Merge 8793ca53e5dbcade50fbf281fe5ad99833cbaa95 into 17500e457b198c37c4374d142fa7a1d36e4651fe

A named argument that arrives const-qualified was not recognized by
is_named_arg, silently dropping its name. This happens both when a
named argument is passed through an intermediate function returning
const T& (https://github.com/fmtlib/fmt/issues/4866) and in fmt's own
compiled format path, which passes arguments as const T&.

Make is_named_arg and is_static_named_arg see through top-level const so
the name is preserved instead of dropped.

.github/workflows/linux.yml

@@ -13,6 +13,10 @@ jobs:
       ${{matrix.shared && 'Shared' || ''}}
       ${{matrix.cxxflags_extra && 'Sanitize' || ''}}
     runs-on: ${{ matrix.os || 'ubuntu-22.04' }}
+    env:
+      # Run tests in a non-UTC timezone. glibc localtime/strftime honor TZ, so
+      # there is no need for timedatectl, which fails without systemd-timedated.
+      TZ: Europe/Kyiv
     strategy:
       matrix:
         cxx: [g++-4.9, g++-11, clang++-3.6, clang++-11]
@@ -75,15 +79,14 @@ jobs:
     steps:
     - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
 
-    - name: Set timezone
-      run: sudo timedatectl set-timezone 'Europe/Kyiv'
-
     - name: Install GCC 4.9
       run: |
         sudo apt update
         sudo apt install libatomic1 libc6-dev libgomp1 libitm1 libmpc3
         # https://launchpad.net/ubuntu/xenial/amd64/g++-4.9/4.9.3-13ubuntu2
-        wget --no-verbose \
+        # launchpad periodically returns 503s, so retry to avoid flaky CI.
+        wget --no-verbose --tries=5 --waitretry=10 \
+          --retry-connrefused --retry-on-http-error=503 \
           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 \
@@ -114,7 +117,9 @@ jobs:
         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 \
+        # launchpad periodically returns 503s, so retry to avoid flaky CI.
+        wget --no-verbose --tries=5 --waitretry=10 \
+          --retry-connrefused --retry-on-http-error=503 \
           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 \

ChangeLog.md

@@ -1,3 +1,70 @@
+# 12.2.1 - TBD
+
+- Added a formatter for `std::exception_ptr` that formats the referenced
+  exception (or `none` when null)
+  (https://github.com/fmtlib/fmt/issues/4808,
+  https://github.com/fmtlib/fmt/pull/4819).
+  Thanks @avikivity and @Atlas-Zero.
+
+- Added unwinding of nested exceptions created via
+  `std::throw_with_nested` to the `std::exception` formatter, joining each
+  level with `": "` (https://github.com/fmtlib/fmt/pull/4844).
+  Thanks @avikivity.
+
+- Exported the ostream formatters (`fmt::basic_ostream_formatter`,
+  `fmt::ostream_formatter`) and `fmt::streamed` from the C++20 module
+  (https://github.com/fmtlib/fmt/pull/4861). Thanks @avikivity.
+
+- Optimized 128-bit integer formatting by reducing the value to 64-bit
+  chunks instead of doing repeated 128-bit division, giving a ~5x speedup
+  on full-range values.
+
+- Fixed handling of out-of-range floating-point durations in chrono
+  formatting (https://github.com/fmtlib/fmt/pull/4802). Thanks @aizu-m.
+
+- Fixed a hang and assertion failure when printing to a pipe whose read
+  end is closed (https://github.com/fmtlib/fmt/issues/4797).
+  Thanks @nikola-sh.
+
+- Fixed formatting of out-of-range integers with the `c` presentation
+  type, which previously mangled negative values and silently truncated
+  out-of-range ones (https://github.com/fmtlib/fmt/issues/4839).
+  Thanks @igoloe.
+
+- Fixed an `FMT_COMPILE` failure for user-defined types formatted via
+  `format_as` (https://github.com/fmtlib/fmt/issues/4794,
+  https://github.com/fmtlib/fmt/pull/4836).
+  Thanks @mjerabek and @upadhyay74aman.
+
+- Fixed the fallback `uint128` bitwise-not implementation
+  (https://github.com/fmtlib/fmt/pull/4813). Thanks @Vcode2407.
+
+- Fixed a false positive in `fmt::is_contiguous` by explicitly checking
+  for `operator[]` on the container itself
+  (https://github.com/fmtlib/fmt/pull/4825). Thanks @tearfur.
+
+- Generated the build-tree CMake export set regardless of `FMT_INSTALL`,
+  so projects consuming {fmt} via `add_subdirectory` or `FetchContent` can
+  export their own `fmt::*`-dependent targets
+  (https://github.com/fmtlib/fmt/issues/4806,
+  https://github.com/fmtlib/fmt/pull/4850). Thanks @Krzmbrzl and @hexonal.
+
+- Made the `fmt-c` library respect `BUILD_SHARED_LIBS` like the main
+  {fmt} library (https://github.com/fmtlib/fmt/pull/4812). Thanks @jengelh.
+
+- Skipped `VERSION`/`SOVERSION`/`DEBUG_POSTFIX` on the header-only
+  `INTERFACE` target (https://github.com/fmtlib/fmt/pull/4830).
+  Thanks @soumik15630m.
+
+- Suppressed the MSVC C4702 (unreachable code) warning
+  (https://github.com/fmtlib/fmt/pull/4822). Thanks @torsten48.
+
+- Documented that the hexfloat `a`/`A` presentation types always emit the
+  `0x` prefix (https://github.com/fmtlib/fmt/pull/4862). Thanks @ny000815.
+
+- Fixed a minor formatting issue in the documentation
+  (https://github.com/fmtlib/fmt/pull/4826). Thanks @brooklynwidz.
+
 # 12.2.0 - 2026-06-16
 
 - Added a C11 API that brings fast, type-safe formatting to C. The new

doc/api.md

@@ -92,6 +92,10 @@ 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
 take an object of your type and return an object of a formattable type.
 It should be defined in the same namespace as your type.
+`format_as` cannot be used when a type also matches another `formatter`
+specialization, such as the range `formatter`, because the specializations
+would be ambiguous. Disable the conflicting specialization, if possible,
+or provide an explicit `formatter` specialization instead.
 
 Example ([run](https://godbolt.org/z/nvME4arz8)):
 

include/fmt/base.h

@@ -1059,6 +1059,10 @@ template <typename T> struct is_static_named_arg : std::false_type {};
 template <typename T, typename Char>
 struct is_named_arg<named_arg<T, Char>> : std::true_type {};
 
+template <typename T> struct is_named_arg<const T> : is_named_arg<T> {};
+template <typename T>
+struct is_static_named_arg<const T> : is_static_named_arg<T> {};
+
 template <typename T, typename Char = char> struct named_arg : view {
   const Char* name;
   const T& value;

include/fmt/ostream.h

@@ -165,7 +165,6 @@ void println(std::ostream& os, format_string<T...> fmt, T&&... args) {
 }
 
 FMT_END_EXPORT
-
 FMT_END_NAMESPACE
 
 #endif  // FMT_OSTREAM_H_

test/add-subdirectory-test/CMakeLists.txt

@@ -19,6 +19,5 @@ endif ()
 # Test that a target depending on fmt can itself be exported (#4806).
 add_library(export-test INTERFACE)
 target_link_libraries(export-test INTERFACE fmt::fmt)
-export(
+export(TARGETS export-test
-  TARGETS export-test
+       FILE ${CMAKE_CURRENT_BINARY_DIR}/export-test-targets.cmake)
-  FILE ${CMAKE_CURRENT_BINARY_DIR}/export-test-targets.cmake)

test/compile-test.cc

@@ -163,6 +163,10 @@ TEST(compile_test, named) {
             fmt::format(FMT_COMPILE("{a0} {a1}"), "a0"_a = 41, "a1"_a = 43));
   EXPECT_EQ("41 43",
             fmt::format(FMT_COMPILE("{a1} {a0}"), "a0"_a = 43, "a1"_a = 41));
+
+  // A statically-named argument with a format spec compiles to spec_field,
+  // which passes the argument to make_format_args as const (#4866).
+  EXPECT_EQ("4.2", fmt::format(FMT_COMPILE("{arg:3.1f}"), "arg"_a = 4.2));
 #  endif
 }
 
@@ -480,12 +484,13 @@ TEST(compile_test, constexpr_string_format) {
 }
 #endif  // FMT_USE_CONSTEXPR_STRING
 
-namespace {
+struct type_with_format_as {
-struct compile_format_as_type {
   int value;
 };
-int format_as(compile_format_as_type f) { return f.value; }
+int format_as(type_with_format_as v) { return v.value; }
-} 
+
 TEST(compile_test, format_as) {
-  EXPECT_EQ("42", fmt::format(FMT_COMPILE("{}"), compile_format_as_type{42}));
+  // Use a format string other than "{}" so that formatting goes through the
-}
+  // compiled field path rather than the to_string fast path.
+  EXPECT_EQ("[42]", fmt::format(FMT_COMPILE("[{}]"), type_with_format_as{42}));
+}