
+  https://github.com/fmtlib/fmt/pull/4310). Thanks @Erroneous1.
+
+- Fixed a bogus MSVC warning (https://github.com/fmtlib/fmt/issues/4314,
+  https://github.com/fmtlib/fmt/pull/4322). Thanks @ZehMatt.
+
+- Fixed a pedantic mode error in the CMake config
+  (https://github.com/fmtlib/fmt/pull/4327). Thanks @rlalik.
+
+# 11.1.2 - 2025-01-12
+
+- Fixed ABI compatibility with earlier 11.x versions
+  (https://github.com/fmtlib/fmt/issues/4292).
+
+- Added `wchar_t` support to the `std::bitset` formatter
+  (https://github.com/fmtlib/fmt/issues/4285,
+  https://github.com/fmtlib/fmt/pull/4286,
+  https://github.com/fmtlib/fmt/issues/4289,
+  https://github.com/fmtlib/fmt/pull/4290). Thanks @phprus.
+
+- Prefixed CMake components with `fmt-` to simplify usage of {fmt} via
+  `add_subdirectory` (https://github.com/fmtlib/fmt/issues/4283).
+
+- Updated docs for meson (https://github.com/fmtlib/fmt/pull/4291).
+  Thanks @trim21.
+
+- Fixed a compilation error in chrono on nvcc
+  (https://github.com/fmtlib/fmt/issues/4297,
+  https://github.com/fmtlib/fmt/pull/4301). Thanks @breyerml.
+
+- Fixed various warnings
+  (https://github.com/fmtlib/fmt/pull/4288,
+  https://github.com/fmtlib/fmt/pull/4299). Thanks @GamesTrap and @edo9300.
+
 # 11.1.1 - 2024-12-27
 
 - Fixed ABI compatibility with earlier 11.x versions

README.md

@@ -4,14 +4,15 @@
 [![image](https://github.com/fmtlib/fmt/workflows/macos/badge.svg)](https://github.com/fmtlib/fmt/actions?query=workflow%3Amacos)
 [![image](https://github.com/fmtlib/fmt/workflows/windows/badge.svg)](https://github.com/fmtlib/fmt/actions?query=workflow%3Awindows)
 [![fmt is continuously fuzzed at oss-fuzz](https://oss-fuzz-build-logs.storage.googleapis.com/badges/fmt.svg)](https://bugs.chromium.org/p/oss-fuzz/issues/list?\%0Acolspec=ID%20Type%20Component%20Status%20Proj%20Reported%20Owner%20\%0ASummary&q=proj%3Dfmt&can=1)
-[![Ask questions at StackOverflow with the tag fmt](https://img.shields.io/badge/stackoverflow-fmt-blue.svg)](https://stackoverflow.com/questions/tagged/fmt)
+[![OpenSSF Best Practices](https://www.bestpractices.dev/projects/8880/badge)](https://www.bestpractices.dev/projects/8880)
 [![image](https://api.securityscorecards.dev/projects/github.com/fmtlib/fmt/badge)](https://securityscorecards.dev/viewer/?uri=github.com/fmtlib/fmt)
+[![Ask questions at StackOverflow with the tag fmt](https://img.shields.io/badge/stackoverflow-fmt-blue.svg)](https://stackoverflow.com/questions/tagged/fmt)
 
 **{fmt}** is an open-source formatting library providing a fast and safe
 alternative to C stdio and C++ iostreams.
 
 If you like this project, please consider donating to one of the funds
-that help victims of the war in Ukraine: <https://www.stopputin.net/>.
+that help victims of the war in Ukraine: <https://u24.gov.ua/>.
 
 [Documentation](https://fmt.dev)
 
@@ -47,7 +48,7 @@ Try {fmt} in [Compiler Explorer](https://godbolt.org/z/8Mx1EW73v).
   hundred million integers to strings per
   second](http://www.zverovich.net/2020/06/13/fast-int-to-string-revisited.html)
 - Small code size both in terms of source code with the minimum
-  configuration consisting of just three files, `core.h`, `format.h`
+  configuration consisting of just three files, `base.h`, `format.h`
   and `format-inl.h`, and compiled code; see [Compile time and code
   bloat](#compile-time-and-code-bloat)
 - Reliability: the library has an extensive set of
@@ -74,7 +75,7 @@ See the [documentation](https://fmt.dev) for more details.
 **Print to stdout** ([run](https://godbolt.org/z/Tevcjh))
 
 ``` c++
-#include <fmt/core.h>
+#include <fmt/base.h>
 
 int main() {
   fmt::print("Hello, world!\n");
@@ -149,8 +150,8 @@ int main() {
 }
 ```
 
-This can be [5 to 9 times faster than
+This can be [up to 9 times faster than `fprintf`](
-fprintf](http://www.zverovich.net/2020/08/04/optimal-file-buffer-size.html).
+http://www.zverovich.net/2020/08/04/optimal-file-buffer-size.html).
 
 **Print with colors and text styles**
 
@@ -177,17 +178,17 @@ Output on a modern terminal with Unicode support:
 
 | Library           | Method        | Run Time, s |
 |-------------------|---------------|-------------|
-| libc              | printf        |   0.91      |
+| libc              | printf        |   0.66      |
-| libc++            | std::ostream  |   2.49      |
+| libc++            | std::ostream  |   1.63      |
-| {fmt} 9.1         | fmt::print    |   0.74      |
+| {fmt} 12.1        | fmt::print    |   0.44      |
-| Boost Format 1.80 | boost::format |   6.26      |
+| Boost Format 1.88 | boost::format |   3.89      |
-| Folly Format      | folly::format |   1.87      |
+| Folly Format      | folly::format |   1.28      |
 
-{fmt} is the fastest of the benchmarked methods, \~20% faster than
+{fmt} is the fastest of the benchmarked methods, \~50% faster than
 `printf`.
 
 The above results were generated by building `tinyformat_test.cpp` on
-macOS 12.6.1 with `clang++ -O3 -DNDEBUG -DSPEED_TEST -DHAVE_FORMAT`, and
+macOS 15.6.1 with `clang++ -O3 -DNDEBUG -DSPEED_TEST -DHAVE_FORMAT`, and
 taking the best of three runs. In the test, the format string
 `"%0.10f:%04d:%+g:%s:%p:%c:%%\n"` or equivalent is filled 2,000,000
 times with output sent to `/dev/null`; for further details refer to the
@@ -215,26 +216,26 @@ in the following tables.
 
 **Optimized build (-O3)**
 
-| Method        | Compile Time, s | Executable size, KiB | Stripped size, KiB |
+| Method          | Compile Time, s | Executable size, KiB | Stripped size, KiB |
-|---------------|-----------------|----------------------|--------------------|
+|-----------------|-----------------|----------------------|--------------------|
-| printf        |             1.6 |                   54 |                 50 |
+| printf          |             1.6 |                   54 |                 50 |
-| IOStreams     |            25.9 |                   98 |                 84 |
+| IOStreams       |            28.4 |                   98 |                 84 |
-| fmt 83652df   |             4.8 |                   54 |                 50 |
+| {fmt} `1122268` |             5.0 |                   54 |                 50 |
-| tinyformat    |            29.1 |                  161 |                136 |
+| tinyformat      |            32.6 |                  164 |                136 |
-| Boost Format  |            55.0 |                  530 |                317 |
+| Boost Format    |            55.0 |                  530 |                317 |
 
 {fmt} is fast to compile and is comparable to `printf` in terms of per-call
 binary size (within a rounding error on this system).
 
 **Non-optimized build**
 
-| Method        | Compile Time, s | Executable size, KiB | Stripped size, KiB |
+| Method          | Compile Time, s | Executable size, KiB | Stripped size, KiB |
-|---------------|-----------------|----------------------|--------------------|
+|-----------------|-----------------|----------------------|--------------------|
-| printf        |             1.4 |                   54 |                 50 |
+| printf          |             1.4 |                   54 |                 50 |
-| IOStreams     |            23.4 |                   92 |                 68 |
+| IOStreams       |            27.0 |                   88 |                 68 |
-| {fmt} 83652df |             4.4 |                   89 |                 85 |
+| {fmt} `1122268` |             4.7 |                   87 |                 84 |
-| tinyformat    |            24.5 |                  204 |                161 |
+| tinyformat      |            28.1 |                  185 |                145 |
-| Boost Format  |            36.4 |                  831 |                462 |
+| Boost Format    |            38.9 |                  678 |                381 |
 
 `libc`, `lib(std)c++`, and `libfmt` are all linked as shared libraries
 to compare formatting function overhead only. Boost Format is a

doc/ChangeLog-old.md

@@ -674,7 +674,7 @@
   https://github.com/fmtlib/fmt/issues/1747,
   https://github.com/fmtlib/fmt/pull/1750).
   Thanks @gsjaardema, @gabime, @johnor, @Kurkin, @invexed, @peterbell10,
-  @daixtrose, @petrutlucian94, @Neargye, @ambitslix, @gabime, @erthink,
+  @daixtrose, @petrutlucian94, @Neargye, @ambitslix, @gabime,
   @tohammer and @0x8000-0000.
 
 # 6.2.1 - 2020-05-09

doc/api.md

@@ -79,6 +79,8 @@ time formatting and [`fmt/std.h`](#std-api) for other standard library types.
 
 There are two ways to make a user-defined type formattable: providing a
 `format_as` function or specializing the `formatter` struct template.
+Formatting of non-void pointer types is intentionally disallowed and they
+cannot be made formattable via either extension API.
 
 Use `format_as` if you want to make your type formattable as some other
 type with the same format specifiers. The `format_as` function should
@@ -220,7 +222,7 @@ You can also write a formatter for a hierarchy of classes:
 ```c++
 // demo.h:
 #include <type_traits>
-#include <fmt/core.h>
+#include <fmt/format.h>
 
 struct A {
   virtual ~A() {}
@@ -403,7 +405,7 @@ All formatting is locale-independent by default. Use the `'L'` format
 specifier to insert the appropriate number separator characters from the
 locale:
 
-    #include <fmt/core.h>
+    #include <fmt/format.h>
     #include <locale>
 
     std::locale::global(std::locale("en_US.UTF-8"));
@@ -413,11 +415,11 @@ locale:
 that take `std::locale` as a parameter. The locale type is a template
 parameter to avoid the expensive `<locale>` include.
 
-::: format(detail::locale_ref, format_string<T...>, T&&...)
+::: format(locale_ref, format_string<T...>, T&&...)
 
-::: format_to(OutputIt, detail::locale_ref, format_string<T...>, T&&...)
+::: format_to(OutputIt, locale_ref, format_string<T...>, T&&...)
 
-::: formatted_size(detail::locale_ref, format_string<T...>, T&&...)
+::: formatted_size(locale_ref, format_string<T...>, T&&...)
 
 <a id="legacy-checks"></a>
 ### Legacy Compile-Time Checks
@@ -473,9 +475,9 @@ chrono-format-specifications).
     #include <fmt/chrono.h>
 
     int main() {
-      std::time_t t = std::time(nullptr);
+      auto now = std::chrono::system_clock::now();
 
-      fmt::print("The date is {:%Y-%m-%d}.", fmt::localtime(t));
+      fmt::print("The date is {:%Y-%m-%d}.\n", now);
       // Output: The date is 2020-11-07.
       // (with 2020-11-07 replaced by the current date)
 
@@ -488,8 +490,6 @@ chrono-format-specifications).
       // Output: strftime-like format: 03:15:30
     }
 
-::: localtime(std::time_t)
-
 ::: gmtime(std::time_t)
 
 <a id="std-api"></a>
@@ -549,38 +549,69 @@ fmt::print("{}", +s.bit);
 This is a known limitation of "perfect" forwarding in C++.
 
 <a id="compile-api"></a>
-## Format String Compilation
+## Compile-Time Support
 
 `fmt/compile.h` provides format string compilation and compile-time
 (`constexpr`) formatting enabled via the `FMT_COMPILE` macro or the `_cf`
 user-defined literal defined in namespace `fmt::literals`. Format strings
 marked with `FMT_COMPILE` or `_cf` are parsed, checked and converted into
 efficient formatting code at compile-time. This supports arguments of built-in
-and string types as well as user-defined types with `format` functions taking
+and string types as well as user-defined types with `format` methods taking
 the format context type as a template parameter in their `formatter`
-specializations. For example:
+specializations. For example ([run](https://www.godbolt.org/z/3c13erEoq)):
+
+    struct point {
+      double x;
+      double y;
+    };
 
     template <> struct fmt::formatter<point> {
-      constexpr auto parse(format_parse_context& ctx);
+      constexpr auto parse(format_parse_context& ctx) { return ctx.begin(); }
 
       template <typename FormatContext>
-      auto format(const point& p, FormatContext& ctx) const;
+      auto format(const point& p, FormatContext& ctx) const {
+        return format_to(ctx.out(), "({}, {})"_cf, p.x, p.y);
+      }
     };
 
+    using namespace fmt::literals;
+    std::string s = fmt::format("{}"_cf, point(4, 2));
+
 Format string compilation can generate more binary code compared to the
 default API and is only recommended in places where formatting is a
 performance bottleneck.
 
-::: FMT_COMPILE
+The same APIs support formatting at compile time e.g. in `constexpr`
+and `consteval` functions. Additionally there is an experimental
+`FMT_STATIC_FORMAT` that allows formatting into a string of the exact
+required size at compile time. Compile-time formatting works with built-in
+and user-defined formatters that have `constexpr` `format` methods.
+Example:
+
+    template <> struct fmt::formatter<point> {
+      constexpr auto parse(format_parse_context& ctx) { return ctx.begin(); }
+
+      template <typename FormatContext>
+      constexpr auto format(const point& p, FormatContext& ctx) const {
+        return format_to(ctx.out(), "({}, {})"_cf, p.x, p.y);
+      }
+    };
+
+    constexpr auto s = FMT_STATIC_FORMAT("{}", point(4, 2));
+    const char* cstr = s.c_str(); // Points the static string "(4, 2)".
 
 ::: operator""_cf
 
+::: FMT_COMPILE
+
+::: FMT_STATIC_FORMAT
+
 <a id="color-api"></a>
 ## Terminal Colors and Text Styles
 
 `fmt/color.h` provides support for terminal color and text style output.
 
-::: print(const text_style&, format_string<T...>, T&&...)
+::: print(text_style, format_string<T...>, T&&...)
 
 ::: fg(detail::color_type)
 
@@ -593,6 +624,8 @@ performance bottleneck.
 
 ::: ostream
 
+::: output_file(cstring_view, T...)
+
 ::: windows_error
 
 <a id="ostream-api"></a>
@@ -643,9 +676,9 @@ if an argument type doesn't match its format specification.
 
 ::: printf(string_view, const T&...)
 
-::: fprintf(std::FILE*, const S&, const T&...)
+::: fprintf(std::FILE*, string_view, const T&...)
 
-::: sprintf(const S&, const T&...)
+::: sprintf(string_view, const T&...)
 
 <a id="xchar-api"></a>
 ## Wide Strings
@@ -653,8 +686,6 @@ if an argument type doesn't match its format specification.
 The optional header `fmt/xchar.h` provides support for `wchar_t` and
 exotic character types.
 
-::: is_char
-
 ::: wstring_view
 
 ::: wformat_context
@@ -669,5 +700,63 @@ following differences:
 
 - Names are defined in the `fmt` namespace instead of `std` to avoid
   collisions with standard library implementations.
+
 - Width calculation doesn't use grapheme clusterization. The latter has
   been implemented in a separate branch but hasn't been integrated yet.
+
+- The default floating-point representation in {fmt} uses the smallest
+  precision that provides round-trip guarantees similarly to other languages
+  like Java and Python. `std::format` is currently specified in terms of
+  `std::to_chars` which tries to generate the smallest number of characters
+  (ignoring redundant digits and sign in exponent) and may produce more
+  decimal digits than necessary.
+
+## Configuration Options
+
+{fmt} provides configuration via CMake options and preprocessor macros to
+enable or disable features and to optimize for binary size. For example, you
+can disable OS-specific APIs defined in `fmt/os.h` with `-DFMT_OS=OFF` when
+configuring CMake.
+
+### CMake Options
+
+- **`FMT_OS`**: When set to `OFF`, disables OS-specific APIs (`fmt/os.h`).
+- **`FMT_UNICODE`**: When set of `OFF`, disables Unicode support on
+  Windows/MSVC. Unicode support is always enabled on other platforms.
+
+### Macros
+
+- **`FMT_HEADER_ONLY`**: Enables the header-only mode when defined. It is an
+  alternative to using the `fmt::fmt-header-only` CMake target.
+  Default: not defined.
+
+- **`FMT_USE_EXCEPTIONS`**: Disables the use of exceptions when set to `0`.
+  Default: `1` (`0` if compiled with `-fno-exceptions`).
+
+- **`FMT_USE_LOCALE`**: When set to `0`, disables locale support.
+  Default: `1` (`0` when `FMT_OPTIMIZE_SIZE > 1`).
+
+- **`FMT_CUSTOM_ASSERT_FAIL`**: When set to `1`, allows users to provide a
+  custom `fmt::assert_fail` function which is called on assertion failures and,
+  if exceptions are disabled, on runtime errors. Default: `0`.
+
+- **`FMT_BUILTIN_TYPES`**: When set to `0`, disables built-in handling of
+  arithmetic and string types other than `int`. This reduces library size at
+  the cost of per-call overhead. Default: `1`.
+
+- **`FMT_OPTIMIZE_SIZE`**: Controls binary size optimizations:
+    - `0` - off (default)
+    - `1` - disables locale support and applies some optimizations
+    - `2` - disables some Unicode features, named arguments and applies more
+      aggressive optimizations
+
+### Binary Size Optimization
+
+To minimize the binary footprint of {fmt} as much as possible at the cost of
+some features, you can use the following configuration:
+
+- CMake options:
+    - `FMT_OS=OFF`
+- Macros:
+    - `FMT_BUILTIN_TYPES=0`
+    - `FMT_OPTIMIZE_SIZE=2`

doc/fmt.css

@@ -20,6 +20,7 @@
   margin-left: 1em;
 }
 
+code,
 pre > code.decl {
   white-space: pre-wrap;
 }

doc/get-started.md

@@ -78,6 +78,17 @@ community contributors. If the version is out of date, please [create an
 issue or pull request](https://github.com/Microsoft/vcpkg) on the vcpkg
 repository. -->
 
+### Conan
+
+You can download and install {fmt} using the [Conan](https://conan.io/) package manager:
+
+    conan install -r conancenter --requires="fmt/[*]" --build=missing
+
+<!-- The {fmt} package in Conan Center is maintained by
+[ConanCenterIndex](https://github.com/conan-io/conan-center-index) community.
+If the version is out of date or the package does not work,
+please create an issue or pull request on the Conan Center Index repository. -->
+
 ## Building from Source
 
 CMake works by generating native makefiles or project files that can be
@@ -202,7 +213,7 @@ For a static build, use the following subproject definition:
 
 For the header-only version, use:
 
-    fmt = subproject('fmt')
+    fmt = subproject('fmt', default_options: ['header-only=true'])
     fmt_dep = fmt.get_variable('fmt_header_only_dep')
 
 ### Android NDK

doc/index.md

@@ -76,7 +76,7 @@ hide:
 <p>
   The default is <b>locale-independent</b>, but you can opt into localized
   formatting and {fmt} makes it work with Unicode, addressing issues in the
-  standard libary.
+  standard library.
 </p>
 </div>
 
@@ -122,7 +122,7 @@ hide:
 </p>
 <p>
   The library is highly portable and requires only a minimal <b>subset of
-  C++11</b> features which are available in GCC 4.9, Clang 3.4, MSVC 19.10
+  C++11</b> features which are available in GCC 4.9, Clang 3.6, MSVC 19.10
   (2017) and later. Newer compiler and standard library features are used
   if available, and enable additional functionality.
 </p>

doc/syntax.md

@@ -718,7 +718,7 @@ These modifiers are only supported for the `'H'`, `'I'`, `'M'`, `'S'`, `'U'`,
 Format specifications for range types have the following syntax:
 
 <pre><code class="language-json"
->range_format_spec ::= ["n"][range_type][range_underlying_spec]</code>
+>range_format_spec ::= ["n"][range_type][":" range_underlying_spec]</code>
 </pre>
 
 The `'n'` option formats the range without the opening and closing brackets.
@@ -761,14 +761,16 @@ fmt::print("{::}", std::vector{'h', 'e', 'l', 'l', 'o'});
 // Output: [h, e, l, l, o]
 fmt::print("{::d}", std::vector{'h', 'e', 'l', 'l', 'o'});
 // Output: [104, 101, 108, 108, 111]
+fmt::print("{:n:f}", std::array{std::numbers::pi, std::numbers::e});
+// Output: 3.141593, 2.718282
 ```
 
 ## Format Examples
 
 This section contains examples of the format syntax and comparison with
-the printf formatting.
+the `printf` formatting.
 
-In most of the cases the syntax is similar to the printf formatting,
+In most of the cases the syntax is similar to the `printf` formatting,
 with the addition of the `{}` and with `:` used instead of `%`. For
 example, `"%03.2f"` can be translated to `"{:03.2f}"`.
 

include/fmt/args.h

@@ -71,7 +71,7 @@ class dynamic_arg_list {
  * It can be implicitly converted into `fmt::basic_format_args` for passing
  * into type-erased formatting functions such as `fmt::vformat`.
  */
-template <typename Context> class dynamic_format_arg_store {
+FMT_EXPORT template <typename Context> class dynamic_format_arg_store {
  private:
   using char_type = typename Context::char_type;
 
@@ -212,7 +212,7 @@ template <typename Context> class dynamic_format_arg_store {
   }
 
   /// Returns the number of elements in the store.
-  size_t size() const noexcept { return data_.size(); }
+  auto size() const noexcept -> size_t { return data_.size(); }
 };
 
 FMT_END_NAMESPACE

include/fmt/base.h

@@ -21,7 +21,7 @@
 #endif
 
 // The fmt library version in the form major * 10000 + minor * 100 + patch.
-#define FMT_VERSION 110101
+#define FMT_VERSION 120100
 
 // Detect compiler versions.
 #if defined(__clang__) && !defined(__ibmxl__)
@@ -96,9 +96,9 @@
 // Detect C++14 relaxed constexpr.
 #ifdef FMT_USE_CONSTEXPR
 // Use the provided definition.
-#elif FMT_GCC_VERSION >= 600 && FMT_CPLUSPLUS >= 201402L
+#elif FMT_GCC_VERSION >= 702 && FMT_CPLUSPLUS >= 201402L
-// GCC only allows throw in constexpr since version 6:
+// GCC only allows constexpr member functions in non-literal types since 7.2:
-// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67371.
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66297.
 #  define FMT_USE_CONSTEXPR 1
 #elif FMT_ICC_VERSION
 #  define FMT_USE_CONSTEXPR 0  // https://github.com/fmtlib/fmt/issues/1628
@@ -114,7 +114,9 @@
 #endif
 
 // Detect consteval, C++20 constexpr extensions and std::is_constant_evaluated.
-#if !defined(__cpp_lib_is_constant_evaluated)
+#ifdef FMT_USE_CONSTEVAL
+// Use the provided definition.
+#elif !defined(__cpp_lib_is_constant_evaluated)
 #  define FMT_USE_CONSTEVAL 0
 #elif FMT_CPLUSPLUS < 201709L
 #  define FMT_USE_CONSTEVAL 0
@@ -201,28 +203,6 @@
 #  define FMT_NODISCARD
 #endif
 
-#ifdef FMT_DEPRECATED
-// Use the provided definition.
-#elif FMT_HAS_CPP14_ATTRIBUTE(deprecated)
-#  define FMT_DEPRECATED [[deprecated]]
-#else
-#  define FMT_DEPRECATED /* deprecated */
-#endif
-
-#ifdef FMT_ALWAYS_INLINE
-// Use the provided definition.
-#elif FMT_GCC_VERSION || FMT_CLANG_VERSION
-#  define FMT_ALWAYS_INLINE inline __attribute__((always_inline))
-#else
-#  define FMT_ALWAYS_INLINE inline
-#endif
-// A version of FMT_ALWAYS_INLINE to prevent code bloat in debug mode.
-#ifdef NDEBUG
-#  define FMT_INLINE FMT_ALWAYS_INLINE
-#else
-#  define FMT_INLINE inline
-#endif
-
 #if FMT_GCC_VERSION || FMT_CLANG_VERSION
 #  define FMT_VISIBILITY(value) __attribute__((visibility(value)))
 #else
@@ -249,10 +229,32 @@
 #  define FMT_MSC_WARNING(...)
 #endif
 
+// Enable minimal optimizations for more compact code in debug mode.
+FMT_PRAGMA_GCC(push_options)
+#if !defined(__OPTIMIZE__) && !defined(__CUDACC__) && !defined(FMT_MODULE)
+FMT_PRAGMA_GCC(optimize("Og"))
+#endif
+FMT_PRAGMA_CLANG(diagnostic push)
+FMT_PRAGMA_GCC(diagnostic push)
+
+#ifdef FMT_ALWAYS_INLINE
+// Use the provided definition.
+#elif FMT_GCC_VERSION || FMT_CLANG_VERSION
+#  define FMT_ALWAYS_INLINE inline __attribute__((always_inline))
+#else
+#  define FMT_ALWAYS_INLINE inline
+#endif
+// A version of FMT_ALWAYS_INLINE to prevent code bloat in debug mode.
+#ifdef NDEBUG
+#  define FMT_INLINE FMT_ALWAYS_INLINE
+#else
+#  define FMT_INLINE inline
+#endif
+
 #ifndef FMT_BEGIN_NAMESPACE
 #  define FMT_BEGIN_NAMESPACE \
     namespace fmt {           \
-    inline namespace v11 {
+    inline namespace v12 {
 #  define FMT_END_NAMESPACE \
     }                       \
     }
@@ -294,15 +296,8 @@
 #endif
 
 #define FMT_APPLY_VARIADIC(expr) \
-  using ignore = int[];          \
+  using unused = int[];          \
-  (void)ignore { 0, (expr, 0)... }
+  (void)unused { 0, (expr, 0)... }
-
-// Enable minimal optimizations for more compact code in debug mode.
-FMT_PRAGMA_GCC(push_options)
-#if !defined(__OPTIMIZE__) && !defined(__CUDACC__)
-FMT_PRAGMA_GCC(optimize("Og"))
-#endif
-FMT_PRAGMA_CLANG(diagnostic push)
 
 FMT_BEGIN_NAMESPACE
 
@@ -325,8 +320,8 @@ using underlying_t = typename std::underlying_type<T>::type;
 template <typename T> using decay_t = typename std::decay<T>::type;
 using nullptr_t = decltype(nullptr);
 
-#if FMT_GCC_VERSION && FMT_GCC_VERSION < 500
+#if (FMT_GCC_VERSION && FMT_GCC_VERSION < 500) || FMT_MSC_VERSION
-// A workaround for gcc 4.9 to make void_t work in a SFINAE context.
+// A workaround for gcc 4.9 & MSVC v141 to make void_t work in a SFINAE context.
 template <typename...> struct void_t_impl {
   using type = void;
 };
@@ -355,6 +350,9 @@ template <typename T> constexpr auto max_of(T a, T b) -> T {
   return a > b ? a : b;
 }
 
+FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
+                                      const char* message);
+
 namespace detail {
 // Suppresses "unused variable" warnings with the method described in
 // https://herbsutter.com/2009/10/18/mailbag-shutting-up-compiler-warnings/.
@@ -395,7 +393,7 @@ FMT_NORETURN FMT_API void assert_fail(const char* file, int line,
 #  define FMT_ASSERT(condition, message)                                    \
     ((condition) /* void() fails with -Winvalid-constexpr on clang 4.0.1 */ \
          ? (void)0                                                          \
-         : fmt::detail::assert_fail(__FILE__, __LINE__, (message)))
+         : ::fmt::assert_fail(__FILE__, __LINE__, (message)))
 #endif
 
 #ifdef FMT_USE_INT128
@@ -418,8 +416,12 @@ inline auto map(int128_opt) -> monostate { return {}; }
 inline auto map(uint128_opt) -> monostate { return {}; }
 #endif
 
-#ifndef FMT_USE_BITINT
+#ifdef FMT_USE_BITINT
-#  define FMT_USE_BITINT (FMT_CLANG_VERSION >= 1500)
+// Use the provided definition.
+#elif FMT_CLANG_VERSION >= 1500 && !defined(__CUDACC__)
+#  define FMT_USE_BITINT 1
+#else
+#  define FMT_USE_BITINT 0
 #endif
 
 #if FMT_USE_BITINT
@@ -462,12 +464,13 @@ enum { use_utf8 = !FMT_WIN32 || is_utf8_enabled };
 static_assert(!FMT_UNICODE || use_utf8,
               "Unicode support requires compiling with /utf-8");
 
-template <typename T> constexpr const char* narrow(const T*) { return nullptr; }
+template <typename T> constexpr auto narrow(T*) -> char* { return nullptr; }
-constexpr FMT_ALWAYS_INLINE const char* narrow(const char* s) { return s; }
+constexpr FMT_ALWAYS_INLINE auto narrow(const char* s) -> const char* {
+  return s;
+}
 
 template <typename Char>
-FMT_CONSTEXPR auto compare(const Char* s1, const Char* s2, std::size_t n)
+FMT_CONSTEXPR auto compare(const Char* s1, const Char* s2, size_t n) -> int {
-    -> int {
   if (!is_constant_evaluated() && sizeof(Char) == 1) return memcmp(s1, s2, n);
   for (; n != 0; ++s1, ++s2, --n) {
     if (*s1 < *s2) return -1;
@@ -526,20 +529,20 @@ template <typename Char> class basic_string_view {
 
   constexpr basic_string_view() noexcept : data_(nullptr), size_(0) {}
 
-  /// Constructs a string reference object from a C string and a size.
+  /// Constructs a string view object from a C string and a size.
   constexpr basic_string_view(const Char* s, size_t count) noexcept
       : data_(s), size_(count) {}
 
   constexpr basic_string_view(nullptr_t) = delete;
 
-  /// Constructs a string reference object from a C string.
+  /// Constructs a string view object from a C string.
 #if FMT_GCC_VERSION
   FMT_ALWAYS_INLINE
 #endif
   FMT_CONSTEXPR20 basic_string_view(const Char* s) : data_(s) {
-#if FMT_HAS_BUILTIN(__buitin_strlen) || FMT_GCC_VERSION || FMT_CLANG_VERSION
+#if FMT_HAS_BUILTIN(__builtin_strlen) || FMT_GCC_VERSION || FMT_CLANG_VERSION
-    if (std::is_same<Char, char>::value) {
+    if (std::is_same<Char, char>::value && !detail::is_constant_evaluated()) {
-      size_ = __builtin_strlen(detail::narrow(s));
+      size_ = __builtin_strlen(detail::narrow(s));  // strlen is not constexpr.
       return;
     }
 #endif
@@ -548,7 +551,7 @@ template <typename Char> class basic_string_view {
     size_ = len;
   }
 
-  /// Constructs a string reference from a `std::basic_string` or a
+  /// Constructs a string view from a `std::basic_string` or a
   /// `std::basic_string_view` object.
   template <typename S,
             FMT_ENABLE_IF(detail::is_std_string_like<S>::value&& std::is_same<
@@ -585,7 +588,6 @@ template <typename Char> class basic_string_view {
     return starts_with(basic_string_view<Char>(s));
   }
 
-  // Lexicographically compare this string reference to other.
   FMT_CONSTEXPR auto compare(basic_string_view other) const -> int {
     int result =
         detail::compare(data_, other.data_, min_of(size_, other.size_));
@@ -616,19 +618,6 @@ template <typename Char> class basic_string_view {
 
 using string_view = basic_string_view<char>;
 
-/// Specifies if `T` is an extended character type. Can be specialized by users.
-template <typename T> struct is_xchar : std::false_type {};
-template <> struct is_xchar<wchar_t> : std::true_type {};
-template <> struct is_xchar<char16_t> : std::true_type {};
-template <> struct is_xchar<char32_t> : std::true_type {};
-#ifdef __cpp_char8_t
-template <> struct is_xchar<char8_t> : std::true_type {};
-#endif
-
-// DEPRECATED! Will be replaced with an alias to prevent specializations.
-template <typename T> struct is_char : is_xchar<T> {};
-template <> struct is_char<char> : std::true_type {};
-
 template <typename T> class basic_appender;
 using appender = basic_appender<char>;
 
@@ -739,13 +728,15 @@ class basic_specs {
     max_fill_size = 4
   };
 
-  size_t data_ = 1 << fill_size_shift;
+  unsigned data_ = 1 << fill_size_shift;
+  static_assert(sizeof(basic_specs::data_) * CHAR_BIT >= 18, "");
 
   // Character (code unit) type is erased to prevent template bloat.
   char fill_data_[max_fill_size] = {' '};
 
   FMT_CONSTEXPR void set_fill_size(size_t size) {
-    data_ = (data_ & ~fill_size_mask) | (size << fill_size_shift);
+    data_ = (data_ & ~fill_size_mask) |
+            (static_cast<unsigned>(size) << fill_size_shift);
   }
 
  public:
@@ -779,7 +770,7 @@ class basic_specs {
             (static_cast<unsigned>(p) << precision_shift);
   }
 
-  constexpr bool dynamic() const {
+  constexpr auto dynamic() const -> bool {
     return (data_ & (width_mask | precision_mask)) != 0;
   }
 
@@ -842,6 +833,12 @@ class basic_specs {
     for (size_t i = 0; i < size; ++i)
       fill_data_[i & 3] = static_cast<char>(s[i]);
   }
+
+  FMT_CONSTEXPR void copy_fill_from(const basic_specs& specs) {
+    set_fill_size(specs.fill_size());
+    for (size_t i = 0; i < max_fill_size; ++i)
+      fill_data_[i] = specs.fill_data_[i];
+  }
 };
 
 // Format specifiers for built-in and string types.
@@ -913,14 +910,50 @@ template <typename Char = char> class parse_context {
   FMT_CONSTEXPR void check_dynamic_spec(int arg_id);
 };
 
+#ifndef FMT_USE_LOCALE
+#  define FMT_USE_LOCALE (FMT_OPTIMIZE_SIZE <= 1)
+#endif
+
+// A type-erased reference to std::locale to avoid the heavy <locale> include.
+class locale_ref {
+#if FMT_USE_LOCALE
+ private:
+  const void* locale_;  // A type-erased pointer to std::locale.
+
+ public:
+  constexpr locale_ref() : locale_(nullptr) {}
+
+  template <typename Locale, FMT_ENABLE_IF(sizeof(Locale::collate) != 0)>
+  locale_ref(const Locale& loc) : locale_(&loc) {
+    // Check if std::isalpha is found via ADL to reduce the chance of misuse.
+    detail::ignore_unused(sizeof(isalpha('x', loc)));
+  }
+
+  inline explicit operator bool() const noexcept { return locale_ != nullptr; }
+#endif  // FMT_USE_LOCALE
+
+ public:
+  template <typename Locale> auto get() const -> Locale;
+};
+
 FMT_END_EXPORT
 
 namespace detail {
 
+// Specifies if `T` is a code unit type.
+template <typename T> struct is_code_unit : std::false_type {};
+template <> struct is_code_unit<char> : std::true_type {};
+template <> struct is_code_unit<wchar_t> : std::true_type {};
+template <> struct is_code_unit<char16_t> : std::true_type {};
+template <> struct is_code_unit<char32_t> : std::true_type {};
+#ifdef __cpp_char8_t
+template <> struct is_code_unit<char8_t> : bool_constant<is_utf8_enabled> {};
+#endif
+
 // Constructs fmt::basic_string_view<Char> from types implicitly convertible
 // to it, deducing Char. Explicitly convertible types such as the ones returned
 // from FMT_STRING are intentionally excluded.
-template <typename Char, FMT_ENABLE_IF(is_char<Char>::value)>
+template <typename Char, FMT_ENABLE_IF(is_code_unit<Char>::value)>
 constexpr auto to_string_view(const Char* s) -> basic_string_view<Char> {
   return s;
 }
@@ -1024,6 +1057,11 @@ enum {
 
 struct view {};
 
+template <typename T, typename Enable = std::true_type>
+struct is_view : std::false_type {};
+template <typename T>
+struct is_view<T, bool_constant<sizeof(T) != 0>> : std::is_base_of<view, T> {};
+
 template <typename Char, typename T> struct named_arg;
 template <typename T> struct is_named_arg : std::false_type {};
 template <typename T> struct is_static_named_arg : std::false_type {};
@@ -1044,11 +1082,11 @@ template <bool B1, bool B2, bool... Tail> constexpr auto count() -> int {
   return (B1 ? 1 : 0) + count<B2, Tail...>();
 }
 
-template <typename... Args> constexpr auto count_named_args() -> int {
+template <typename... T> constexpr auto count_named_args() -> int {
-  return count<is_named_arg<Args>::value...>();
+  return count<is_named_arg<T>::value...>();
 }
-template <typename... Args> constexpr auto count_static_named_args() -> int {
+template <typename... T> constexpr auto count_static_named_args() -> int {
-  return count<is_static_named_arg<Args>::value...>();
+  return count<is_static_named_arg<T>::value...>();
 }
 
 template <typename Char> struct named_arg_info {
@@ -1056,6 +1094,16 @@ template <typename Char> struct named_arg_info {
   int id;
 };
 
+// named_args is non-const to suppress a bogus -Wmaybe-uninitialized in gcc 13.
+template <typename Char>
+FMT_CONSTEXPR void check_for_duplicate(named_arg_info<Char>* named_args,
+                                       int named_arg_index,
+                                       basic_string_view<Char> arg_name) {
+  for (int i = 0; i < named_arg_index; ++i) {
+    if (named_args[i].name == arg_name) report_error("duplicate named arg");
+  }
+}
+
 template <typename Char, typename T, FMT_ENABLE_IF(!is_named_arg<T>::value)>
 void init_named_arg(named_arg_info<Char>*, int& arg_index, int&, const T&) {
   ++arg_index;
@@ -1063,6 +1111,7 @@ void init_named_arg(named_arg_info<Char>*, int& arg_index, int&, const T&) {
 template <typename Char, typename T, FMT_ENABLE_IF(is_named_arg<T>::value)>
 void init_named_arg(named_arg_info<Char>* named_args, int& arg_index,
                     int& named_arg_index, const T& arg) {
+  check_for_duplicate<Char>(named_args, named_arg_index, arg.name);
   named_args[named_arg_index++] = {arg.name, arg_index++};
 }
 
@@ -1076,12 +1125,13 @@ template <typename T, typename Char,
           FMT_ENABLE_IF(is_static_named_arg<T>::value)>
 FMT_CONSTEXPR void init_static_named_arg(named_arg_info<Char>* named_args,
                                          int& arg_index, int& named_arg_index) {
+  check_for_duplicate<Char>(named_args, named_arg_index, T::name);
   named_args[named_arg_index++] = {T::name, arg_index++};
 }
 
 // To minimize the number of types we need to deal with, long is translated
 // either to int or to long long depending on its size.
-enum { long_short = sizeof(long) == sizeof(int) };
+enum { long_short = sizeof(long) == sizeof(int) && FMT_BUILTIN_TYPES };
 using long_type = conditional_t<long_short, int, long long>;
 using ulong_type = conditional_t<long_short, unsigned, unsigned long long>;
 
@@ -1113,7 +1163,7 @@ using use_formatter =
     bool_constant<(std::is_class<T>::value || std::is_enum<T>::value ||
                    std::is_union<T>::value || std::is_array<T>::value) &&
                   !has_to_string_view<T>::value && !is_named_arg<T>::value &&
-                  !use_format_as<T>::value && !use_format_as_member<T>::value>;
+                  !use_format_as<T>::value && !use_format_as_member<U>::value>;
 
 template <typename Char, typename T, typename U = remove_const_t<T>>
 auto has_formatter_impl(T* p, buffered_context<Char>* ctx = nullptr)
@@ -1148,7 +1198,7 @@ template <typename Char> struct type_mapper {
   static auto map(ubitint<N>)
       -> conditional_t<N <= 64, unsigned long long, void>;
 
-  template <typename T, FMT_ENABLE_IF(is_char<T>::value)>
+  template <typename T, FMT_ENABLE_IF(is_code_unit<T>::value)>
   static auto map(T) -> conditional_t<
       std::is_same<T, char>::value || std::is_same<T, Char>::value, Char, void>;
 
@@ -1654,12 +1704,12 @@ template <typename... T> struct arg_pack {};
 template <typename Char, int NUM_ARGS, int NUM_NAMED_ARGS, bool DYNAMIC_NAMES>
 class format_string_checker {
  private:
-  type types_[max_of(1, NUM_ARGS)];
+  type types_[max_of<size_t>(1, NUM_ARGS)];
-  named_arg_info<Char> named_args_[max_of(1, NUM_NAMED_ARGS)];
+  named_arg_info<Char> named_args_[max_of<size_t>(1, NUM_NAMED_ARGS)];
   compile_parse_context<Char> context_;
 
   using parse_func = auto (*)(parse_context<Char>&) -> const Char*;
-  parse_func parse_funcs_[max_of(1, NUM_ARGS)];
+  parse_func parse_funcs_[max_of<size_t>(1, NUM_ARGS)];
 
  public:
   template <typename... T>
@@ -1698,7 +1748,17 @@ class format_string_checker {
       -> const Char* {
     context_.advance_to(begin);
     if (id >= 0 && id < NUM_ARGS) return parse_funcs_[id](context_);
-    while (begin != end && *begin != '}') ++begin;
+
+    // If id is out of range, it means we do not know the type and cannot parse
+    // the format at compile time. Instead, skip over content until we finish
+    // the format spec, accounting for any nested replacements.
+    for (int bracket_count = 0;
+         begin != end && (bracket_count > 0 || *begin != '}'); ++begin) {
+      if (*begin == '{')
+        ++bracket_count;
+      else if (*begin == '}')
+        --bracket_count;
+    }
     return begin;
   }
 
@@ -1790,15 +1850,19 @@ template <typename T> class buffer {
 #if !FMT_MSC_VERSION || FMT_MSC_VERSION >= 1940
   FMT_CONSTEXPR20
 #endif
-      void
+      void append(const U* begin, const U* end) {
-      append(const U* begin, const U* end) {
     while (begin != end) {
+      auto size = size_;
+      auto free_cap = capacity_ - size;
       auto count = to_unsigned(end - begin);
-      try_reserve(size_ + count);
+      if (free_cap < count) {
-      auto free_cap = capacity_ - size_;
+        grow_(*this, size + count);
-      if (free_cap < count) count = free_cap;
+        size = size_;
+        free_cap = capacity_ - size;
+        count = count < free_cap ? count : free_cap;
+      }
       // A loop is faster than memcpy on small sizes.
-      T* out = ptr_ + size_;
+      T* out = ptr_ + size;
       for (size_t i = 0; i < count; ++i) out[i] = begin[i];
       size_ += count;
       begin += count;
@@ -1998,6 +2062,17 @@ struct has_back_insert_iterator_container_append<
                         .append(std::declval<InputIt>(),
                                 std::declval<InputIt>()))>> : std::true_type {};
 
+template <typename OutputIt, typename InputIt, typename = void>
+struct has_back_insert_iterator_container_insert_at_end : std::false_type {};
+
+template <typename OutputIt, typename InputIt>
+struct has_back_insert_iterator_container_insert_at_end<
+    OutputIt, InputIt,
+    void_t<decltype(get_container(std::declval<OutputIt>())
+                        .insert(get_container(std::declval<OutputIt>()).end(),
+                                std::declval<InputIt>(),
+                                std::declval<InputIt>()))>> : std::true_type {};
+
 // An optimized version of std::copy with the output value type (T).
 template <typename T, typename InputIt, typename OutputIt,
           FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value&&
@@ -2012,6 +2087,8 @@ FMT_CONSTEXPR20 auto copy(InputIt begin, InputIt end, OutputIt out)
 template <typename T, typename InputIt, typename OutputIt,
           FMT_ENABLE_IF(is_back_insert_iterator<OutputIt>::value &&
                         !has_back_insert_iterator_container_append<
+                            OutputIt, InputIt>::value &&
+                        has_back_insert_iterator_container_insert_at_end<
                             OutputIt, InputIt>::value)>
 FMT_CONSTEXPR20 auto copy(InputIt begin, InputIt end, OutputIt out)
     -> OutputIt {
@@ -2021,7 +2098,11 @@ FMT_CONSTEXPR20 auto copy(InputIt begin, InputIt end, OutputIt out)
 }
 
 template <typename T, typename InputIt, typename OutputIt,
-          FMT_ENABLE_IF(!is_back_insert_iterator<OutputIt>::value)>
+          FMT_ENABLE_IF(!(is_back_insert_iterator<OutputIt>::value &&
+                          (has_back_insert_iterator_container_append<
+                               OutputIt, InputIt>::value ||
+                           has_back_insert_iterator_container_insert_at_end<
+                               OutputIt, InputIt>::value)))>
 FMT_CONSTEXPR auto copy(InputIt begin, InputIt end, OutputIt out) -> OutputIt {
   while (begin != end) *out++ = static_cast<T>(*begin++);
   return out;
@@ -2141,7 +2222,7 @@ template <typename Context> class value {
     static_assert(N <= 64, "unsupported _BitInt");
   }
 
-  template <typename T, FMT_ENABLE_IF(is_char<T>::value)>
+  template <typename T, FMT_ENABLE_IF(is_code_unit<T>::value)>
   constexpr FMT_INLINE value(T x FMT_BUILTIN) : char_value(x) {
     static_assert(
         std::is_same<T, char>::value || std::is_same<T, char_type>::value,
@@ -2217,7 +2298,7 @@ template <typename Context> class value {
         custom.value = const_cast<value_type*>(&x);
 #endif
     }
-    custom.format = format_custom<value_type, formatter<value_type, char_type>>;
+    custom.format = format_custom<value_type>;
   }
 
   template <typename T, FMT_ENABLE_IF(!has_formatter<T, char_type>())>
@@ -2228,10 +2309,10 @@ template <typename Context> class value {
   }
 
   // Formats an argument of a custom type, such as a user-defined class.
-  template <typename T, typename Formatter>
+  template <typename T>
   static void format_custom(void* arg, parse_context<char_type>& parse_ctx,
                             Context& ctx) {
-    auto f = Formatter();
+    auto f = formatter<T, char_type>();
     parse_ctx.advance_to(f.parse(parse_ctx));
     using qualified_type =
         conditional_t<has_formatter<const T, char_type>(), const T, T>;
@@ -2255,39 +2336,17 @@ template <> struct is_output_iterator<appender, char> : std::true_type {};
 template <typename It, typename T>
 struct is_output_iterator<
     It, T,
-    void_t<decltype(*std::declval<decay_t<It>&>()++ = std::declval<T>())>>
+    enable_if_t<std::is_assignable<decltype(*std::declval<decay_t<It>&>()++),
-    : std::true_type {};
+                                   T>::value>> : std::true_type {};
-
-#ifndef FMT_USE_LOCALE
-#  define FMT_USE_LOCALE (FMT_OPTIMIZE_SIZE <= 1)
-#endif
-
-// A type-erased reference to an std::locale to avoid a heavy <locale> include.
-struct locale_ref {
-#if FMT_USE_LOCALE
- private:
-  const void* locale_;  // A type-erased pointer to std::locale.
-
- public:
-  constexpr locale_ref() : locale_(nullptr) {}
-
-  template <typename Locale, FMT_ENABLE_IF(sizeof(Locale::collate) != 0)>
-  locale_ref(const Locale& loc);
-
-  inline explicit operator bool() const noexcept { return locale_ != nullptr; }
-#endif  // FMT_USE_LOCALE
-
-  template <typename Locale> auto get() const -> Locale;
-};
 
 template <typename> constexpr auto encode_types() -> unsigned long long {
   return 0;
 }
 
-template <typename Context, typename Arg, typename... Args>
+template <typename Context, typename First, typename... T>
 constexpr auto encode_types() -> unsigned long long {
-  return static_cast<unsigned>(stored_type_constant<Arg, Context>::value) |
+  return static_cast<unsigned>(stored_type_constant<First, Context>::value) |
-         (encode_types<Context, Args...>() << packed_arg_bits);
+         (encode_types<Context, T...>() << packed_arg_bits);
 }
 
 template <typename Context, typename... T, size_t NUM_ARGS = sizeof...(T)>
@@ -2304,8 +2363,9 @@ template <typename Context, int NUM_ARGS, int NUM_NAMED_ARGS,
           unsigned long long DESC>
 struct named_arg_store {
   // args_[0].named_args points to named_args to avoid bloating format_args.
-  arg_t<Context, NUM_ARGS> args[1 + NUM_ARGS];
+  arg_t<Context, NUM_ARGS> args[1u + NUM_ARGS];
-  named_arg_info<typename Context::char_type> named_args[NUM_NAMED_ARGS];
+  named_arg_info<typename Context::char_type>
+      named_args[static_cast<size_t>(NUM_NAMED_ARGS)];
 
   template <typename... T>
   FMT_CONSTEXPR FMT_ALWAYS_INLINE named_arg_store(T&... values)
@@ -2324,8 +2384,8 @@ struct named_arg_store {
   }
 
   named_arg_store(const named_arg_store& rhs) = delete;
-  named_arg_store& operator=(const named_arg_store& rhs) = delete;
+  auto operator=(const named_arg_store& rhs) -> named_arg_store& = delete;
-  named_arg_store& operator=(named_arg_store&& rhs) = delete;
+  auto operator=(named_arg_store&& rhs) -> named_arg_store& = delete;
   operator const arg_t<Context, NUM_ARGS>*() const { return args + 1; }
 };
 
@@ -2338,7 +2398,7 @@ struct format_arg_store {
   // +1 to workaround a bug in gcc 7.5 that causes duplicated-branches warning.
   using type =
       conditional_t<NUM_NAMED_ARGS == 0,
-                    arg_t<Context, NUM_ARGS>[max_of(1, NUM_ARGS)],
+                    arg_t<Context, NUM_ARGS>[max_of<size_t>(1, NUM_ARGS)],
                     named_arg_store<Context, NUM_ARGS, NUM_NAMED_ARGS, DESC>>;
   type args;
 };
@@ -2622,22 +2682,17 @@ class context {
  private:
   appender out_;
   format_args args_;
-  FMT_NO_UNIQUE_ADDRESS detail::locale_ref loc_;
+  FMT_NO_UNIQUE_ADDRESS locale_ref loc_;
 
  public:
-  /// The character type for the output.
+  using char_type = char;  ///< The character type for the output.
-  using char_type = char;
-
   using iterator = appender;
   using format_arg = basic_format_arg<context>;
-  using parse_context_type FMT_DEPRECATED = parse_context<>;
-  template <typename T> using formatter_type FMT_DEPRECATED = formatter<T>;
   enum { builtin_types = FMT_BUILTIN_TYPES };
 
   /// Constructs a `context` object. References to the arguments are stored
   /// in the object so make sure they have appropriate lifetimes.
-  FMT_CONSTEXPR context(iterator out, format_args args,
+  FMT_CONSTEXPR context(iterator out, format_args args, locale_ref loc = {})
-                        detail::locale_ref loc = {})
       : out_(out), args_(args), loc_(loc) {}
   context(context&&) = default;
   context(const context&) = delete;
@@ -2650,6 +2705,7 @@ class context {
   FMT_CONSTEXPR auto arg_id(string_view name) const -> int {
     return args_.get_id(name);
   }
+  auto args() const -> const format_args& { return args_; }
 
   // Returns an iterator to the beginning of the output range.
   FMT_CONSTEXPR auto out() const -> iterator { return out_; }
@@ -2657,7 +2713,7 @@ class context {
   // Advances the begin iterator to `it`.
   FMT_CONSTEXPR void advance_to(iterator) {}
 
-  FMT_CONSTEXPR auto locale() const -> detail::locale_ref { return loc_; }
+  FMT_CONSTEXPR auto locale() const -> locale_ref { return loc_; }
 };
 
 template <typename Char = char> struct runtime_format_string {
@@ -2695,10 +2751,12 @@ template <typename... T> struct fstring {
   template <size_t N>
   FMT_CONSTEVAL FMT_ALWAYS_INLINE fstring(const char (&s)[N]) : str(s, N - 1) {
     using namespace detail;
-    static_assert(count<(std::is_base_of<view, remove_reference_t<T>>::value &&
+    static_assert(count<(is_view<remove_cvref_t<T>>::value &&
                          std::is_reference<T>::value)...>() == 0,
                   "passing views as lvalues is disallowed");
-    if (FMT_USE_CONSTEVAL) parse_format_string<char>(s, checker(s, arg_pack()));
+#if FMT_USE_CONSTEVAL
+    parse_format_string<char>(s, checker(s, arg_pack()));
+#endif
 #ifdef FMT_ENFORCE_COMPILE_STRING
     static_assert(
         FMT_USE_CONSTEVAL && sizeof(s) != 0,
@@ -2722,9 +2780,9 @@ template <typename... T> struct fstring {
                               std::is_same<typename S::char_type, char>::value)>
   FMT_ALWAYS_INLINE fstring(const S&) : str(S()) {
     FMT_CONSTEXPR auto sv = string_view(S());
-    FMT_CONSTEXPR int ignore =
+    FMT_CONSTEXPR int unused =
         (parse_format_string(sv, checker(sv, arg_pack())), 0);
-    detail::ignore_unused(ignore);
+    detail::ignore_unused(unused);
   }
   fstring(runtime_format_string<> fmt) : str(fmt.str) {}
 
@@ -2744,9 +2802,6 @@ template <typename T, typename Char = char>
 concept formattable = is_formattable<remove_reference_t<T>, Char>::value;
 #endif
 
-template <typename T, typename Char>
-using has_formatter FMT_DEPRECATED = std::is_constructible<formatter<T, Char>>;
-
 // A formatter specialization for natively supported types.
 template <typename T, typename Char>
 struct formatter<T, Char,
@@ -2943,9 +2998,10 @@ FMT_INLINE void println(format_string<T...> fmt, T&&... args) {
   return fmt::println(stdout, fmt, static_cast<T&&>(args)...);
 }
 
-FMT_END_EXPORT
+FMT_PRAGMA_GCC(diagnostic pop)
 FMT_PRAGMA_CLANG(diagnostic pop)
 FMT_PRAGMA_GCC(pop_options)
+FMT_END_EXPORT
 FMT_END_NAMESPACE
 
 #ifdef FMT_HEADER_ONLY

include/fmt/chrono.h

@@ -22,21 +22,6 @@
 
 #include "format.h"
 
-namespace fmt_detail {
-struct time_zone {
-  template <typename Duration, typename T>
-  auto to_sys(T)
-      -> std::chrono::time_point<std::chrono::system_clock, Duration> {
-    return {};
-  }
-};
-template <typename... T> inline auto current_zone(T...) -> time_zone* {
-  return nullptr;
-}
-
-template <typename... T> inline void _tzset(T...) {}
-}  // namespace fmt_detail
-
 FMT_BEGIN_NAMESPACE
 
 // Enable safe chrono durations, unless explicitly disabled.
@@ -53,6 +38,7 @@ FMT_BEGIN_NAMESPACE
 // Copyright Paul Dreik 2019
 namespace safe_duration_cast {
 
+// DEPRECATED!
 template <typename To, typename From,
           FMT_ENABLE_IF(!std::is_same<From, To>::value &&
                         std::numeric_limits<From>::is_signed ==
@@ -176,17 +162,6 @@ auto safe_duration_cast(std::chrono::duration<FromRep, FromPeriod> from,
                         int& ec) -> To {
   using From = std::chrono::duration<FromRep, FromPeriod>;
   ec = 0;
-  if (std::isnan(from.count())) {
-    // nan in, gives nan out. easy.
-    return To{std::numeric_limits<typename To::rep>::quiet_NaN()};
-  }
-  // maybe we should also check if from is denormal, and decide what to do about
-  // it.
-
-  // +-inf should be preserved.
-  if (std::isinf(from.count())) {
-    return To{from.count()};
-  }
 
   // the basic idea is that we need to convert from count() in the from type
   // to count() in the To type, by multiplying it with this:
@@ -261,7 +236,7 @@ namespace detail {
 using utc_clock = std::chrono::utc_clock;
 #else
 struct utc_clock {
-  void to_sys();
+  template <typename T> void to_sys(T);
 };
 #endif
 
@@ -297,8 +272,6 @@ namespace detail {
 #define FMT_NOMACRO
 
 template <typename T = void> struct null {};
-inline auto localtime_r FMT_NOMACRO(...) -> null<> { return null<>(); }
-inline auto localtime_s(...) -> null<> { return null<>(); }
 inline auto gmtime_r(...) -> null<> { return null<>(); }
 inline auto gmtime_s(...) -> null<> { return null<>(); }
 
@@ -341,7 +314,7 @@ inline auto get_classic_locale() -> const std::locale& {
 }
 
 template <typename CodeUnit> struct codecvt_result {
-  static constexpr const size_t max_size = 32;
+  static constexpr size_t max_size = 32;
   CodeUnit buf[max_size];
   CodeUnit* end;
 };
@@ -364,7 +337,7 @@ void write_codecvt(codecvt_result<CodeUnit>& out, string_view in,
 template <typename OutputIt>
 auto write_encoded_tm_str(OutputIt out, string_view in, const std::locale& loc)
     -> OutputIt {
-  if (detail::use_utf8 && loc != get_classic_locale()) {
+  if (const_check(detail::use_utf8) && loc != get_classic_locale()) {
     // char16_t and char32_t codecvts are broken in MSVC (linkage errors) and
     // gcc-4.
 #if FMT_MSC_VERSION != 0 ||  \
@@ -435,14 +408,11 @@ auto write(OutputIt out, const std::tm& time, const std::locale& loc,
   return write_encoded_tm_str(out, string_view(buf.data(), buf.size()), loc);
 }
 
-template <typename Rep1, typename Rep2>
+template <typename T, typename U>
-struct is_same_arithmetic_type
+using is_similar_arithmetic_type =
-    : public std::integral_constant<bool,
+    bool_constant<(std::is_integral<T>::value && std::is_integral<U>::value) ||
-                                    (std::is_integral<Rep1>::value &&
+                  (std::is_floating_point<T>::value &&
-                                     std::is_integral<Rep2>::value) ||
+                   std::is_floating_point<U>::value)>;
-                                        (std::is_floating_point<Rep1>::value &&
-                                         std::is_floating_point<Rep2>::value)> {
-};
 
 FMT_NORETURN inline void throw_duration_error() {
   FMT_THROW(format_error("cannot format duration"));
@@ -461,11 +431,7 @@ auto duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
 
   using common_rep = typename std::common_type<FromRep, typename To::rep,
                                                decltype(factor::num)>::type;
-
+  common_rep count = from.count();  // This conversion is lossless.
-  int ec = 0;
-  auto count = safe_duration_cast::lossless_integral_conversion<common_rep>(
-      from.count(), ec);
-  if (ec) throw_duration_error();
 
   // Multiply from.count() by factor and check for overflow.
   if (const_check(factor::num != 1)) {
@@ -476,6 +442,7 @@ auto duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
     count *= factor::num;
   }
   if (const_check(factor::den != 1)) count /= factor::den;
+  int ec = 0;
   auto to =
       To(safe_duration_cast::lossless_integral_conversion<typename To::rep>(
           count, ec));
@@ -489,6 +456,8 @@ template <typename To, typename FromRep, typename FromPeriod,
                             std::is_floating_point<typename To::rep>::value)>
 auto duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
 #if FMT_SAFE_DURATION_CAST
+  // Preserve infinity and NaN.
+  if (!isfinite(from.count())) return static_cast<To>(from.count());
   // Throwing version of safe_duration_cast is only available for
   // integer to integer or float to float casts.
   int ec;
@@ -501,11 +470,11 @@ auto duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
 #endif
 }
 
-template <
+template <typename To, typename FromRep, typename FromPeriod,
-    typename To, typename FromRep, typename FromPeriod,
+          FMT_ENABLE_IF(
-    FMT_ENABLE_IF(!is_same_arithmetic_type<FromRep, typename To::rep>::value)>
+              !is_similar_arithmetic_type<FromRep, typename To::rep>::value)>
 auto duration_cast(std::chrono::duration<FromRep, FromPeriod> from) -> To {
-  // Mixed integer <-> float cast is not supported by safe_duration_cast.
+  // Mixed integer <-> float cast is not supported by safe duration_cast.
   return std::chrono::duration_cast<To>(from);
 }
 
@@ -519,68 +488,10 @@ auto to_time_t(sys_time<Duration> time_point) -> std::time_t {
       .count();
 }
 
-// Workaround a bug in libstdc++ which sets __cpp_lib_chrono to 201907 without
-// providing current_zone(): https://github.com/fmtlib/fmt/issues/4160.
-template <typename T> FMT_CONSTEXPR auto has_current_zone() -> bool {
-  using namespace std::chrono;
-  using namespace fmt_detail;
-  return !std::is_same<decltype(current_zone()), fmt_detail::time_zone*>::value;
-}
 }  // namespace detail
 
 FMT_BEGIN_EXPORT
 
-/**
- * Converts given time since epoch as `std::time_t` value into calendar time,
- * expressed in local time. Unlike `std::localtime`, this function is
- * thread-safe on most platforms.
- */
-inline auto localtime(std::time_t time) -> std::tm {
-  struct dispatcher {
-    std::time_t time_;
-    std::tm tm_;
-
-    inline dispatcher(std::time_t t) : time_(t) {}
-
-    inline auto run() -> bool {
-      using namespace fmt::detail;
-      return handle(localtime_r(&time_, &tm_));
-    }
-
-    inline auto handle(std::tm* tm) -> bool { return tm != nullptr; }
-
-    inline auto handle(detail::null<>) -> bool {
-      using namespace fmt::detail;
-      return fallback(localtime_s(&tm_, &time_));
-    }
-
-    inline auto fallback(int res) -> bool { return res == 0; }
-
-#if !FMT_MSC_VERSION
-    inline auto fallback(detail::null<>) -> bool {
-      using namespace fmt::detail;
-      std::tm* tm = std::localtime(&time_);
-      if (tm) tm_ = *tm;
-      return tm != nullptr;
-    }
-#endif
-  };
-  dispatcher lt(time);
-  // Too big time values may be unsupported.
-  if (!lt.run()) FMT_THROW(format_error("time_t value out of range"));
-  return lt.tm_;
-}
-
-#if FMT_USE_LOCAL_TIME
-template <typename Duration,
-          FMT_ENABLE_IF(detail::has_current_zone<Duration>())>
-inline auto localtime(std::chrono::local_time<Duration> time) -> std::tm {
-  using namespace std::chrono;
-  using namespace fmt_detail;
-  return localtime(detail::to_time_t(current_zone()->to_sys<Duration>(time)));
-}
-#endif
-
 /**
  * Converts given time since epoch as `std::time_t` value into calendar time,
  * expressed in Coordinated Universal Time (UTC). Unlike `std::gmtime`, this
@@ -652,7 +563,7 @@ inline void write_digit2_separated(char* buf, unsigned a, unsigned b,
   // Add ASCII '0' to each digit byte and insert separators.
   digits |= 0x3030003030003030 | (usep << 16) | (usep << 40);
 
-  constexpr const size_t len = 8;
+  constexpr size_t len = 8;
   if (const_check(is_big_endian())) {
     char tmp[len];
     std::memcpy(tmp, &digits, len);
@@ -911,7 +822,14 @@ template <typename Derived> struct null_chrono_spec_handler {
   FMT_CONSTEXPR void on_tz_name() { unsupported(); }
 };
 
-struct tm_format_checker : null_chrono_spec_handler<tm_format_checker> {
+class tm_format_checker : public null_chrono_spec_handler<tm_format_checker> {
+ private:
+  bool has_timezone_ = false;
+
+ public:
+  constexpr explicit tm_format_checker(bool has_timezone)
+      : has_timezone_(has_timezone) {}
+
   FMT_NORETURN inline void unsupported() {
     FMT_THROW(format_error("no format"));
   }
@@ -949,8 +867,12 @@ struct tm_format_checker : null_chrono_spec_handler<tm_format_checker> {
   FMT_CONSTEXPR void on_24_hour_time() {}
   FMT_CONSTEXPR void on_iso_time() {}
   FMT_CONSTEXPR void on_am_pm() {}
-  FMT_CONSTEXPR void on_utc_offset(numeric_system) {}
+  FMT_CONSTEXPR void on_utc_offset(numeric_system) {
-  FMT_CONSTEXPR void on_tz_name() {}
+    if (!has_timezone_) FMT_THROW(format_error("no timezone"));
+  }
+  FMT_CONSTEXPR void on_tz_name() {
+    if (!has_timezone_) FMT_THROW(format_error("no timezone"));
+  }
 };
 
 inline auto tm_wday_full_name(int wday) -> const char* {
@@ -980,24 +902,27 @@ inline auto tm_mon_short_name(int mon) -> const char* {
 }
 
 template <typename T, typename = void>
-struct has_member_data_tm_gmtoff : std::false_type {};
+struct has_tm_gmtoff : std::false_type {};
 template <typename T>
-struct has_member_data_tm_gmtoff<T, void_t<decltype(T::tm_gmtoff)>>
+struct has_tm_gmtoff<T, void_t<decltype(T::tm_gmtoff)>> : std::true_type {};
-    : std::true_type {};
 
-template <typename T, typename = void>
+template <typename T, typename = void> struct has_tm_zone : std::false_type {};
-struct has_member_data_tm_zone : std::false_type {};
 template <typename T>
-struct has_member_data_tm_zone<T, void_t<decltype(T::tm_zone)>>
+struct has_tm_zone<T, void_t<decltype(T::tm_zone)>> : std::true_type {};
-    : std::true_type {};
 
-inline void tzset_once() {
+template <typename T, FMT_ENABLE_IF(has_tm_zone<T>::value)>
-  static bool init = []() {
+auto set_tm_zone(T& time, char* tz) -> bool {
-    using namespace fmt_detail;
+  time.tm_zone = tz;
-    _tzset();
+  return true;
-    return false;
+}
-  }();
+template <typename T, FMT_ENABLE_IF(!has_tm_zone<T>::value)>
-  ignore_unused(init);
+auto set_tm_zone(T&, char*) -> bool {
+  return false;
+}
+
+inline auto utc() -> char* {
+  static char tz[] = "UTC";
+  return tz;
 }
 
 // Converts value to Int and checks that it's in the range [0, upper).
@@ -1005,7 +930,7 @@ template <typename T, typename Int, FMT_ENABLE_IF(std::is_integral<T>::value)>
 inline auto to_nonnegative_int(T value, Int upper) -> Int {
   if (!std::is_unsigned<Int>::value &&
       (value < 0 || to_unsigned(value) > to_unsigned(upper))) {
-    FMT_THROW(fmt::format_error("chrono value is out of range"));
+    FMT_THROW(format_error("chrono value is out of range"));
   }
   return static_cast<Int>(value);
 }
@@ -1090,7 +1015,7 @@ void write_fractional_seconds(OutputIt& out, Duration d, int precision = -1) {
 
 // Format subseconds which are given as a floating point type with an
 // appropriate number of digits. We cannot pass the Duration here, as we
-// explicitly need to pass the Rep value in the chrono_formatter.
+// explicitly need to pass the Rep value in the duration_formatter.
 template <typename Duration>
 void write_floating_seconds(memory_buffer& buf, Duration duration,
                             int num_fractional_digits = -1) {
@@ -1124,7 +1049,7 @@ class tm_writer {
   static constexpr int days_per_week = 7;
 
   const std::locale& loc_;
-  const bool is_classic_;
+  bool is_classic_;
   OutputIt out_;
   const Duration* subsecs_;
   const std::tm& tm_;
@@ -1160,8 +1085,8 @@ class tm_writer {
   }
 
   auto tm_hour12() const noexcept -> int {
-    const auto h = tm_hour();
+    auto h = tm_hour();
-    const auto z = h < 12 ? h : h - 12;
+    auto z = h < 12 ? h : h - 12;
     return z == 0 ? 12 : z;
   }
 
@@ -1177,11 +1102,11 @@ class tm_writer {
 
   // Algorithm: https://en.wikipedia.org/wiki/ISO_week_date.
   auto iso_year_weeks(long long curr_year) const noexcept -> int {
-    const auto prev_year = curr_year - 1;
+    auto prev_year = curr_year - 1;
-    const auto curr_p =
+    auto curr_p =
         (curr_year + curr_year / 4 - curr_year / 100 + curr_year / 400) %
         days_per_week;
-    const auto prev_p =
+    auto prev_p =
         (prev_year + prev_year / 4 - prev_year / 100 + prev_year / 400) %
         days_per_week;
     return 52 + ((curr_p == 4 || prev_p == 3) ? 1 : 0);
@@ -1191,15 +1116,15 @@ class tm_writer {
            days_per_week;
   }
   auto tm_iso_week_year() const noexcept -> long long {
-    const auto year = tm_year();
+    auto year = tm_year();
-    const auto w = iso_week_num(tm_yday(), tm_wday());
+    auto w = iso_week_num(tm_yday(), tm_wday());
     if (w < 1) return year - 1;
     if (w > iso_year_weeks(year)) return year + 1;
     return year;
   }
   auto tm_iso_week_of_year() const noexcept -> int {
-    const auto year = tm_year();
+    auto year = tm_year();
-    const auto w = iso_week_num(tm_yday(), tm_wday());
+    auto w = iso_week_num(tm_yday(), tm_wday());
     if (w < 1) return iso_year_weeks(year - 1);
     if (w > iso_year_weeks(year)) return 1;
     return w;
@@ -1236,9 +1161,8 @@ class tm_writer {
     uint32_or_64_or_128_t<long long> n = to_unsigned(year);
     const int num_digits = count_digits(n);
     if (negative && pad == pad_type::zero) *out_++ = '-';
-    if (width > num_digits) {
+    if (width > num_digits)
       out_ = detail::write_padding(out_, pad, width - num_digits);
-    }
     if (negative && pad != pad_type::zero) *out_++ = '-';
     out_ = format_decimal<Char>(out_, n, num_digits);
   }
@@ -1259,45 +1183,22 @@ class tm_writer {
     write2(static_cast<int>(offset % 60));
   }
 
-  template <typename T, FMT_ENABLE_IF(has_member_data_tm_gmtoff<T>::value)>
+  template <typename T, FMT_ENABLE_IF(has_tm_gmtoff<T>::value)>
-  void format_utc_offset_impl(const T& tm, numeric_system ns) {
+  void format_utc_offset(const T& tm, numeric_system ns) {
     write_utc_offset(tm.tm_gmtoff, ns);
   }
-  template <typename T, FMT_ENABLE_IF(!has_member_data_tm_gmtoff<T>::value)>
+  template <typename T, FMT_ENABLE_IF(!has_tm_gmtoff<T>::value)>
-  void format_utc_offset_impl(const T& tm, numeric_system ns) {
+  void format_utc_offset(const T&, numeric_system ns) {
-#if defined(_WIN32) && defined(_UCRT)
+    write_utc_offset(0, ns);
-    tzset_once();
-    long offset = 0;
-    _get_timezone(&offset);
-    if (tm.tm_isdst) {
-      long dstbias = 0;
-      _get_dstbias(&dstbias);
-      offset += dstbias;
-    }
-    write_utc_offset(-offset, ns);
-#else
-    if (ns == numeric_system::standard) return format_localized('z');
-
-    // Extract timezone offset from timezone conversion functions.
-    std::tm gtm = tm;
-    std::time_t gt = std::mktime(&gtm);
-    std::tm ltm = gmtime(gt);
-    std::time_t lt = std::mktime(&ltm);
-    long long offset = gt - lt;
-    write_utc_offset(offset, ns);
-#endif
   }
 
-  template <typename T, FMT_ENABLE_IF(has_member_data_tm_zone<T>::value)>
+  template <typename T, FMT_ENABLE_IF(has_tm_zone<T>::value)>
-  void format_tz_name_impl(const T& tm) {
+  void format_tz_name(const T& tm) {
-    if (is_classic_)
+    out_ = write_tm_str<Char>(out_, tm.tm_zone, loc_);
-      out_ = write_tm_str<Char>(out_, tm.tm_zone, loc_);
-    else
-      format_localized('Z');
   }
-  template <typename T, FMT_ENABLE_IF(!has_member_data_tm_zone<T>::value)>
+  template <typename T, FMT_ENABLE_IF(!has_tm_zone<T>::value)>
-  void format_tz_name_impl(const T&) {
+  void format_tz_name(const T&) {
-    format_localized('Z');
+    out_ = std::copy_n(utc(), 3, out_);
   }
 
   void format_localized(char format, char modifier = 0) {
@@ -1408,8 +1309,8 @@ class tm_writer {
     out_ = copy<Char>(std::begin(buf) + offset, std::end(buf), out_);
   }
 
-  void on_utc_offset(numeric_system ns) { format_utc_offset_impl(tm_, ns); }
+  void on_utc_offset(numeric_system ns) { format_utc_offset(tm_, ns); }
-  void on_tz_name() { format_tz_name_impl(tm_); }
+  void on_tz_name() { format_tz_name(tm_); }
 
   void on_year(numeric_system ns, pad_type pad) {
     if (is_classic_ || ns == numeric_system::standard)
@@ -1483,11 +1384,10 @@ class tm_writer {
   void on_day_of_year(pad_type pad) {
     auto yday = tm_yday() + 1;
     auto digit1 = yday / 100;
-    if (digit1 != 0) {
+    if (digit1 != 0)
       write1(digit1);
-    } else {
+    else
       out_ = detail::write_padding(out_, pad);
-    }
     write2(yday % 100, pad);
   }
 
@@ -1624,18 +1524,16 @@ template <typename Rep, typename Period,
           FMT_ENABLE_IF(std::is_integral<Rep>::value)>
 inline auto get_milliseconds(std::chrono::duration<Rep, Period> d)
     -> std::chrono::duration<Rep, std::milli> {
-  // this may overflow and/or the result may not fit in the
+  // This may overflow and/or the result may not fit in the target type.
-  // target type.
 #if FMT_SAFE_DURATION_CAST
-  using CommonSecondsType =
+  using common_seconds_type =
       typename std::common_type<decltype(d), std::chrono::seconds>::type;
-  const auto d_as_common = detail::duration_cast<CommonSecondsType>(d);
+  auto d_as_common = detail::duration_cast<common_seconds_type>(d);
-  const auto d_as_whole_seconds =
+  auto d_as_whole_seconds =
       detail::duration_cast<std::chrono::seconds>(d_as_common);
-  // this conversion should be nonproblematic
+  // This conversion should be nonproblematic.
-  const auto diff = d_as_common - d_as_whole_seconds;
+  auto diff = d_as_common - d_as_whole_seconds;
-  const auto ms =
+  auto ms = detail::duration_cast<std::chrono::duration<Rep, std::milli>>(diff);
-      detail::duration_cast<std::chrono::duration<Rep, std::milli>>(diff);
   return ms;
 #else
   auto s = detail::duration_cast<std::chrono::seconds>(d);
@@ -1696,8 +1594,13 @@ class get_locale {
 
  public:
   inline get_locale(bool localized, locale_ref loc) : has_locale_(localized) {
-    if (localized)
+    if (!localized) return;
-      ::new (&locale_) std::locale(loc.template get<std::locale>());
+    ignore_unused(loc);
+    ::new (&locale_) std::locale(
+#if FMT_USE_LOCALE
+        loc.template get<std::locale>()
+#endif
+    );
   }
   inline ~get_locale() {
     if (has_locale_) locale_.~locale();
@@ -1707,32 +1610,28 @@ class get_locale {
   }
 };
 
-template <typename FormatContext, typename OutputIt, typename Rep,
+template <typename Char, typename Rep, typename Period>
-          typename Period>
+struct duration_formatter {
-struct chrono_formatter {
+  using iterator = basic_appender<Char>;
-  FormatContext& context;
+  iterator out;
-  OutputIt out;
-  int precision;
-  bool localized = false;
   // rep is unsigned to avoid overflow.
   using rep =
       conditional_t<std::is_integral<Rep>::value && sizeof(Rep) < sizeof(int),
                     unsigned, typename make_unsigned_or_unchanged<Rep>::type>;
   rep val;
+  int precision;
+  locale_ref locale;
+  bool localized = false;
   using seconds = std::chrono::duration<rep>;
   seconds s;
   using milliseconds = std::chrono::duration<rep, std::milli>;
   bool negative;
 
-  using char_type = typename FormatContext::char_type;
+  using tm_writer_type = tm_writer<iterator, Char>;
-  using tm_writer_type = tm_writer<OutputIt, char_type>;
 
-  chrono_formatter(FormatContext& ctx, OutputIt o,
+  duration_formatter(iterator o, std::chrono::duration<Rep, Period> d,
-                   std::chrono::duration<Rep, Period> d)
+                     locale_ref loc)
-      : context(ctx),
+      : out(o), val(static_cast<rep>(d.count())), locale(loc), negative(false) {
-        out(o),
-        val(static_cast<rep>(d.count())),
-        negative(false) {
     if (d.count() < 0) {
       val = 0 - val;
       negative = true;
@@ -1746,19 +1645,16 @@ struct chrono_formatter {
 
   // returns true if nan or inf, writes to out.
   auto handle_nan_inf() -> bool {
-    if (isfinite(val)) {
+    if (isfinite(val)) return false;
-      return false;
-    }
     if (isnan(val)) {
       write_nan();
       return true;
     }
     // must be +-inf
-    if (val > 0) {
+    if (val > 0)
-      write_pinf();
+      std::copy_n("inf", 3, out);
-    } else {
+    else
-      write_ninf();
+      std::copy_n("-inf", 4, out);
-    }
     return true;
   }
 
@@ -1786,10 +1682,9 @@ struct chrono_formatter {
   }
 
   void write_sign() {
-    if (negative) {
+    if (!negative) return;
-      *out++ = '-';
+    *out++ = '-';
-      negative = false;
+    negative = false;
-    }
   }
 
   void write(Rep value, int width, pad_type pad = pad_type::zero) {
@@ -1801,24 +1696,22 @@ struct chrono_formatter {
     if (width > num_digits) {
       out = detail::write_padding(out, pad, width - num_digits);
     }
-    out = format_decimal<char_type>(out, n, num_digits);
+    out = format_decimal<Char>(out, n, num_digits);
   }
 
   void write_nan() { std::copy_n("nan", 3, out); }
-  void write_pinf() { std::copy_n("inf", 3, out); }
-  void write_ninf() { std::copy_n("-inf", 4, out); }
 
   template <typename Callback, typename... Args>
   void format_tm(const tm& time, Callback cb, Args... args) {
     if (isnan(val)) return write_nan();
-    get_locale loc(localized, context.locale());
+    get_locale loc(localized, locale);
     auto w = tm_writer_type(loc, out, time);
     (w.*cb)(args...);
     out = w.out();
   }
 
-  void on_text(const char_type* begin, const char_type* end) {
+  void on_text(const Char* begin, const Char* end) {
-    copy<char_type>(begin, end, out);
+    copy<Char>(begin, end, out);
   }
 
   // These are not implemented because durations don't have date information.
@@ -1888,13 +1781,12 @@ struct chrono_formatter {
         write_floating_seconds(buf, std::chrono::duration<rep, Period>(val),
                                precision);
         if (negative) *out++ = '-';
-        if (buf.size() < 2 || buf[1] == '.') {
+        if (buf.size() < 2 || buf[1] == '.')
           out = detail::write_padding(out, pad);
-        }
+        out = copy<Char>(buf.begin(), buf.end(), out);
-        out = copy<char_type>(buf.begin(), buf.end(), out);
       } else {
         write(second(), 2, pad);
-        write_fractional_seconds<char_type>(
+        write_fractional_seconds<Char>(
             out, std::chrono::duration<rep, Period>(val), precision);
       }
       return;
@@ -1936,12 +1828,10 @@ struct chrono_formatter {
   void on_duration_value() {
     if (handle_nan_inf()) return;
     write_sign();
-    out = format_duration_value<char_type>(out, val, precision);
+    out = format_duration_value<Char>(out, val, precision);
   }
 
-  void on_duration_unit() {
+  void on_duration_unit() { out = format_duration_unit<Char, Period>(out); }
-    out = format_duration_unit<char_type, Period>(out);
-  }
 };
 
 }  // namespace detail
@@ -2011,12 +1901,11 @@ class year_month_day {
   constexpr auto month() const noexcept -> fmt::month { return month_; }
   constexpr auto day() const noexcept -> fmt::day { return day_; }
 };
-#endif
+#endif  // __cpp_lib_chrono >= 201907
 
 template <typename Char>
 struct formatter<weekday, Char> : private formatter<std::tm, Char> {
  private:
-  bool localized_ = false;
   bool use_tm_formatter_ = false;
 
  public:
@@ -2024,8 +1913,7 @@ struct formatter<weekday, Char> : private formatter<std::tm, Char> {
     auto it = ctx.begin(), end = ctx.end();
     if (it != end && *it == 'L') {
       ++it;
-      localized_ = true;
+      this->set_localized();
-      return it;
     }
     use_tm_formatter_ = it != end && *it != '}';
     return use_tm_formatter_ ? formatter<std::tm, Char>::parse(ctx) : it;
@@ -2036,7 +1924,7 @@ struct formatter<weekday, Char> : private formatter<std::tm, Char> {
     auto time = std::tm();
     time.tm_wday = static_cast<int>(wd.c_encoding());
     if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
-    detail::get_locale loc(localized_, ctx.locale());
+    detail::get_locale loc(this->localized(), ctx.locale());
     auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
     w.on_abbr_weekday();
     return w.out();
@@ -2070,7 +1958,6 @@ struct formatter<day, Char> : private formatter<std::tm, Char> {
 template <typename Char>
 struct formatter<month, Char> : private formatter<std::tm, Char> {
  private:
-  bool localized_ = false;
   bool use_tm_formatter_ = false;
 
  public:
@@ -2078,8 +1965,7 @@ struct formatter<month, Char> : private formatter<std::tm, Char> {
     auto it = ctx.begin(), end = ctx.end();
     if (it != end && *it == 'L') {
       ++it;
-      localized_ = true;
+      this->set_localized();
-      return it;
     }
     use_tm_formatter_ = it != end && *it != '}';
     return use_tm_formatter_ ? formatter<std::tm, Char>::parse(ctx) : it;
@@ -2090,7 +1976,7 @@ struct formatter<month, Char> : private formatter<std::tm, Char> {
     auto time = std::tm();
     time.tm_mon = static_cast<int>(static_cast<unsigned>(m)) - 1;
     if (use_tm_formatter_) return formatter<std::tm, Char>::format(time, ctx);
-    detail::get_locale loc(localized_, ctx.locale());
+    detail::get_locale loc(this->localized(), ctx.locale());
     auto w = detail::tm_writer<decltype(ctx.out()), Char>(loc, ctx.out(), time);
     w.on_abbr_month();
     return w.out();
@@ -2154,7 +2040,6 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
   format_specs specs_;
   detail::arg_ref<Char> width_ref_;
   detail::arg_ref<Char> precision_ref_;
-  bool localized_ = false;
   basic_string_view<Char> fmt_;
 
  public:
@@ -2177,7 +2062,7 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
       it = detail::parse_precision(it, end, specs_, precision_ref_, ctx);
     }
     if (it != end && *it == 'L') {
-      localized_ = true;
+      specs_.set_localized();
       ++it;
     }
     end = detail::parse_chrono_format(it, end, checker);
@@ -2204,11 +2089,10 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
       out = detail::format_duration_value<Char>(out, d.count(), precision);
       detail::format_duration_unit<Char, Period>(out);
     } else {
-      using chrono_formatter =
+      auto f =
-          detail::chrono_formatter<FormatContext, decltype(out), Rep, Period>;
+          detail::duration_formatter<Char, Rep, Period>(out, d, ctx.locale());
-      auto f = chrono_formatter(ctx, out, d);
       f.precision = precision;
-      f.localized = localized_;
+      f.localized = specs_.localized();
       detail::parse_chrono_format(begin, end, f);
     }
     return detail::write(
@@ -2220,30 +2104,15 @@ template <typename Char> struct formatter<std::tm, Char> {
  private:
   format_specs specs_;
   detail::arg_ref<Char> width_ref_;
+  basic_string_view<Char> fmt_ =
+      detail::string_literal<Char, '%', 'F', ' ', '%', 'T'>();
 
  protected:
-  basic_string_view<Char> fmt_;
+  auto localized() const -> bool { return specs_.localized(); }
+  FMT_CONSTEXPR void set_localized() { specs_.set_localized(); }
 
-  template <typename Duration, typename FormatContext>
+  FMT_CONSTEXPR auto do_parse(parse_context<Char>& ctx, bool has_timezone)
-  auto do_format(const std::tm& tm, FormatContext& ctx,
+      -> const Char* {
-                 const Duration* subsecs) const -> decltype(ctx.out()) {
-    auto specs = specs_;
-    auto buf = basic_memory_buffer<Char>();
-    auto out = basic_appender<Char>(buf);
-    detail::handle_dynamic_spec(specs.dynamic_width(), specs.width, width_ref_,
-                                ctx);
-
-    auto loc_ref = ctx.locale();
-    detail::get_locale loc(static_cast<bool>(loc_ref), loc_ref);
-    auto w =
-        detail::tm_writer<decltype(out), Char, Duration>(loc, out, tm, subsecs);
-    detail::parse_chrono_format(fmt_.begin(), fmt_.end(), w);
-    return detail::write(
-        ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
-  }
-
- public:
-  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     auto it = ctx.begin(), end = ctx.end();
     if (it == end || *it == '}') return it;
 
@@ -2256,12 +2125,41 @@ template <typename Char> struct formatter<std::tm, Char> {
       if (it == end) return it;
     }
 
-    end = detail::parse_chrono_format(it, end, detail::tm_format_checker());
+    if (*it == 'L') {
+      specs_.set_localized();
+      ++it;
+    }
+
+    end = detail::parse_chrono_format(it, end,
+                                      detail::tm_format_checker(has_timezone));
     // Replace the default format string only if the new spec is not empty.
     if (end != it) fmt_ = {it, detail::to_unsigned(end - it)};
     return end;
   }
 
+  template <typename Duration, typename FormatContext>
+  auto do_format(const std::tm& tm, FormatContext& ctx,
+                 const Duration* subsecs) const -> decltype(ctx.out()) {
+    auto specs = specs_;
+    auto buf = basic_memory_buffer<Char>();
+    auto out = basic_appender<Char>(buf);
+    detail::handle_dynamic_spec(specs.dynamic_width(), specs.width, width_ref_,
+                                ctx);
+
+    auto loc_ref = specs.localized() ? ctx.locale() : locale_ref();
+    detail::get_locale loc(static_cast<bool>(loc_ref), loc_ref);
+    auto w = detail::tm_writer<basic_appender<Char>, Char, Duration>(
+        loc, out, tm, subsecs);
+    detail::parse_chrono_format(fmt_.begin(), fmt_.end(), w);
+    return detail::write(
+        ctx.out(), basic_string_view<Char>(buf.data(), buf.size()), specs);
+  }
+
+ public:
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+    return do_parse(ctx, detail::has_tm_gmtoff<std::tm>::value);
+  }
+
   template <typename FormatContext>
   auto format(const std::tm& tm, FormatContext& ctx) const
       -> decltype(ctx.out()) {
@@ -2269,10 +2167,11 @@ template <typename Char> struct formatter<std::tm, Char> {
   }
 };
 
+// DEPRECATED! Reversed order of template parameters.
 template <typename Char, typename Duration>
-struct formatter<sys_time<Duration>, Char> : formatter<std::tm, Char> {
+struct formatter<sys_time<Duration>, Char> : private formatter<std::tm, Char> {
-  FMT_CONSTEXPR formatter() {
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
-    this->fmt_ = detail::string_literal<Char, '%', 'F', ' ', '%', 'T'>();
+    return this->do_parse(ctx, true);
   }
 
   template <typename FormatContext>
@@ -2283,6 +2182,7 @@ struct formatter<sys_time<Duration>, Char> : formatter<std::tm, Char> {
     if (detail::const_check(
             period::num == 1 && period::den == 1 &&
             !std::is_floating_point<typename Duration::rep>::value)) {
+      detail::set_tm_zone(tm, detail::utc());
       return formatter<std::tm, Char>::format(tm, ctx);
     }
     Duration epoch = val.time_since_epoch();
@@ -2290,11 +2190,13 @@ struct formatter<sys_time<Duration>, Char> : formatter<std::tm, Char> {
         epoch - detail::duration_cast<std::chrono::seconds>(epoch));
     if (subsecs.count() < 0) {
       auto second = detail::duration_cast<Duration>(std::chrono::seconds(1));
-      if (tm.tm_sec != 0)
+      if (tm.tm_sec != 0) {
         --tm.tm_sec;
-      else
+      } else {
         tm = gmtime(val - second);
-      subsecs += detail::duration_cast<Duration>(std::chrono::seconds(1));
+        detail::set_tm_zone(tm, detail::utc());
+      }
+      subsecs += second;
     }
     return formatter<std::tm, Char>::do_format(tm, ctx, &subsecs);
   }
@@ -2312,23 +2214,29 @@ struct formatter<utc_time<Duration>, Char>
 };
 
 template <typename Duration, typename Char>
-struct formatter<local_time<Duration>, Char> : formatter<std::tm, Char> {
+struct formatter<local_time<Duration>, Char>
-  FMT_CONSTEXPR formatter() {
+    : private formatter<std::tm, Char> {
-    this->fmt_ = detail::string_literal<Char, '%', 'F', ' ', '%', 'T'>();
+  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+    return this->do_parse(ctx, false);
   }
 
   template <typename FormatContext>
   auto format(local_time<Duration> val, FormatContext& ctx) const
       -> decltype(ctx.out()) {
+    auto time_since_epoch = val.time_since_epoch();
+    auto seconds_since_epoch =
+        detail::duration_cast<std::chrono::seconds>(time_since_epoch);
+    // Use gmtime to prevent time zone conversion since local_time has an
+    // unspecified time zone.
+    std::tm t = gmtime(seconds_since_epoch.count());
     using period = typename Duration::period;
     if (period::num == 1 && period::den == 1 &&
         !std::is_floating_point<typename Duration::rep>::value) {
-      return formatter<std::tm, Char>::format(localtime(val), ctx);
+      return formatter<std::tm, Char>::format(t, ctx);
     }
-    auto epoch = val.time_since_epoch();
+    auto subsecs =
-    auto subsecs = detail::duration_cast<Duration>(
+        detail::duration_cast<Duration>(time_since_epoch - seconds_since_epoch);
-        epoch - detail::duration_cast<std::chrono::seconds>(epoch));
+    return formatter<std::tm, Char>::do_format(t, ctx, &subsecs);
-    return formatter<std::tm, Char>::do_format(localtime(val), ctx, &subsecs);
   }
 };
 

include/fmt/color.h

@@ -155,7 +155,7 @@ enum class color : uint32_t {
   white_smoke = 0xF5F5F5,              // rgb(245,245,245)
   yellow = 0xFFFF00,                   // rgb(255,255,0)
   yellow_green = 0x9ACD32              // rgb(154,205,50)
-};                                     // enum class color
+};  // enum class color
 
 enum class terminal_color : uint8_t {
   black = 30,
@@ -190,11 +190,11 @@ enum class emphasis : uint8_t {
 // rgb is a struct for red, green and blue colors.
 // Using the name "rgb" makes some editors show the color in a tooltip.
 struct rgb {
-  FMT_CONSTEXPR rgb() : r(0), g(0), b(0) {}
+  constexpr rgb() : r(0), g(0), b(0) {}
-  FMT_CONSTEXPR rgb(uint8_t r_, uint8_t g_, uint8_t b_) : r(r_), g(g_), b(b_) {}
+  constexpr rgb(uint8_t r_, uint8_t g_, uint8_t b_) : r(r_), g(g_), b(b_) {}
-  FMT_CONSTEXPR rgb(uint32_t hex)
+  constexpr rgb(uint32_t hex)
       : r((hex >> 16) & 0xFF), g((hex >> 8) & 0xFF), b(hex & 0xFF) {}
-  FMT_CONSTEXPR rgb(color hex)
+  constexpr rgb(color hex)
       : r((uint32_t(hex) >> 16) & 0xFF),
         g((uint32_t(hex) >> 8) & 0xFF),
         b(uint32_t(hex) & 0xFF) {}
@@ -205,97 +205,135 @@ struct rgb {
 
 namespace detail {
 
-// color is a struct of either a rgb color or a terminal color.
+// A bit-packed variant of an RGB color, a terminal color, or unset color.
+// see text_style for the bit-packing scheme.
 struct color_type {
-  FMT_CONSTEXPR color_type() noexcept : is_rgb(), value{} {}
+  constexpr color_type() noexcept = default;
-  FMT_CONSTEXPR color_type(color rgb_color) noexcept : is_rgb(true), value{} {
+  constexpr color_type(color rgb_color) noexcept
-    value.rgb_color = static_cast<uint32_t>(rgb_color);
+      : value_(static_cast<uint32_t>(rgb_color) | (1 << 24)) {}
+  constexpr color_type(rgb rgb_color) noexcept
+      : color_type(static_cast<color>(
+            (static_cast<uint32_t>(rgb_color.r) << 16) |
+            (static_cast<uint32_t>(rgb_color.g) << 8) | rgb_color.b)) {}
+  constexpr color_type(terminal_color term_color) noexcept
+      : value_(static_cast<uint32_t>(term_color) | (3 << 24)) {}
+
+  constexpr auto is_terminal_color() const noexcept -> bool {
+    return (value_ & (1 << 25)) != 0;
   }
-  FMT_CONSTEXPR color_type(rgb rgb_color) noexcept : is_rgb(true), value{} {
+
-    value.rgb_color = (static_cast<uint32_t>(rgb_color.r) << 16) |
+  constexpr auto value() const noexcept -> uint32_t {
-                      (static_cast<uint32_t>(rgb_color.g) << 8) | rgb_color.b;
+    return value_ & 0xFFFFFF;
   }
-  FMT_CONSTEXPR color_type(terminal_color term_color) noexcept
+
-      : is_rgb(), value{} {
+  constexpr color_type(uint32_t value) noexcept : value_(value) {}
-    value.term_color = static_cast<uint8_t>(term_color);
+
-  }
+  uint32_t value_ = 0;
-  bool is_rgb;
-  union color_union {
-    uint8_t term_color;
-    uint32_t rgb_color;
-  } value;
 };
 }  // namespace detail
 
 /// A text style consisting of foreground and background colors and emphasis.
 class text_style {
+  // The information is packed as follows:
+  // ┌──┐
+  // │ 0│─┐
+  // │..│ ├── foreground color value
+  // │23│─┘
+  // ├──┤
+  // │24│─┬── discriminator for the above value. 00 if unset, 01 if it's
+  // │25│─┘   an RGB color, or 11 if it's a terminal color (10 is unused)
+  // ├──┤
+  // │26│──── overflow bit, always zero (see below)
+  // ├──┤
+  // │27│─┐
+  // │..│ │
+  // │50│ │
+  // ├──┤ │
+  // │51│ ├── background color (same format as the foreground color)
+  // │52│ │
+  // ├──┤ │
+  // │53│─┘
+  // ├──┤
+  // │54│─┐
+  // │..│ ├── emphases
+  // │61│─┘
+  // ├──┤
+  // │62│─┬── unused
+  // │63│─┘
+  // └──┘
+  // The overflow bits are there to make operator|= efficient.
+  // When ORing, we must throw if, for either the foreground or background,
+  // one style specifies a terminal color and the other specifies any color
+  // (terminal or RGB); in other words, if one discriminator is 11 and the
+  // other is 11 or 01.
+  //
+  // We do that check by adding the styles. Consider what adding does to each
+  // possible pair of discriminators:
+  //    00 + 00 = 000
+  //    01 + 00 = 001
+  //    11 + 00 = 011
+  //    01 + 01 = 010
+  //    11 + 01 = 100 (!!)
+  //    11 + 11 = 110 (!!)
+  // In the last two cases, the ones we want to catch, the third bit——the
+  // overflow bit——is set. Bingo.
+  //
+  // We must take into account the possible carry bit from the bits
+  // before the discriminator. The only potentially problematic case is
+  // 11 + 00 = 011 (a carry bit would make it 100, not good!), but a carry
+  // bit is impossible in that case, because 00 (unset color) means the
+  // 24 bits that precede the discriminator are all zero.
+  //
+  // This test can be applied to both colors simultaneously.
+
  public:
   FMT_CONSTEXPR text_style(emphasis em = emphasis()) noexcept
-      : set_foreground_color(), set_background_color(), ems(em) {}
+      : style_(static_cast<uint64_t>(em) << 54) {}
 
-  FMT_CONSTEXPR auto operator|=(const text_style& rhs) -> text_style& {
+  FMT_CONSTEXPR auto operator|=(text_style rhs) -> text_style& {
-    if (!set_foreground_color) {
+    if (((style_ + rhs.style_) & ((1ULL << 26) | (1ULL << 53))) != 0)
-      set_foreground_color = rhs.set_foreground_color;
+      report_error("can't OR a terminal color");
-      foreground_color = rhs.foreground_color;
+    style_ |= rhs.style_;
-    } else if (rhs.set_foreground_color) {
-      if (!foreground_color.is_rgb || !rhs.foreground_color.is_rgb)
-        report_error("can't OR a terminal color");
-      foreground_color.value.rgb_color |= rhs.foreground_color.value.rgb_color;
-    }
-
-    if (!set_background_color) {
-      set_background_color = rhs.set_background_color;
-      background_color = rhs.background_color;
-    } else if (rhs.set_background_color) {
-      if (!background_color.is_rgb || !rhs.background_color.is_rgb)
-        report_error("can't OR a terminal color");
-      background_color.value.rgb_color |= rhs.background_color.value.rgb_color;
-    }
-
-    ems = static_cast<emphasis>(static_cast<uint8_t>(ems) |
-                                static_cast<uint8_t>(rhs.ems));
     return *this;
   }
 
-  friend FMT_CONSTEXPR auto operator|(text_style lhs, const text_style& rhs)
+  friend FMT_CONSTEXPR auto operator|(text_style lhs, text_style rhs)
       -> text_style {
     return lhs |= rhs;
   }
 
+  FMT_CONSTEXPR auto operator==(text_style rhs) const noexcept -> bool {
+    return style_ == rhs.style_;
+  }
+
+  FMT_CONSTEXPR auto operator!=(text_style rhs) const noexcept -> bool {
+    return !(*this == rhs);
+  }
+
   FMT_CONSTEXPR auto has_foreground() const noexcept -> bool {
-    return set_foreground_color;
+    return (style_ & (1 << 24)) != 0;
   }
   FMT_CONSTEXPR auto has_background() const noexcept -> bool {
-    return set_background_color;
+    return (style_ & (1ULL << 51)) != 0;
   }
   FMT_CONSTEXPR auto has_emphasis() const noexcept -> bool {
-    return static_cast<uint8_t>(ems) != 0;
+    return (style_ >> 54) != 0;
   }
   FMT_CONSTEXPR auto get_foreground() const noexcept -> detail::color_type {
     FMT_ASSERT(has_foreground(), "no foreground specified for this style");
-    return foreground_color;
+    return style_ & 0x3FFFFFF;
   }
   FMT_CONSTEXPR auto get_background() const noexcept -> detail::color_type {
     FMT_ASSERT(has_background(), "no background specified for this style");
-    return background_color;
+    return (style_ >> 27) & 0x3FFFFFF;
   }
   FMT_CONSTEXPR auto get_emphasis() const noexcept -> emphasis {
     FMT_ASSERT(has_emphasis(), "no emphasis specified for this style");
-    return ems;
+    return static_cast<emphasis>(style_ >> 54);
   }
 
  private:
-  FMT_CONSTEXPR text_style(bool is_foreground,
+  FMT_CONSTEXPR text_style(uint64_t style) noexcept : style_(style) {}
-                           detail::color_type text_color) noexcept
-      : set_foreground_color(), set_background_color(), ems() {
-    if (is_foreground) {
-      foreground_color = text_color;
-      set_foreground_color = true;
-    } else {
-      background_color = text_color;
-      set_background_color = true;
-    }
-  }
 
   friend FMT_CONSTEXPR auto fg(detail::color_type foreground) noexcept
       -> text_style;
@@ -303,23 +341,19 @@ class text_style {
   friend FMT_CONSTEXPR auto bg(detail::color_type background) noexcept
       -> text_style;
 
-  detail::color_type foreground_color;
+  uint64_t style_ = 0;
-  detail::color_type background_color;
-  bool set_foreground_color;
-  bool set_background_color;
-  emphasis ems;
 };
 
 /// Creates a text style from the foreground (text) color.
 FMT_CONSTEXPR inline auto fg(detail::color_type foreground) noexcept
     -> text_style {
-  return text_style(true, foreground);
+  return foreground.value_;
 }
 
 /// Creates a text style from the background color.
 FMT_CONSTEXPR inline auto bg(detail::color_type background) noexcept
     -> text_style {
-  return text_style(false, background);
+  return static_cast<uint64_t>(background.value_) << 27;
 }
 
 FMT_CONSTEXPR inline auto operator|(emphasis lhs, emphasis rhs) noexcept
@@ -334,37 +368,35 @@ template <typename Char> struct ansi_color_escape {
                                   const char* esc) noexcept {
     // If we have a terminal color, we need to output another escape code
     // sequence.
-    if (!text_color.is_rgb) {
+    if (text_color.is_terminal_color()) {
       bool is_background = esc == string_view("\x1b[48;2;");
-      uint32_t value = text_color.value.term_color;
+      uint32_t value = text_color.value();
       // Background ASCII codes are the same as the foreground ones but with
       // 10 more.
       if (is_background) value += 10u;
 
-      size_t index = 0;
+      buffer[size++] = static_cast<Char>('\x1b');
-      buffer[index++] = static_cast<Char>('\x1b');
+      buffer[size++] = static_cast<Char>('[');
-      buffer[index++] = static_cast<Char>('[');
 
       if (value >= 100u) {
-        buffer[index++] = static_cast<Char>('1');
+        buffer[size++] = static_cast<Char>('1');
         value %= 100u;
       }
-      buffer[index++] = static_cast<Char>('0' + value / 10u);
+      buffer[size++] = static_cast<Char>('0' + value / 10u);
-      buffer[index++] = static_cast<Char>('0' + value % 10u);
+      buffer[size++] = static_cast<Char>('0' + value % 10u);
 
-      buffer[index++] = static_cast<Char>('m');
+      buffer[size++] = static_cast<Char>('m');
-      buffer[index++] = static_cast<Char>('\0');
       return;
     }
 
     for (int i = 0; i < 7; i++) {
       buffer[i] = static_cast<Char>(esc[i]);
     }
-    rgb color(text_color.value.rgb_color);
+    rgb color(text_color.value());
     to_esc(color.r, buffer + 7, ';');
     to_esc(color.g, buffer + 11, ';');
     to_esc(color.b, buffer + 15, 'm');
-    buffer[19] = static_cast<Char>(0);
+    size = 19;
   }
   FMT_CONSTEXPR ansi_color_escape(emphasis em) noexcept {
     uint8_t em_codes[num_emphases] = {};
@@ -377,26 +409,28 @@ template <typename Char> struct ansi_color_escape {
     if (has_emphasis(em, emphasis::conceal)) em_codes[6] = 8;
     if (has_emphasis(em, emphasis::strikethrough)) em_codes[7] = 9;
 
-    size_t index = 0;
+    buffer[size++] = static_cast<Char>('\x1b');
+    buffer[size++] = static_cast<Char>('[');
+
     for (size_t i = 0; i < num_emphases; ++i) {
       if (!em_codes[i]) continue;
-      buffer[index++] = static_cast<Char>('\x1b');
+      buffer[size++] = static_cast<Char>('0' + em_codes[i]);
-      buffer[index++] = static_cast<Char>('[');
+      buffer[size++] = static_cast<Char>(';');
-      buffer[index++] = static_cast<Char>('0' + em_codes[i]);
-      buffer[index++] = static_cast<Char>('m');
     }
-    buffer[index++] = static_cast<Char>(0);
+
+    buffer[size - 1] = static_cast<Char>('m');
   }
   FMT_CONSTEXPR operator const Char*() const noexcept { return buffer; }
 
   FMT_CONSTEXPR auto begin() const noexcept -> const Char* { return buffer; }
-  FMT_CONSTEXPR20 auto end() const noexcept -> const Char* {
+  FMT_CONSTEXPR auto end() const noexcept -> const Char* {
-    return buffer + basic_string_view<Char>(buffer).size();
+    return buffer + size;
   }
 
  private:
   static constexpr size_t num_emphases = 8;
-  Char buffer[7u + 3u * num_emphases + 1u];
+  Char buffer[7u + 4u * num_emphases] = {};
+  size_t size = 0;
 
   static FMT_CONSTEXPR void to_esc(uint8_t c, Char* out,
                                    char delimiter) noexcept {
@@ -441,32 +475,26 @@ template <typename T> struct styled_arg : view {
 };
 
 template <typename Char>
-void vformat_to(buffer<Char>& buf, const text_style& ts,
+void vformat_to(buffer<Char>& buf, text_style ts, basic_string_view<Char> fmt,
-                basic_string_view<Char> fmt,
                 basic_format_args<buffered_context<Char>> args) {
-  bool has_style = false;
   if (ts.has_emphasis()) {
-    has_style = true;
     auto emphasis = make_emphasis<Char>(ts.get_emphasis());
     buf.append(emphasis.begin(), emphasis.end());
   }
   if (ts.has_foreground()) {
-    has_style = true;
     auto foreground = make_foreground_color<Char>(ts.get_foreground());
     buf.append(foreground.begin(), foreground.end());
   }
   if (ts.has_background()) {
-    has_style = true;
     auto background = make_background_color<Char>(ts.get_background());
     buf.append(background.begin(), background.end());
   }
   vformat_to(buf, fmt, args);
-  if (has_style) reset_color<Char>(buf);
+  if (ts != text_style()) reset_color<Char>(buf);
 }
 }  // namespace detail
 
-inline void vprint(FILE* f, const text_style& ts, string_view fmt,
+inline void vprint(FILE* f, text_style ts, string_view fmt, format_args args) {
-                   format_args args) {
   auto buf = memory_buffer();
   detail::vformat_to(buf, ts, fmt, args);
   print(f, FMT_STRING("{}"), string_view(buf.begin(), buf.size()));
@@ -482,8 +510,7 @@ inline void vprint(FILE* f, const text_style& ts, string_view fmt,
  *                "Elapsed time: {0:.2f} seconds", 1.23);
  */
 template <typename... T>
-void print(FILE* f, const text_style& ts, format_string<T...> fmt,
+void print(FILE* f, text_style ts, format_string<T...> fmt, T&&... args) {
-           T&&... args) {
   vprint(f, ts, fmt.str, vargs<T...>{{args...}});
 }
 
@@ -497,11 +524,11 @@ void print(FILE* f, const text_style& ts, format_string<T...> fmt,
  *                "Elapsed time: {0:.2f} seconds", 1.23);
  */
 template <typename... T>
-void print(const text_style& ts, format_string<T...> fmt, T&&... args) {
+void print(text_style ts, format_string<T...> fmt, T&&... args) {
   return print(stdout, ts, fmt, std::forward<T>(args)...);
 }
 
-inline auto vformat(const text_style& ts, string_view fmt, format_args args)
+inline auto vformat(text_style ts, string_view fmt, format_args args)
     -> std::string {
   auto buf = memory_buffer();
   detail::vformat_to(buf, ts, fmt, args);
@@ -521,7 +548,7 @@ inline auto vformat(const text_style& ts, string_view fmt, format_args args)
  * ```
  */
 template <typename... T>
-inline auto format(const text_style& ts, format_string<T...> fmt, T&&... args)
+inline auto format(text_style ts, format_string<T...> fmt, T&&... args)
     -> std::string {
   return fmt::vformat(ts, fmt.str, vargs<T...>{{args...}});
 }
@@ -529,8 +556,8 @@ inline auto format(const text_style& ts, format_string<T...> fmt, T&&... args)
 /// Formats a string with the given text_style and writes the output to `out`.
 template <typename OutputIt,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
-auto vformat_to(OutputIt out, const text_style& ts, string_view fmt,
+auto vformat_to(OutputIt out, text_style ts, string_view fmt, format_args args)
-                format_args args) -> OutputIt {
+    -> OutputIt {
   auto&& buf = detail::get_buffer<char>(out);
   detail::vformat_to(buf, ts, fmt, args);
   return detail::get_iterator(buf, out);
@@ -548,8 +575,8 @@ auto vformat_to(OutputIt out, const text_style& ts, string_view fmt,
  */
 template <typename OutputIt, typename... T,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, char>::value)>
-inline auto format_to(OutputIt out, const text_style& ts,
+inline auto format_to(OutputIt out, text_style ts, format_string<T...> fmt,
-                      format_string<T...> fmt, T&&... args) -> OutputIt {
+                      T&&... args) -> OutputIt {
   return vformat_to(out, ts, fmt.str, vargs<T...>{{args...}});
 }
 

include/fmt/compile.h

@@ -15,11 +15,10 @@
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
+FMT_BEGIN_EXPORT
 
 // A compile-time string which is compiled into fast formatting code.
-FMT_EXPORT class compiled_string {};
+class compiled_string {};
-
-namespace detail {
 
 template <typename S>
 struct is_compiled_string : std::is_base_of<compiled_string, S> {};
@@ -41,28 +40,42 @@ struct is_compiled_string : std::is_base_of<compiled_string, S> {};
 #  define FMT_COMPILE(s) FMT_STRING(s)
 #endif
 
+/**
+ * Converts a string literal into a format string that will be parsed at
+ * compile time and converted into efficient formatting code. Requires support
+ * for class types in constant template parameters (a C++20 feature).
+ *
+ *  **Example**:
+ *
+ *     // Converts 42 into std::string using the most efficient method and no
+ *     // runtime format string processing.
+ *     using namespace fmt::literals;
+ *     std::string s = fmt::format("{}"_cf, 42);
+ */
 #if FMT_USE_NONTYPE_TEMPLATE_ARGS
-template <typename Char, size_t N, fmt::detail::fixed_string<Char, N> Str>
+inline namespace literals {
-struct udl_compiled_string : compiled_string {
+template <detail::fixed_string Str> constexpr auto operator""_cf() {
-  using char_type = Char;
+  return FMT_COMPILE(Str.data);
-  constexpr explicit operator basic_string_view<char_type>() const {
+}
-    return {Str.data, N - 1};
+}  // namespace literals
-  }
-};
 #endif
 
+FMT_END_EXPORT
+
+namespace detail {
+
 template <typename T, typename... Tail>
-auto first(const T& value, const Tail&...) -> const T& {
+constexpr auto first(const T& value, const Tail&...) -> const T& {
   return value;
 }
 
 #if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
-template <typename... Args> struct type_list {};
+template <typename... T> struct type_list {};
 
 // Returns a reference to the argument at index N from [first, rest...].
 template <int N, typename T, typename... Args>
-constexpr const auto& get([[maybe_unused]] const T& first,
+constexpr auto get([[maybe_unused]] const T& first,
-                          [[maybe_unused]] const Args&... rest) {
+                   [[maybe_unused]] const Args&... rest) -> const auto& {
   static_assert(N < 1 + sizeof...(Args), "index is out of bounds");
   if constexpr (N == 0)
     return first;
@@ -94,8 +107,8 @@ FMT_CONSTEXPR auto get_arg_index_by_name(basic_string_view<Char> name) -> int {
 }
 
 template <typename Char, typename... Args>
-constexpr int get_arg_index_by_name(basic_string_view<Char> name,
+constexpr auto get_arg_index_by_name(basic_string_view<Char> name,
-                                    type_list<Args...>) {
+                                     type_list<Args...>) -> int {
   return get_arg_index_by_name<Args...>(name);
 }
 
@@ -115,8 +128,8 @@ template <typename Char> struct text {
   basic_string_view<Char> data;
   using char_type = Char;
 
-  template <typename OutputIt, typename... Args>
+  template <typename OutputIt, typename... T>
-  constexpr OutputIt format(OutputIt out, const Args&...) const {
+  constexpr auto format(OutputIt out, const T&...) const -> OutputIt {
     return write<Char>(out, data);
   }
 };
@@ -125,8 +138,8 @@ template <typename Char>
 struct is_compiled_format<text<Char>> : std::true_type {};
 
 template <typename Char>
-constexpr text<Char> make_text(basic_string_view<Char> s, size_t pos,
+constexpr auto make_text(basic_string_view<Char> s, size_t pos, size_t size)
-                               size_t size) {
+    -> text<Char> {
   return {{&s[pos], size}};
 }
 
@@ -134,8 +147,8 @@ template <typename Char> struct code_unit {
   Char value;
   using char_type = Char;
 
-  template <typename OutputIt, typename... Args>
+  template <typename OutputIt, typename... T>
-  constexpr OutputIt format(OutputIt out, const Args&...) const {
+  constexpr auto format(OutputIt out, const T&...) const -> OutputIt {
     *out++ = value;
     return out;
   }
@@ -143,7 +156,7 @@ template <typename Char> struct code_unit {
 
 // This ensures that the argument type is convertible to `const T&`.
 template <typename T, int N, typename... Args>
-constexpr const T& get_arg_checked(const Args&... args) {
+constexpr auto get_arg_checked(const Args&... args) -> const T& {
   const auto& arg = detail::get<N>(args...);
   if constexpr (detail::is_named_arg<remove_cvref_t<decltype(arg)>>()) {
     return arg.value;
@@ -156,13 +169,13 @@ template <typename Char>
 struct is_compiled_format<code_unit<Char>> : std::true_type {};
 
 // A replacement field that refers to argument N.
-template <typename Char, typename T, int N> struct field {
+template <typename Char, typename V, int N> struct field {
   using char_type = Char;
 
-  template <typename OutputIt, typename... Args>
+  template <typename OutputIt, typename... T>
-  constexpr OutputIt format(OutputIt out, const Args&... args) const {
+  constexpr auto format(OutputIt out, const T&... args) const -> OutputIt {
-    const T& arg = get_arg_checked<T, N>(args...);
+    const V& arg = get_arg_checked<V, N>(args...);
-    if constexpr (std::is_convertible<T, basic_string_view<Char>>::value) {
+    if constexpr (std::is_convertible<V, basic_string_view<Char>>::value) {
       auto s = basic_string_view<Char>(arg);
       return copy<Char>(s.begin(), s.end(), out);
     } else {
@@ -180,10 +193,10 @@ template <typename Char> struct runtime_named_field {
   basic_string_view<Char> name;
 
   template <typename OutputIt, typename T>
-  constexpr static bool try_format_argument(
+  constexpr static auto try_format_argument(
       OutputIt& out,
       // [[maybe_unused]] due to unused-but-set-parameter warning in GCC 7,8,9
-      [[maybe_unused]] basic_string_view<Char> arg_name, const T& arg) {
+      [[maybe_unused]] basic_string_view<Char> arg_name, const T& arg) -> bool {
     if constexpr (is_named_arg<typename std::remove_cv<T>::type>::value) {
       if (arg_name == arg.name) {
         out = write<Char>(out, arg.value);
@@ -193,8 +206,8 @@ template <typename Char> struct runtime_named_field {
     return false;
   }
 
-  template <typename OutputIt, typename... Args>
+  template <typename OutputIt, typename... T>
-  constexpr OutputIt format(OutputIt out, const Args&... args) const {
+  constexpr auto format(OutputIt out, const T&... args) const -> OutputIt {
     bool found = (try_format_argument(out, name, args) || ...);
     if (!found) {
       FMT_THROW(format_error("argument with specified name is not found"));
@@ -207,17 +220,17 @@ template <typename Char>
 struct is_compiled_format<runtime_named_field<Char>> : std::true_type {};
 
 // A replacement field that refers to argument N and has format specifiers.
-template <typename Char, typename T, int N> struct spec_field {
+template <typename Char, typename V, int N> struct spec_field {
   using char_type = Char;
-  formatter<T, Char> fmt;
+  formatter<V, Char> fmt;
 
-  template <typename OutputIt, typename... Args>
+  template <typename OutputIt, typename... T>
-  constexpr FMT_INLINE OutputIt format(OutputIt out,
+  constexpr FMT_INLINE auto format(OutputIt out, const T&... args) const
-                                       const Args&... args) const {
+      -> OutputIt {
     const auto& vargs =
         fmt::make_format_args<basic_format_context<OutputIt, Char>>(args...);
     basic_format_context<OutputIt, Char> ctx(out, vargs);
-    return fmt.format(get_arg_checked<T, N>(args...), ctx);
+    return fmt.format(get_arg_checked<V, N>(args...), ctx);
   }
 };
 
@@ -229,8 +242,8 @@ template <typename L, typename R> struct concat {
   R rhs;
   using char_type = typename L::char_type;
 
-  template <typename OutputIt, typename... Args>
+  template <typename OutputIt, typename... T>
-  constexpr OutputIt format(OutputIt out, const Args&... args) const {
+  constexpr auto format(OutputIt out, const T&... args) const -> OutputIt {
     out = lhs.format(out, args...);
     return rhs.format(out, args...);
   }
@@ -240,14 +253,14 @@ template <typename L, typename R>
 struct is_compiled_format<concat<L, R>> : std::true_type {};
 
 template <typename L, typename R>
-constexpr concat<L, R> make_concat(L lhs, R rhs) {
+constexpr auto make_concat(L lhs, R rhs) -> concat<L, R> {
   return {lhs, rhs};
 }
 
 struct unknown_format {};
 
 template <typename Char>
-constexpr size_t parse_text(basic_string_view<Char> str, size_t pos) {
+constexpr auto parse_text(basic_string_view<Char> str, size_t pos) -> size_t {
   for (size_t size = str.size(); pos != size; ++pos) {
     if (str[pos] == '{' || str[pos] == '}') break;
   }
@@ -280,8 +293,8 @@ template <typename T, typename Char> struct parse_specs_result {
 enum { manual_indexing_id = -1 };
 
 template <typename T, typename Char>
-constexpr parse_specs_result<T, Char> parse_specs(basic_string_view<Char> str,
+constexpr auto parse_specs(basic_string_view<Char> str, size_t pos,
-                                                  size_t pos, int next_arg_id) {
+                           int next_arg_id) -> parse_specs_result<T, Char> {
   str.remove_prefix(pos);
   auto ctx =
       compile_parse_context<Char>(str, max_value<int>(), nullptr, next_arg_id);
@@ -295,16 +308,16 @@ template <typename Char> struct arg_id_handler {
   arg_id_kind kind;
   arg_ref<Char> arg_id;
 
-  constexpr int on_auto() {
+  constexpr auto on_auto() -> int {
     FMT_ASSERT(false, "handler cannot be used with automatic indexing");
     return 0;
   }
-  constexpr int on_index(int id) {
+  constexpr auto on_index(int id) -> int {
     kind = arg_id_kind::index;
     arg_id = arg_ref<Char>(id);
     return 0;
   }
-  constexpr int on_name(basic_string_view<Char> id) {
+  constexpr auto on_name(basic_string_view<Char> id) -> int {
     kind = arg_id_kind::name;
     arg_id = arg_ref<Char>(id);
     return 0;
@@ -425,7 +438,7 @@ constexpr auto compile_format_string(S fmt) {
 }
 
 template <typename... Args, typename S,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
 constexpr auto compile(S fmt) {
   constexpr auto str = basic_string_view<typename S::char_type>(fmt);
   if constexpr (str.size() == 0) {
@@ -443,27 +456,28 @@ FMT_BEGIN_EXPORT
 
 #if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 
-template <typename CompiledFormat, typename... Args,
+template <typename CompiledFormat, typename... T,
           typename Char = typename CompiledFormat::char_type,
           FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
-FMT_INLINE std::basic_string<Char> format(const CompiledFormat& cf,
+FMT_INLINE FMT_CONSTEXPR_STRING auto format(const CompiledFormat& cf,
-                                          const Args&... args) {
+                                            const T&... args)
+    -> std::basic_string<Char> {
   auto s = std::basic_string<Char>();
   cf.format(std::back_inserter(s), args...);
   return s;
 }
 
-template <typename OutputIt, typename CompiledFormat, typename... Args,
+template <typename OutputIt, typename CompiledFormat, typename... T,
           FMT_ENABLE_IF(detail::is_compiled_format<CompiledFormat>::value)>
-constexpr FMT_INLINE OutputIt format_to(OutputIt out, const CompiledFormat& cf,
+constexpr FMT_INLINE auto format_to(OutputIt out, const CompiledFormat& cf,
-                                        const Args&... args) {
+                                    const T&... args) -> OutputIt {
   return cf.format(out, args...);
 }
 
-template <typename S, typename... Args,
+template <typename S, typename... T,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
-FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
+FMT_INLINE FMT_CONSTEXPR_STRING auto format(const S&, T&&... args)
-                                                           Args&&... args) {
+    -> std::basic_string<typename S::char_type> {
   if constexpr (std::is_same<typename S::char_type, char>::value) {
     constexpr auto str = basic_string_view<typename S::char_type>(S());
     if constexpr (str.size() == 2 && str[0] == '{' && str[1] == '}') {
@@ -476,74 +490,97 @@ FMT_INLINE std::basic_string<typename S::char_type> format(const S&,
       }
     }
   }
-  constexpr auto compiled = detail::compile<Args...>(S());
+  constexpr auto compiled = detail::compile<T...>(S());
   if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
                              detail::unknown_format>()) {
     return fmt::format(
         static_cast<basic_string_view<typename S::char_type>>(S()),
-        std::forward<Args>(args)...);
+        std::forward<T>(args)...);
   } else {
-    return fmt::format(compiled, std::forward<Args>(args)...);
+    return fmt::format(compiled, std::forward<T>(args)...);
   }
 }
 
-template <typename OutputIt, typename S, typename... Args,
+template <typename OutputIt, typename S, typename... T,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
-FMT_CONSTEXPR OutputIt format_to(OutputIt out, const S&, Args&&... args) {
+FMT_CONSTEXPR auto format_to(OutputIt out, const S&, T&&... args) -> OutputIt {
-  constexpr auto compiled = detail::compile<Args...>(S());
+  constexpr auto compiled = detail::compile<T...>(S());
   if constexpr (std::is_same<remove_cvref_t<decltype(compiled)>,
                              detail::unknown_format>()) {
     return fmt::format_to(
         out, static_cast<basic_string_view<typename S::char_type>>(S()),
-        std::forward<Args>(args)...);
+        std::forward<T>(args)...);
   } else {
-    return fmt::format_to(out, compiled, std::forward<Args>(args)...);
+    return fmt::format_to(out, compiled, std::forward<T>(args)...);
   }
 }
 #endif
 
-template <typename OutputIt, typename S, typename... Args,
+template <typename OutputIt, typename S, typename... T,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
-auto format_to_n(OutputIt out, size_t n, const S& fmt, Args&&... args)
+auto format_to_n(OutputIt out, size_t n, const S& fmt, T&&... args)
     -> format_to_n_result<OutputIt> {
   using traits = detail::fixed_buffer_traits;
   auto buf = detail::iterator_buffer<OutputIt, char, traits>(out, n);
-  fmt::format_to(std::back_inserter(buf), fmt, std::forward<Args>(args)...);
+  fmt::format_to(appender(buf), fmt, std::forward<T>(args)...);
   return {buf.out(), buf.count()};
 }
 
-template <typename S, typename... Args,
+template <typename S, typename... T,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
-FMT_CONSTEXPR20 auto formatted_size(const S& fmt, const Args&... args)
+FMT_CONSTEXPR20 auto formatted_size(const S& fmt, T&&... args) -> size_t {
-    -> size_t {
   auto buf = detail::counting_buffer<>();
-  fmt::format_to(appender(buf), fmt, args...);
+  fmt::format_to(appender(buf), fmt, std::forward<T>(args)...);
   return buf.count();
 }
 
-template <typename S, typename... Args,
+template <typename S, typename... T,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
-void print(std::FILE* f, const S& fmt, const Args&... args) {
+void print(std::FILE* f, const S& fmt, T&&... args) {
   auto buf = memory_buffer();
-  fmt::format_to(appender(buf), fmt, args...);
+  fmt::format_to(appender(buf), fmt, std::forward<T>(args)...);
   detail::print(f, {buf.data(), buf.size()});
 }
 
-template <typename S, typename... Args,
+template <typename S, typename... T,
-          FMT_ENABLE_IF(detail::is_compiled_string<S>::value)>
+          FMT_ENABLE_IF(is_compiled_string<S>::value)>
-void print(const S& fmt, const Args&... args) {
+void print(const S& fmt, T&&... args) {
-  print(stdout, fmt, args...);
+  print(stdout, fmt, std::forward<T>(args)...);
 }
 
-#if FMT_USE_NONTYPE_TEMPLATE_ARGS
+template <size_t N> class static_format_result {
-inline namespace literals {
+ private:
-template <detail::fixed_string Str> constexpr auto operator""_cf() {
+  char data[N];
-  using char_t = remove_cvref_t<decltype(Str.data[0])>;
+
-  return detail::udl_compiled_string<char_t, sizeof(Str.data) / sizeof(char_t),
+ public:
-                                     Str>();
+  template <typename S, typename... T,
-}
+            FMT_ENABLE_IF(is_compiled_string<S>::value)>
-}  // namespace literals
+  explicit FMT_CONSTEXPR static_format_result(const S& fmt, T&&... args) {
-#endif
+    *fmt::format_to(data, fmt, std::forward<T>(args)...) = '\0';
+  }
+
+  FMT_CONSTEXPR auto str() const -> fmt::string_view { return {data, N - 1}; }
+  FMT_CONSTEXPR auto c_str() const -> const char* { return data; }
+};
+
+/**
+ * Formats arguments according to the format string `fmt_str` and produces
+ * a string of the exact required size at compile time. Both the format string
+ * and the arguments must be compile-time expressions.
+ *
+ * The resulting string can be accessed as a C string via `c_str()` or as
+ * a `fmt::string_view` via `str()`.
+ *
+ * **Example**:
+ *
+ *     // Produces the static string "42" at compile time.
+ *     static constexpr auto result = FMT_STATIC_FORMAT("{}", 42);
+ *     const char* s = result.c_str();
+ */
+#define FMT_STATIC_FORMAT(fmt_str, ...)                            \
+  fmt::static_format_result<                                       \
+      fmt::formatted_size(FMT_COMPILE(fmt_str), __VA_ARGS__) + 1>( \
+      FMT_COMPILE(fmt_str), __VA_ARGS__)
 
 FMT_END_EXPORT
 FMT_END_NAMESPACE

include/fmt/os.h

@@ -29,7 +29,8 @@
 #  if (FMT_HAS_INCLUDE(<fcntl.h>) || defined(__APPLE__) || \
        defined(__linux__)) &&                              \
       (!defined(WINAPI_FAMILY) ||                          \
-       (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
+       (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP)) &&    \
+      !defined(__wasm__)
 #    include <fcntl.h>  // for O_RDONLY
 #    define FMT_USE_FCNTL 1
 #  else
@@ -135,10 +136,9 @@ FMT_API std::system_error vwindows_error(int error_code, string_view fmt,
  * **Example**:
  *
  *     // This throws a system_error with the description
- *     //   cannot open file 'madeup': The system cannot find the file
+ *     //   cannot open file 'foo': The system cannot find the file specified.
- * specified.
+ *     // or similar (system message may vary) if the file doesn't exist.
- *     // or similar (system message may vary).
+ *     const char *filename = "foo";
- *     const char *filename = "madeup";
  *     LPOFSTRUCT of = LPOFSTRUCT();
  *     HFILE file = OpenFile(filename, &of, OF_READ);
  *     if (file == HFILE_ERROR) {
@@ -161,14 +161,6 @@ inline auto system_category() noexcept -> const std::error_category& {
 }
 #endif  // _WIN32
 
-// std::system is not available on some platforms such as iOS (#2248).
-#ifdef __OSX__
-template <typename S, typename... Args, typename Char = char_t<S>>
-void say(const S& fmt, Args&&... args) {
-  std::system(format("say \"{}\"", format(fmt, args...)).c_str());
-}
-#endif
-
 // A buffered file.
 class buffered_file {
  private:
@@ -364,17 +356,17 @@ FMT_INLINE_VARIABLE constexpr auto buffer_size = detail::buffer_size();
 
 /// A fast buffered output stream for writing from a single thread. Writing from
 /// multiple threads without external synchronization may result in a data race.
-class FMT_API ostream : private detail::buffer<char> {
+class ostream : private detail::buffer<char> {
  private:
   file file_;
 
-  ostream(cstring_view path, const detail::ostream_params& params);
+  FMT_API ostream(cstring_view path, const detail::ostream_params& params);
 
-  static void grow(buffer<char>& buf, size_t);
+  FMT_API static void grow(buffer<char>& buf, size_t);
 
  public:
-  ostream(ostream&& other) noexcept;
+  FMT_API ostream(ostream&& other) noexcept;
-  ~ostream();
+  FMT_API ~ostream();
 
   operator writer() {
     detail::buffer<char>& buf = *this;

include/fmt/ostream.h

@@ -33,12 +33,12 @@
 FMT_BEGIN_NAMESPACE
 namespace detail {
 
-// Generate a unique explicit instantion in every translation unit using a tag
+// Generate a unique explicit instantiation in every translation unit using a
-// type in an anonymous namespace.
+// tag type in an anonymous namespace.
 namespace {
 struct file_access_tag {};
 }  // namespace
-template <typename Tag, typename BufType, FILE* BufType::*FileMemberPtr>
+template <typename Tag, typename BufType, FILE* BufType::* FileMemberPtr>
 class file_access {
   friend auto get_file(BufType& obj) -> FILE* { return obj.*FileMemberPtr; }
 };
@@ -150,7 +150,7 @@ inline void vprint(std::ostream& os, string_view fmt, format_args args) {
 FMT_EXPORT template <typename... T>
 void print(std::ostream& os, format_string<T...> fmt, T&&... args) {
   fmt::vargs<T...> vargs = {{args...}};
-  if (detail::use_utf8) return vprint(os, fmt.str, vargs);
+  if (detail::const_check(detail::use_utf8)) return vprint(os, fmt.str, vargs);
   auto buffer = memory_buffer();
   detail::vformat_to(buffer, fmt.str, vargs);
   detail::write_buffer(os, buffer);
@@ -158,7 +158,8 @@ void print(std::ostream& os, format_string<T...> fmt, T&&... args) {
 
 FMT_EXPORT template <typename... T>
 void println(std::ostream& os, format_string<T...> fmt, T&&... args) {
-  fmt::print(os, "{}\n", fmt::format(fmt, std::forward<T>(args)...));
+  fmt::print(os, FMT_STRING("{}\n"),
+             fmt::format(fmt, std::forward<T>(args)...));
 }
 
 FMT_END_NAMESPACE

include/fmt/printf.h

@@ -9,7 +9,7 @@
 #define FMT_PRINTF_H_
 
 #ifndef FMT_MODULE
-#  include <algorithm>  // std::max
+#  include <algorithm>  // std::find
 #  include <limits>     // std::numeric_limits
 #endif
 
@@ -18,10 +18,6 @@
 FMT_BEGIN_NAMESPACE
 FMT_BEGIN_EXPORT
 
-template <typename T> struct printf_formatter {
-  printf_formatter() = delete;
-};
-
 template <typename Char> class basic_printf_context {
  private:
   basic_appender<Char> out_;
@@ -33,8 +29,6 @@ template <typename Char> class basic_printf_context {
 
  public:
   using char_type = Char;
-  using parse_context_type = parse_context<Char>;
-  template <typename T> using formatter_type = printf_formatter<T>;
   enum { builtin_types = 1 };
 
   /// Constructs a `printf_context` object. References to the arguments are
@@ -46,7 +40,7 @@ template <typename Char> class basic_printf_context {
   auto out() -> basic_appender<Char> { return out_; }
   void advance_to(basic_appender<Char>) {}
 
-  auto locale() -> detail::locale_ref { return {}; }
+  auto locale() -> locale_ref { return {}; }
 
   auto arg(int id) const -> basic_format_arg<basic_printf_context> {
     return args_.get(id);
@@ -74,10 +68,9 @@ inline auto find<false, char>(const char* first, const char* last, char value,
 
 // Checks if a value fits in int - used to avoid warnings about comparing
 // signed and unsigned integers.
-template <bool IsSigned> struct int_checker {
+template <bool IS_SIGNED> struct int_checker {
   template <typename T> static auto fits_in_int(T value) -> bool {
-    unsigned max = to_unsigned(max_value<int>());
+    return value <= to_unsigned(max_value<int>());
-    return value <= max;
   }
   inline static auto fits_in_int(bool) -> bool { return true; }
 };
@@ -95,7 +88,7 @@ struct printf_precision_handler {
   auto operator()(T value) -> int {
     if (!int_checker<std::numeric_limits<T>::is_signed>::fits_in_int(value))
       report_error("number is too big");
-    return (std::max)(static_cast<int>(value), 0);
+    return max_of(static_cast<int>(value), 0);
   }
 
   template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
@@ -410,7 +403,9 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
       arg_index = parse_ctx.next_arg_id();
     else
       parse_ctx.check_arg_id(--arg_index);
-    return detail::get_arg(context, arg_index);
+    auto arg = context.arg(arg_index);
+    if (!arg) report_error("argument not found");
+    return arg;
   };
 
   const Char* start = parse_ctx.begin();
@@ -571,15 +566,19 @@ inline auto vsprintf(basic_string_view<Char> fmt,
  *
  *     std::string message = fmt::sprintf("The answer is %d", 42);
  */
-template <typename S, typename... T, typename Char = detail::char_t<S>>
+template <typename... T>
-inline auto sprintf(const S& fmt, const T&... args) -> std::basic_string<Char> {
+inline auto sprintf(string_view fmt, const T&... args) -> std::string {
-  return vsprintf(detail::to_string_view(fmt),
+  return vsprintf(fmt, make_printf_args(args...));
-                  fmt::make_format_args<basic_printf_context<Char>>(args...));
+}
+template <typename... T>
+FMT_DEPRECATED auto sprintf(basic_string_view<wchar_t> fmt, const T&... args)
+    -> std::wstring {
+  return vsprintf(fmt, make_printf_args<wchar_t>(args...));
 }
 
 template <typename Char>
-inline auto vfprintf(std::FILE* f, basic_string_view<Char> fmt,
+auto vfprintf(std::FILE* f, basic_string_view<Char> fmt,
-                     typename vprintf_args<Char>::type args) -> int {
+              typename vprintf_args<Char>::type args) -> int {
   auto buf = basic_memory_buffer<Char>();
   detail::vprintf(buf, fmt, args);
   size_t size = buf.size();
@@ -596,17 +595,14 @@ inline auto vfprintf(std::FILE* f, basic_string_view<Char> fmt,
  *
  *     fmt::fprintf(stderr, "Don't %s!", "panic");
  */
-template <typename S, typename... T, typename Char = detail::char_t<S>>
+template <typename... T>
-inline auto fprintf(std::FILE* f, const S& fmt, const T&... args) -> int {
+inline auto fprintf(std::FILE* f, string_view fmt, const T&... args) -> int {
-  return vfprintf(f, detail::to_string_view(fmt),
+  return vfprintf(f, fmt, make_printf_args(args...));
-                  make_printf_args<Char>(args...));
 }
-
+template <typename... T>
-template <typename Char>
+FMT_DEPRECATED auto fprintf(std::FILE* f, basic_string_view<wchar_t> fmt,
-FMT_DEPRECATED inline auto vprintf(basic_string_view<Char> fmt,
+                            const T&... args) -> int {
-                                   typename vprintf_args<Char>::type args)
+  return vfprintf(f, fmt, make_printf_args<wchar_t>(args...));
-    -> int {
-  return vfprintf(stdout, fmt, args);
 }
 
 /**
@@ -621,11 +617,6 @@ template <typename... T>
 inline auto printf(string_view fmt, const T&... args) -> int {
   return vfprintf(stdout, fmt, make_printf_args(args...));
 }
-template <typename... T>
-FMT_DEPRECATED inline auto printf(basic_string_view<wchar_t> fmt,
-                                  const T&... args) -> int {
-  return vfprintf(stdout, fmt, make_printf_args<wchar_t>(args...));
-}
 
 FMT_END_EXPORT
 FMT_END_NAMESPACE

include/fmt/ranges.h

@@ -11,7 +11,6 @@
 #ifndef FMT_MODULE
 #  include <initializer_list>
 #  include <iterator>
-#  include <string>
 #  include <tuple>
 #  include <type_traits>
 #  include <utility>
@@ -19,6 +18,13 @@
 
 #include "format.h"
 
+#if FMT_HAS_CPP_ATTRIBUTE(clang::lifetimebound)
+#  define FMT_LIFETIMEBOUND [[clang::lifetimebound]]
+#else
+#  define FMT_LIFETIMEBOUND
+#endif
+FMT_PRAGMA_CLANG(diagnostic error "-Wreturn-stack-address")
+
 FMT_BEGIN_NAMESPACE
 
 FMT_EXPORT
@@ -31,7 +37,7 @@ template <typename T> class is_map {
   template <typename> static void check(...);
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       !std::is_void<decltype(check<T>(nullptr))>::value;
 };
 
@@ -40,17 +46,16 @@ template <typename T> class is_set {
   template <typename> static void check(...);
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       !std::is_void<decltype(check<T>(nullptr))>::value && !is_map<T>::value;
 };
 
 // C array overload
-template <typename T, std::size_t N>
+template <typename T, size_t N>
 auto range_begin(const T (&arr)[N]) -> const T* {
   return arr;
 }
-template <typename T, std::size_t N>
+template <typename T, size_t N> auto range_end(const T (&arr)[N]) -> const T* {
-auto range_end(const T (&arr)[N]) -> const T* {
   return arr + N;
 }
 
@@ -120,7 +125,7 @@ template <typename T> class is_tuple_like_ {
   template <typename> static void check(...);
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       !std::is_void<decltype(check<T>(nullptr))>::value;
 };
 
@@ -154,7 +159,7 @@ using tuple_index_sequence = make_index_sequence<std::tuple_size<T>::value>;
 template <typename T, typename C, bool = is_tuple_like_<T>::value>
 class is_tuple_formattable_ {
  public:
-  static constexpr const bool value = false;
+  static constexpr bool value = false;
 };
 template <typename T, typename C> class is_tuple_formattable_<T, C, true> {
   template <size_t... Is>
@@ -170,7 +175,7 @@ template <typename T, typename C> class is_tuple_formattable_<T, C, true> {
                                        C>::value)...>{}));
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       decltype(check(tuple_index_sequence<T>{}))::value;
 };
 
@@ -208,7 +213,7 @@ template <typename Char, typename... T>
 using result_t = std::tuple<formatter<remove_cvref_t<T>, Char>...>;
 
 using std::get;
-template <typename Tuple, typename Char, std::size_t... Is>
+template <typename Tuple, typename Char, size_t... Is>
 auto get_formatters(index_sequence<Is...>)
     -> result_t<Char, decltype(get<Is>(std::declval<Tuple>()))...>;
 }  // namespace tuple
@@ -219,7 +224,7 @@ template <typename R> struct range_reference_type_impl {
   using type = decltype(*detail::range_begin(std::declval<R&>()));
 };
 
-template <typename T, std::size_t N> struct range_reference_type_impl<T[N]> {
+template <typename T, size_t N> struct range_reference_type_impl<T[N]> {
   using type = T&;
 };
 
@@ -236,14 +241,6 @@ using range_reference_type =
 template <typename Range>
 using uncvref_type = remove_cvref_t<range_reference_type<Range>>;
 
-template <typename Formatter>
-FMT_CONSTEXPR auto maybe_set_debug_format(Formatter& f, bool set)
-    -> decltype(f.set_debug_format(set)) {
-  f.set_debug_format(set);
-}
-template <typename Formatter>
-FMT_CONSTEXPR void maybe_set_debug_format(Formatter&, ...) {}
-
 template <typename T>
 struct range_format_kind_
     : std::integral_constant<range_format,
@@ -281,14 +278,15 @@ template <typename FormatContext> struct format_tuple_element {
 
 }  // namespace detail
 
+FMT_EXPORT
 template <typename T> struct is_tuple_like {
-  static constexpr const bool value =
+  static constexpr bool value =
       detail::is_tuple_like_<T>::value && !detail::is_range_<T>::value;
 };
 
+FMT_EXPORT
 template <typename T, typename C> struct is_tuple_formattable {
-  static constexpr const bool value =
+  static constexpr bool value = detail::is_tuple_formattable_<T, C>::value;
-      detail::is_tuple_formattable_<T, C>::value;
 };
 
 template <typename Tuple, typename Char>
@@ -343,8 +341,9 @@ struct formatter<Tuple, Char,
   }
 };
 
+FMT_EXPORT
 template <typename T, typename Char> struct is_range {
-  static constexpr const bool value =
+  static constexpr bool value =
       detail::is_range_<T>::value && !detail::has_to_string_view<T>::value;
 };
 
@@ -368,6 +367,7 @@ template <typename P1, typename... Pn>
 struct conjunction<P1, Pn...>
     : conditional_t<bool(P1::value), conjunction<Pn...>, P1> {};
 
+FMT_EXPORT
 template <typename T, typename Char, typename Enable = void>
 struct range_formatter;
 
@@ -527,7 +527,9 @@ struct formatter<
 template <typename R, typename Char>
 struct formatter<
     R, Char,
-    enable_if_t<range_format_kind<R, Char>::value == range_format::map>> {
+    enable_if_t<conjunction<
+        bool_constant<range_format_kind<R, Char>::value == range_format::map>,
+        detail::is_formattable_delayed<R, Char>>::value>> {
  private:
   using map_type = detail::maybe_const_range<R>;
   using element_type = detail::uncvref_type<map_type>;
@@ -668,7 +670,8 @@ struct formatter<join_view<It, Sentinel, Char>, Char> {
   }
 };
 
-template <typename Char, typename Tuple> struct tuple_join_view : detail::view {
+FMT_EXPORT
+template <typename Tuple, typename Char> struct tuple_join_view : detail::view {
   const Tuple& tuple;
   basic_string_view<Char> sep;
 
@@ -683,15 +686,15 @@ template <typename Char, typename Tuple> struct tuple_join_view : detail::view {
 #  define FMT_TUPLE_JOIN_SPECIFIERS 0
 #endif
 
-template <typename Char, typename Tuple>
+template <typename Tuple, typename Char>
-struct formatter<tuple_join_view<Char, Tuple>, Char,
+struct formatter<tuple_join_view<Tuple, Char>, Char,
                  enable_if_t<is_tuple_like<Tuple>::value>> {
   FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return do_parse(ctx, std::tuple_size<Tuple>());
   }
 
   template <typename FormatContext>
-  auto format(const tuple_join_view<Char, Tuple>& value,
+  auto format(const tuple_join_view<Tuple, Char>& value,
               FormatContext& ctx) const -> typename FormatContext::iterator {
     return do_format(value, ctx, std::tuple_size<Tuple>());
   }
@@ -723,14 +726,14 @@ struct formatter<tuple_join_view<Char, Tuple>, Char,
   }
 
   template <typename FormatContext>
-  auto do_format(const tuple_join_view<Char, Tuple>&, FormatContext& ctx,
+  auto do_format(const tuple_join_view<Tuple, Char>&, FormatContext& ctx,
                  std::integral_constant<size_t, 0>) const ->
       typename FormatContext::iterator {
     return ctx.out();
   }
 
   template <typename FormatContext, size_t N>
-  auto do_format(const tuple_join_view<Char, Tuple>& value, FormatContext& ctx,
+  auto do_format(const tuple_join_view<Tuple, Char>& value, FormatContext& ctx,
                  std::integral_constant<size_t, N>) const ->
       typename FormatContext::iterator {
     using std::get;
@@ -752,7 +755,7 @@ template <typename T> class is_container_adaptor_like {
   template <typename> static void check(...);
 
  public:
-  static constexpr const bool value =
+  static constexpr bool value =
       !std::is_void<decltype(check<T>(nullptr))>::value;
 };
 
@@ -772,13 +775,13 @@ struct formatter<
     : formatter<detail::all<typename T::container_type>, Char> {
   using all = detail::all<typename T::container_type>;
   template <typename FormatContext>
-  auto format(const T& t, FormatContext& ctx) const -> decltype(ctx.out()) {
+  auto format(const T& value, FormatContext& ctx) const -> decltype(ctx.out()) {
     struct getter : T {
-      static auto get(const T& t) -> all {
+      static auto get(const T& v) -> all {
-        return {t.*(&getter::c)};  // Access c through the derived class.
+        return {v.*(&getter::c)};  // Access c through the derived class.
       }
     };
-    return formatter<all>::format(getter::get(t), ctx);
+    return formatter<all>::format(getter::get(value), ctx);
   }
 };
 
@@ -817,13 +820,13 @@ auto join(Range&& r, string_view sep)
  *
  * **Example**:
  *
- *     auto t = std::tuple<int, char>{1, 'a'};
+ *     auto t = std::tuple<int, char>(1, 'a');
  *     fmt::print("{}", fmt::join(t, ", "));
  *     // Output: 1, a
  */
 template <typename Tuple, FMT_ENABLE_IF(is_tuple_like<Tuple>::value)>
-FMT_CONSTEXPR auto join(const Tuple& tuple, string_view sep)
+FMT_CONSTEXPR auto join(const Tuple& tuple FMT_LIFETIMEBOUND, string_view sep)
-    -> tuple_join_view<char, Tuple> {
+    -> tuple_join_view<Tuple, char> {
   return {tuple, sep};
 }
 

include/fmt/std.h

@@ -15,15 +15,13 @@
 #  include <atomic>
 #  include <bitset>
 #  include <complex>
-#  include <cstdlib>
 #  include <exception>
-#  include <functional>
+#  include <functional>  // std::reference_wrapper
 #  include <memory>
 #  include <thread>
 #  include <type_traits>
-#  include <typeinfo>
+#  include <typeinfo>  // std::type_info
-#  include <utility>
+#  include <utility>   // std::make_index_sequence
-#  include <vector>
 
 // Check FMT_CPLUSPLUS to suppress a bogus warning in MSVC.
 #  if FMT_CPLUSPLUS >= 201703L
@@ -62,35 +60,36 @@
 #  endif
 #endif
 
-// For older Xcode versions, __cpp_lib_xxx flags are inaccurately defined.
+#ifdef FMT_CPP_LIB_FILESYSTEM
-#ifndef FMT_CPP_LIB_FILESYSTEM
+// Use the provided definition.
-#  ifdef __cpp_lib_filesystem
+#elif defined(__cpp_lib_filesystem)
-#    define FMT_CPP_LIB_FILESYSTEM __cpp_lib_filesystem
+#  define FMT_CPP_LIB_FILESYSTEM __cpp_lib_filesystem
-#  else
+#else
-#    define FMT_CPP_LIB_FILESYSTEM 0
+#  define FMT_CPP_LIB_FILESYSTEM 0
-#  endif
 #endif
 
-#ifndef FMT_CPP_LIB_VARIANT
+#ifdef FMT_CPP_LIB_VARIANT
-#  ifdef __cpp_lib_variant
+// Use the provided definition.
-#    define FMT_CPP_LIB_VARIANT __cpp_lib_variant
+#elif defined(__cpp_lib_variant)
-#  else
+#  define FMT_CPP_LIB_VARIANT __cpp_lib_variant
-#    define FMT_CPP_LIB_VARIANT 0
+#else
-#  endif
+#  define FMT_CPP_LIB_VARIANT 0
 #endif
 
+FMT_BEGIN_NAMESPACE
+namespace detail {
+
 #if FMT_CPP_LIB_FILESYSTEM
-FMT_BEGIN_NAMESPACE
-
-namespace detail {
 
 template <typename Char, typename PathChar>
 auto get_path_string(const std::filesystem::path& p,
                      const std::basic_string<PathChar>& native) {
-  if constexpr (std::is_same_v<Char, char> && std::is_same_v<PathChar, wchar_t>)
+  if constexpr (std::is_same_v<Char, char> &&
-    return to_utf8<wchar_t>(native, to_utf8_error_policy::replace);
+                std::is_same_v<PathChar, wchar_t>) {
-  else
+    return to_utf8<wchar_t>(native, to_utf8_error_policy::wtf);
+  } else {
     return p.string<Char>();
+  }
 }
 
 template <typename Char, typename PathChar>
@@ -111,9 +110,180 @@ void write_escaped_path(basic_memory_buffer<Char>& quoted,
   }
 }
 
+#endif  // FMT_CPP_LIB_FILESYSTEM
+
+#if defined(__cpp_lib_expected) || FMT_CPP_LIB_VARIANT
+
+template <typename Char, typename OutputIt, typename T, typename FormatContext>
+auto write_escaped_alternative(OutputIt out, const T& v, FormatContext& ctx)
+    -> OutputIt {
+  if constexpr (has_to_string_view<T>::value)
+    return write_escaped_string<Char>(out, detail::to_string_view(v));
+  if constexpr (std::is_same_v<T, Char>) return write_escaped_char(out, v);
+
+  formatter<std::remove_cv_t<T>, Char> underlying;
+  maybe_set_debug_format(underlying, true);
+  return underlying.format(v, ctx);
+}
+#endif
+
+#if FMT_CPP_LIB_VARIANT
+
+template <typename> struct is_variant_like_ : std::false_type {};
+template <typename... Types>
+struct is_variant_like_<std::variant<Types...>> : std::true_type {};
+
+template <typename Variant, typename Char> class is_variant_formattable {
+  template <size_t... Is>
+  static auto check(std::index_sequence<Is...>) -> std::conjunction<
+      is_formattable<std::variant_alternative_t<Is, Variant>, Char>...>;
+
+ public:
+  static constexpr bool value = decltype(check(
+      std::make_index_sequence<std::variant_size<Variant>::value>()))::value;
+};
+
+#endif  // FMT_CPP_LIB_VARIANT
+
+#if FMT_USE_RTTI
+inline auto normalize_libcxx_inline_namespaces(string_view demangled_name_view,
+                                               char* begin) -> string_view {
+  // Normalization of stdlib inline namespace names.
+  // libc++ inline namespaces.
+  //  std::__1::*       -> std::*
+  //  std::__1::__fs::* -> std::*
+  // libstdc++ inline namespaces.
+  //  std::__cxx11::*             -> std::*
+  //  std::filesystem::__cxx11::* -> std::filesystem::*
+  if (demangled_name_view.starts_with("std::")) {
+    char* to = begin + 5;  // std::
+    for (const char *from = to, *end = begin + demangled_name_view.size();
+         from < end;) {
+      // This is safe, because demangled_name is NUL-terminated.
+      if (from[0] == '_' && from[1] == '_') {
+        const char* next = from + 1;
+        while (next < end && *next != ':') next++;
+        if (next[0] == ':' && next[1] == ':') {
+          from = next + 2;
+          continue;
+        }
+      }
+      *to++ = *from++;
+    }
+    demangled_name_view = {begin, detail::to_unsigned(to - begin)};
+  }
+  return demangled_name_view;
+}
+
+template <class OutputIt>
+auto normalize_msvc_abi_name(string_view abi_name_view, OutputIt out)
+    -> OutputIt {
+  const string_view demangled_name(abi_name_view);
+  for (size_t i = 0; i < demangled_name.size(); ++i) {
+    auto sub = demangled_name;
+    sub.remove_prefix(i);
+    if (sub.starts_with("enum ")) {
+      i += 4;
+      continue;
+    }
+    if (sub.starts_with("class ") || sub.starts_with("union ")) {
+      i += 5;
+      continue;
+    }
+    if (sub.starts_with("struct ")) {
+      i += 6;
+      continue;
+    }
+    if (*sub.begin() != ' ') *out++ = *sub.begin();
+  }
+  return out;
+}
+
+template <typename OutputIt>
+auto write_demangled_name(OutputIt out, const std::type_info& ti) -> OutputIt {
+#  ifdef FMT_HAS_ABI_CXA_DEMANGLE
+  int status = 0;
+  size_t size = 0;
+  std::unique_ptr<char, void (*)(void*)> demangled_name_ptr(
+      abi::__cxa_demangle(ti.name(), nullptr, &size, &status), &free);
+
+  string_view demangled_name_view;
+  if (demangled_name_ptr) {
+    demangled_name_view = normalize_libcxx_inline_namespaces(
+        demangled_name_ptr.get(), demangled_name_ptr.get());
+  } else {
+    demangled_name_view = string_view(ti.name());
+  }
+  return detail::write_bytes<char>(out, demangled_name_view);
+#  elif FMT_MSC_VERSION && defined(_MSVC_STL_UPDATE)
+  return normalize_msvc_abi_name(ti.name(), out);
+#  elif FMT_MSC_VERSION && defined(_LIBCPP_VERSION)
+  const string_view demangled_name = ti.name();
+  std::string name_copy(demangled_name.size(), '\0');
+  // normalize_msvc_abi_name removes class, struct, union etc that MSVC has in
+  // front of types
+  name_copy.erase(normalize_msvc_abi_name(demangled_name, name_copy.begin()),
+                  name_copy.end());
+  // normalize_libcxx_inline_namespaces removes the inline __1, __2, etc
+  // namespaces libc++ uses for ABI versioning On MSVC ABI + libc++
+  // environments, we need to eliminate both of them.
+  const string_view normalized_name =
+      normalize_libcxx_inline_namespaces(name_copy, name_copy.data());
+  return detail::write_bytes<char>(out, normalized_name);
+#  else
+  return detail::write_bytes<char>(out, string_view(ti.name()));
+#  endif
+}
+
+#endif  // FMT_USE_RTTI
+
+template <typename T, typename Enable = void>
+struct has_flip : std::false_type {};
+
+template <typename T>
+struct has_flip<T, void_t<decltype(std::declval<T>().flip())>>
+    : std::true_type {};
+
+template <typename T> struct is_bit_reference_like {
+  static constexpr bool value = std::is_convertible<T, bool>::value &&
+                                std::is_nothrow_assignable<T, bool>::value &&
+                                has_flip<T>::value;
+};
+
+// Workaround for libc++ incompatibility with C++ standard.
+// According to the Standard, `bitset::operator[] const` returns bool.
+#if defined(_LIBCPP_VERSION) && !defined(FMT_IMPORT_STD)
+template <typename C>
+struct is_bit_reference_like<std::__bit_const_reference<C>> {
+  static constexpr bool value = true;
+};
+#endif
+
+template <typename T, typename Enable = void>
+struct has_format_as : std::false_type {};
+template <typename T>
+struct has_format_as<T, void_t<decltype(format_as(std::declval<const T&>()))>>
+    : std::true_type {};
+
+template <typename T, typename Enable = void>
+struct has_format_as_member : std::false_type {};
+template <typename T>
+struct has_format_as_member<
+    T, void_t<decltype(formatter<T>::format_as(std::declval<const T&>()))>>
+    : std::true_type {};
+
 }  // namespace detail
 
-FMT_EXPORT
+template <typename T, typename Deleter>
+auto ptr(const std::unique_ptr<T, Deleter>& p) -> const void* {
+  return p.get();
+}
+template <typename T> auto ptr(const std::shared_ptr<T>& p) -> const void* {
+  return p.get();
+}
+
+#if FMT_CPP_LIB_FILESYSTEM
+
 template <typename Char> struct formatter<std::filesystem::path, Char> {
  private:
   format_specs specs_;
@@ -178,24 +348,20 @@ class path : public std::filesystem::path {
   auto generic_system_string() const -> std::string { return generic_string(); }
 };
 
-FMT_END_NAMESPACE
 #endif  // FMT_CPP_LIB_FILESYSTEM
 
-FMT_BEGIN_NAMESPACE
+template <size_t N, typename Char>
-FMT_EXPORT
+struct formatter<std::bitset<N>, Char>
-template <std::size_t N, typename Char>
+    : nested_formatter<basic_string_view<Char>, Char> {
-struct formatter<std::bitset<N>, Char> : nested_formatter<string_view> {
  private:
-  // Functor because C++11 doesn't support generic lambdas.
+  // This is a functor because C++11 doesn't support generic lambdas.
   struct writer {
     const std::bitset<N>& bs;
 
     template <typename OutputIt>
     FMT_CONSTEXPR auto operator()(OutputIt out) -> OutputIt {
-      for (auto pos = N; pos > 0; --pos) {
+      for (auto pos = N; pos > 0; --pos)
         out = detail::write<Char>(out, bs[pos - 1] ? Char('1') : Char('0'));
-      }
-
       return out;
     }
   };
@@ -204,41 +370,28 @@ struct formatter<std::bitset<N>, Char> : nested_formatter<string_view> {
   template <typename FormatContext>
   auto format(const std::bitset<N>& bs, FormatContext& ctx) const
       -> decltype(ctx.out()) {
-    return write_padded(ctx, writer{bs});
+    return this->write_padded(ctx, writer{bs});
   }
 };
 
-FMT_EXPORT
 template <typename Char>
 struct formatter<std::thread::id, Char> : basic_ostream_formatter<Char> {};
-FMT_END_NAMESPACE
 
 #ifdef __cpp_lib_optional
-FMT_BEGIN_NAMESPACE
-FMT_EXPORT
 template <typename T, typename Char>
 struct formatter<std::optional<T>, Char,
                  std::enable_if_t<is_formattable<T, Char>::value>> {
  private:
-  formatter<T, Char> underlying_;
+  formatter<std::remove_cv_t<T>, Char> underlying_;
   static constexpr basic_string_view<Char> optional =
       detail::string_literal<Char, 'o', 'p', 't', 'i', 'o', 'n', 'a', 'l',
                              '('>{};
   static constexpr basic_string_view<Char> none =
       detail::string_literal<Char, 'n', 'o', 'n', 'e'>{};
 
-  template <class U>
-  FMT_CONSTEXPR static auto maybe_set_debug_format(U& u, bool set)
-      -> decltype(u.set_debug_format(set)) {
-    u.set_debug_format(set);
-  }
-
-  template <class U>
-  FMT_CONSTEXPR static void maybe_set_debug_format(U&, ...) {}
-
  public:
   FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) {
-    maybe_set_debug_format(underlying_, true);
+    detail::maybe_set_debug_format(underlying_, true);
     return underlying_.parse(ctx);
   }
 
@@ -254,31 +407,9 @@ struct formatter<std::optional<T>, Char,
     return detail::write(out, ')');
   }
 };
-FMT_END_NAMESPACE
 #endif  // __cpp_lib_optional
 
-#if defined(__cpp_lib_expected) || FMT_CPP_LIB_VARIANT
-
-FMT_BEGIN_NAMESPACE
-namespace detail {
-
-template <typename Char, typename OutputIt, typename T>
-auto write_escaped_alternative(OutputIt out, const T& v) -> OutputIt {
-  if constexpr (has_to_string_view<T>::value)
-    return write_escaped_string<Char>(out, detail::to_string_view(v));
-  if constexpr (std::is_same_v<T, Char>) return write_escaped_char(out, v);
-  return write<Char>(out, v);
-}
-
-}  // namespace detail
-
-FMT_END_NAMESPACE
-#endif
-
 #ifdef __cpp_lib_expected
-FMT_BEGIN_NAMESPACE
-
-FMT_EXPORT
 template <typename T, typename E, typename Char>
 struct formatter<std::expected<T, E>, Char,
                  std::enable_if_t<(std::is_void<T>::value ||
@@ -296,21 +427,18 @@ struct formatter<std::expected<T, E>, Char,
     if (value.has_value()) {
       out = detail::write<Char>(out, "expected(");
       if constexpr (!std::is_void<T>::value)
-        out = detail::write_escaped_alternative<Char>(out, *value);
+        out = detail::write_escaped_alternative<Char>(out, *value, ctx);
     } else {
       out = detail::write<Char>(out, "unexpected(");
-      out = detail::write_escaped_alternative<Char>(out, value.error());
+      out = detail::write_escaped_alternative<Char>(out, value.error(), ctx);
     }
     *out++ = ')';
     return out;
   }
 };
-FMT_END_NAMESPACE
 #endif  // __cpp_lib_expected
 
 #ifdef __cpp_lib_source_location
-FMT_BEGIN_NAMESPACE
-FMT_EXPORT
 template <> struct formatter<std::source_location> {
   FMT_CONSTEXPR auto parse(parse_context<>& ctx) { return ctx.begin(); }
 
@@ -328,45 +456,14 @@ template <> struct formatter<std::source_location> {
     return out;
   }
 };
-FMT_END_NAMESPACE
 #endif
 
 #if FMT_CPP_LIB_VARIANT
-FMT_BEGIN_NAMESPACE
-namespace detail {
-
-template <typename T>
-using variant_index_sequence =
-    std::make_index_sequence<std::variant_size<T>::value>;
-
-template <typename> struct is_variant_like_ : std::false_type {};
-template <typename... Types>
-struct is_variant_like_<std::variant<Types...>> : std::true_type {};
-
-// formattable element check.
-template <typename T, typename C> class is_variant_formattable_ {
-  template <std::size_t... Is>
-  static std::conjunction<
-      is_formattable<std::variant_alternative_t<Is, T>, C>...>
-      check(std::index_sequence<Is...>);
-
- public:
-  static constexpr const bool value =
-      decltype(check(variant_index_sequence<T>{}))::value;
-};
-
-}  // namespace detail
 
 template <typename T> struct is_variant_like {
-  static constexpr const bool value = detail::is_variant_like_<T>::value;
+  static constexpr bool value = detail::is_variant_like_<T>::value;
 };
 
-template <typename T, typename C> struct is_variant_formattable {
-  static constexpr const bool value =
-      detail::is_variant_formattable_<T, C>::value;
-};
-
-FMT_EXPORT
 template <typename Char> struct formatter<std::monostate, Char> {
   FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return ctx.begin();
@@ -379,12 +476,11 @@ template <typename Char> struct formatter<std::monostate, Char> {
   }
 };
 
-FMT_EXPORT
 template <typename Variant, typename Char>
-struct formatter<
+struct formatter<Variant, Char,
-    Variant, Char,
+                 std::enable_if_t<std::conjunction_v<
-    std::enable_if_t<std::conjunction_v<
+                     is_variant_like<Variant>,
-        is_variant_like<Variant>, is_variant_formattable<Variant, Char>>>> {
+                     detail::is_variant_formattable<Variant, Char>>>> {
   FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
     return ctx.begin();
   }
@@ -398,7 +494,7 @@ struct formatter<
     FMT_TRY {
       std::visit(
           [&](const auto& v) {
-            out = detail::write_escaped_alternative<Char>(out, v);
+            out = detail::write_escaped_alternative<Char>(out, v, ctx);
           },
           value);
     }
@@ -409,27 +505,36 @@ struct formatter<
     return out;
   }
 };
-FMT_END_NAMESPACE
+
 #endif  // FMT_CPP_LIB_VARIANT
 
-FMT_BEGIN_NAMESPACE
-FMT_EXPORT
 template <> struct formatter<std::error_code> {
  private:
   format_specs specs_;
   detail::arg_ref<char> width_ref_;
+  bool debug_ = false;
 
  public:
+  FMT_CONSTEXPR void set_debug_format(bool set = true) { debug_ = set; }
+
   FMT_CONSTEXPR auto parse(parse_context<>& ctx) -> const char* {
     auto it = ctx.begin(), end = ctx.end();
     if (it == end) return it;
 
     it = detail::parse_align(it, end, specs_);
-    if (it == end) return it;
 
     char c = *it;
-    if ((c >= '0' && c <= '9') || c == '{')
+    if (it != end && ((c >= '0' && c <= '9') || c == '{'))
       it = detail::parse_width(it, end, specs_, width_ref_, ctx);
+
+    if (it != end && *it == '?') {
+      debug_ = true;
+      ++it;
+    }
+    if (it != end && *it == 's') {
+      specs_.set_type(presentation_type::string);
+      ++it;
+    }
     return it;
   }
 
@@ -439,113 +544,48 @@ template <> struct formatter<std::error_code> {
     auto specs = specs_;
     detail::handle_dynamic_spec(specs.dynamic_width(), specs.width, width_ref_,
                                 ctx);
-    memory_buffer buf;
+    auto buf = memory_buffer();
-    buf.append(string_view(ec.category().name()));
+    if (specs_.type() == presentation_type::string) {
-    buf.push_back(':');
+      buf.append(ec.message());
-    detail::write<char>(appender(buf), ec.value());
+    } else {
-    return detail::write<char>(ctx.out(), string_view(buf.data(), buf.size()),
+      buf.append(string_view(ec.category().name()));
-                               specs);
+      buf.push_back(':');
+      detail::write<char>(appender(buf), ec.value());
+    }
+    auto quoted = memory_buffer();
+    auto str = string_view(buf.data(), buf.size());
+    if (debug_) {
+      detail::write_escaped_string<char>(std::back_inserter(quoted), str);
+      str = string_view(quoted.data(), quoted.size());
+    }
+    return detail::write<char>(ctx.out(), str, specs);
   }
 };
 
 #if FMT_USE_RTTI
-namespace detail {
+template <> struct formatter<std::type_info> {
-
-template <typename Char, typename OutputIt>
-auto write_demangled_name(OutputIt out, const std::type_info& ti) -> OutputIt {
-#  ifdef FMT_HAS_ABI_CXA_DEMANGLE
-  int status = 0;
-  std::size_t size = 0;
-  std::unique_ptr<char, void (*)(void*)> demangled_name_ptr(
-      abi::__cxa_demangle(ti.name(), nullptr, &size, &status), &std::free);
-
-  string_view demangled_name_view;
-  if (demangled_name_ptr) {
-    demangled_name_view = demangled_name_ptr.get();
-
-    // Normalization of stdlib inline namespace names.
-    // libc++ inline namespaces.
-    //  std::__1::*       -> std::*
-    //  std::__1::__fs::* -> std::*
-    // libstdc++ inline namespaces.
-    //  std::__cxx11::*             -> std::*
-    //  std::filesystem::__cxx11::* -> std::filesystem::*
-    if (demangled_name_view.starts_with("std::")) {
-      char* begin = demangled_name_ptr.get();
-      char* to = begin + 5;  // std::
-      for (char *from = to, *end = begin + demangled_name_view.size();
-           from < end;) {
-        // This is safe, because demangled_name is NUL-terminated.
-        if (from[0] == '_' && from[1] == '_') {
-          char* next = from + 1;
-          while (next < end && *next != ':') next++;
-          if (next[0] == ':' && next[1] == ':') {
-            from = next + 2;
-            continue;
-          }
-        }
-        *to++ = *from++;
-      }
-      demangled_name_view = {begin, detail::to_unsigned(to - begin)};
-    }
-  } else {
-    demangled_name_view = string_view(ti.name());
-  }
-  return detail::write_bytes<Char>(out, demangled_name_view);
-#  elif FMT_MSC_VERSION
-  const string_view demangled_name(ti.name());
-  for (std::size_t i = 0; i < demangled_name.size(); ++i) {
-    auto sub = demangled_name;
-    sub.remove_prefix(i);
-    if (sub.starts_with("enum ")) {
-      i += 4;
-      continue;
-    }
-    if (sub.starts_with("class ") || sub.starts_with("union ")) {
-      i += 5;
-      continue;
-    }
-    if (sub.starts_with("struct ")) {
-      i += 6;
-      continue;
-    }
-    if (*sub.begin() != ' ') *out++ = *sub.begin();
-  }
-  return out;
-#  else
-  return detail::write_bytes<Char>(out, string_view(ti.name()));
-#  endif
-}
-
-}  // namespace detail
-
-FMT_EXPORT
-template <typename Char>
-struct formatter<std::type_info, Char  // DEPRECATED! Mixing code unit types.
-                 > {
  public:
-  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+  FMT_CONSTEXPR auto parse(parse_context<>& ctx) -> const char* {
     return ctx.begin();
   }
 
   template <typename Context>
   auto format(const std::type_info& ti, Context& ctx) const
       -> decltype(ctx.out()) {
-    return detail::write_demangled_name<Char>(ctx.out(), ti);
+    return detail::write_demangled_name(ctx.out(), ti);
   }
 };
-#endif
+#endif  // FMT_USE_RTTI
 
-FMT_EXPORT
+template <typename T>
-template <typename T, typename Char>
 struct formatter<
-    T, Char,  // DEPRECATED! Mixing code unit types.
+    T, char,
     typename std::enable_if<std::is_base_of<std::exception, T>::value>::type> {
  private:
   bool with_typename_ = false;
 
  public:
-  FMT_CONSTEXPR auto parse(parse_context<Char>& ctx) -> const Char* {
+  FMT_CONSTEXPR auto parse(parse_context<>& ctx) -> const char* {
     auto it = ctx.begin();
     auto end = ctx.end();
     if (it == end || *it == '}') return it;
@@ -562,47 +602,18 @@ struct formatter<
     auto out = ctx.out();
 #if FMT_USE_RTTI
     if (with_typename_) {
-      out = detail::write_demangled_name<Char>(out, typeid(ex));
+      out = detail::write_demangled_name(out, typeid(ex));
       *out++ = ':';
       *out++ = ' ';
     }
 #endif
-    return detail::write_bytes<Char>(out, string_view(ex.what()));
+    return detail::write_bytes<char>(out, string_view(ex.what()));
   }
 };
 
-namespace detail {
-
-template <typename T, typename Enable = void>
-struct has_flip : std::false_type {};
-
-template <typename T>
-struct has_flip<T, void_t<decltype(std::declval<T>().flip())>>
-    : std::true_type {};
-
-template <typename T> struct is_bit_reference_like {
-  static constexpr const bool value =
-      std::is_convertible<T, bool>::value &&
-      std::is_nothrow_assignable<T, bool>::value && has_flip<T>::value;
-};
-
-#ifdef _LIBCPP_VERSION
-
-// Workaround for libc++ incompatibility with C++ standard.
-// According to the Standard, `bitset::operator[] const` returns bool.
-template <typename C>
-struct is_bit_reference_like<std::__bit_const_reference<C>> {
-  static constexpr const bool value = true;
-};
-
-#endif
-
-}  // namespace detail
-
 // We can't use std::vector<bool, Allocator>::reference and
 // std::bitset<N>::reference because the compiler can't deduce Allocator and N
 // in partial specialization.
-FMT_EXPORT
 template <typename BitRef, typename Char>
 struct formatter<BitRef, Char,
                  enable_if_t<detail::is_bit_reference_like<BitRef>::value>>
@@ -614,15 +625,6 @@ struct formatter<BitRef, Char,
   }
 };
 
-template <typename T, typename Deleter>
-auto ptr(const std::unique_ptr<T, Deleter>& p) -> const void* {
-  return p.get();
-}
-template <typename T> auto ptr(const std::shared_ptr<T>& p) -> const void* {
-  return p.get();
-}
-
-FMT_EXPORT
 template <typename T, typename Char>
 struct formatter<std::atomic<T>, Char,
                  enable_if_t<is_formattable<T, Char>::value>>
@@ -635,7 +637,6 @@ struct formatter<std::atomic<T>, Char,
 };
 
 #ifdef __cpp_lib_atomic_flag_test
-FMT_EXPORT
 template <typename Char>
 struct formatter<std::atomic_flag, Char> : formatter<bool, Char> {
   template <typename FormatContext>
@@ -646,7 +647,11 @@ struct formatter<std::atomic_flag, Char> : formatter<bool, Char> {
 };
 #endif  // __cpp_lib_atomic_flag_test
 
-FMT_EXPORT
+template <typename T> struct is_tuple_like;
+
+template <typename T>
+struct is_tuple_like<std::complex<T>> : std::false_type {};
+
 template <typename T, typename Char> struct formatter<std::complex<T>, Char> {
  private:
   detail::dynamic_format_specs<Char> specs_;
@@ -695,9 +700,7 @@ template <typename T, typename Char> struct formatter<std::complex<T>, Char> {
 
     auto outer_specs = format_specs();
     outer_specs.width = specs.width;
-    auto fill = specs.template fill<Char>();
+    outer_specs.copy_fill_from(specs);
-    if (fill)
-      outer_specs.set_fill(basic_string_view<Char>(fill, specs.fill_size()));
     outer_specs.set_align(specs.align());
 
     specs.width = 0;
@@ -711,10 +714,13 @@ template <typename T, typename Char> struct formatter<std::complex<T>, Char> {
   }
 };
 
-FMT_EXPORT
 template <typename T, typename Char>
 struct formatter<std::reference_wrapper<T>, Char,
-                 enable_if_t<is_formattable<remove_cvref_t<T>, Char>::value>>
+                 // Guard against format_as because reference_wrapper is
+                 // implicitly convertible to T&.
+                 enable_if_t<is_formattable<remove_cvref_t<T>, Char>::value &&
+                             !detail::has_format_as<T>::value &&
+                             !detail::has_format_as_member<T>::value>>
     : formatter<remove_cvref_t<T>, Char> {
   template <typename FormatContext>
   auto format(std::reference_wrapper<T> ref, FormatContext& ctx) const
@@ -724,4 +730,5 @@ struct formatter<std::reference_wrapper<T>, Char,
 };
 
 FMT_END_NAMESPACE
+
 #endif  // FMT_STD_H_

include/fmt/xchar.h

@@ -55,6 +55,16 @@ inline auto write_loc(basic_appender<wchar_t> out, loc_value value,
 #endif
   return false;
 }
+
+template <typename Char>
+void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
+                basic_format_args<buffered_context<Char>> args,
+                locale_ref loc = {}) {
+  static_assert(!std::is_same<Char, char>::value, "");
+  auto out = basic_appender<Char>(buf);
+  parse_format_string(
+      fmt, format_handler<Char>{parse_context<Char>(fmt), {out, args, loc}});
+}
 }  // namespace detail
 
 FMT_BEGIN_EXPORT
@@ -112,14 +122,6 @@ inline auto runtime(wstring_view s) -> runtime_format_string<wchar_t> {
   return {{s}};
 }
 
-template <> struct is_char<wchar_t> : std::true_type {};
-template <> struct is_char<char16_t> : std::true_type {};
-template <> struct is_char<char32_t> : std::true_type {};
-
-#ifdef __cpp_char8_t
-template <> struct is_char<char8_t> : bool_constant<detail::is_utf8_enabled> {};
-#endif
-
 template <typename... T>
 constexpr auto make_wformat_args(T&... args)
     -> decltype(fmt::make_format_args<wformat_context>(args...)) {
@@ -155,13 +157,13 @@ auto join(std::initializer_list<T> list, wstring_view sep)
 
 template <typename Tuple, FMT_ENABLE_IF(is_tuple_like<Tuple>::value)>
 auto join(const Tuple& tuple, basic_string_view<wchar_t> sep)
-    -> tuple_join_view<wchar_t, Tuple> {
+    -> tuple_join_view<Tuple, wchar_t> {
   return {tuple, sep};
 }
 
 template <typename Char, FMT_ENABLE_IF(!std::is_same<Char, char>::value)>
 auto vformat(basic_string_view<Char> fmt,
-             typename detail::vformat_args<Char>::type args)
+             basic_format_args<buffered_context<Char>> args)
     -> std::basic_string<Char> {
   auto buf = basic_memory_buffer<Char>();
   detail::vformat_to(buf, fmt, args);
@@ -193,19 +195,18 @@ auto format(const S& fmt, T&&... args) -> std::basic_string<Char> {
 
 template <typename S, typename Char = detail::format_string_char_t<S>,
           FMT_ENABLE_IF(detail::is_exotic_char<Char>::value)>
-inline auto vformat(detail::locale_ref loc, const S& fmt,
+inline auto vformat(locale_ref loc, const S& fmt,
-                    typename detail::vformat_args<Char>::type args)
+                    basic_format_args<buffered_context<Char>> args)
     -> std::basic_string<Char> {
   auto buf = basic_memory_buffer<Char>();
-  detail::vformat_to(buf, detail::to_string_view(fmt), args,
+  detail::vformat_to(buf, detail::to_string_view(fmt), args, loc);
-                     detail::locale_ref(loc));
   return {buf.data(), buf.size()};
 }
 
 template <typename S, typename... T,
           typename Char = detail::format_string_char_t<S>,
           FMT_ENABLE_IF(detail::is_exotic_char<Char>::value)>
-inline auto format(detail::locale_ref loc, const S& fmt, T&&... args)
+inline auto format(locale_ref loc, const S& fmt, T&&... args)
     -> std::basic_string<Char> {
   return vformat(loc, detail::to_string_view(fmt),
                  fmt::make_format_args<buffered_context<Char>>(args...));
@@ -216,7 +217,7 @@ template <typename OutputIt, typename S,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
                             detail::is_exotic_char<Char>::value)>
 auto vformat_to(OutputIt out, const S& fmt,
-                typename detail::vformat_args<Char>::type args) -> OutputIt {
+                basic_format_args<buffered_context<Char>> args) -> OutputIt {
   auto&& buf = detail::get_buffer<Char>(out);
   detail::vformat_to(buf, detail::to_string_view(fmt), args);
   return detail::get_iterator(buf, out);
@@ -236,11 +237,11 @@ template <typename S, typename OutputIt, typename... Args,
           typename Char = detail::format_string_char_t<S>,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
                             detail::is_exotic_char<Char>::value)>
-inline auto vformat_to(OutputIt out, detail::locale_ref loc, const S& fmt,
+inline auto vformat_to(OutputIt out, locale_ref loc, const S& fmt,
-                       typename detail::vformat_args<Char>::type args)
+                       basic_format_args<buffered_context<Char>> args)
     -> OutputIt {
   auto&& buf = detail::get_buffer<Char>(out);
-  vformat_to(buf, detail::to_string_view(fmt), args, detail::locale_ref(loc));
+  vformat_to(buf, detail::to_string_view(fmt), args, loc);
   return detail::get_iterator(buf, out);
 }
 
@@ -248,9 +249,8 @@ template <typename OutputIt, typename S, typename... T,
           typename Char = detail::format_string_char_t<S>,
           bool enable = detail::is_output_iterator<OutputIt, Char>::value &&
                         detail::is_exotic_char<Char>::value>
-inline auto format_to(OutputIt out, detail::locale_ref loc, const S& fmt,
+inline auto format_to(OutputIt out, locale_ref loc, const S& fmt, T&&... args)
-                      T&&... args) ->
+    -> typename std::enable_if<enable, OutputIt>::type {
-    typename std::enable_if<enable, OutputIt>::type {
   return vformat_to(out, loc, detail::to_string_view(fmt),
                     fmt::make_format_args<buffered_context<Char>>(args...));
 }
@@ -259,7 +259,7 @@ template <typename OutputIt, typename Char, typename... Args,
           FMT_ENABLE_IF(detail::is_output_iterator<OutputIt, Char>::value&&
                             detail::is_exotic_char<Char>::value)>
 inline auto vformat_to_n(OutputIt out, size_t n, basic_string_view<Char> fmt,
-                         typename detail::vformat_args<Char>::type args)
+                         basic_format_args<buffered_context<Char>> args)
     -> format_to_n_result<OutputIt> {
   using traits = detail::fixed_buffer_traits;
   auto buf = detail::iterator_buffer<OutputIt, Char, traits>(out, n);
@@ -317,7 +317,7 @@ template <typename... T> void println(wformat_string<T...> fmt, T&&... args) {
   return print(L"{}\n", fmt::format(fmt, std::forward<T>(args)...));
 }
 
-inline auto vformat(const text_style& ts, wstring_view fmt, wformat_args args)
+inline auto vformat(text_style ts, wstring_view fmt, wformat_args args)
     -> std::wstring {
   auto buf = wmemory_buffer();
   detail::vformat_to(buf, ts, fmt, args);
@@ -325,23 +325,11 @@ inline auto vformat(const text_style& ts, wstring_view fmt, wformat_args args)
 }
 
 template <typename... T>
-inline auto format(const text_style& ts, wformat_string<T...> fmt, T&&... args)
+inline auto format(text_style ts, wformat_string<T...> fmt, T&&... args)
     -> std::wstring {
   return fmt::vformat(ts, fmt, fmt::make_wformat_args(args...));
 }
 
-template <typename... T>
-FMT_DEPRECATED void print(std::FILE* f, const text_style& ts,
-                          wformat_string<T...> fmt, const T&... args) {
-  vprint(f, ts, fmt, fmt::make_wformat_args(args...));
-}
-
-template <typename... T>
-FMT_DEPRECATED void print(const text_style& ts, wformat_string<T...> fmt,
-                          const T&... args) {
-  return print(stdout, ts, fmt, args...);
-}
-
 inline void vprint(std::wostream& os, wstring_view fmt, wformat_args args) {
   auto buffer = basic_memory_buffer<wchar_t>();
   detail::vformat_to(buffer, fmt, args);

src/fmt.cc

@@ -1,5 +1,7 @@
 module;
 
+#define FMT_MODULE
+
 #ifdef _MSVC_LANG
 #  define FMT_CPLUSPLUS _MSVC_LANG
 #else
@@ -48,6 +50,8 @@ module;
 #  include <limits.h>
 #  include <stdint.h>
 #  include <stdio.h>
+#  include <stdlib.h>
+#  include <string.h>
 #  include <time.h>
 #endif
 #include <cerrno>

src/format.cc

@@ -8,6 +8,12 @@
 #include "fmt/format-inl.h"
 
 FMT_BEGIN_NAMESPACE
+
+#if FMT_USE_LOCALE
+template FMT_API locale_ref::locale_ref(const std::locale& loc);  // DEPRECATED!
+template FMT_API auto locale_ref::get<std::locale>() const -> std::locale;
+#endif
+
 namespace detail {
 
 template FMT_API auto dragonbox::to_decimal(float x) noexcept
@@ -15,12 +21,6 @@ template FMT_API auto dragonbox::to_decimal(float x) noexcept
 template FMT_API auto dragonbox::to_decimal(double x) noexcept
     -> dragonbox::decimal_fp<double>;
 
-#if FMT_USE_LOCALE
-// DEPRECATED! locale_ref in the detail namespace
-template FMT_API locale_ref::locale_ref(const std::locale& loc);
-template FMT_API auto locale_ref::get<std::locale>() const -> std::locale;
-#endif
-
 // Explicit instantiations for char.
 
 template FMT_API auto thousands_sep_impl(locale_ref)
@@ -30,16 +30,13 @@ template FMT_API auto decimal_point_impl(locale_ref) -> char;
 // DEPRECATED!
 template FMT_API void buffer<char>::append(const char*, const char*);
 
-// DEPRECATED!
-template FMT_API void vformat_to(buffer<char>&, string_view,
-                                 typename vformat_args<>::type, locale_ref);
-
 // Explicit instantiations for wchar_t.
 
 template FMT_API auto thousands_sep_impl(locale_ref)
     -> thousands_sep_result<wchar_t>;
 template FMT_API auto decimal_point_impl(locale_ref) -> wchar_t;
 
+// DEPRECATED!
 template FMT_API void buffer<wchar_t>::append(const wchar_t*, const wchar_t*);
 
 }  // namespace detail

src/os.cc

@@ -66,14 +66,14 @@ using rwresult = int;
 
 // On Windows the count argument to read and write is unsigned, so convert
 // it from size_t preventing integer overflow.
-inline unsigned convert_rwcount(std::size_t count) {
+inline unsigned convert_rwcount(size_t count) {
   return count <= UINT_MAX ? static_cast<unsigned>(count) : UINT_MAX;
 }
 #elif FMT_USE_FCNTL
 // Return type of read and write functions.
 using rwresult = ssize_t;
 
-inline std::size_t convert_rwcount(std::size_t count) { return count; }
+inline auto convert_rwcount(size_t count) -> size_t { return count; }
 #endif
 }  // namespace
 
@@ -185,7 +185,7 @@ void buffered_file::close() {
     FMT_THROW(system_error(errno, FMT_STRING("cannot close file")));
 }
 
-int buffered_file::descriptor() const {
+auto buffered_file::descriptor() const -> int {
 #ifdef FMT_HAS_SYSTEM
   // fileno is a macro on OpenBSD.
 #  ifdef fileno
@@ -240,7 +240,7 @@ void file::close() {
     FMT_THROW(system_error(errno, FMT_STRING("cannot close file")));
 }
 
-long long file::size() const {
+auto file::size() const -> long long {
 #  ifdef _WIN32
   // Use GetFileSize instead of GetFileSizeEx for the case when _WIN32_WINNT
   // is less than 0x0500 as is the case with some default MinGW builds.
@@ -251,7 +251,7 @@ long long file::size() const {
   if (size_lower == INVALID_FILE_SIZE) {
     DWORD error = GetLastError();
     if (error != NO_ERROR)
-      FMT_THROW(windows_error(GetLastError(), "cannot get file size"));
+      FMT_THROW(windows_error(error, "cannot get file size"));
   }
   unsigned long long long_size = size_upper;
   return (long_size << sizeof(DWORD) * CHAR_BIT) | size_lower;
@@ -266,7 +266,7 @@ long long file::size() const {
 #  endif
 }
 
-std::size_t file::read(void* buffer, std::size_t count) {
+auto file::read(void* buffer, size_t count) -> size_t {
   rwresult result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(read(fd_, buffer, convert_rwcount(count))));
   if (result < 0)
@@ -274,7 +274,7 @@ std::size_t file::read(void* buffer, std::size_t count) {
   return detail::to_unsigned(result);
 }
 
-std::size_t file::write(const void* buffer, std::size_t count) {
+auto file::write(const void* buffer, size_t count) -> size_t {
   rwresult result = 0;
   FMT_RETRY(result, FMT_POSIX_CALL(write(fd_, buffer, convert_rwcount(count))));
   if (result < 0)
@@ -282,7 +282,7 @@ std::size_t file::write(const void* buffer, std::size_t count) {
   return detail::to_unsigned(result);
 }
 
-file file::dup(int fd) {
+auto file::dup(int fd) -> file {
   // Don't retry as dup doesn't return EINTR.
   // http://pubs.opengroup.org/onlinepubs/009695399/functions/dup.html
   int new_fd = FMT_POSIX_CALL(dup(fd));
@@ -308,7 +308,7 @@ void file::dup2(int fd, std::error_code& ec) noexcept {
   if (result == -1) ec = std::error_code(errno, std::generic_category());
 }
 
-buffered_file file::fdopen(const char* mode) {
+auto file::fdopen(const char* mode) -> buffered_file {
 // Don't retry as fdopen doesn't return EINTR.
 #  if defined(__MINGW32__) && defined(_POSIX_)
   FILE* f = ::fdopen(fd_, mode);
@@ -355,7 +355,7 @@ pipe::pipe() {
 }
 
 #  if !defined(__MSDOS__)
-long getpagesize() {
+auto getpagesize() -> long {
 #    ifdef _WIN32
   SYSTEM_INFO si;
   GetSystemInfo(&si);

support/bazel/.bazelversion

@@ -1 +0,0 @@
-7.1.2

support/bazel/BUILD.bazel

@@ -1,20 +0,0 @@
-cc_library(
-    name = "fmt",
-    srcs = [
-        #"src/fmt.cc", # No C++ module support, yet in Bazel (https://github.com/bazelbuild/bazel/pull/19940)
-        "src/format.cc",
-        "src/os.cc",
-    ],
-    hdrs = glob([
-        "include/fmt/*.h",
-    ]),
-    copts = select({
-        "@platforms//os:windows": ["-utf-8"],
-        "//conditions:default": [],
-    }),
-    includes = [
-        "include",
-    ],
-    strip_include_prefix = "include",
-    visibility = ["//visibility:public"],
-)

support/bazel/MODULE.bazel

@@ -1,6 +0,0 @@
-module(
-   name = "fmt",
-   compatibility_level = 10,
-)
-
-bazel_dep(name = "platforms", version = "0.0.10")

support/bazel/README.md

@@ -1,28 +0,0 @@
-# Bazel support
-
-To get [Bazel](https://bazel.build/) working with {fmt} you can copy the files `BUILD.bazel`, 
-`MODULE.bazel`, `WORKSPACE.bazel`, and `.bazelversion` from this folder (`support/bazel`) to the root folder of this project. 
-This way {fmt} gets bazelized and can be used with Bazel (e.g. doing a `bazel build //...` on {fmt}). 
-
-## Using {fmt} as a dependency
-
-### Using Bzlmod
-
-The [Bazel Central Registry](https://github.com/bazelbuild/bazel-central-registry/tree/main/modules/fmt) provides support for {fmt}.
-
-For instance, to use {fmt} add to your `MODULE.bazel` file:
-
-```
-bazel_dep(name = "fmt", version = "10.2.1")
-```
-
-### Live at head
-
-For a live-at-head approach, you can copy the contents of this repository and move the Bazel-related build files to the root folder of this project as described above and make use of `local_path_override`, e.g.:
-
-```
-local_path_override(
-    module_name = "fmt",
-    path = "../third_party/fmt",
-)
-```

support/bazel/WORKSPACE.bazel

@@ -1,2 +0,0 @@
-# WORKSPACE marker file needed by Bazel
-

support/mkdocs

@@ -2,6 +2,10 @@
 # A script to invoke mkdocs with the correct environment.
 # Additionally supports deploying via mike:
 #   ./mkdocs deploy [mike-deploy-options]
+# For example:
+#   ./mkdocs deploy <version>
+# This will checkout the website to fmt/build/fmt.dev and deploy documentation
+# <version> there.
 
 import errno, os, shutil, sys
 from subprocess import call
@@ -40,7 +44,7 @@ config_path = os.path.join(support_dir, 'mkdocs.yml')
 args = sys.argv[1:]
 if len(args) > 0:
   command = args[0]
-  if command == 'deploy':
+  if command == 'deploy' or command == 'set-default':
     git_url = 'https://github.com/' if 'CI' in os.environ else 'git@github.com:'
     site_repo = git_url + 'fmtlib/fmt.dev.git'
 
@@ -63,13 +67,19 @@ if len(args) > 0:
                '--branch', 'master'], cwd=site_dir, env=env)
     if ret != 0 or version == 'dev':
       sys.exit(ret)
-    redirect_page_path = os.path.join(site_dir, version, 'api.html')
+    current_doc_path = os.path.join(site_dir, version)
-    with open(redirect_page_path, "w") as file:
+    # mike stages files added by deploy for deletion for unclear reason,
-      file.write(redirect_page)
+    # undo it.
-    ret = call(['git', 'add', redirect_page_path], cwd=site_dir)
+    ret = call(['git', 'reset', '--hard'], cwd=site_dir)
-    if ret != 0:
+    if False:
-      sys.exit(ret)
+      os.makedirs(current_doc_path, exist_ok=True)
-    ret = call(['git', 'commit', '--amend', '--no-edit'], cwd=site_dir)
+      redirect_page_path = os.path.join(current_doc_path, 'api.html')
+      with open(redirect_page_path, "w") as file:
+        file.write(redirect_page)
+      ret = call(['git', 'add', redirect_page_path], cwd=site_dir)
+      if ret != 0:
+        sys.exit(ret)
+      ret = call(['git', 'commit', '--amend', '--no-edit'], cwd=site_dir)
     sys.exit(ret)
   elif not command.startswith('-'):
     args += ['-f', config_path]

support/python/mkdocstrings_handlers/cxx/__init__.py

@@ -34,8 +34,8 @@ tag_map = {
     'emphasis': 'em',
     'computeroutput': 'code',
     'para': 'p',
-    'programlisting': 'pre',
+    'itemizedlist': 'ul',
-    'verbatim': 'pre'
+    'listitem': 'li'
 }
 
 # A map from Doxygen tags to text.
@@ -50,21 +50,37 @@ def escape_html(s: str) -> str:
     return s.replace("<", "&lt;")
 
 
+# Converts a node from doxygen to HTML format.
+def convert_node(node: ElementTree.Element, tag: str, attrs: dict = {}):
+    out = '<' + tag
+    for key, value in attrs.items():
+        out += ' ' + key + '="' + value + '"'
+    out += '>'
+    if node.text:
+        out += escape_html(node.text)
+    out += doxyxml2html(list(node))
+    out += '</' + tag + '>'
+    if node.tail:
+        out += node.tail
+    return out
+
+
 def doxyxml2html(nodes: List[ElementTree.Element]):
     out = ''
     for n in nodes:
         tag = tag_map.get(n.tag)
-        if not tag:
+        if tag:
-            out += tag_text_map[n.tag]
+            out += convert_node(n, tag)
-        out += '<' + tag + '>' if tag else ''
+            continue
-        out += '<code class="language-cpp">' if tag == 'pre' else ''
+        if n.tag == 'programlisting' or n.tag == 'verbatim':
-        if n.text:
+            out += '<pre>'
-            out += escape_html(n.text)
+            out += convert_node(n, 'code', {'class': 'language-cpp'})
-        out += doxyxml2html(list(n))
+            out += '</pre>'
-        out += '</code>' if tag == 'pre' else ''
+            continue
-        out += '</' + tag + '>' if tag else ''
+        if n.tag == 'ulink':
-        if n.tail:
+            out += convert_node(n, 'a', {'href': n.attrib['url']})
-            out += n.tail
+            continue
+        out += tag_text_map[n.tag]
     return out
 
 

test/CMakeLists.txt

@@ -62,11 +62,6 @@ if (NOT (MSVC AND BUILD_SHARED_LIBS))
 endif ()
 add_fmt_test(ostream-test)
 add_fmt_test(compile-test)
-add_fmt_test(compile-fp-test)
-if (MSVC)
-  # Without this option, MSVC returns 199711L for the __cplusplus macro.
-  target_compile_options(compile-fp-test PRIVATE /Zc:__cplusplus)
-endif()
 add_fmt_test(printf-test)
 add_fmt_test(ranges-test ranges-odr-test.cc)
 add_fmt_test(no-builtin-types-test HEADER_ONLY)

test/args-test.cc

@@ -64,7 +64,7 @@ TEST(args_test, custom_format) {
 }
 
 struct to_stringable {
-  friend fmt::string_view to_string_view(to_stringable) { return {}; }
+  friend auto to_string_view(to_stringable) -> fmt::string_view { return {}; }
 };
 
 FMT_BEGIN_NAMESPACE

test/base-test.cc

@@ -5,14 +5,16 @@
 //
 // For the license information refer to format.h.
 
+// Turn assertion failures into exceptions for testing.
 // clang-format off
 #include "test-assert.h"
 // clang-format on
 
 #include "fmt/base.h"
 
-#include <climits>      // INT_MAX
+#include <limits.h>  // INT_MAX
-#include <cstring>      // std::strlen
+#include <string.h>  // strlen
+
 #include <functional>   // std::equal_to
 #include <iterator>     // std::back_insert_iterator, std::distance
 #include <limits>       // std::numeric_limits
@@ -21,39 +23,36 @@
 
 #include "gmock/gmock.h"
 
-using fmt::string_view;
+#ifdef FMT_FORMAT_H_
-using fmt::detail::buffer;
+#  error base-test includes format.h
+#endif
 
 using testing::_;
 using testing::Invoke;
 using testing::Return;
 
-#ifdef FMT_FORMAT_H_
+auto copy(fmt::string_view s, fmt::appender out) -> fmt::appender {
-#  error core-test includes format.h
-#endif
-
-fmt::appender copy(fmt::string_view s, fmt::appender out) {
   for (char c : s) *out++ = c;
   return out;
 }
 
 TEST(string_view_test, value_type) {
-  static_assert(std::is_same<string_view::value_type, char>::value, "");
+  static_assert(std::is_same<fmt::string_view::value_type, char>::value, "");
 }
 
 TEST(string_view_test, ctor) {
-  EXPECT_STREQ("abc", fmt::string_view("abc").data());
+  EXPECT_STREQ(fmt::string_view("abc").data(), "abc");
-  EXPECT_EQ(3u, fmt::string_view("abc").size());
+  EXPECT_EQ(fmt::string_view("abc").size(), 3u);
 
-  EXPECT_STREQ("defg", fmt::string_view(std::string("defg")).data());
+  EXPECT_STREQ(fmt::string_view(std::string("defg")).data(), "defg");
-  EXPECT_EQ(4u, fmt::string_view(std::string("defg")).size());
+  EXPECT_EQ(fmt::string_view(std::string("defg")).size(), 4u);
 }
 
 TEST(string_view_test, length) {
   // Test that string_view::size() returns string length, not buffer size.
   char str[100] = "some string";
-  EXPECT_EQ(std::strlen(str), string_view(str).size());
+  EXPECT_EQ(fmt::string_view(str).size(), strlen(str));
-  EXPECT_LT(std::strlen(str), sizeof(str));
+  EXPECT_LT(strlen(str), sizeof(str));
 }
 
 // Check string_view's comparison operator.
@@ -62,13 +61,16 @@ template <template <typename> class Op> void check_op() {
   size_t num_inputs = sizeof(inputs) / sizeof(*inputs);
   for (size_t i = 0; i < num_inputs; ++i) {
     for (size_t j = 0; j < num_inputs; ++j) {
-      string_view lhs(inputs[i]), rhs(inputs[j]);
+      fmt::string_view lhs(inputs[i]), rhs(inputs[j]);
-      EXPECT_EQ(Op<int>()(lhs.compare(rhs), 0), Op<string_view>()(lhs, rhs));
+      EXPECT_EQ(Op<int>()(lhs.compare(rhs), 0),
+                Op<fmt::string_view>()(lhs, rhs));
     }
   }
 }
 
 TEST(string_view_test, compare) {
+  using fmt::string_view;
+
   EXPECT_EQ(string_view("foo").compare(string_view("foo")), 0);
   EXPECT_GT(string_view("fop").compare(string_view("foo")), 0);
   EXPECT_LT(string_view("foo").compare(string_view("fop")), 0);
@@ -92,6 +94,167 @@ TEST(string_view_test, compare) {
   check_op<std::greater_equal>();
 }
 
+#if FMT_USE_CONSTEVAL
+TEST(string_view_test, from_constexpr_fixed_string) {
+  constexpr int size = 4;
+
+  struct fixed_string {
+    char data[size] = {};
+
+    constexpr fixed_string(const char (&m)[size]) {
+      for (size_t i = 0; i != size; ++i) data[i] = m[i];
+    }
+  };
+
+  static constexpr auto fs = fixed_string("foo");
+  static constexpr auto sv = fmt::string_view(fs.data);
+  EXPECT_EQ(sv, "foo");
+}
+#endif  // FMT_USE_CONSTEVAL
+
+TEST(buffer_test, noncopyable) {
+  EXPECT_FALSE(std::is_copy_constructible<fmt::detail::buffer<char>>::value);
+  EXPECT_FALSE(std::is_copy_assignable<fmt::detail::buffer<char>>::value);
+}
+
+TEST(buffer_test, nonmoveable) {
+  EXPECT_FALSE(std::is_move_constructible<fmt::detail::buffer<char>>::value);
+  EXPECT_FALSE(std::is_move_assignable<fmt::detail::buffer<char>>::value);
+}
+
+TEST(buffer_test, indestructible) {
+  static_assert(!std::is_destructible<fmt::detail::buffer<int>>(),
+                "buffer's destructor is protected");
+}
+
+template <typename T> struct mock_buffer final : fmt::detail::buffer<T> {
+  MOCK_METHOD(size_t, do_grow, (size_t));
+
+  static void grow(fmt::detail::buffer<T>& buf, size_t capacity) {
+    auto& self = static_cast<mock_buffer&>(buf);
+    self.set(buf.data(), self.do_grow(capacity));
+  }
+
+  mock_buffer(T* data = nullptr, size_t buf_capacity = 0)
+      : fmt::detail::buffer<T>(grow) {
+    this->set(data, buf_capacity);
+    ON_CALL(*this, do_grow(_)).WillByDefault(Invoke([](size_t capacity) {
+      return capacity;
+    }));
+  }
+};
+
+TEST(buffer_test, ctor) {
+  {
+    mock_buffer<int> buffer;
+    EXPECT_EQ(buffer.data(), nullptr);
+    EXPECT_EQ(buffer.size(), 0u);
+    EXPECT_EQ(buffer.capacity(), 0u);
+  }
+  {
+    int data;
+    mock_buffer<int> buffer(&data);
+    EXPECT_EQ(&buffer[0], &data);
+    EXPECT_EQ(buffer.size(), 0u);
+    EXPECT_EQ(buffer.capacity(), 0u);
+  }
+  {
+    int data;
+    size_t capacity = std::numeric_limits<size_t>::max();
+    mock_buffer<int> buffer(&data, capacity);
+    EXPECT_EQ(&buffer[0], &data);
+    EXPECT_EQ(buffer.size(), 0u);
+    EXPECT_EQ(buffer.capacity(), capacity);
+  }
+}
+
+TEST(buffer_test, access) {
+  char data[10];
+  mock_buffer<char> buffer(data, sizeof(data));
+  buffer[0] = 11;
+  EXPECT_EQ(buffer[0], 11);
+  buffer[3] = 42;
+  EXPECT_EQ(*(&buffer[0] + 3), 42);
+  const fmt::detail::buffer<char>& const_buffer = buffer;
+  EXPECT_EQ(const_buffer[3], 42);
+}
+
+TEST(buffer_test, try_resize) {
+  char data[123];
+  mock_buffer<char> buffer(data, sizeof(data));
+  buffer[10] = 42;
+  EXPECT_EQ(buffer[10], 42);
+  buffer.try_resize(20);
+  EXPECT_EQ(buffer.size(), 20u);
+  EXPECT_EQ(buffer.capacity(), 123u);
+  EXPECT_EQ(buffer[10], 42);
+  buffer.try_resize(5);
+  EXPECT_EQ(buffer.size(), 5u);
+  EXPECT_EQ(buffer.capacity(), 123u);
+  EXPECT_EQ(buffer[10], 42);
+  // Check if try_resize calls grow.
+  EXPECT_CALL(buffer, do_grow(124));
+  buffer.try_resize(124);
+  EXPECT_CALL(buffer, do_grow(200));
+  buffer.try_resize(200);
+}
+
+TEST(buffer_test, try_resize_partial) {
+  char data[10];
+  mock_buffer<char> buffer(data, sizeof(data));
+  EXPECT_CALL(buffer, do_grow(20)).WillOnce(Return(15));
+  buffer.try_resize(20);
+  EXPECT_EQ(buffer.capacity(), 15);
+  EXPECT_EQ(buffer.size(), 15);
+}
+
+TEST(buffer_test, clear) {
+  mock_buffer<char> buffer;
+  EXPECT_CALL(buffer, do_grow(20));
+  buffer.try_resize(20);
+  buffer.try_resize(0);
+  EXPECT_EQ(buffer.size(), 0u);
+  EXPECT_EQ(buffer.capacity(), 20u);
+}
+
+TEST(buffer_test, append) {
+  char data[15];
+  mock_buffer<char> buffer(data, 10);
+  auto test = "test";
+  buffer.append(test, test + 5);
+  EXPECT_STREQ(&buffer[0], test);
+  EXPECT_EQ(buffer.size(), 5u);
+  buffer.try_resize(10);
+  EXPECT_CALL(buffer, do_grow(12));
+  buffer.append(test, test + 2);
+  EXPECT_EQ(buffer[10], 't');
+  EXPECT_EQ(buffer[11], 'e');
+  EXPECT_EQ(buffer.size(), 12u);
+}
+
+TEST(buffer_test, append_partial) {
+  char data[10];
+  mock_buffer<char> buffer(data, sizeof(data));
+  testing::InSequence seq;
+  EXPECT_CALL(buffer, do_grow(15)).WillOnce(Return(10));
+  EXPECT_CALL(buffer, do_grow(15)).WillOnce(Invoke([&buffer](size_t) {
+    EXPECT_EQ(fmt::string_view(buffer.data(), buffer.size()), "0123456789");
+    buffer.clear();
+    return 10;
+  }));
+  auto test = "0123456789abcde";
+  buffer.append(test, test + 15);
+}
+
+TEST(buffer_test, append_allocates_enough_storage) {
+  char data[19];
+  mock_buffer<char> buffer(data, 10);
+  auto test = "abcdefgh";
+  buffer.try_resize(10);
+  EXPECT_CALL(buffer, do_grow(19));
+  buffer.append(test, test + 9);
+}
+
 TEST(base_test, is_locking) {
   EXPECT_FALSE(fmt::detail::is_locking<const char(&)[3]>());
 }
@@ -116,154 +279,15 @@ TEST(base_test, is_back_insert_iterator) {
                std::front_insert_iterator<std::string>>::value);
 }
 
-#if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 470
+struct minimal_container {
-TEST(buffer_test, noncopyable) {
+  using value_type = char;
-  EXPECT_FALSE(std::is_copy_constructible<buffer<char>>::value);
+  void push_back(char) {}
-#  if !FMT_MSC_VERSION
-  // std::is_copy_assignable is broken in MSVC2013.
-  EXPECT_FALSE(std::is_copy_assignable<buffer<char>>::value);
-#  endif
-}
-
-TEST(buffer_test, nonmoveable) {
-  EXPECT_FALSE(std::is_move_constructible<buffer<char>>::value);
-#  if !FMT_MSC_VERSION
-  // std::is_move_assignable is broken in MSVC2013.
-  EXPECT_FALSE(std::is_move_assignable<buffer<char>>::value);
-#  endif
-}
-#endif
-
-TEST(buffer_test, indestructible) {
-  static_assert(!std::is_destructible<fmt::detail::buffer<int>>(),
-                "buffer's destructor is protected");
-}
-
-template <typename T> struct mock_buffer final : buffer<T> {
-  MOCK_METHOD(size_t, do_grow, (size_t));
-
-  static void grow(buffer<T>& buf, size_t capacity) {
-    auto& self = static_cast<mock_buffer&>(buf);
-    self.set(buf.data(), self.do_grow(capacity));
-  }
-
-  mock_buffer(T* data = nullptr, size_t buf_capacity = 0) : buffer<T>(grow) {
-    this->set(data, buf_capacity);
-    ON_CALL(*this, do_grow(_)).WillByDefault(Invoke([](size_t capacity) {
-      return capacity;
-    }));
-  }
 };
 
-TEST(buffer_test, ctor) {
+TEST(base_test, copy) {
-  {
+  minimal_container c;
-    mock_buffer<int> buffer;
+  static constexpr char str[] = "a";
-    EXPECT_EQ(nullptr, buffer.data());
+  fmt::detail::copy<char>(str, str + 1, std::back_inserter(c));
-    EXPECT_EQ(static_cast<size_t>(0), buffer.size());
-    EXPECT_EQ(static_cast<size_t>(0), buffer.capacity());
-  }
-  {
-    int dummy;
-    mock_buffer<int> buffer(&dummy);
-    EXPECT_EQ(&dummy, &buffer[0]);
-    EXPECT_EQ(static_cast<size_t>(0), buffer.size());
-    EXPECT_EQ(static_cast<size_t>(0), buffer.capacity());
-  }
-  {
-    int dummy;
-    size_t capacity = std::numeric_limits<size_t>::max();
-    mock_buffer<int> buffer(&dummy, capacity);
-    EXPECT_EQ(&dummy, &buffer[0]);
-    EXPECT_EQ(static_cast<size_t>(0), buffer.size());
-    EXPECT_EQ(capacity, buffer.capacity());
-  }
-}
-
-TEST(buffer_test, access) {
-  char data[10];
-  mock_buffer<char> buffer(data, sizeof(data));
-  buffer[0] = 11;
-  EXPECT_EQ(11, buffer[0]);
-  buffer[3] = 42;
-  EXPECT_EQ(42, *(&buffer[0] + 3));
-  const fmt::detail::buffer<char>& const_buffer = buffer;
-  EXPECT_EQ(42, const_buffer[3]);
-}
-
-TEST(buffer_test, try_resize) {
-  char data[123];
-  mock_buffer<char> buffer(data, sizeof(data));
-  buffer[10] = 42;
-  EXPECT_EQ(42, buffer[10]);
-  buffer.try_resize(20);
-  EXPECT_EQ(20u, buffer.size());
-  EXPECT_EQ(123u, buffer.capacity());
-  EXPECT_EQ(42, buffer[10]);
-  buffer.try_resize(5);
-  EXPECT_EQ(5u, buffer.size());
-  EXPECT_EQ(123u, buffer.capacity());
-  EXPECT_EQ(42, buffer[10]);
-  // Check if try_resize calls grow.
-  EXPECT_CALL(buffer, do_grow(124));
-  buffer.try_resize(124);
-  EXPECT_CALL(buffer, do_grow(200));
-  buffer.try_resize(200);
-}
-
-TEST(buffer_test, try_resize_partial) {
-  char data[10];
-  mock_buffer<char> buffer(data, sizeof(data));
-  EXPECT_CALL(buffer, do_grow(20)).WillOnce(Return(15));
-  buffer.try_resize(20);
-  EXPECT_EQ(buffer.capacity(), 15);
-  EXPECT_EQ(buffer.size(), 15);
-}
-
-TEST(buffer_test, clear) {
-  mock_buffer<char> buffer;
-  EXPECT_CALL(buffer, do_grow(20));
-  buffer.try_resize(20);
-  buffer.try_resize(0);
-  EXPECT_EQ(static_cast<size_t>(0), buffer.size());
-  EXPECT_EQ(20u, buffer.capacity());
-}
-
-TEST(buffer_test, append) {
-  char data[15];
-  mock_buffer<char> buffer(data, 10);
-  auto test = "test";
-  buffer.append(test, test + 5);
-  EXPECT_STREQ(test, &buffer[0]);
-  EXPECT_EQ(5u, buffer.size());
-  buffer.try_resize(10);
-  EXPECT_CALL(buffer, do_grow(12));
-  buffer.append(test, test + 2);
-  EXPECT_EQ('t', buffer[10]);
-  EXPECT_EQ('e', buffer[11]);
-  EXPECT_EQ(12u, buffer.size());
-}
-
-TEST(buffer_test, append_partial) {
-  char data[10];
-  mock_buffer<char> buffer(data, sizeof(data));
-  testing::InSequence seq;
-  EXPECT_CALL(buffer, do_grow(15)).WillOnce(Return(10));
-  EXPECT_CALL(buffer, do_grow(15)).WillOnce(Invoke([&buffer](size_t) {
-    EXPECT_EQ(fmt::string_view(buffer.data(), buffer.size()), "0123456789");
-    buffer.clear();
-    return 10;
-  }));
-  auto test = "0123456789abcde";
-  buffer.append(test, test + 15);
-}
-
-TEST(buffer_test, append_allocates_enough_storage) {
-  char data[19];
-  mock_buffer<char> buffer(data, 10);
-  auto test = "abcdefgh";
-  buffer.try_resize(10);
-  EXPECT_CALL(buffer, do_grow(19));
-  buffer.append(test, test + 9);
 }
 
 TEST(base_test, get_buffer) {
@@ -290,11 +314,6 @@ template <typename Char> struct formatter<test_struct, Char> {
 };
 FMT_END_NAMESPACE
 
-TEST(arg_test, format_args) {
-  auto args = fmt::format_args();
-  EXPECT_FALSE(args.get(1));
-}
-
 // Use a unique result type to make sure that there are no undesirable
 // conversions.
 struct test_result {};
@@ -360,33 +379,9 @@ VISIT_TYPE(unsigned long, unsigned long long);
     CHECK_ARG(expected, value)                              \
   }
 
-template <typename T> class numeric_arg_test : public testing::Test {};
+TEST(arg_test, format_args) {
-
+  auto args = fmt::format_args();
-#if FMT_BUILTIN_TYPES
+  EXPECT_FALSE(args.get(1));
-using test_types =
-    testing::Types<bool, signed char, unsigned char, short, unsigned short, int,
-                   unsigned, long, unsigned long, long long, unsigned long long,
-                   float, double, long double>;
-#else
-using test_types = testing::Types<int>;
-#endif
-TYPED_TEST_SUITE(numeric_arg_test, test_types);
-
-template <typename T, fmt::enable_if_t<std::is_integral<T>::value, int> = 0>
-auto test_value() -> T {
-  return static_cast<T>(42);
-}
-
-template <typename T,
-          fmt::enable_if_t<std::is_floating_point<T>::value, int> = 0>
-auto test_value() -> T {
-  return static_cast<T>(4.2);
-}
-
-TYPED_TEST(numeric_arg_test, make_and_visit) {
-  CHECK_ARG_SIMPLE(test_value<TypeParam>());
-  CHECK_ARG_SIMPLE(std::numeric_limits<TypeParam>::min());
-  CHECK_ARG_SIMPLE(std::numeric_limits<TypeParam>::max());
 }
 
 TEST(arg_test, char_arg) { CHECK_ARG('a', 'a'); }
@@ -428,7 +423,7 @@ struct check_custom {
     auto parse_ctx = fmt::format_parse_context("");
     auto ctx = fmt::format_context(fmt::appender(buffer), fmt::format_args());
     h.format(parse_ctx, ctx);
-    EXPECT_EQ("test", std::string(buffer.data, buffer.size()));
+    EXPECT_EQ(std::string(buffer.data, buffer.size()), "test");
     return test_result();
   }
 };
@@ -448,27 +443,57 @@ TEST(arg_test, visit_invalid_arg) {
   fmt::basic_format_arg<fmt::format_context>().visit(visitor);
 }
 
+template <typename T> class numeric_arg_test : public testing::Test {};
+
+#if FMT_BUILTIN_TYPES
+using test_types =
+    testing::Types<bool, signed char, unsigned char, short, unsigned short, int,
+                   unsigned, long, unsigned long, long long, unsigned long long,
+                   float, double, long double>;
+#else
+using test_types = testing::Types<int>;
+#endif
+TYPED_TEST_SUITE(numeric_arg_test, test_types);
+
+template <typename T, fmt::enable_if_t<std::is_integral<T>::value, int> = 0>
+auto test_value() -> T {
+  return static_cast<T>(42);
+}
+
+template <typename T,
+          fmt::enable_if_t<std::is_floating_point<T>::value, int> = 0>
+auto test_value() -> T {
+  return static_cast<T>(4.2);
+}
+
+TYPED_TEST(numeric_arg_test, make_and_visit) {
+  CHECK_ARG_SIMPLE(test_value<TypeParam>());
+  CHECK_ARG_SIMPLE(std::numeric_limits<TypeParam>::min());
+  CHECK_ARG_SIMPLE(std::numeric_limits<TypeParam>::max());
+}
+
 #if FMT_USE_CONSTEXPR
 
 enum class arg_id_result { none, index, name };
+
 struct test_arg_id_handler {
   arg_id_result res = arg_id_result::none;
   int index = 0;
-  string_view name;
+  fmt::string_view name;
 
   constexpr void on_index(int i) {
     res = arg_id_result::index;
     index = i;
   }
 
-  constexpr void on_name(string_view n) {
+  constexpr void on_name(fmt::string_view n) {
     res = arg_id_result::name;
     name = n;
   }
 };
 
 template <size_t N>
-constexpr test_arg_id_handler parse_arg_id(const char (&s)[N]) {
+constexpr auto parse_arg_id(const char (&s)[N]) -> test_arg_id_handler {
   auto h = test_arg_id_handler();
   fmt::detail::parse_arg_id(s, s + N, h);
   return h;
@@ -526,7 +551,7 @@ struct test_format_string_handler {
   bool error = false;
 };
 
-template <size_t N> constexpr bool parse_string(const char (&s)[N]) {
+template <size_t N> constexpr auto parse_string(const char (&s)[N]) -> bool {
   auto h = test_format_string_handler();
   fmt::detail::parse_format_string(fmt::string_view(s, N - 1), h);
   return !h.error;
@@ -540,6 +565,7 @@ TEST(base_test, constexpr_parse_format_string) {
   static_assert(parse_string("{foo}"), "");
   static_assert(parse_string("{:}"), "");
 }
+
 #endif  // FMT_USE_CONSTEXPR
 
 struct enabled_formatter {};
@@ -684,46 +710,46 @@ TEST(base_test, format_to) {
 TEST(base_test, format_to_array) {
   char buffer[4];
   auto result = fmt::format_to(buffer, "{}", 12345);
-  EXPECT_EQ(4, std::distance(&buffer[0], result.out));
+  EXPECT_EQ(std::distance(&buffer[0], result.out), 4);
   EXPECT_TRUE(result.truncated);
-  EXPECT_EQ(buffer + 4, result.out);
+  EXPECT_EQ(result.out, buffer + 4);
-  EXPECT_EQ("1234", fmt::string_view(buffer, 4));
+  EXPECT_EQ(fmt::string_view(buffer, 4), "1234");
 
   char* out = nullptr;
   EXPECT_THROW(out = result, std::runtime_error);
   (void)out;
 
   result = fmt::format_to(buffer, "{:s}", "foobar");
-  EXPECT_EQ(4, std::distance(&buffer[0], result.out));
+  EXPECT_EQ(std::distance(&buffer[0], result.out), 4);
   EXPECT_TRUE(result.truncated);
-  EXPECT_EQ(buffer + 4, result.out);
+  EXPECT_EQ(result.out, buffer + 4);
-  EXPECT_EQ("foob", fmt::string_view(buffer, 4));
+  EXPECT_EQ(fmt::string_view(buffer, 4), "foob");
 
   buffer[0] = 'x';
   buffer[1] = 'x';
   buffer[2] = 'x';
   buffer[3] = 'x';
   result = fmt::format_to(buffer, "{}", 'A');
-  EXPECT_EQ(1, std::distance(&buffer[0], result.out));
+  EXPECT_EQ(std::distance(&buffer[0], result.out), 1);
   EXPECT_FALSE(result.truncated);
-  EXPECT_EQ(buffer + 1, result.out);
+  EXPECT_EQ(result.out, buffer + 1);
-  EXPECT_EQ("Axxx", fmt::string_view(buffer, 4));
+  EXPECT_EQ(fmt::string_view(buffer, 4), "Axxx");
 
   result = fmt::format_to(buffer, "{}{} ", 'B', 'C');
-  EXPECT_EQ(3, std::distance(&buffer[0], result.out));
+  EXPECT_EQ(std::distance(&buffer[0], result.out), 3);
   EXPECT_FALSE(result.truncated);
-  EXPECT_EQ(buffer + 3, result.out);
+  EXPECT_EQ(result.out, buffer + 3);
-  EXPECT_EQ("BC x", fmt::string_view(buffer, 4));
+  EXPECT_EQ(fmt::string_view(buffer, 4), "BC x");
 
   result = fmt::format_to(buffer, "{}", "ABCDE");
-  EXPECT_EQ(4, std::distance(&buffer[0], result.out));
+  EXPECT_EQ(std::distance(&buffer[0], result.out), 4);
   EXPECT_TRUE(result.truncated);
-  EXPECT_EQ("ABCD", fmt::string_view(buffer, 4));
+  EXPECT_EQ(fmt::string_view(buffer, 4), "ABCD");
 
   result = fmt::format_to(buffer, "{}", std::string(1000, '*').c_str());
-  EXPECT_EQ(4, std::distance(&buffer[0], result.out));
+  EXPECT_EQ(std::distance(&buffer[0], result.out), 4);
   EXPECT_TRUE(result.truncated);
-  EXPECT_EQ("****", fmt::string_view(buffer, 4));
+  EXPECT_EQ(fmt::string_view(buffer, 4), "****");
 }
 
 // Test that check is not found by ADL.
@@ -790,7 +816,7 @@ TEST(base_test, format_nonconst) {
 }
 
 TEST(base_test, throw_in_buffer_dtor) {
-  enum { buffer_size = 256 };
+  constexpr int buffer_size = 256;
 
   struct throwing_iterator {
     int& count;
@@ -812,7 +838,7 @@ TEST(base_test, throw_in_buffer_dtor) {
   }
 }
 
-struct its_a_trap {
+struct convertible_to_any_type_with_member_x {
   template <typename T> operator T() const {
     auto v = T();
     v.x = 42;
@@ -821,12 +847,12 @@ struct its_a_trap {
 };
 
 FMT_BEGIN_NAMESPACE
-template <> struct formatter<its_a_trap> {
+template <> struct formatter<convertible_to_any_type_with_member_x> {
   FMT_CONSTEXPR auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
     return ctx.begin();
   }
 
-  auto format(its_a_trap, format_context& ctx) const
+  auto format(convertible_to_any_type_with_member_x, format_context& ctx) const
       -> decltype(ctx.out()) const {
     auto out = ctx.out();
     *out++ = 'x';
@@ -835,9 +861,10 @@ template <> struct formatter<its_a_trap> {
 };
 FMT_END_NAMESPACE
 
-TEST(base_test, trappy_conversion) {
+TEST(base_test, promiscuous_conversions) {
   auto s = std::string();
-  fmt::format_to(std::back_inserter(s), "{}", its_a_trap());
+  fmt::format_to(std::back_inserter(s), "{}",
+                 convertible_to_any_type_with_member_x());
   EXPECT_EQ(s, "x");
 }
 
@@ -846,11 +873,11 @@ struct custom_container {
 
   using value_type = char;
 
-  size_t size() const { return 0; }
+  auto size() const -> size_t { return 0; }
   void resize(size_t) {}
 
   void push_back(char) {}
-  char& operator[](size_t) { return data; }
+  auto operator[](size_t) -> char& { return data; }
 };
 
 FMT_BEGIN_NAMESPACE
@@ -862,16 +889,23 @@ TEST(base_test, format_to_custom_container) {
   fmt::format_to(std::back_inserter(c), "");
 }
 
-struct nondeterministic_format_string {
-  mutable int i = 0;
-  FMT_CONSTEXPR operator string_view() const {
-    return string_view("{}", i++ != 0 ? 2 : 0);
-  }
-};
-
 TEST(base_test, no_repeated_format_string_conversions) {
-#if !FMT_GCC_VERSION
+  struct nondeterministic_format_string {
+    mutable int i = 0;
+    FMT_CONSTEXPR operator fmt::string_view() const {
+      return {"{}", i++ != 0 ? 2u : 0u};
+    }
+  };
+
+#if !FMT_GCC_VERSION || FMT_GCC_VERSION >= 1200
   char buf[10];
   fmt::format_to(buf, nondeterministic_format_string());
 #endif
 }
+
+TEST(base_test, format_context_accessors) {
+  auto copy = [](fmt::appender app, const fmt::format_context& ctx) {
+    return fmt::format_context(app, ctx.args(), ctx.locale());
+  };
+  fmt::detail::ignore_unused(copy);
+}

test/chrono-test.cc

@@ -15,11 +15,9 @@
 #include "util.h"         // get_locale
 
 using fmt::runtime;
+using fmt::sys_time;
 using testing::Contains;
 
-template <typename Duration>
-using sys_time = std::chrono::time_point<std::chrono::system_clock, Duration>;
-
 #if defined(__MINGW32__) && !defined(_UCRT)
 // Only C89 conversion specifiers when using MSVCRT instead of UCRT
 #  define FMT_HAS_C99_STRFTIME 0
@@ -57,8 +55,8 @@ auto make_second(int s) -> std::tm {
   return time;
 }
 
-std::string system_strftime(const std::string& format, const std::tm* timeptr,
+auto system_strftime(const std::string& format, const std::tm* timeptr,
-                            std::locale* locptr = nullptr) {
+                     std::locale* locptr = nullptr) -> std::string {
   auto loc = locptr ? *locptr : std::locale::classic();
   auto& facet = std::use_facet<std::time_put<char>>(loc);
   std::ostringstream os;
@@ -75,8 +73,8 @@ std::string system_strftime(const std::string& format, const std::tm* timeptr,
 #endif
 }
 
-FMT_CONSTEXPR std::tm make_tm(int year, int mon, int mday, int hour, int min,
+FMT_CONSTEXPR auto make_tm(int year, int mon, int mday, int hour, int min,
-                              int sec) {
+                           int sec) -> std::tm {
   auto tm = std::tm();
   tm.tm_sec = sec;
   tm.tm_min = min;
@@ -240,196 +238,145 @@ TEST(chrono_test, format_to_empty_container) {
   EXPECT_EQ(s, "42");
 }
 
-TEST(chrono_test, empty_result) { EXPECT_EQ(fmt::format("{}", std::tm()), ""); }
-
-auto equal(const std::tm& lhs, const std::tm& rhs) -> bool {
-  return lhs.tm_sec == rhs.tm_sec && lhs.tm_min == rhs.tm_min &&
-         lhs.tm_hour == rhs.tm_hour && lhs.tm_mday == rhs.tm_mday &&
-         lhs.tm_mon == rhs.tm_mon && lhs.tm_year == rhs.tm_year &&
-         lhs.tm_wday == rhs.tm_wday && lhs.tm_yday == rhs.tm_yday &&
-         lhs.tm_isdst == rhs.tm_isdst;
-}
-
 TEST(chrono_test, gmtime) {
   auto t = std::time(nullptr);
-  auto tm = *std::gmtime(&t);
+  auto expected = *std::gmtime(&t);
-  EXPECT_TRUE(equal(tm, fmt::gmtime(t)));
+  auto actual = fmt::gmtime(t);
+  EXPECT_EQ(actual.tm_sec, expected.tm_sec);
+  EXPECT_EQ(actual.tm_min, expected.tm_min);
+  EXPECT_EQ(actual.tm_hour, expected.tm_hour);
+  EXPECT_EQ(actual.tm_mday, expected.tm_mday);
+  EXPECT_EQ(actual.tm_mon, expected.tm_mon);
+  EXPECT_EQ(actual.tm_year, expected.tm_year);
+  EXPECT_EQ(actual.tm_wday, expected.tm_wday);
+  EXPECT_EQ(actual.tm_yday, expected.tm_yday);
+  EXPECT_EQ(actual.tm_isdst, expected.tm_isdst);
 }
 
-template <typename TimePoint>
+template <typename Time> void test_time(Time time) {
-auto strftime_full_utc(TimePoint tp) -> std::string {
+  EXPECT_EQ(fmt::format("{}", time), "1979-03-12 12:00:00");
-  auto t = std::chrono::system_clock::to_time_t(tp);
+  EXPECT_EQ(fmt::format("{:}", time), "1979-03-12 12:00:00");
-  auto tm = *std::gmtime(&t);
+
-  return system_strftime("%Y-%m-%d %H:%M:%S", &tm);
+  EXPECT_EQ(fmt::format("{:%%}", time), "%");
+  EXPECT_EQ(fmt::format("{:%n}", time), "\n");
+  EXPECT_EQ(fmt::format("{:%t}", time), "\t");
+  EXPECT_EQ(fmt::format("{:%Y}", time), "1979");
+  EXPECT_EQ(fmt::format("{:%EY}", time), "1979");
+  EXPECT_EQ(fmt::format("{:%y}", time), "79");
+  EXPECT_EQ(fmt::format("{:%Oy}", time), "79");
+  EXPECT_EQ(fmt::format("{:%Ey}", time), "79");
+  EXPECT_EQ(fmt::format("{:%C}", time), "19");
+  EXPECT_EQ(fmt::format("{:%EC}", time), "19");
+  EXPECT_EQ(fmt::format("{:%G}", time), "1979");
+  EXPECT_EQ(fmt::format("{:%g}", time), "79");
+  EXPECT_EQ(fmt::format("{:%b}", time), "Mar");
+  EXPECT_EQ(fmt::format("{:%h}", time), "Mar");
+  EXPECT_EQ(fmt::format("{:%B}", time), "March");
+  EXPECT_EQ(fmt::format("{:%m}", time), "03");
+  EXPECT_EQ(fmt::format("{:%Om}", time), "03");
+  EXPECT_EQ(fmt::format("{:%U}", time), "10");
+  EXPECT_EQ(fmt::format("{:%OU}", time), "10");
+  EXPECT_EQ(fmt::format("{:%W}", time), "11");
+  EXPECT_EQ(fmt::format("{:%OW}", time), "11");
+  EXPECT_EQ(fmt::format("{:%V}", time), "11");
+  EXPECT_EQ(fmt::format("{:%OV}", time), "11");
+  EXPECT_EQ(fmt::format("{:%j}", time), "071");
+  EXPECT_EQ(fmt::format("{:%d}", time), "12");
+  EXPECT_EQ(fmt::format("{:%Od}", time), "12");
+  EXPECT_EQ(fmt::format("{:%e}", time), "12");
+  EXPECT_EQ(fmt::format("{:%Oe}", time), "12");
+  EXPECT_EQ(fmt::format("{:%a}", time), "Mon");
+  EXPECT_EQ(fmt::format("{:%A}", time), "Monday");
+  EXPECT_EQ(fmt::format("{:%w}", time), "1");
+  EXPECT_EQ(fmt::format("{:%Ow}", time), "1");
+  EXPECT_EQ(fmt::format("{:%u}", time), "1");
+  EXPECT_EQ(fmt::format("{:%Ou}", time), "1");
+  EXPECT_EQ(fmt::format("{:%H}", time), "12");
+  EXPECT_EQ(fmt::format("{:%OH}", time), "12");
+  EXPECT_EQ(fmt::format("{:%I}", time), "12");
+  EXPECT_EQ(fmt::format("{:%OI}", time), "12");
+  EXPECT_EQ(fmt::format("{:%M}", time), "00");
+  EXPECT_EQ(fmt::format("{:%OM}", time), "00");
+  EXPECT_EQ(fmt::format("{:%S}", time), "00");
+  EXPECT_EQ(fmt::format("{:%OS}", time), "00");
+  EXPECT_EQ(fmt::format("{:%x}", time), "03/12/79");
+  EXPECT_EQ(fmt::format("{:%Ex}", time), "03/12/79");
+  EXPECT_EQ(fmt::format("{:%X}", time), "12:00:00");
+  EXPECT_EQ(fmt::format("{:%EX}", time), "12:00:00");
+  EXPECT_EQ(fmt::format("{:%D}", time), "03/12/79");
+  EXPECT_EQ(fmt::format("{:%F}", time), "1979-03-12");
+  EXPECT_EQ(fmt::format("{:%R}", time), "12:00");
+  EXPECT_EQ(fmt::format("{:%T}", time), "12:00:00");
+  EXPECT_EQ(fmt::format("{:%p}", time), "PM");
+  EXPECT_EQ(fmt::format("{:%c}", time), "Mon Mar 12 12:00:00 1979");
+  EXPECT_EQ(fmt::format("{:%Ec}", time), "Mon Mar 12 12:00:00 1979");
+  EXPECT_EQ(fmt::format("{:%r}", time), "12:00:00 PM");
+
+  EXPECT_EQ(fmt::format("{:%Y-%m-%d %H:%M:%S}", time), "1979-03-12 12:00:00");
 }
 
-TEST(chrono_test, system_clock_time_point) {
+TEST(chrono_test, sys_time) {
-  auto t1 = std::chrono::time_point_cast<std::chrono::seconds>(
+  auto time =
-      std::chrono::system_clock::now());
+      fmt::sys_time<std::chrono::seconds>(std::chrono::seconds(290088000));
-  EXPECT_EQ(strftime_full_utc(t1), fmt::format("{:%Y-%m-%d %H:%M:%S}", t1));
+  test_time(time);
-  EXPECT_EQ(strftime_full_utc(t1), fmt::format("{}", t1));
+  EXPECT_EQ(fmt::format("{:%z}", time), "+0000");
-  EXPECT_EQ(strftime_full_utc(t1), fmt::format("{:}", t1));
+  EXPECT_EQ(fmt::format("{:%Ez}", time), "+00:00");
+  EXPECT_EQ(fmt::format("{:%Oz}", time), "+00:00");
+  EXPECT_EQ(fmt::format("{:%Z}", time), "UTC");
+}
 
-  auto t2 = sys_time<std::chrono::seconds>(std::chrono::seconds(42));
+TEST(chrono_test, local_time) {
-  EXPECT_EQ(strftime_full_utc(t2), fmt::format("{:%Y-%m-%d %H:%M:%S}", t2));
+  auto time =
+      fmt::local_time<std::chrono::seconds>(std::chrono::seconds(290088000));
+  test_time(time);
+  EXPECT_THROW_MSG((void)fmt::format(fmt::runtime("{:%z}"), time),
+                   fmt::format_error, "no timezone");
+  EXPECT_THROW_MSG((void)fmt::format(fmt::runtime("{:%Z}"), time),
+                   fmt::format_error, "no timezone");
+}
 
-  std::vector<std::string> spec_list = {
+template <typename T, FMT_ENABLE_IF(fmt::detail::has_tm_gmtoff<T>::value)>
-      "%%",  "%n",  "%t",  "%Y",  "%EY", "%y",  "%Oy", "%Ey", "%C",
+auto set_tm_gmtoff(T& time, long offset) -> bool {
-      "%EC", "%G",  "%g",  "%b",  "%h",  "%B",  "%m",  "%Om", "%U",
+  time.tm_gmtoff = offset;
-      "%OU", "%W",  "%OW", "%V",  "%OV", "%j",  "%d",  "%Od", "%e",
+  return true;
-      "%Oe", "%a",  "%A",  "%w",  "%Ow", "%u",  "%Ou", "%H",  "%OH",
+}
-      "%I",  "%OI", "%M",  "%OM", "%S",  "%OS", "%x",  "%Ex", "%X",
+template <typename T, FMT_ENABLE_IF(!fmt::detail::has_tm_gmtoff<T>::value)>
-      "%EX", "%D",  "%F",  "%R",  "%T",  "%p"};
+auto set_tm_gmtoff(T&, long) -> bool {
-#ifndef _WIN32
+  return false;
-  // Disabled on Windows because these formats are not consistent among
+}
-  // platforms.
-  spec_list.insert(spec_list.end(), {"%c", "%Ec", "%r"});
-#elif !FMT_HAS_C99_STRFTIME
-  // Only C89 conversion specifiers when using MSVCRT instead of UCRT
-  spec_list = {"%%", "%Y", "%y", "%b", "%B", "%m", "%U", "%W", "%j", "%d",
-               "%a", "%A", "%w", "%H", "%I", "%M", "%S", "%x", "%X", "%p"};
-#endif
-  spec_list.push_back("%Y-%m-%d %H:%M:%S");
 
-  for (const auto& spec : spec_list) {
+TEST(chrono_test, tm) {
-    auto t = std::chrono::system_clock::to_time_t(t1);
+  auto time = fmt::gmtime(290088000);
-    auto tm = *std::gmtime(&t);
+  test_time(time);
-
+  if (set_tm_gmtoff(time, -28800)) {
-    auto sys_output = system_strftime(spec, &tm);
+    EXPECT_EQ(fmt::format(fmt::runtime("{:%z}"), time), "-0800");
-
+    EXPECT_EQ(fmt::format(fmt::runtime("{:%Ez}"), time), "-08:00");
-    auto fmt_spec = fmt::format("{{:{}}}", spec);
+    EXPECT_EQ(fmt::format(fmt::runtime("{:%Oz}"), time), "-08:00");
-    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), t1));
+  } else {
-    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
+    EXPECT_THROW_MSG((void)fmt::format(fmt::runtime("{:%z}"), time),
+                     fmt::format_error, "no timezone");
   }
-
+  char tz[] = "EET";
-  // Timezone formatters tests makes sense for localtime.
+  if (fmt::detail::set_tm_zone(time, tz)) {
-#if FMT_HAS_C99_STRFTIME
+    EXPECT_EQ(fmt::format(fmt::runtime("{:%Z}"), time), "EET");
-  spec_list = {"%z", "%Z"};
+  } else {
-#else
+    EXPECT_THROW_MSG((void)fmt::format(fmt::runtime("{:%Z}"), time),
-  spec_list = {"%Z"};
+                     fmt::format_error, "no timezone");
-#endif
-  for (const auto& spec : spec_list) {
-    auto t = std::chrono::system_clock::to_time_t(t1);
-    auto tm = *std::localtime(&t);
-
-    auto sys_output = system_strftime(spec, &tm);
-
-    auto fmt_spec = fmt::format("{{:{}}}", spec);
-    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
-
-    if (spec == "%z") {
-      sys_output.insert(sys_output.end() - 2, 1, ':');
-      EXPECT_EQ(sys_output, fmt::format("{:%Ez}", tm));
-      EXPECT_EQ(sys_output, fmt::format("{:%Oz}", tm));
-    }
-  }
-
-  // Separate tests for UTC, since std::time_put can use local time and ignoring
-  // the timezone in std::tm (if it presents on platform).
-  if (fmt::detail::has_member_data_tm_zone<std::tm>::value) {
-    auto t = std::chrono::system_clock::to_time_t(t1);
-    auto tm = *std::gmtime(&t);
-
-    std::vector<std::string> tz_names = {"GMT", "UTC"};
-    EXPECT_THAT(tz_names, Contains(fmt::format("{:%Z}", t1)));
-    EXPECT_THAT(tz_names, Contains(fmt::format("{:%Z}", tm)));
-  }
-
-  if (fmt::detail::has_member_data_tm_gmtoff<std::tm>::value) {
-    auto t = std::chrono::system_clock::to_time_t(t1);
-    auto tm = *std::gmtime(&t);
-
-    EXPECT_EQ(fmt::format("{:%z}", t1), "+0000");
-    EXPECT_EQ(fmt::format("{:%z}", tm), "+0000");
-
-    EXPECT_EQ(fmt::format("{:%Ez}", t1), "+00:00");
-    EXPECT_EQ(fmt::format("{:%Ez}", tm), "+00:00");
-
-    EXPECT_EQ(fmt::format("{:%Oz}", t1), "+00:00");
-    EXPECT_EQ(fmt::format("{:%Oz}", tm), "+00:00");
   }
 }
 
-#if FMT_USE_LOCAL_TIME
+TEST(chrono_test, daylight_savings_time_end) {
-
+  // 2024-10-27 03:05 as the number of seconds since epoch in Europe/Kyiv time.
-TEST(chrono_test, localtime) {
+  // It is slightly after the DST end and passing it to to_sys will result in
-  auto t = std::time(nullptr);
+  // an ambiguous time error:
-  auto tm = *std::localtime(&t);
+  //   2024-10-27 03:05:00 is ambiguous.  It could be
-  EXPECT_TRUE(equal(tm, fmt::localtime(t)));
+  //   2024-10-27 03:05:00 EEST == 2024-10-27 00:05:00 UTC or
+  //   2024-10-27 03:05:00 EET == 2024-10-27 01:05:00 UTC
+  auto t =
+      fmt::local_time<std::chrono::seconds>(std::chrono::seconds(1729998300));
+  EXPECT_EQ(fmt::format("{}", t), "2024-10-27 03:05:00");
 }
 
-template <typename Duration>
-auto strftime_full_local(std::chrono::local_time<Duration> tp) -> std::string {
-  auto t = std::chrono::system_clock::to_time_t(
-      std::chrono::current_zone()->to_sys(tp));
-  auto tm = *std::localtime(&t);
-  return system_strftime("%Y-%m-%d %H:%M:%S", &tm);
-}
-
-TEST(chrono_test, local_system_clock_time_point) {
-#  ifdef _WIN32
-  return;  // Not supported on Windows.
-#  endif
-  auto t1 = std::chrono::time_point_cast<std::chrono::seconds>(
-      std::chrono::current_zone()->to_local(std::chrono::system_clock::now()));
-  EXPECT_EQ(strftime_full_local(t1), fmt::format("{:%Y-%m-%d %H:%M:%S}", t1));
-  EXPECT_EQ(strftime_full_local(t1), fmt::format("{}", t1));
-  EXPECT_EQ(strftime_full_local(t1), fmt::format("{:}", t1));
-  using time_point = std::chrono::local_time<std::chrono::seconds>;
-  auto t2 = time_point(std::chrono::seconds(86400 + 42));
-  EXPECT_EQ(strftime_full_local(t2), fmt::format("{:%Y-%m-%d %H:%M:%S}", t2));
-
-  std::vector<std::string> spec_list = {
-      "%%",  "%n",  "%t",  "%Y",  "%EY", "%y",  "%Oy", "%Ey", "%C",
-      "%EC", "%G",  "%g",  "%b",  "%h",  "%B",  "%m",  "%Om", "%U",
-      "%OU", "%W",  "%OW", "%V",  "%OV", "%j",  "%d",  "%Od", "%e",
-      "%Oe", "%a",  "%A",  "%w",  "%Ow", "%u",  "%Ou", "%H",  "%OH",
-      "%I",  "%OI", "%M",  "%OM", "%S",  "%OS", "%x",  "%Ex", "%X",
-      "%EX", "%D",  "%F",  "%R",  "%T",  "%p",  "%z",  "%Z"};
-#  ifndef _WIN32
-  // Disabled on Windows because these formats are not consistent among
-  // platforms.
-  spec_list.insert(spec_list.end(), {"%c", "%Ec", "%r"});
-#  elif !FMT_HAS_C99_STRFTIME
-  // Only C89 conversion specifiers when using MSVCRT instead of UCRT
-  spec_list = {"%%", "%Y", "%y", "%b", "%B", "%m", "%U", "%W", "%j", "%d", "%a",
-               "%A", "%w", "%H", "%I", "%M", "%S", "%x", "%X", "%p", "%Z"};
-#  endif
-  spec_list.push_back("%Y-%m-%d %H:%M:%S");
-
-  for (const auto& spec : spec_list) {
-    auto t = std::chrono::system_clock::to_time_t(
-        std::chrono::current_zone()->to_sys(t1));
-    auto tm = *std::localtime(&t);
-
-    auto sys_output = system_strftime(spec, &tm);
-
-    auto fmt_spec = fmt::format("{{:{}}}", spec);
-    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), t1));
-    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
-  }
-
-  if (std::find(spec_list.cbegin(), spec_list.cend(), "%z") !=
-      spec_list.cend()) {
-    auto t = std::chrono::system_clock::to_time_t(
-        std::chrono::current_zone()->to_sys(t1));
-    auto tm = *std::localtime(&t);
-
-    auto sys_output = system_strftime("%z", &tm);
-    sys_output.insert(sys_output.end() - 2, 1, ':');
-
-    EXPECT_EQ(sys_output, fmt::format("{:%Ez}", t1));
-    EXPECT_EQ(sys_output, fmt::format("{:%Ez}", tm));
-
-    EXPECT_EQ(sys_output, fmt::format("{:%Oz}", t1));
-    EXPECT_EQ(sys_output, fmt::format("{:%Oz}", tm));
-  }
-}
-
-#endif  // FMT_USE_LOCAL_TIME
-
-#ifndef FMT_STATIC_THOUSANDS_SEPARATOR
-
 TEST(chrono_test, format_default) {
   EXPECT_EQ(fmt::format("{}", std::chrono::seconds(42)), "42s");
   EXPECT_EQ(fmt::format("{}", std::chrono::duration<int, std::atto>(42)),
@@ -606,12 +553,12 @@ auto format_tm(const std::tm& time, fmt::string_view spec,
 TEST(chrono_test, locale) {
   auto loc = get_locale("ja_JP.utf8");
   if (loc == std::locale::classic()) return;
-#  define EXPECT_TIME(spec, time, duration)                     \
+#define EXPECT_TIME(spec, time, duration)                     \
-    {                                                           \
+  {                                                           \
-      auto jp_loc = std::locale("ja_JP.utf8");                  \
+    auto jp_loc = std::locale("ja_JP.utf8");                  \
-      EXPECT_EQ(format_tm(time, spec, jp_loc),                  \
+    EXPECT_EQ(format_tm(time, spec, jp_loc),                  \
-                fmt::format(jp_loc, "{:L" spec "}", duration)); \
+              fmt::format(jp_loc, "{:L" spec "}", duration)); \
-    }
+  }
   EXPECT_TIME("%OH", make_hour(14), std::chrono::hours(14));
   EXPECT_TIME("%OI", make_hour(14), std::chrono::hours(14));
   EXPECT_TIME("%OM", make_minute(42), std::chrono::minutes(42));
@@ -766,8 +713,8 @@ TEST(chrono_test, weekday) {
   if (loc != std::locale::classic()) {
     auto saturdays = std::vector<std::string>{"sáb", "sá.", "sáb."};
     EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:L}", sat)));
-    EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:%a}", sat)));
+    EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:L%a}", sat)));
-    EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:%a}", tm)));
+    EXPECT_THAT(saturdays, Contains(fmt::format(loc, "{:L%a}", tm)));
   }
 }
 
@@ -817,11 +764,11 @@ TEST(chrono_test, cpp20_duration_subsecond_support) {
     EXPECT_EQ(fmt::format("{:.6%H:%M:%S}", dur), "01:00:01.234000");
   }
   using nanoseconds_dbl = std::chrono::duration<double, std::nano>;
-  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl{-123456789}), "-00.123456789");
+  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl(-123456789)), "-00.123456789");
-  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl{9123456789}), "09.123456789");
+  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl(9123456789)), "09.123456789");
   // Verify that only the seconds part is extracted and printed.
-  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl{99123456789}), "39.123456789");
+  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl(99123456789)), "39.123456789");
-  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl{99123000000}), "39.123000000");
+  EXPECT_EQ(fmt::format("{:%S}", nanoseconds_dbl(99123000000)), "39.123000000");
   {
     // Now the hour is printed, and we also test if negative doubles work.
     auto dur = nanoseconds_dbl{-99123456789};
@@ -832,7 +779,7 @@ TEST(chrono_test, cpp20_duration_subsecond_support) {
   }
   // Check that durations with precision greater than std::chrono::seconds have
   // fixed precision, and print zeros even if there is no fractional part.
-  EXPECT_EQ(fmt::format("{:%S}", std::chrono::microseconds{7000000}),
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::microseconds(7000000)),
             "07.000000");
   EXPECT_EQ(fmt::format("{:%S}",
                         std::chrono::duration<long long, std::ratio<1, 3>>(1)),
@@ -852,14 +799,12 @@ TEST(chrono_test, cpp20_duration_subsecond_support) {
       "-05:27.68");
 
   // Check that floating point seconds with ratio<1,1> are printed.
-  EXPECT_EQ(fmt::format("{:%S}", std::chrono::duration<double>{1.5}),
+  EXPECT_EQ(fmt::format("{:%S}", std::chrono::duration<double>(1.5)),
             "01.500000");
-  EXPECT_EQ(fmt::format("{:%M:%S}", std::chrono::duration<double>{-61.25}),
+  EXPECT_EQ(fmt::format("{:%M:%S}", std::chrono::duration<double>(-61.25)),
             "-01:01.250000");
 }
 
-#endif  // FMT_STATIC_THOUSANDS_SEPARATOR
-
 // Disable the utc_clock test for windows, as the icu.dll used for tzdb
 // (time zone database) is not shipped with many windows versions.
 #if FMT_USE_UTC_TIME && !defined(_WIN32)
@@ -932,19 +877,11 @@ TEST(chrono_test, timestamp_sub_seconds) {
   auto t8 =
       sys_time<std::chrono::nanoseconds>(std::chrono::nanoseconds(123456789));
   EXPECT_EQ(fmt::format("{:%S}", t8), "00.123456789");
+  EXPECT_EQ(fmt::format("{:%T}", t8), "00:00:00.123456789");
 
-  auto t9 = std::chrono::time_point_cast<std::chrono::nanoseconds>(
+  auto t9 =
-      std::chrono::system_clock::now());
-  auto t9_sec = std::chrono::time_point_cast<std::chrono::seconds>(t9);
-  auto t9_sub_sec_part = fmt::format("{0:09}", (t9 - t9_sec).count());
-  EXPECT_EQ(fmt::format("{}.{}", strftime_full_utc(t9_sec), t9_sub_sec_part),
-            fmt::format("{:%Y-%m-%d %H:%M:%S}", t9));
-  EXPECT_EQ(fmt::format("{}.{}", strftime_full_utc(t9_sec), t9_sub_sec_part),
-            fmt::format("{:%Y-%m-%d %T}", t9));
-
-  auto t10 =
       sys_time<std::chrono::milliseconds>(std::chrono::milliseconds(2000));
-  EXPECT_EQ(fmt::format("{:%S}", t10), "02.000");
+  EXPECT_EQ(fmt::format("{:%S}", t9), "02.000");
 
   auto epoch = sys_time<std::chrono::milliseconds>();
   auto d = std::chrono::milliseconds(250);
@@ -1033,7 +970,7 @@ TEST(chrono_test, glibc_extensions) {
   {
     auto t = std::tm();
     t.tm_year = -5 - 1900;
-    EXPECT_EQ(fmt::format( "{:%Y}", t), "-005");
+    EXPECT_EQ(fmt::format("{:%Y}", t), "-005");
     EXPECT_EQ(fmt::format("{:%_Y}", t), "  -5");
     EXPECT_EQ(fmt::format("{:%-Y}", t), "-5");
   }
@@ -1045,8 +982,6 @@ TEST(chrono_test, glibc_extensions) {
     EXPECT_EQ(fmt::format("{:%_m}", t), " 7");
     EXPECT_EQ(fmt::format("{:%-m}", t), "7");
   }
-
-
 }
 
 TEST(chrono_test, out_of_range) {
@@ -1083,6 +1018,6 @@ TEST(chrono_test, year_month_day) {
   if (loc != std::locale::classic()) {
     auto months = std::vector<std::string>{"ene.", "ene"};
     EXPECT_THAT(months, Contains(fmt::format(loc, "{:L}", month)));
-    EXPECT_THAT(months, Contains(fmt::format(loc, "{:%b}", month)));
+    EXPECT_THAT(months, Contains(fmt::format(loc, "{:L%b}", month)));
   }
 }

test/color-test.cc

@@ -9,11 +9,68 @@
 
 #include <iterator>  // std::back_inserter
 
-#include "gtest-extra.h"  // EXPECT_WRITE
+#include "gtest-extra.h"  // EXPECT_WRITE, EXPECT_THROW_MSG
+
+TEST(color_test, text_style) {
+  EXPECT_FALSE(fmt::text_style().has_foreground());
+  EXPECT_FALSE(fmt::text_style().has_background());
+  EXPECT_FALSE(fmt::text_style().has_emphasis());
+
+  EXPECT_TRUE(fg(fmt::rgb(0)).has_foreground());
+  EXPECT_FALSE(fg(fmt::rgb(0)).has_background());
+  EXPECT_FALSE(fg(fmt::rgb(0)).has_emphasis());
+  EXPECT_TRUE(bg(fmt::rgb(0)).has_background());
+  EXPECT_FALSE(bg(fmt::rgb(0)).has_foreground());
+  EXPECT_FALSE(bg(fmt::rgb(0)).has_emphasis());
+
+  EXPECT_TRUE(
+      (fg(fmt::rgb(0xFFFFFF)) | bg(fmt::rgb(0xFFFFFF))).has_foreground());
+  EXPECT_TRUE(
+      (fg(fmt::rgb(0xFFFFFF)) | bg(fmt::rgb(0xFFFFFF))).has_background());
+  EXPECT_FALSE(
+      (fg(fmt::rgb(0xFFFFFF)) | bg(fmt::rgb(0xFFFFFF))).has_emphasis());
+
+  EXPECT_EQ(fg(fmt::rgb(0x000000)) | fg(fmt::rgb(0x000000)),
+            fg(fmt::rgb(0x000000)));
+  EXPECT_EQ(fg(fmt::rgb(0x00000F)) | fg(fmt::rgb(0x00000F)),
+            fg(fmt::rgb(0x00000F)));
+  EXPECT_EQ(fg(fmt::rgb(0xC0F000)) | fg(fmt::rgb(0x000FEE)),
+            fg(fmt::rgb(0xC0FFEE)));
+
+  EXPECT_THROW_MSG(
+      fg(fmt::terminal_color::black) | fg(fmt::terminal_color::black),
+      fmt::format_error, "can't OR a terminal color");
+  EXPECT_THROW_MSG(
+      fg(fmt::terminal_color::black) | fg(fmt::terminal_color::white),
+      fmt::format_error, "can't OR a terminal color");
+  EXPECT_THROW_MSG(
+      bg(fmt::terminal_color::black) | bg(fmt::terminal_color::black),
+      fmt::format_error, "can't OR a terminal color");
+  EXPECT_THROW_MSG(
+      bg(fmt::terminal_color::black) | bg(fmt::terminal_color::white),
+      fmt::format_error, "can't OR a terminal color");
+  EXPECT_THROW_MSG(fg(fmt::terminal_color::black) | fg(fmt::color::black),
+                   fmt::format_error, "can't OR a terminal color");
+  EXPECT_THROW_MSG(bg(fmt::terminal_color::black) | bg(fmt::color::black),
+                   fmt::format_error, "can't OR a terminal color");
+
+  EXPECT_NO_THROW(fg(fmt::terminal_color::white) |
+                  bg(fmt::terminal_color::white));
+  EXPECT_NO_THROW(fg(fmt::terminal_color::white) | bg(fmt::rgb(0xFFFFFF)));
+  EXPECT_NO_THROW(fg(fmt::terminal_color::white) | fmt::text_style());
+  EXPECT_NO_THROW(bg(fmt::terminal_color::white) | fmt::text_style());
+}
 
 TEST(color_test, format) {
+  EXPECT_EQ(fmt::format(fmt::text_style(), "no style"), "no style");
   EXPECT_EQ(fmt::format(fg(fmt::rgb(255, 20, 30)), "rgb(255,20,30)"),
             "\x1b[38;2;255;020;030mrgb(255,20,30)\x1b[0m");
+  EXPECT_EQ(fmt::format(fg(fmt::rgb(255, 0, 0)) | fg(fmt::rgb(0, 20, 30)),
+                        "rgb(255,20,30)"),
+            "\x1b[38;2;255;020;030mrgb(255,20,30)\x1b[0m");
+  EXPECT_EQ(
+      fmt::format(fg(fmt::rgb(0, 0, 0)) | fg(fmt::rgb(0, 0, 0)), "rgb(0,0,0)"),
+      "\x1b[38;2;000;000;000mrgb(0,0,0)\x1b[0m");
   EXPECT_EQ(fmt::format(fg(fmt::color::blue), "blue"),
             "\x1b[38;2;000;000;255mblue\x1b[0m");
   EXPECT_EQ(
@@ -56,6 +113,15 @@ TEST(color_test, format) {
   EXPECT_EQ(fmt::format("{}", fmt::styled("bar", fg(fmt::color::blue) |
                                                      fmt::emphasis::underline)),
             "\x1b[4m\x1b[38;2;000;000;255mbar\x1b[0m");
+  EXPECT_EQ(
+      fmt::format(
+          "{}", fmt::styled(
+                    "all", fmt::emphasis::bold | fmt::emphasis::faint |
+                               fmt::emphasis::italic |
+                               fmt::emphasis::underline | fmt::emphasis::blink |
+                               fmt::emphasis::reverse | fmt::emphasis::conceal |
+                               fmt::emphasis::strikethrough)),
+      "\x1b[1;2;3;4;5;7;8;9mall\x1b[0m");
 }
 
 TEST(color_test, format_to) {

test/compile-fp-test.cc

@@ -1,61 +0,0 @@
-// Formatting library for C++ - formatting library tests
-//
-// Copyright (c) 2012 - present, Victor Zverovich
-// All rights reserved.
-//
-// For the license information refer to format.h.
-
-#include "fmt/compile.h"
-#include "gmock/gmock.h"
-
-#if FMT_USE_CONSTEVAL
-
-template <size_t max_string_length, typename Char = char> struct test_string {
-  template <typename T> constexpr bool operator==(const T& rhs) const noexcept {
-    return fmt::basic_string_view<Char>(rhs).compare(buffer) == 0;
-  }
-  Char buffer[max_string_length]{};
-};
-
-template <size_t max_string_length, typename Char = char, typename... Args>
-consteval auto test_format(auto format, const Args&... args) {
-  test_string<max_string_length, Char> string{};
-  fmt::format_to(string.buffer, format, args...);
-  return string;
-}
-
-TEST(compile_time_formatting_test, floating_point) {
-  EXPECT_EQ("0", test_format<2>(FMT_COMPILE("{}"), 0.0f));
-  EXPECT_EQ("392.500000", test_format<11>(FMT_COMPILE("{0:f}"), 392.5f));
-
-  EXPECT_EQ("0", test_format<2>(FMT_COMPILE("{:}"), 0.0));
-  EXPECT_EQ("0.000000", test_format<9>(FMT_COMPILE("{:f}"), 0.0));
-  EXPECT_EQ("0", test_format<2>(FMT_COMPILE("{:g}"), 0.0));
-  EXPECT_EQ("392.65", test_format<7>(FMT_COMPILE("{:}"), 392.65));
-  EXPECT_EQ("392.65", test_format<7>(FMT_COMPILE("{:g}"), 392.65));
-  EXPECT_EQ("392.65", test_format<7>(FMT_COMPILE("{:G}"), 392.65));
-  EXPECT_EQ("4.9014e+06", test_format<11>(FMT_COMPILE("{:g}"), 4.9014e6));
-  EXPECT_EQ("-392.650000", test_format<12>(FMT_COMPILE("{:f}"), -392.65));
-  EXPECT_EQ("-392.650000", test_format<12>(FMT_COMPILE("{:F}"), -392.65));
-
-  EXPECT_EQ("3.926500e+02", test_format<13>(FMT_COMPILE("{0:e}"), 392.65));
-  EXPECT_EQ("3.926500E+02", test_format<13>(FMT_COMPILE("{0:E}"), 392.65));
-  EXPECT_EQ("+0000392.6", test_format<11>(FMT_COMPILE("{0:+010.4g}"), 392.65));
-  EXPECT_EQ("9223372036854775808.000000",
-            test_format<27>(FMT_COMPILE("{:f}"), 9223372036854775807.0));
-
-  constexpr double nan = std::numeric_limits<double>::quiet_NaN();
-  EXPECT_EQ("nan", test_format<4>(FMT_COMPILE("{}"), nan));
-  EXPECT_EQ("+nan", test_format<5>(FMT_COMPILE("{:+}"), nan));
-  if (std::signbit(-nan))
-    EXPECT_EQ("-nan", test_format<5>(FMT_COMPILE("{}"), -nan));
-  else
-    fmt::print("Warning: compiler doesn't handle negative NaN correctly");
-
-  constexpr double inf = std::numeric_limits<double>::infinity();
-  EXPECT_EQ("inf", test_format<4>(FMT_COMPILE("{}"), inf));
-  EXPECT_EQ("+inf", test_format<5>(FMT_COMPILE("{:+}"), inf));
-  EXPECT_EQ("-inf", test_format<5>(FMT_COMPILE("{}"), -inf));
-}
-
-#endif  // FMT_USE_CONSTEVAL

test/compile-test.cc

@@ -7,6 +7,8 @@
 
 #include "fmt/compile.h"
 
+#include <iterator>
+#include <list>
 #include <type_traits>
 #include <vector>
 
@@ -88,9 +90,6 @@ TEST(compile_test, format_escape) {
   EXPECT_EQ("\"abc\"  ", fmt::format(FMT_COMPILE("{0:<7?}"), "abc"));
 }
 
-TEST(compile_test, format_wide_string) {
-  EXPECT_EQ(L"42", fmt::format(FMT_COMPILE(L"{}"), 42));
-}
 
 TEST(compile_test, format_specs) {
   EXPECT_EQ("42", fmt::format(FMT_COMPILE("{:x}"), 0x42));
@@ -122,7 +121,6 @@ TEST(compile_test, manual_ordering) {
       "true 42 42 foo 0x1234 foo",
       fmt::format(FMT_COMPILE("{0} {1} {2} {3} {4} {5}"), true, 42, 42.0f,
                   "foo", reinterpret_cast<void*>(0x1234), test_formattable()));
-  EXPECT_EQ(L"42", fmt::format(FMT_COMPILE(L"{0}"), 42));
 }
 
 TEST(compile_test, named) {
@@ -131,10 +129,6 @@ TEST(compile_test, named) {
   static_assert(std::is_same_v<decltype(runtime_named_field_compiled),
                                fmt::detail::runtime_named_field<char>>);
 
-  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), fmt::arg("arg", 42)));
-  EXPECT_EQ("41 43", fmt::format(FMT_COMPILE("{} {}"), fmt::arg("arg", 41),
-                                 fmt::arg("arg", 43)));
-
   EXPECT_EQ("foobar",
             fmt::format(FMT_COMPILE("{a0}{a1}"), fmt::arg("a0", "foo"),
                         fmt::arg("a1", "bar")));
@@ -199,6 +193,21 @@ TEST(compile_test, format_to_n) {
   EXPECT_STREQ("2a", buffer);
 }
 
+TEST(compile_test, output_iterators) {
+  std::list<char> out;
+  fmt::format_to(std::back_inserter(out), FMT_COMPILE("{}"), 42);
+  EXPECT_EQ("42", std::string(out.begin(), out.end()));
+
+  std::stringstream s;
+  fmt::format_to(std::ostream_iterator<char>(s), FMT_COMPILE("{}"), 42);
+  EXPECT_EQ("42", s.str());
+
+  std::stringstream s2;
+  fmt::format_to(std::ostreambuf_iterator<char>(s2), FMT_COMPILE("{}.{:06d}"),
+                 42, 43);
+  EXPECT_EQ("42.000043", s2.str());
+}
+
 #  if FMT_USE_CONSTEVAL && (!FMT_MSC_VERSION || FMT_MSC_VERSION >= 1940)
 TEST(compile_test, constexpr_formatted_size) {
   FMT_CONSTEXPR20 size_t size = fmt::formatted_size(FMT_COMPILE("{}"), 42);
@@ -219,6 +228,12 @@ TEST(compile_test, constexpr_formatted_size) {
       fmt::formatted_size(FMT_COMPILE("{:s}"), "abc");
   EXPECT_EQ(str_size, 3);
 }
+
+TEST(compile_test, static_format) {
+  constexpr auto result = FMT_STATIC_FORMAT("{}", 42);
+  EXPECT_STREQ(result.c_str(), "42");
+  EXPECT_EQ(result.str(), "42");
+}
 #  endif
 
 TEST(compile_test, text_and_arg) {
@@ -295,7 +310,17 @@ TEST(compile_test, compile_format_string_literal) {
   using namespace fmt::literals;
   EXPECT_EQ("", fmt::format(""_cf));
   EXPECT_EQ("42", fmt::format("{}"_cf, 42));
-  EXPECT_EQ(L"42", fmt::format(L"{}"_cf, 42));
+}
+#endif
+
+#if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
+template <typename S> auto check_is_compiled_string(const S&) -> bool {
+  return fmt::is_compiled_string<S>::value;
+}
+
+TEST(compile_test, is_compiled_string) {
+  EXPECT_TRUE(check_is_compiled_string(FMT_COMPILE("asdf")));
+  EXPECT_TRUE(check_is_compiled_string(FMT_COMPILE("{}")));
 }
 #endif
 
@@ -310,7 +335,7 @@ TEST(compile_test, compile_format_string_literal) {
      (FMT_MSC_VERSION >= 1928 && FMT_MSC_VERSION < 1930)) && \
     defined(__cpp_lib_is_constant_evaluated)
 template <size_t max_string_length, typename Char = char> struct test_string {
-  template <typename T> constexpr bool operator==(const T& rhs) const noexcept {
+  template <typename T> constexpr auto operator==(const T& rhs) const -> bool {
     return fmt::basic_string_view<Char>(rhs).compare(buffer) == 0;
   }
   Char buffer[max_string_length]{};
@@ -392,4 +417,53 @@ TEST(compile_time_formatting_test, custom_type) {
 TEST(compile_time_formatting_test, multibyte_fill) {
   EXPECT_EQ("жж42", test_format<8>(FMT_COMPILE("{:ж>4}"), 42));
 }
+
+TEST(compile_time_formatting_test, floating_point) {
+  EXPECT_EQ("0", test_format<2>(FMT_COMPILE("{}"), 0.0f));
+  EXPECT_EQ("392.500000", test_format<11>(FMT_COMPILE("{0:f}"), 392.5f));
+
+  EXPECT_EQ("0", test_format<2>(FMT_COMPILE("{:}"), 0.0));
+  EXPECT_EQ("0.000000", test_format<9>(FMT_COMPILE("{:f}"), 0.0));
+  EXPECT_EQ("0", test_format<2>(FMT_COMPILE("{:g}"), 0.0));
+  EXPECT_EQ("392.65", test_format<7>(FMT_COMPILE("{:}"), 392.65));
+  EXPECT_EQ("392.65", test_format<7>(FMT_COMPILE("{:g}"), 392.65));
+  EXPECT_EQ("392.65", test_format<7>(FMT_COMPILE("{:G}"), 392.65));
+  EXPECT_EQ("4.9014e+06", test_format<11>(FMT_COMPILE("{:g}"), 4.9014e6));
+  EXPECT_EQ("-392.650000", test_format<12>(FMT_COMPILE("{:f}"), -392.65));
+  EXPECT_EQ("-392.650000", test_format<12>(FMT_COMPILE("{:F}"), -392.65));
+
+  EXPECT_EQ("3.926500e+02", test_format<13>(FMT_COMPILE("{0:e}"), 392.65));
+  EXPECT_EQ("3.926500E+02", test_format<13>(FMT_COMPILE("{0:E}"), 392.65));
+  EXPECT_EQ("+0000392.6", test_format<11>(FMT_COMPILE("{0:+010.4g}"), 392.65));
+  EXPECT_EQ("9223372036854775808.000000",
+            test_format<27>(FMT_COMPILE("{:f}"), 9223372036854775807.0));
+
+  constexpr double nan = std::numeric_limits<double>::quiet_NaN();
+  EXPECT_EQ("nan", test_format<4>(FMT_COMPILE("{}"), nan));
+  EXPECT_EQ("+nan", test_format<5>(FMT_COMPILE("{:+}"), nan));
+  if (std::signbit(-nan))
+    EXPECT_EQ("-nan", test_format<5>(FMT_COMPILE("{}"), -nan));
+  else
+    fmt::print("Warning: compiler doesn't handle negative NaN correctly");
+
+  constexpr double inf = std::numeric_limits<double>::infinity();
+  EXPECT_EQ("inf", test_format<4>(FMT_COMPILE("{}"), inf));
+  EXPECT_EQ("+inf", test_format<5>(FMT_COMPILE("{:+}"), inf));
+  EXPECT_EQ("-inf", test_format<5>(FMT_COMPILE("{}"), -inf));
+}
 #endif
+
+#if FMT_USE_CONSTEXPR_STRING
+TEST(compile_test, constexpr_string_format) {
+  constexpr auto result = []() {
+    return fmt::format(FMT_COMPILE("{}"), 42) == "42";
+  }();
+  EXPECT_TRUE(result);
+
+  // Test with a larger string to avoid small string optimization.
+  constexpr auto big = []() {
+    return fmt::format(FMT_COMPILE("{:100}"), ' ') == std::string(100, ' ');
+  }();
+  EXPECT_TRUE(big);
+}
+#endif  // FMT_USE_CONSTEXPR_STRING

test/format-impl-test.cc

@@ -292,7 +292,7 @@ struct double_double {
 
 auto format_as(double_double d) -> double { return d; }
 
-bool operator>=(const double_double& lhs, const double_double& rhs) {
+auto operator>=(const double_double& lhs, const double_double& rhs) -> bool {
   return lhs.a + lhs.b >= rhs.a + rhs.b;
 }
 
@@ -307,19 +307,20 @@ struct slow_float {
 auto format_as(slow_float f) -> float { return f; }
 
 namespace std {
-template <> struct is_floating_point<double_double> : std::true_type {};
 template <> struct numeric_limits<double_double> {
   // is_iec559 is true for double-double in libstdc++.
   static constexpr bool is_iec559 = true;
   static constexpr int digits = 106;
+  static constexpr int digits10 = 33;
 };
 
-template <> struct is_floating_point<slow_float> : std::true_type {};
 template <> struct numeric_limits<slow_float> : numeric_limits<float> {};
 }  // namespace std
 
 FMT_BEGIN_NAMESPACE
 namespace detail {
+template <> struct is_floating_point<double_double> : std::true_type {};
+template <> struct is_floating_point<slow_float> : std::true_type {};
 template <> struct is_fast_float<slow_float> : std::false_type {};
 namespace dragonbox {
 template <> struct float_info<slow_float> {
@@ -341,7 +342,7 @@ TEST(format_impl_test, write_dragon_even) {
   auto s = std::string();
   fmt::detail::write<char>(std::back_inserter(s), slow_float(33554450.0f), {});
   // Specializing is_floating_point is broken in MSVC.
-  if (!FMT_MSC_VERSION) EXPECT_EQ(s, "33554450");
+  if (!FMT_MSC_VERSION) EXPECT_EQ(s, "3.355445e+07");
 }
 
 #if defined(_WIN32) && !defined(FMT_USE_WRITE_CONSOLE)
@@ -355,11 +356,11 @@ TEST(format_impl_test, write_console_signature) {
 
 // A public domain branchless UTF-8 decoder by Christopher Wellons:
 // https://github.com/skeeto/branchless-utf8
-constexpr bool unicode_is_surrogate(uint32_t c) {
+constexpr auto unicode_is_surrogate(uint32_t c) -> bool {
   return c >= 0xD800U && c <= 0xDFFFU;
 }
 
-FMT_CONSTEXPR char* utf8_encode(char* s, uint32_t c) {
+FMT_CONSTEXPR auto utf8_encode(char* s, uint32_t c) -> char* {
   if (c >= (1UL << 16)) {
     s[0] = static_cast<char>(0xf0 | (c >> 18));
     s[1] = static_cast<char>(0x80 | ((c >> 12) & 0x3f));

test/format-test.cc

@@ -206,10 +206,6 @@ TEST(util_test, parse_nonnegative_int) {
   EXPECT_EQ(fmt::detail::parse_nonnegative_int(begin, end, -1), -1);
 }
 
-TEST(format_impl_test, compute_width) {
-  EXPECT_EQ(fmt::detail::compute_width("вожык"), 5);
-}
-
 TEST(util_test, utf8_to_utf16) {
   auto u = fmt::detail::utf8_to_utf16("лошадка");
   EXPECT_EQ(L"\x043B\x043E\x0448\x0430\x0434\x043A\x0430", u.str());
@@ -319,18 +315,17 @@ TEST(memory_buffer_test, move_ctor_inline_buffer) {
         std::allocator<char>* alloc = buffer.get_allocator().get();
         basic_memory_buffer<char, 5, std_allocator> buffer2(std::move(buffer));
         // Move shouldn't destroy the inline content of the first buffer.
-        EXPECT_EQ(str, std::string(&buffer[0], buffer.size()));
+        EXPECT_EQ(std::string(buffer.data(), buffer.size()), str);
-        EXPECT_EQ(str, std::string(&buffer2[0], buffer2.size()));
+        EXPECT_EQ(std::string(&buffer2[0], buffer2.size()), str);
-        EXPECT_EQ(5u, buffer2.capacity());
+        EXPECT_EQ(buffer2.capacity(), 5u);
         // Move should transfer allocator.
-        EXPECT_EQ(nullptr, buffer.get_allocator().get());
+        EXPECT_EQ(buffer.get_allocator().get(), nullptr);
-        EXPECT_EQ(alloc, buffer2.get_allocator().get());
+        EXPECT_EQ(buffer2.get_allocator().get(), alloc);
       };
 
   auto alloc = std::allocator<char>();
   basic_memory_buffer<char, 5, std_allocator> buffer((std_allocator(&alloc)));
-  const char test[] = "test";
+  buffer.append(string_view("test"));
-  buffer.append(string_view(test, 4));
   check_move_buffer("test", buffer);
   // Adding one more character fills the inline buffer, but doesn't cause
   // dynamic allocation.
@@ -355,14 +350,63 @@ TEST(memory_buffer_test, move_ctor_dynamic_buffer) {
   EXPECT_GT(buffer2.capacity(), 4u);
 }
 
+using std_allocator_noprop = allocator_ref<std::allocator<char>, false>;
+
+TEST(memory_buffer_test, move_ctor_inline_buffer_non_propagating) {
+  auto check_move_buffer =
+      [](const char* str,
+         basic_memory_buffer<char, 5, std_allocator_noprop>& buffer) {
+        std::allocator<char>* original_alloc_ptr = buffer.get_allocator().get();
+        const char* original_data_ptr = &buffer[0];
+        basic_memory_buffer<char, 5, std_allocator_noprop> buffer2(
+            std::move(buffer));
+        const char* new_data_ptr = &buffer2[0];
+        EXPECT_NE(new_data_ptr, original_data_ptr);
+        EXPECT_EQ(std::string(buffer.data(), buffer.size()), str);
+        EXPECT_EQ(std::string(buffer2.data(), buffer2.size()), str);
+        EXPECT_EQ(buffer2.capacity(), 5u);
+        // Allocators should NOT be transferred; they remain distinct instances.
+        // The original buffer's allocator pointer should still be valid (not
+        // nullptr).
+        EXPECT_EQ(buffer.get_allocator().get(), original_alloc_ptr);
+        EXPECT_NE(buffer2.get_allocator().get(), original_alloc_ptr);
+      };
+  auto alloc = std::allocator<char>();
+  basic_memory_buffer<char, 5, std_allocator_noprop> buffer(
+      (std_allocator_noprop(&alloc)));
+  buffer.append(string_view("test", 4));
+  check_move_buffer("test", buffer);
+  buffer.push_back('a');
+  check_move_buffer("testa", buffer);
+}
+
+TEST(memory_buffer_test, move_ctor_dynamic_buffer_non_propagating) {
+  auto alloc = std::allocator<char>();
+  basic_memory_buffer<char, 4, std_allocator_noprop> buffer(
+      (std_allocator_noprop(&alloc)));
+  const char test[] = "test";
+  buffer.append(test, test + 4);
+  const char* inline_buffer_ptr = &buffer[0];
+  buffer.push_back('a');
+  EXPECT_NE(buffer.data(), inline_buffer_ptr);
+  std::allocator<char>* original_alloc_ptr = buffer.get_allocator().get();
+  basic_memory_buffer<char, 4, std_allocator_noprop> buffer2;
+  buffer2 = std::move(buffer);
+  EXPECT_EQ(std::string(buffer2.data(), buffer2.size()), "testa");
+  EXPECT_GT(buffer2.capacity(), 4u);
+  EXPECT_NE(buffer2.data(), inline_buffer_ptr);
+  EXPECT_EQ(buffer.get_allocator().get(), original_alloc_ptr);
+  EXPECT_NE(buffer2.get_allocator().get(), original_alloc_ptr);
+}
+
 void check_move_assign_buffer(const char* str,
                               basic_memory_buffer<char, 5>& buffer) {
   basic_memory_buffer<char, 5> buffer2;
   buffer2 = std::move(buffer);
   // Move shouldn't destroy the inline content of the first buffer.
-  EXPECT_EQ(str, std::string(&buffer[0], buffer.size()));
+  EXPECT_EQ(std::string(&buffer[0], buffer.size()), str);
-  EXPECT_EQ(str, std::string(&buffer2[0], buffer2.size()));
+  EXPECT_EQ(std::string(&buffer2[0], buffer2.size()), str);
-  EXPECT_EQ(5u, buffer2.capacity());
+  EXPECT_EQ(buffer2.capacity(), 5u);
 }
 
 TEST(memory_buffer_test, move_assignment) {
@@ -381,8 +425,8 @@ TEST(memory_buffer_test, move_assignment) {
   basic_memory_buffer<char, 5> buffer2;
   buffer2 = std::move(buffer);
   // Move should rip the guts of the first buffer.
-  EXPECT_EQ(inline_buffer_ptr, &buffer[0]);
+  EXPECT_EQ(buffer.data(), inline_buffer_ptr);
-  EXPECT_EQ("testab", std::string(&buffer2[0], buffer2.size()));
+  EXPECT_EQ(std::string(buffer2.data(), buffer2.size()), "testab");
   EXPECT_GT(buffer2.capacity(), 5u);
 }
 
@@ -481,6 +525,12 @@ TEST(memory_buffer_test, max_size_allocator_overflow) {
   EXPECT_THROW(buffer.resize(161), std::exception);
 }
 
+TEST(memory_buffer_test, back_insert_iterator) {
+  fmt::memory_buffer buf;
+  using iterator = decltype(std::back_inserter(buf));
+  EXPECT_TRUE(fmt::detail::is_back_insert_iterator<iterator>::value);
+}
+
 TEST(format_test, digits2_alignment) {
   auto p =
       fmt::detail::bit_cast<fmt::detail::uintptr_t>(fmt::detail::digits2(0));
@@ -552,6 +602,10 @@ TEST(format_test, arg_errors) {
                    format_error, "argument not found");
 }
 
+TEST(format_test, display_width_precision) {
+  EXPECT_EQ(fmt::format("{:.5}", "🐱🐱🐱"), "🐱🐱");
+}
+
 template <int N> struct test_format {
   template <typename... T>
   static auto format(fmt::string_view fmt, const T&... args) -> std::string {
@@ -582,6 +636,9 @@ TEST(format_test, named_arg) {
   EXPECT_EQ("1/a/A", fmt::format("{_1}/{a_}/{A_}", fmt::arg("a_", 'a'),
                                  fmt::arg("A_", "A"), fmt::arg("_1", 1)));
   EXPECT_EQ(fmt::format("{0:{width}}", -42, fmt::arg("width", 4)), " -42");
+  EXPECT_EQ(fmt::format("{value:{width}}", fmt::arg("value", -42),
+                        fmt::arg("width", 4)),
+            " -42");
   EXPECT_EQ("st",
             fmt::format("{0:.{precision}}", "str", fmt::arg("precision", 2)));
   EXPECT_EQ(fmt::format("{} {two}", 1, fmt::arg("two", 2)), "1 2");
@@ -599,6 +656,9 @@ TEST(format_test, named_arg) {
   EXPECT_THROW_MSG((void)fmt::format(runtime("{a} {}"), fmt::arg("a", 2), 42),
                    format_error,
                    "cannot switch from manual to automatic argument indexing");
+  EXPECT_THROW_MSG(
+      (void)fmt::format("{a}", fmt::arg("a", 1), fmt::arg("a", 10)),
+      format_error, "duplicate named arg");
 }
 
 TEST(format_test, auto_arg_index) {
@@ -871,6 +931,7 @@ TEST(format_test, width) {
             "    0xcafe");
   EXPECT_EQ(fmt::format("{:11}", 'x'), "x          ");
   EXPECT_EQ(fmt::format("{:12}", "str"), "str         ");
+  EXPECT_EQ(fmt::format("{:*^5}", "🤡"), "*🤡**");
   EXPECT_EQ(fmt::format("{:*^6}", "🤡"), "**🤡**");
   EXPECT_EQ(fmt::format("{:*^8}", "你好"), "**你好**");
   EXPECT_EQ(fmt::format("{:#6}", 42.0), "   42.");
@@ -878,6 +939,31 @@ TEST(format_test, width) {
   EXPECT_EQ(fmt::format("{:>06.0f}", 0.00884311), "     0");
 }
 
+TEST(format_test, debug_presentation) {
+  EXPECT_EQ(fmt::format("{:?}", ""), R"("")");
+
+  EXPECT_EQ(fmt::format("{:*<5.0?}", "\n"), R"(*****)");
+  EXPECT_EQ(fmt::format("{:*<5.1?}", "\n"), R"("****)");
+  EXPECT_EQ(fmt::format("{:*<5.2?}", "\n"), R"("\***)");
+  EXPECT_EQ(fmt::format("{:*<5.3?}", "\n"), R"("\n**)");
+  EXPECT_EQ(fmt::format("{:*<5.4?}", "\n"), R"("\n"*)");
+
+  EXPECT_EQ(fmt::format("{:*<5.1?}", "Σ"), R"("****)");
+  EXPECT_EQ(fmt::format("{:*<5.2?}", "Σ"), R"("Σ***)");
+  EXPECT_EQ(fmt::format("{:*<5.3?}", "Σ"), R"("Σ"**)");
+
+  EXPECT_EQ(fmt::format("{:*<5.1?}", "笑"), R"("****)");
+  EXPECT_EQ(fmt::format("{:*<5.2?}", "笑"), R"("****)");
+  EXPECT_EQ(fmt::format("{:*<5.3?}", "笑"), R"("笑**)");
+  EXPECT_EQ(fmt::format("{:*<5.4?}", "笑"), R"("笑"*)");
+
+  EXPECT_EQ(fmt::format("{:*<8?}", "туда"), R"("туда"**)");
+  EXPECT_EQ(fmt::format("{:*>8?}", "сюда"), R"(**"сюда")");
+  EXPECT_EQ(fmt::format("{:*^8?}", "中心"), R"(*"中心"*)");
+
+  EXPECT_EQ(fmt::format("{:*^14?}", "A\t👈🤯ы猫"), R"(*"A\t👈🤯ы猫"*)");
+}
+
 auto bad_dynamic_spec_msg = FMT_BUILTIN_TYPES
                                 ? "width/precision is out of range"
                                 : "width/precision is not integer";
@@ -1068,7 +1154,8 @@ TEST(format_test, precision) {
   EXPECT_EQ(fmt::format("{:#.0f}", 123.0), "123.");
   EXPECT_EQ(fmt::format("{:.02f}", 1.234), "1.23");
   EXPECT_EQ(fmt::format("{:.1g}", 0.001), "0.001");
-  EXPECT_EQ(fmt::format("{}", 1019666432.0f), "1019666400");
+  EXPECT_EQ(fmt::format("{}", 123456789.0f), "1.2345679e+08");
+  EXPECT_EQ(fmt::format("{}", 1019666432.0f), "1.0196664e+09");
   EXPECT_EQ(fmt::format("{:.0e}", 9.5), "1e+01");
   EXPECT_EQ(fmt::format("{:.1e}", 1e-34), "1.0e-34");
 
@@ -1078,9 +1165,6 @@ TEST(format_test, precision) {
   EXPECT_THROW_MSG(
       (void)fmt::format(runtime("{0:.2f}"), reinterpret_cast<void*>(0xcafe)),
       format_error, "invalid format specifier");
-  EXPECT_THROW_MSG((void)fmt::format(runtime("{:.{}e}"), 42.0,
-                                     fmt::detail::max_value<int>()),
-                   format_error, "number is too big");
   EXPECT_THROW_MSG(
       (void)fmt::format("{:.2147483646f}", -2.2121295195081227E+304),
       format_error, "number is too big");
@@ -1092,9 +1176,34 @@ TEST(format_test, precision) {
   EXPECT_EQ(fmt::format("{0:.6}", "123456\xad"), "123456");
 }
 
+TEST(format_test, large_precision) {
+  // Iterator used to abort the actual output.
+  struct throwing_iterator {
+    auto operator=(char) -> throwing_iterator& {
+      throw std::runtime_error("aborted");
+      return *this;
+    }
+    auto operator*() -> throwing_iterator& { return *this; }
+    auto operator++() -> throwing_iterator& { return *this; }
+    auto operator++(int) -> throwing_iterator { return *this; }
+  };
+  auto it = throwing_iterator();
+
+  EXPECT_THROW_MSG(fmt::format_to(it, fmt::runtime("{:#.{}}"), 1.0,
+                                  fmt::detail::max_value<int>()),
+                   std::runtime_error, "aborted");
+
+  EXPECT_THROW_MSG(fmt::format_to(it, fmt::runtime("{:#.{}e}"), 1.0,
+                                  fmt::detail::max_value<int>() - 1),
+                   std::runtime_error, "aborted");
+
+  EXPECT_THROW_MSG((void)fmt::format(fmt::runtime("{:.{}e}"), 42.0,
+                                     fmt::detail::max_value<int>()),
+                   format_error, "number is too big");
+}
+
 TEST(format_test, utf8_precision) {
   auto result = fmt::format("{:.4}", "caf\u00e9s");  // cafés
-  EXPECT_EQ(fmt::detail::compute_width(result), 4);
   EXPECT_EQ(result, "caf\u00e9");
 }
 
@@ -1748,19 +1857,15 @@ TEST(format_test, format_examples) {
   fmt::format_to(std::back_inserter(out), "The answer is {}.", 42);
   EXPECT_EQ("The answer is 42.", to_string(out));
 
-  const char* filename = "nonexistent";
+  EXPECT_THROW(
-  FILE* ftest = safe_fopen(filename, "r");
-  if (ftest) fclose(ftest);
-  int error_code = errno;
-  EXPECT_TRUE(ftest == nullptr);
-  EXPECT_SYSTEM_ERROR(
       {
-        FILE* f = safe_fopen(filename, "r");
+        const char* filename = "madeup";
-        if (!f)
+        FILE* file = fopen(filename, "r");
-          throw fmt::system_error(errno, "Cannot open file '{}'", filename);
+        if (!file)
-        fclose(f);
+          throw fmt::system_error(errno, "cannot open file '{}'", filename);
+        fclose(file);
       },
-      error_code, "Cannot open file 'nonexistent'");
+      std::system_error);
 
   EXPECT_EQ("First, thou shalt count to three",
             fmt::format("First, thou shalt count to {0}", "three"));
@@ -1820,54 +1925,6 @@ TEST(format_test, big_print) {
   EXPECT_WRITE(stdout, big_print(), std::string(count, 'x'));
 }
 
-// Windows CRT implements _IOLBF incorrectly (full buffering).
-#if FMT_USE_FCNTL
-
-#  ifndef _WIN32
-TEST(format_test, line_buffering) {
-  auto pipe = fmt::pipe();
-
-  int write_fd = pipe.write_end.descriptor();
-  auto write_end = pipe.write_end.fdopen("w");
-  setvbuf(write_end.get(), nullptr, _IOLBF, 4096);
-  write_end.print("42\n");
-  close(write_fd);
-  try {
-    write_end.close();
-  } catch (const std::system_error&) {
-  }
-
-  auto read_end = pipe.read_end.fdopen("r");
-  std::thread reader([&]() {
-    int n = 0;
-    int result = fscanf(read_end.get(), "%d", &n);
-    (void)result;
-    EXPECT_EQ(n, 42);
-  });
-
-  reader.join();
-}
-#  endif
-
-TEST(format_test, buffer_boundary) {
-  auto pipe = fmt::pipe();
-
-  auto write_end = pipe.write_end.fdopen("w");
-  setvbuf(write_end.get(), nullptr, _IOFBF, 4096);
-  for (int i = 3; i < 4094; i++)
-    write_end.print("{}", (i % 73) != 0 ? 'x' : '\n');
-  write_end.print("{} {}", 1234, 567);
-  write_end.close();
-
-  auto read_end = pipe.read_end.fdopen("r");
-  char buf[4091] = {};
-  size_t n = fread(buf, 1, sizeof(buf), read_end.get());
-  EXPECT_EQ(n, sizeof(buf));
-  EXPECT_STREQ(fgets(buf, sizeof(buf), read_end.get()), "1234 567");
-}
-
-#endif  // FMT_USE_FCNTL
-
 struct deadlockable {
   int value = 0;
   mutable std::mutex mutex;
@@ -1979,11 +2036,6 @@ TEST(format_test, unpacked_args) {
                         6, 7, 8, 9, 'a', 'b', 'c', 'd', 'e', 'f', 'g'));
 }
 
-constexpr char with_null[3] = {'{', '}', '\0'};
-constexpr char no_null[2] = {'{', '}'};
-static constexpr const char static_with_null[3] = {'{', '}', '\0'};
-static constexpr const char static_no_null[2] = {'{', '}'};
-
 TEST(format_test, compile_time_string) {
   EXPECT_EQ(fmt::format(FMT_STRING("foo")), "foo");
   EXPECT_EQ(fmt::format(FMT_STRING("{}"), 42), "42");
@@ -1998,19 +2050,12 @@ TEST(format_test, compile_time_string) {
   EXPECT_EQ(fmt::format(FMT_STRING("{} {two}"), 1, "two"_a = 2), "1 2");
 #endif
 
-  (void)static_with_null;
+  static constexpr char format_str[3] = {'{', '}', '\0'};
-  (void)static_no_null;
+  (void)format_str;
 #ifndef _MSC_VER
-  EXPECT_EQ(fmt::format(FMT_STRING(static_with_null), 42), "42");
+  EXPECT_EQ(fmt::format(FMT_STRING(format_str), 42), "42");
-  EXPECT_EQ(fmt::format(FMT_STRING(static_no_null), 42), "42");
 #endif
 
-  (void)with_null;
-  (void)no_null;
-#if FMT_CPLUSPLUS >= 201703L
-  EXPECT_EQ(fmt::format(FMT_STRING(with_null), 42), "42");
-  EXPECT_EQ(fmt::format(FMT_STRING(no_null), 42), "42");
-#endif
 #if defined(FMT_USE_STRING_VIEW) && FMT_CPLUSPLUS >= 201703L
   EXPECT_EQ(fmt::format(FMT_STRING(std::string_view("{}")), 42), "42");
 #endif
@@ -2102,6 +2147,10 @@ TEST(format_test, output_iterators) {
   std::stringstream s;
   fmt::format_to(std::ostream_iterator<char>(s), "{}", 42);
   EXPECT_EQ("42", s.str());
+
+  std::stringstream s2;
+  fmt::format_to(std::ostreambuf_iterator<char>(s2), "{}.{:06d}", 42, 43);
+  EXPECT_EQ("42.000043", s2.str());
 }
 
 TEST(format_test, fill_via_appender) {
@@ -2536,6 +2585,20 @@ TEST(format_test, writer) {
   EXPECT_EQ(s.str(), "foo");
 }
 
+#if FMT_USE_FCNTL && !defined(_WIN32)
+TEST(format_test, invalid_glibc_buffer) {
+  auto pipe = fmt::pipe();
+  auto write_end = pipe.write_end.fdopen("w");
+  auto file = write_end.get();
+
+  // This results in _IO_write_ptr < _IO_write_end.
+  fprintf(file, "111\n");
+  setvbuf(file, nullptr, _IOLBF, 0);
+
+  fmt::print(file, "------\n");
+}
+#endif  // FMT_USE_FCNTL
+
 #if FMT_USE_BITINT
 FMT_PRAGMA_CLANG(diagnostic ignored "-Wbit-int-extension")
 
@@ -2579,3 +2642,26 @@ TEST(base_test, format_byte) {
   EXPECT_EQ(s, "42");
 }
 #endif
+
+// Only defined after the test case.
+struct incomplete_type;
+extern const incomplete_type& external_instance;
+
+FMT_BEGIN_NAMESPACE
+template <> struct formatter<incomplete_type> : formatter<int> {
+  auto format(const incomplete_type& x, context& ctx) const -> appender;
+};
+FMT_END_NAMESPACE
+
+TEST(incomplete_type_test, format) {
+  EXPECT_EQ(fmt::format("{}", external_instance), "42");
+}
+
+struct incomplete_type {};
+const incomplete_type& external_instance = {};
+
+auto fmt::formatter<incomplete_type>::format(const incomplete_type&,
+                                             fmt::context& ctx) const
+    -> fmt::appender {
+  return formatter<int>::format(42, ctx);
+}

test/fuzzing/chrono-duration.cc

@@ -12,10 +12,10 @@ void invoke_inner(fmt::string_view format_str, Rep rep) {
   auto value = std::chrono::duration<Rep, Period>(rep);
   try {
 #if FMT_FUZZ_FORMAT_TO_STRING
-    std::string message = fmt::format(format_str, value);
+    std::string message = fmt::format(fmt::runtime(format_str), value);
 #else
     auto buf = fmt::memory_buffer();
-    fmt::format_to(std::back_inserter(buf), format_str, value);
+    fmt::format_to(std::back_inserter(buf), fmt::runtime(format_str), value);
 #endif
   } catch (std::exception&) {
   }

test/fuzzing/fuzzer-common.h

@@ -22,7 +22,7 @@
 #define FMT_FUZZ_SEPARATE_ALLOCATION 1
 
 // The size of the largest possible type in use.
-// To let the the fuzzer mutation be efficient at cross pollinating between
+// To let the fuzzer mutation be efficient at cross pollinating between
 // different types, use a fixed size format. The same bit pattern, interpreted
 // as another type, is likely interesting.
 constexpr auto fixed_size = 16;

test/gtest-extra.h

@@ -15,6 +15,10 @@
 #include "fmt/os.h"
 #include "gmock/gmock.h"
 
+#ifdef _MSC_VER
+#  include <crtdbg.h>
+#endif
+
 #define FMT_TEST_THROW_(statement, expected_exception, expected_message, fail) \
   GTEST_AMBIGUOUS_ELSE_BLOCKER_                                                \
   if (::testing::AssertionResult gtest_ar = ::testing::AssertionSuccess()) {   \

test/mock-allocator.h

@@ -37,7 +37,7 @@ template <typename T> class mock_allocator {
   MOCK_METHOD(void, deallocate, (T*, size_t));
 };
 
-template <typename Allocator> class allocator_ref {
+template <typename Allocator, bool PropagateOnMove = true> class allocator_ref {
  private:
   Allocator* alloc_;
 
@@ -48,6 +48,8 @@ template <typename Allocator> class allocator_ref {
 
  public:
   using value_type = typename Allocator::value_type;
+  using propagate_on_container_move_assignment =
+      fmt::bool_constant<PropagateOnMove>;
 
   explicit allocator_ref(Allocator* alloc = nullptr) : alloc_(alloc) {}
 
@@ -66,12 +68,21 @@ template <typename Allocator> class allocator_ref {
   }
 
  public:
-  Allocator* get() const { return alloc_; }
+  auto get() const -> Allocator* { return alloc_; }
 
-  value_type* allocate(size_t n) {
+  auto allocate(size_t n) -> value_type* {
     return std::allocator_traits<Allocator>::allocate(*alloc_, n);
   }
   void deallocate(value_type* p, size_t n) { alloc_->deallocate(p, n); }
+
+  friend auto operator==(allocator_ref a, allocator_ref b) noexcept -> bool {
+    if (a.alloc_ == b.alloc_) return true;
+    return a.alloc_ && b.alloc_ && *a.alloc_ == *b.alloc_;
+  }
+
+  friend auto operator!=(allocator_ref a, allocator_ref b) noexcept -> bool {
+    return !(a == b);
+  }
 };
 
 #endif  // FMT_MOCK_ALLOCATOR_H_

test/no-builtin-types-test.cc

@@ -8,11 +8,12 @@
 #include "gtest/gtest.h"
 
 #if !defined(__GNUC__) || __GNUC__ >= 5
-#define FMT_BUILTIN_TYPES 0
+#  define FMT_BUILTIN_TYPES 0
-#include "fmt/format.h"
+#  include "fmt/format.h"
 
 TEST(no_builtin_types_test, format) {
   EXPECT_EQ(fmt::format("{}", 42), "42");
+  EXPECT_EQ(fmt::format("{}", 42L), "42");
 }
 
 TEST(no_builtin_types_test, double_is_custom_type) {

test/os-test.cc

@@ -10,6 +10,7 @@
 #include <cstdlib>  // std::exit
 #include <cstring>
 #include <memory>
+#include <thread>
 
 #include "gtest-extra.h"
 #include "util.h"
@@ -18,10 +19,21 @@ using fmt::buffered_file;
 using testing::HasSubstr;
 using wstring_view = fmt::basic_string_view<wchar_t>;
 
-static std::string uniq_file_name(unsigned line_number) {
+static auto uniq_file_name(unsigned line_number) -> std::string {
   return "test-file" + std::to_string(line_number);
 }
 
+auto safe_fopen(const char* filename, const char* mode) -> FILE* {
+#if defined(_WIN32) && !defined(__MINGW32__)
+  // Fix MSVC warning about "unsafe" fopen.
+  FILE* f = nullptr;
+  errno = fopen_s(&f, filename, mode);
+  return f;
+#else
+  return std::fopen(filename, mode);
+#endif
+}
+
 #ifdef _WIN32
 
 #  include <windows.h>
@@ -236,8 +248,7 @@ TEST(buffered_file_test, descriptor) {
 }
 
 TEST(ostream_test, move) {
-  auto test_file = uniq_file_name(__LINE__);
+  fmt::ostream out = fmt::output_file(uniq_file_name(__LINE__));
-  fmt::ostream out = fmt::output_file(test_file);
   fmt::ostream moved(std::move(out));
   moved.print("hello");
 }
@@ -429,8 +440,7 @@ TEST(file_test, read) {
 }
 
 TEST(file_test, read_error) {
-  auto test_file = uniq_file_name(__LINE__);
+  file f(uniq_file_name(__LINE__), file::WRONLY | file::CREATE);
-  file f(test_file, file::WRONLY | file::CREATE);
   char buf;
   // We intentionally read from a file opened in the write-only mode to
   // cause error.
@@ -439,15 +449,13 @@ TEST(file_test, read_error) {
 
 TEST(file_test, write) {
   auto pipe = fmt::pipe();
-  auto test_file = uniq_file_name(__LINE__);
+  write(pipe.write_end, "test");
-  write(pipe.write_end, test_file);
   pipe.write_end.close();
-  EXPECT_READ(pipe.read_end, test_file);
+  EXPECT_READ(pipe.read_end, "test");
 }
 
 TEST(file_test, write_error) {
-  auto test_file = uniq_file_name(__LINE__);
+  file f(uniq_file_name(__LINE__), file::RDONLY | file::CREATE);
-  file f(test_file, file::RDONLY | file::CREATE);
   // We intentionally write to a file opened in the read-only mode to
   // cause error.
   EXPECT_SYSTEM_ERROR(f.write(" ", 1), EBADF, "cannot write to file");
@@ -513,4 +521,79 @@ TEST(file_test, fdopen) {
   int read_fd = pipe.read_end.descriptor();
   EXPECT_EQ(read_fd, FMT_POSIX(fileno(pipe.read_end.fdopen("r").get())));
 }
+
+// Windows CRT implements _IOLBF incorrectly (full buffering).
+#  ifndef _WIN32
+TEST(file_test, line_buffering) {
+  auto pipe = fmt::pipe();
+
+  int write_fd = pipe.write_end.descriptor();
+  auto write_end = pipe.write_end.fdopen("w");
+  setvbuf(write_end.get(), nullptr, _IOLBF, 4096);
+  write_end.print("42\n");
+  close(write_fd);
+  try {
+    write_end.close();
+  } catch (const std::system_error&) {
+  }
+
+  auto read_end = pipe.read_end.fdopen("r");
+  std::thread reader([&]() {
+    int n = 0;
+    int result = fscanf(read_end.get(), "%d", &n);
+    (void)result;
+    EXPECT_EQ(n, 42);
+  });
+
+  reader.join();
+}
+#  endif  // _WIN32
+
+TEST(file_test, buffer_boundary) {
+  auto pipe = fmt::pipe();
+
+  auto write_end = pipe.write_end.fdopen("w");
+  setvbuf(write_end.get(), nullptr, _IOFBF, 4096);
+  for (int i = 3; i < 4094; i++)
+    write_end.print("{}", (i % 73) != 0 ? 'x' : '\n');
+  write_end.print("{} {}", 1234, 567);
+  write_end.close();
+
+  auto read_end = pipe.read_end.fdopen("r");
+  char buf[4091] = {};
+  size_t n = fread(buf, 1, sizeof(buf), read_end.get());
+  EXPECT_EQ(n, sizeof(buf));
+  EXPECT_STREQ(fgets(buf, sizeof(buf), read_end.get()), "1234 567");
+}
+
+TEST(file_test, io_putting) {
+  auto pipe = fmt::pipe();
+  auto read_end = pipe.read_end.fdopen("r");
+  auto write_end = pipe.write_end.fdopen("w");
+
+  size_t read_size = 0;
+  auto reader = std::thread([&]() {
+    size_t n = 0;
+    do {
+      char buf[4096] = {};
+      n = fread(buf, 1, sizeof(buf), read_end.get());
+      read_size += n;
+    } while (n != 0);
+  });
+
+  // This initialize buffers but doesn't set _IO_CURRENTLY_PUTTING.
+  fseek(write_end.get(), 0, SEEK_SET);
+
+  size_t write_size = 0;
+  for (int i = 0; i <= 20000; ++i) {
+    auto s = fmt::format("{}\n", i);
+    fmt::print(write_end.get(), "{}", s);
+    write_size += s.size();
+  }
+
+  write_end.close();
+  reader.join();
+  EXPECT_EQ(read_size, write_size);
+}
+
 #endif  // FMT_USE_FCNTL

test/ostream-test.cc

@@ -265,7 +265,7 @@ template <> struct formatter<abstract> : ostream_formatter {};
 }  // namespace fmt
 
 void format_abstract_compiles(const abstract& a) {
-  fmt::format(FMT_COMPILE("{}"), a);
+  (void)fmt::format(FMT_COMPILE("{}"), a);
 }
 
 TEST(ostream_test, is_formattable) {

test/printf-test.cc

@@ -6,16 +6,12 @@
 // For the license information refer to format.h.
 
 #include "fmt/printf.h"
-// include <format> if possible for https://github.com/fmtlib/fmt/pull/4042
-#if FMT_HAS_INCLUDE(<format>) && FMT_CPLUSPLUS > 201703L
-#  include <format>
-#endif
 
 #include <cctype>
 #include <climits>
 #include <cstring>
 
-#include "fmt/xchar.h"
+#include "fmt/xchar.h"  // DEPRECATED!
 #include "gtest-extra.h"
 #include "util.h"
 
@@ -26,27 +22,21 @@ using fmt::detail::max_value;
 const unsigned big_num = INT_MAX + 1u;
 
 // Makes format string argument positional.
-static std::string make_positional(fmt::string_view format) {
+static auto make_positional(fmt::string_view format) -> std::string {
   std::string s(format.data(), format.size());
   s.replace(s.find('%'), 1, "%1$");
   return s;
 }
 
-static std::wstring make_positional(fmt::basic_string_view<wchar_t> format) {
-  std::wstring s(format.data(), format.size());
-  s.replace(s.find(L'%'), 1, L"%1$");
-  return s;
-}
-
 // A wrapper around fmt::sprintf to workaround bogus warnings about invalid
 // format strings in MSVC.
 template <typename... Args>
-std::string test_sprintf(fmt::string_view format, const Args&... args) {
+auto test_sprintf(fmt::string_view format, const Args&... args) -> std::string {
   return fmt::sprintf(format, args...);
 }
 template <typename... Args>
-std::wstring test_sprintf(fmt::basic_string_view<wchar_t> format,
+auto test_sprintf(fmt::basic_string_view<wchar_t> format, const Args&... args)
-                          const Args&... args) {
+    -> std::wstring {
   return fmt::sprintf(format, args...);
 }
 
@@ -55,10 +45,7 @@ std::wstring test_sprintf(fmt::basic_string_view<wchar_t> format,
       << "format: " << format;                          \
   EXPECT_EQ(expected_output, fmt::sprintf(make_positional(format), arg))
 
-TEST(printf_test, no_args) {
+TEST(printf_test, no_args) { EXPECT_EQ("test", test_sprintf("test")); }
-  EXPECT_EQ("test", test_sprintf("test"));
-  EXPECT_EQ(L"test", fmt::sprintf(L"test"));
-}
 
 TEST(printf_test, escape) {
   EXPECT_EQ("%", test_sprintf("%%"));
@@ -66,11 +53,6 @@ TEST(printf_test, escape) {
   EXPECT_EQ("% after", test_sprintf("%% after"));
   EXPECT_EQ("before % after", test_sprintf("before %% after"));
   EXPECT_EQ("%s", test_sprintf("%%s"));
-  EXPECT_EQ(L"%", fmt::sprintf(L"%%"));
-  EXPECT_EQ(L"before %", fmt::sprintf(L"before %%"));
-  EXPECT_EQ(L"% after", fmt::sprintf(L"%% after"));
-  EXPECT_EQ(L"before % after", fmt::sprintf(L"before %% after"));
-  EXPECT_EQ(L"%s", fmt::sprintf(L"%%s"));
 }
 
 TEST(printf_test, positional_args) {
@@ -467,9 +449,6 @@ TEST(printf_test, char) {
   EXPECT_PRINTF("x", "%c", 'x');
   int max = max_value<int>();
   EXPECT_PRINTF(fmt::format("{}", static_cast<char>(max)), "%c", max);
-  // EXPECT_PRINTF("x", "%lc", L'x');
-  EXPECT_PRINTF(L"x", L"%c", L'x');
-  EXPECT_PRINTF(fmt::format(L"{}", static_cast<wchar_t>(max)), L"%c", max);
 }
 
 TEST(printf_test, string) {
@@ -477,10 +456,6 @@ TEST(printf_test, string) {
   const char* null_str = nullptr;
   EXPECT_PRINTF("(null)", "%s", null_str);
   EXPECT_PRINTF("    (null)", "%10s", null_str);
-  EXPECT_PRINTF(L"abc", L"%s", L"abc");
-  const wchar_t* null_wstr = nullptr;
-  EXPECT_PRINTF(L"(null)", L"%s", null_wstr);
-  EXPECT_PRINTF(L"    (null)", L"%10s", null_wstr);
 }
 
 TEST(printf_test, pointer) {
@@ -494,16 +469,6 @@ TEST(printf_test, pointer) {
   EXPECT_PRINTF(fmt::format("{:p}", s), "%p", s);
   const char* null_str = nullptr;
   EXPECT_PRINTF("(nil)", "%p", null_str);
-
-  p = &n;
-  EXPECT_PRINTF(fmt::format(L"{}", p), L"%p", p);
-  p = nullptr;
-  EXPECT_PRINTF(L"(nil)", L"%p", p);
-  EXPECT_PRINTF(L"     (nil)", L"%10p", p);
-  const wchar_t* w = L"test";
-  EXPECT_PRINTF(fmt::format(L"{:p}", w), L"%p", w);
-  const wchar_t* null_wstr = nullptr;
-  EXPECT_PRINTF(L"(nil)", L"%p", null_wstr);
 }
 
 enum test_enum { answer = 42 };
@@ -531,10 +496,6 @@ TEST(printf_test, printf_error) {
 }
 #endif
 
-TEST(printf_test, wide_string) {
-  EXPECT_EQ(L"abc", fmt::sprintf(L"%s", L"abc"));
-}
-
 TEST(printf_test, vprintf) {
   int n = 42;
   auto store = fmt::make_format_args<fmt::printf_context>(n);

test/ranges-test.cc

@@ -47,6 +47,8 @@ TEST(ranges_test, format_array_of_literals) {
 }
 #endif  // FMT_RANGES_TEST_ENABLE_C_STYLE_ARRAY
 
+struct unformattable {};
+
 TEST(ranges_test, format_vector) {
   auto v = std::vector<int>{1, 2, 3, 5, 7, 11};
   EXPECT_EQ(fmt::format("{}", v), "[1, 2, 3, 5, 7, 11]");
@@ -65,6 +67,9 @@ TEST(ranges_test, format_vector) {
   EXPECT_EQ(fmt::format("{:n}", vvc), "['a', 'b', 'c'], ['a', 'b', 'c']");
   EXPECT_EQ(fmt::format("{:n:n}", vvc), "'a', 'b', 'c', 'a', 'b', 'c'");
   EXPECT_EQ(fmt::format("{:n:n:}", vvc), "a, b, c, a, b, c");
+
+  EXPECT_FALSE(fmt::is_formattable<unformattable>::value);
+  EXPECT_FALSE(fmt::is_formattable<std::vector<unformattable>>::value);
 }
 
 TEST(ranges_test, format_nested_vector) {
@@ -83,6 +88,8 @@ TEST(ranges_test, format_map) {
   auto m = std::map<std::string, int>{{"one", 1}, {"two", 2}};
   EXPECT_EQ(fmt::format("{}", m), "{\"one\": 1, \"two\": 2}");
   EXPECT_EQ(fmt::format("{:n}", m), "\"one\": 1, \"two\": 2");
+
+  EXPECT_FALSE((fmt::is_formattable<std::map<int, unformattable>>::value));
 }
 
 struct test_map_value {};
@@ -146,6 +153,7 @@ template <typename T> class flat_set {
 TEST(ranges_test, format_flat_set) {
   EXPECT_EQ(fmt::format("{}", flat_set<std::string>{"one", "two"}),
             "{\"one\", \"two\"}");
+  EXPECT_FALSE(fmt::is_formattable<flat_set<unformattable>>::value);
 }
 
 namespace adl {
@@ -169,8 +177,6 @@ TEST(ranges_test, format_pair) {
   EXPECT_EQ(fmt::format("{:n}", p), "421.5");
 }
 
-struct unformattable {};
-
 TEST(ranges_test, format_tuple) {
   auto t =
       std::tuple<int, float, std::string, char>(42, 1.5f, "this is tuple", 'i');
@@ -180,7 +186,6 @@ TEST(ranges_test, format_tuple) {
   EXPECT_EQ(fmt::format("{}", std::tuple<>()), "()");
 
   EXPECT_TRUE((fmt::is_formattable<std::tuple<>>::value));
-  EXPECT_FALSE((fmt::is_formattable<unformattable>::value));
   EXPECT_FALSE((fmt::is_formattable<std::tuple<unformattable>>::value));
   EXPECT_FALSE((fmt::is_formattable<std::tuple<unformattable, int>>::value));
   EXPECT_FALSE((fmt::is_formattable<std::tuple<int, unformattable>>::value));
@@ -227,9 +232,12 @@ auto get(const tuple_like& t) noexcept -> decltype(t.get<N>()) {
   return t.get<N>();
 }
 
+// https://github.com/llvm/llvm-project/issues/39218
+FMT_PRAGMA_CLANG(diagnostic ignored "-Wmismatched-tags")
+
 namespace std {
 template <>
-struct tuple_size<tuple_like> : std::integral_constant<size_t, 2> {};
+struct tuple_size<tuple_like> : public std::integral_constant<size_t, 2> {};
 
 template <size_t N> struct tuple_element<N, tuple_like> {
   using type = decltype(std::declval<tuple_like>().get<N>());
@@ -322,7 +330,7 @@ template <typename T> class noncopyable_range {
   explicit noncopyable_range(Args&&... args)
       : vec(std::forward<Args>(args)...) {}
 
-  noncopyable_range(noncopyable_range const&) = delete;
+  noncopyable_range(const noncopyable_range&) = delete;
   noncopyable_range(noncopyable_range&) = delete;
 
   auto begin() -> iterator { return vec.begin(); }
@@ -416,7 +424,7 @@ TEST(ranges_test, join_tuple) {
   auto t5 = tuple_like{42, "foo"};
   EXPECT_EQ(fmt::format("{}", fmt::join(t5, ", ")), "42, foo");
 
-#  if FMT_TUPLE_JOIN_SPECIFIERS
+#if FMT_TUPLE_JOIN_SPECIFIERS
   // Specs applied to each element.
   auto t5 = std::tuple<int, int, long>(-3, 100, 1);
   EXPECT_EQ(fmt::format("{:+03}", fmt::join(t5, ", ")), "-03, +100, +01");
@@ -429,7 +437,7 @@ TEST(ranges_test, join_tuple) {
   int y = -1;
   auto t7 = std::tuple<int, int&, const int&>(3, y, y);
   EXPECT_EQ(fmt::format("{:03}", fmt::join(t7, ", ")), "003, -01, -01");
-#  endif
+#endif
 }
 
 TEST(ranges_test, join_initializer_list) {
@@ -449,7 +457,7 @@ struct zstring {
   auto end() const -> zstring_sentinel { return {}; }
 };
 
-#  ifdef __cpp_lib_ranges
+#ifdef __cpp_lib_ranges
 struct cpp20_only_range {
   struct iterator {
     int val = 0;
@@ -479,7 +487,7 @@ struct cpp20_only_range {
 };
 
 static_assert(std::input_iterator<cpp20_only_range::iterator>);
-#  endif
+#endif
 
 TEST(ranges_test, join_sentinel) {
   auto hello = zstring{"hello"};
@@ -507,13 +515,13 @@ TEST(ranges_test, join_range) {
   const auto z = std::vector<int>(3u, 0);
   EXPECT_EQ(fmt::format("{}", fmt::join(z, ",")), "0,0,0");
 
-#  ifdef __cpp_lib_ranges
+#ifdef __cpp_lib_ranges
   EXPECT_EQ(fmt::format("{}", cpp20_only_range{.lo = 0, .hi = 5}),
             "[0, 1, 2, 3, 4]");
   EXPECT_EQ(
       fmt::format("{}", fmt::join(cpp20_only_range{.lo = 0, .hi = 5}, ",")),
       "0,1,2,3,4");
-#  endif
+#endif
 }
 
 namespace adl {
@@ -655,6 +663,8 @@ TEST(ranges_test, container_adaptor) {
     m.push(2);
     EXPECT_EQ(fmt::format("{}", m), "[1, 2]");
   }
+
+  EXPECT_FALSE(fmt::is_formattable<std::stack<unformattable>>::value);
 }
 
 struct tieable {

test/scan.h

@@ -229,6 +229,8 @@ enum class scan_type {
   uint_type,
   long_long_type,
   ulong_long_type,
+  double_type,
+  float_type,
   string_type,
   string_view_type,
   custom_type
@@ -251,6 +253,8 @@ template <typename Context> class basic_scan_arg {
     unsigned* uint_value_;
     long long* long_long_value_;
     unsigned long long* ulong_long_value_;
+    double* double_value_;
+    float* float_value_;
     std::string* string_;
     string_view* string_view_;
     detail::custom_scan_arg<Context> custom_;
@@ -276,6 +280,10 @@ template <typename Context> class basic_scan_arg {
       : type_(scan_type::long_long_type), long_long_value_(&value) {}
   FMT_CONSTEXPR basic_scan_arg(unsigned long long& value)
       : type_(scan_type::ulong_long_type), ulong_long_value_(&value) {}
+  FMT_CONSTEXPR basic_scan_arg(double& value)
+      : type_(scan_type::double_type), double_value_(&value) {}
+  FMT_CONSTEXPR basic_scan_arg(float& value)
+      : type_(scan_type::float_type), float_value_(&value) {}
   FMT_CONSTEXPR basic_scan_arg(std::string& value)
       : type_(scan_type::string_type), string_(&value) {}
   FMT_CONSTEXPR basic_scan_arg(string_view& value)
@@ -305,6 +313,10 @@ template <typename Context> class basic_scan_arg {
       return vis(*long_long_value_);
     case scan_type::ulong_long_type:
       return vis(*ulong_long_value_);
+    case scan_type::double_type:
+      return vis(*double_value_);
+    case scan_type::float_type:
+      return vis(*float_value_);
     case scan_type::string_type:
       return vis(*string_);
     case scan_type::string_view_type:
@@ -457,6 +469,47 @@ auto read(scan_iterator it, T& value, const format_specs& specs = {})
   return it;
 }
 
+auto read(scan_iterator it, double& value, const format_specs& = {})
+    -> scan_iterator {
+  if (it == scan_sentinel()) return it;
+  
+  // Simple floating-point parsing
+  bool negative = *it == '-';
+  if (negative) {
+    ++it;
+    if (it == scan_sentinel()) report_error("invalid input");
+  }
+  
+  double result = 0.0;
+  // Parse integer part
+  while (it != scan_sentinel() && *it >= '0' && *it <= '9') {
+    result = result * 10.0 + (*it - '0');
+    ++it;
+  }
+  
+  // Parse decimal part if present
+  if (it != scan_sentinel() && *it == '.') {
+    ++it;
+    double fraction = 0.1;
+    while (it != scan_sentinel() && *it >= '0' && *it <= '9') {
+      result += (*it - '0') * fraction;
+      fraction *= 0.1;
+      ++it;
+    }
+  }
+  
+  value = negative ? -result : result;
+  return it;
+}
+
+auto read(scan_iterator it, float& value, const format_specs& specs = {})
+    -> scan_iterator {
+  double temp;
+  it = read(it, temp, specs);
+  value = static_cast<float>(temp);
+  return it;
+}
+
 auto read(scan_iterator it, std::string& value, const format_specs& = {})
     -> scan_iterator {
   while (it != scan_sentinel() && *it != ' ') value.push_back(*it++);

test/std-test.cc

@@ -12,7 +12,7 @@
 #include <string>
 #include <vector>
 
-#include "fmt/os.h"  // fmt::system_category
+#include "fmt/os.h"       // fmt::system_category
 #include "fmt/ranges.h"
 #include "gtest-extra.h"  // StartsWith
 
@@ -20,6 +20,11 @@
 TEST(std_test, path) {
   using std::filesystem::path;
   EXPECT_EQ(fmt::format("{}", path("/usr/bin")), "/usr/bin");
+
+  // see #4303
+  const path p = "/usr/bin";
+  EXPECT_EQ(fmt::format("{}", p), "/usr/bin");
+
   EXPECT_EQ(fmt::format("{:?}", path("/usr/bin")), "\"/usr/bin\"");
   EXPECT_EQ(fmt::format("{:8}", path("foo")), "foo     ");
 
@@ -34,16 +39,18 @@ TEST(std_test, path) {
   EXPECT_EQ(fmt::format("{}", path(L"\x0428\x0447\x0443\x0447\x044B\x043D\x0448"
                                    L"\x0447\x044B\x043D\x0430")),
             "Шчучыншчына");
-  EXPECT_EQ(fmt::format("{}", path(L"\xd800")), "<EFBFBD>");
+  EXPECT_EQ(fmt::format("{}", path(L"\xD800")), "\xED\xA0\x80");
-  EXPECT_EQ(fmt::format("{}", path(L"HEAD \xd800 TAIL")), "HEAD <20> TAIL");
+  EXPECT_EQ(fmt::format("{}", path(L"[\xD800]")), "[\xED\xA0\x80]");
-  EXPECT_EQ(fmt::format("{}", path(L"HEAD \xD83D\xDE00 TAIL")),
+  EXPECT_EQ(fmt::format("{}", path(L"[\xD83D\xDE00]")), "[\xF0\x9F\x98\x80]");
-            "HEAD \xF0\x9F\x98\x80 TAIL");
+  EXPECT_EQ(fmt::format("{}", path(L"[\xD83D\xD83D\xDE00]")),
-  EXPECT_EQ(fmt::format("{}", path(L"HEAD \xD83D\xD83D\xDE00 TAIL")),
+            "[\xED\xA0\xBD\xF0\x9F\x98\x80]");
-            "HEAD <20>\xF0\x9F\x98\x80 TAIL");
+  EXPECT_EQ(fmt::format("{:?}", path(L"\xD800")), "\"\\ud800\"");
-  EXPECT_EQ(fmt::format("{:?}", path(L"\xd800")), "\"\\ud800\"");
 #  endif
 }
 
+// Intentionally delayed include to test #4303
+#  include "fmt/ranges.h"
+
 // Test ambiguity problem described in #2954.
 TEST(ranges_std_test, format_vector_path) {
   auto p = std::filesystem::path("foo/bar.txt");
@@ -91,6 +98,9 @@ TEST(std_test, complex) {
   EXPECT_EQ(fmt::format("{: }", std::complex<double>(1, 2.2)), "( 1+2.2i)");
   EXPECT_EQ(fmt::format("{: }", std::complex<double>(1, -2.2)), "( 1-2.2i)");
 
+  EXPECT_EQ(fmt::format("{:8}", std::complex<double>(1, 2)), "(1+2i)  ");
+  EXPECT_EQ(fmt::format("{:-<8}", std::complex<double>(1, 2)), "(1+2i)--");
+
   EXPECT_EQ(fmt::format("{:>20.2f}", std::complex<double>(1, 2.2)),
             "        (1.00+2.20i)");
   EXPECT_EQ(fmt::format("{:<20.2f}", std::complex<double>(1, 2.2)),
@@ -135,6 +145,7 @@ TEST(std_test, optional) {
   EXPECT_FALSE((fmt::is_formattable<unformattable>::value));
   EXPECT_FALSE((fmt::is_formattable<std::optional<unformattable>>::value));
   EXPECT_TRUE((fmt::is_formattable<std::optional<int>>::value));
+  EXPECT_TRUE((fmt::is_formattable<std::optional<const int>>::value));
 #endif
 }
 
@@ -186,7 +197,33 @@ class my_class {
     return fmt::to_string(elm.av);
   }
 };
+
+class my_class_int {
+ public:
+  int av;
+
+ private:
+  friend auto format_as(const my_class_int& elm) -> int { return elm.av; }
+};
 }  // namespace my_nso
+
+TEST(std_test, expected_format_as) {
+#ifdef __cpp_lib_expected
+  EXPECT_EQ(
+      fmt::format(
+          "{}", std::expected<my_nso::my_number, int>{my_nso::my_number::one}),
+      "expected(\"first\")");
+  EXPECT_EQ(
+      fmt::format("{}",
+                  std::expected<my_nso::my_class, int>{my_nso::my_class{7}}),
+      "expected(\"7\")");
+  EXPECT_EQ(fmt::format("{}",
+                        std::expected<my_nso::my_class_int, int>{
+                            my_nso::my_class_int{8}}),
+            "expected(8)");
+#endif
+}
+
 TEST(std_test, optional_format_as) {
 #ifdef __cpp_lib_optional
   EXPECT_EQ(fmt::format("{}", std::optional<my_nso::my_number>{}), "none");
@@ -195,6 +232,8 @@ TEST(std_test, optional_format_as) {
   EXPECT_EQ(fmt::format("{}", std::optional<my_nso::my_class>{}), "none");
   EXPECT_EQ(fmt::format("{}", std::optional{my_nso::my_class{7}}),
             "optional(\"7\")");
+  EXPECT_EQ(fmt::format("{}", std::optional{my_nso::my_class_int{8}}),
+            "optional(8)");
 #endif
 }
 
@@ -264,20 +303,42 @@ TEST(std_test, variant) {
 #endif
 }
 
+TEST(std_test, variant_format_as) {
+#ifdef __cpp_lib_variant
+
+  EXPECT_EQ(fmt::format("{}", std::variant<my_nso::my_number>{}),
+            "variant(\"first\")");
+  EXPECT_EQ(fmt::format(
+                "{}", std::variant<my_nso::my_number>{my_nso::my_number::one}),
+            "variant(\"first\")");
+  EXPECT_EQ(
+      fmt::format("{}", std::variant<my_nso::my_class>{my_nso::my_class{7}}),
+      "variant(\"7\")");
+  EXPECT_EQ(
+      fmt::format("{}",
+                  std::variant<my_nso::my_class_int>{my_nso::my_class_int{8}}),
+      "variant(8)");
+#endif
+}
+
 TEST(std_test, error_code) {
   auto& generic = std::generic_category();
-  EXPECT_EQ("generic:42",
+  EXPECT_EQ(fmt::format("{}", std::error_code(42, generic)), "generic:42");
-            fmt::format(FMT_STRING("{0}"), std::error_code(42, generic)));
+  EXPECT_EQ(fmt::format("{:>12}", std::error_code(42, generic)),
-  EXPECT_EQ("  generic:42",
+            "  generic:42");
-            fmt::format(FMT_STRING("{:>12}"), std::error_code(42, generic)));
+  EXPECT_EQ(fmt::format("{:12}", std::error_code(42, generic)), "generic:42  ");
-  EXPECT_EQ("generic:42  ",
+  EXPECT_EQ(fmt::format("{}", std::error_code(42, fmt::system_category())),
-            fmt::format(FMT_STRING("{:12}"), std::error_code(42, generic)));
+            "system:42");
-  EXPECT_EQ("system:42",
+  EXPECT_EQ(fmt::format("{}", std::error_code(-42, fmt::system_category())),
-            fmt::format(FMT_STRING("{0}"),
+            "system:-42");
-                        std::error_code(42, fmt::system_category())));
+  auto ec = std::make_error_code(std::errc::value_too_large);
-  EXPECT_EQ("system:-42",
+  EXPECT_EQ(fmt::format("{:s}", ec), ec.message());
-            fmt::format(FMT_STRING("{0}"),
+  EXPECT_EQ(fmt::format("{:?}", std::error_code(42, generic)),
-                        std::error_code(-42, fmt::system_category())));
+            "\"generic:42\"");
+  EXPECT_EQ(fmt::format("{}",
+                        std::map<std::error_code, int>{
+                            {std::error_code(42, generic), 0}}),
+            "{\"generic:42\": 0}");
 }
 
 template <typename Catch> void exception_test() {
@@ -373,11 +434,12 @@ TEST(std_test, format_atomic) {
 
 #ifdef __cpp_lib_atomic_flag_test
 TEST(std_test, format_atomic_flag) {
-  std::atomic_flag f = ATOMIC_FLAG_INIT;
+  std::atomic_flag f;
   (void)f.test_and_set();
   EXPECT_EQ(fmt::format("{}", f), "true");
 
-  const std::atomic_flag cf = ATOMIC_FLAG_INIT;
+  f.clear();
+  const std::atomic_flag& cf = f;
   EXPECT_EQ(fmt::format("{}", cf), "false");
 }
 #endif  // __cpp_lib_atomic_flag_test
@@ -402,5 +464,31 @@ TEST(std_test, format_shared_ptr) {
 
 TEST(std_test, format_reference_wrapper) {
   int num = 35;
-  EXPECT_EQ("35", fmt::to_string(std::cref(num)));
+  EXPECT_EQ(fmt::to_string(std::cref(num)), "35");
+  EXPECT_EQ(fmt::to_string(std::ref(num)), "35");
+  EXPECT_EQ(fmt::format("{}", std::cref(num)), "35");
+  EXPECT_EQ(fmt::format("{}", std::ref(num)), "35");
+}
+
+// Regression test for https://github.com/fmtlib/fmt/issues/4424.
+struct type_with_format_as {};
+int format_as(type_with_format_as) { return 20; }
+
+TEST(std_test, format_reference_wrapper_with_format_as) {
+  type_with_format_as t;
+  EXPECT_EQ(fmt::to_string(std::cref(t)), "20");
+  EXPECT_EQ(fmt::to_string(std::ref(t)), "20");
+  EXPECT_EQ(fmt::format("{}", std::cref(t)), "20");
+  EXPECT_EQ(fmt::format("{}", std::ref(t)), "20");
+}
+
+struct type_with_format_as_string {};
+std::string format_as(type_with_format_as_string) { return "foo"; }
+
+TEST(std_test, format_reference_wrapper_with_format_as_string) {
+  type_with_format_as_string t;
+  EXPECT_EQ(fmt::to_string(std::cref(t)), "foo");
+  EXPECT_EQ(fmt::to_string(std::ref(t)), "foo");
+  EXPECT_EQ(fmt::format("{}", std::cref(t)), "foo");
+  EXPECT_EQ(fmt::format("{}", std::ref(t)), "foo");
 }

test/util.h

@@ -31,17 +31,6 @@ extern const char* const file_content;
 // Opens a buffered file for reading.
 auto open_buffered_file(FILE** fp = nullptr) -> fmt::buffered_file;
 
-inline auto safe_fopen(const char* filename, const char* mode) -> FILE* {
-#if defined(_WIN32) && !defined(__MINGW32__)
-  // Fix MSVC warning about "unsafe" fopen.
-  FILE* f = nullptr;
-  errno = fopen_s(&f, filename, mode);
-  return f;
-#else
-  return std::fopen(filename, mode);
-#endif
-}
-
 template <typename Char> class basic_test_string {
  private:
   std::basic_string<Char> value_;

test/xchar-test.cc

@@ -74,12 +74,13 @@ TEST(xchar_test, format_explicitly_convertible_to_wstring_view) {
 TEST(xchar_test, format) {
   EXPECT_EQ(fmt::format(L"{}", 42), L"42");
   EXPECT_EQ(fmt::format(L"{}", 4.2), L"4.2");
+  EXPECT_EQ(fmt::format(L"{}", 1e100), L"1e+100");
   EXPECT_EQ(fmt::format(L"{}", L"abc"), L"abc");
   EXPECT_EQ(fmt::format(L"{}", L'z'), L"z");
   EXPECT_THROW(fmt::format(fmt::runtime(L"{:*\x343E}"), 42), fmt::format_error);
   EXPECT_EQ(fmt::format(L"{}", true), L"true");
   EXPECT_EQ(fmt::format(L"{0}", L'a'), L"a");
-  EXPECT_EQ(fmt::format(L"Letter {}", L'\x40e'), L"Letter \x40e"); // Ў
+  EXPECT_EQ(fmt::format(L"Letter {}", L'\x40e'), L"Letter \x40e");  // Ў
   if (sizeof(wchar_t) == 4)
     EXPECT_EQ(fmt::format(fmt::runtime(L"{:𓀨>3}"), 42), L"𓀨42");
   EXPECT_EQ(fmt::format(L"{}c{}", L"ab", 1), L"abc1");
@@ -171,6 +172,13 @@ TEST(xchar_test, join) {
   EXPECT_EQ(fmt::format(L"({})", fmt::join(t, L", ")), L"(a, 1, 2)");
 }
 
+#ifdef __cpp_lib_byte
+TEST(xchar_test, join_bytes) {
+  auto v = std::vector<std::byte>{std::byte(1), std::byte(2), std::byte(3)};
+  EXPECT_EQ(fmt::format(L"{}", fmt::join(v, L", ")), L"1, 2, 3");
+}
+#endif
+
 enum streamable_enum {};
 
 std::wostream& operator<<(std::wostream& os, streamable_enum) {
@@ -224,106 +232,9 @@ TEST(xchar_test, chrono) {
   EXPECT_EQ(L"42s", fmt::format(L"{}", std::chrono::seconds(42)));
   EXPECT_EQ(fmt::format(L"{:%F}", tm), L"2016-04-25");
   EXPECT_EQ(fmt::format(L"{:%T}", tm), L"11:22:33");
-}
 
-std::wstring system_wcsftime(const std::wstring& format, const std::tm* timeptr,
+  auto t = fmt::sys_time<std::chrono::seconds>(std::chrono::seconds(290088000));
-                             std::locale* locptr = nullptr) {
+  EXPECT_EQ(fmt::format("{:%Y-%m-%d %H:%M:%S}", t), "1979-03-12 12:00:00");
-  auto loc = locptr ? *locptr : std::locale::classic();
-  auto& facet = std::use_facet<std::time_put<wchar_t>>(loc);
-  std::wostringstream os;
-  os.imbue(loc);
-  facet.put(os, os, L' ', timeptr, format.c_str(),
-            format.c_str() + format.size());
-#ifdef _WIN32
-  // Workaround a bug in older versions of Universal CRT.
-  auto str = os.str();
-  if (str == L"-0000") str = L"+0000";
-  return str;
-#else
-  return os.str();
-#endif
-}
-
-TEST(chrono_test_wchar, time_point) {
-  auto t1 = std::chrono::time_point_cast<std::chrono::seconds>(
-      std::chrono::system_clock::now());
-
-  std::vector<std::wstring> spec_list = {
-      L"%%",  L"%n",  L"%t",  L"%Y",  L"%EY", L"%y",  L"%Oy", L"%Ey", L"%C",
-      L"%EC", L"%G",  L"%g",  L"%b",  L"%h",  L"%B",  L"%m",  L"%Om", L"%U",
-      L"%OU", L"%W",  L"%OW", L"%V",  L"%OV", L"%j",  L"%d",  L"%Od", L"%e",
-      L"%Oe", L"%a",  L"%A",  L"%w",  L"%Ow", L"%u",  L"%Ou", L"%H",  L"%OH",
-      L"%I",  L"%OI", L"%M",  L"%OM", L"%S",  L"%OS", L"%x",  L"%Ex", L"%X",
-      L"%EX", L"%D",  L"%F",  L"%R",  L"%T",  L"%p"};
-#ifndef _WIN32
-  // Disabled on Windows, because these formats is not consistent among
-  // platforms.
-  spec_list.insert(spec_list.end(), {L"%c", L"%Ec", L"%r"});
-#elif !FMT_HAS_C99_STRFTIME
-  // Only C89 conversion specifiers when using MSVCRT instead of UCRT
-  spec_list = {L"%%", L"%Y", L"%y", L"%b", L"%B", L"%m", L"%U",
-               L"%W", L"%j", L"%d", L"%a", L"%A", L"%w", L"%H",
-               L"%I", L"%M", L"%S", L"%x", L"%X", L"%p"};
-#endif
-  spec_list.push_back(L"%Y-%m-%d %H:%M:%S");
-
-  for (const auto& spec : spec_list) {
-    auto t = std::chrono::system_clock::to_time_t(t1);
-    auto tm = *std::gmtime(&t);
-
-    auto sys_output = system_wcsftime(spec, &tm);
-
-    auto fmt_spec = fmt::format(L"{{:{}}}", spec);
-    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), t1));
-    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
-  }
-
-  // Timezone formatters tests makes sense for localtime.
-#if FMT_HAS_C99_STRFTIME
-  spec_list = {L"%z", L"%Z"};
-#else
-  spec_list = {L"%Z"};
-#endif
-  for (const auto& spec : spec_list) {
-    auto t = std::chrono::system_clock::to_time_t(t1);
-    auto tm = *std::localtime(&t);
-
-    auto sys_output = system_wcsftime(spec, &tm);
-
-    auto fmt_spec = fmt::format(L"{{:{}}}", spec);
-    EXPECT_EQ(sys_output, fmt::format(fmt::runtime(fmt_spec), tm));
-
-    if (spec == L"%z") {
-      sys_output.insert(sys_output.end() - 2, 1, L':');
-      EXPECT_EQ(sys_output, fmt::format(L"{:%Ez}", tm));
-      EXPECT_EQ(sys_output, fmt::format(L"{:%Oz}", tm));
-    }
-  }
-
-  // Separate tests for UTC, since std::time_put can use local time and ignoring
-  // the timezone in std::tm (if it presents on platform).
-  if (fmt::detail::has_member_data_tm_zone<std::tm>::value) {
-    auto t = std::chrono::system_clock::to_time_t(t1);
-    auto tm = *std::gmtime(&t);
-
-    std::vector<std::wstring> tz_names = {L"GMT", L"UTC"};
-    EXPECT_THAT(tz_names, Contains(fmt::format(L"{:%Z}", t1)));
-    EXPECT_THAT(tz_names, Contains(fmt::format(L"{:%Z}", tm)));
-  }
-
-  if (fmt::detail::has_member_data_tm_gmtoff<std::tm>::value) {
-    auto t = std::chrono::system_clock::to_time_t(t1);
-    auto tm = *std::gmtime(&t);
-
-    EXPECT_EQ(L"+0000", fmt::format(L"{:%z}", t1));
-    EXPECT_EQ(L"+0000", fmt::format(L"{:%z}", tm));
-
-    EXPECT_EQ(L"+00:00", fmt::format(L"{:%Ez}", t1));
-    EXPECT_EQ(L"+00:00", fmt::format(L"{:%Ez}", tm));
-
-    EXPECT_EQ(L"+00:00", fmt::format(L"{:%Oz}", t1));
-    EXPECT_EQ(L"+00:00", fmt::format(L"{:%Oz}", tm));
-  }
 }
 
 TEST(xchar_test, color) {
@@ -468,7 +379,7 @@ TEST(locale_test, int_formatter) {
   f.parse(parse_ctx);
   auto buf = fmt::memory_buffer();
   fmt::basic_format_context<fmt::appender, char> format_ctx(
-      fmt::appender(buf), {}, fmt::detail::locale_ref(loc));
+      fmt::appender(buf), {}, fmt::locale_ref(loc));
   f.format(12345, format_ctx);
   EXPECT_EQ(fmt::to_string(buf), "12,345");
 }
@@ -491,12 +402,20 @@ TEST(locale_test, sign) {
   EXPECT_EQ(fmt::format(std::locale(), L"{:L}", -50), L"-50");
 }
 
+TEST(std_test_xchar, format_bitset) {
+  auto bs = std::bitset<6>(42);
+  EXPECT_EQ(fmt::format(L"{}", bs), L"101010");
+  EXPECT_EQ(fmt::format(L"{:0>8}", bs), L"00101010");
+  EXPECT_EQ(fmt::format(L"{:-^12}", bs), L"---101010---");
+}
+
 TEST(std_test_xchar, complex) {
   auto s = fmt::format(L"{}", std::complex<double>(1, 2));
   EXPECT_EQ(s, L"(1+2i)");
   EXPECT_EQ(fmt::format(L"{:.2f}", std::complex<double>(1, 2)),
             L"(1.00+2.00i)");
   EXPECT_EQ(fmt::format(L"{:8}", std::complex<double>(1, 2)), L"(1+2i)  ");
+  EXPECT_EQ(fmt::format(L"{:-<8}", std::complex<double>(1, 2)), L"(1+2i)--");
 }
 
 TEST(std_test_xchar, optional) {