From e424a934afdc26589432f9102c3435e98d58ab67 Mon Sep 17 00:00:00 2001
From: ClausKlein <claus.klein@arcormail.de>
Date: Mon, 13 Jul 2026 23:41:32 +0200
Subject: [PATCH] Fix for find-package-test and C++20 link issues

---
 .github/workflows/linux.yml           | 4 ++--
 CMakeLists.txt                        | 6 ++++++
 GNUmakefile                           | 6 +++---
 test/CMakeLists.txt                   | 2 ++
 test/find-package-test/CMakeLists.txt | 3 ---
 5 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 36a50306..8dec8b1b 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -15,7 +15,7 @@ jobs:
     runs-on: ${{ matrix.os || 'ubuntu-22.04' }}
     strategy:
       matrix:
-        cxx: [g++-4.9, g++-11, clang++-3.6, clang++-11]
+        cxx: [g++-4.9, g++-11, clang++-11]
         build_type: [Debug, Release]
         std: [11]
         shared: [""]
@@ -42,7 +42,7 @@ jobs:
             std: 23
             os: ubuntu-24.04
             gen: Ninja
-          - cxx: clang++-3.6
+          # - cxx: clang++-3.6
           - cxx: clang++-11
             build_type: Debug
             std: 17
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 682bfc7c..e2a52e8c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -416,6 +416,12 @@ endfunction ()
 if (FMT_MODULE)
   add_module_library(fmt-module src/fmt.cc USE_CMAKE_MODULES
                      ${FMT_USE_CMAKE_MODULES})
+  # Add implementation sources as separate compilation units
+  # This ensures symbols are available for linking even in C++20
+  target_sources(fmt-module PRIVATE src/format.cc)
+  if (FMT_OS)
+    target_sources(fmt-module PRIVATE src/os.cc)
+  endif ()
   setup_target(fmt-module PUBLIC)
 endif ()
 
diff --git a/GNUmakefile b/GNUmakefile
index 2657ce53..158a0973 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -18,18 +18,18 @@ build: GNUmakefile CMakeLists.txt
 	cmake --version # NOTE: v4.4 expected! CK
 	cmake -G Ninja -S . -B build --fresh \
 	  -D CMAKE_SKIP_TEST_ALL_DEPENDENCY=NO \
-	  -D FMT_MODULE=1 -D FMT_IMPORT_STD=1 -D CMAKE_CXX_STANDARD=23 \
+	  -D FMT_PEDANTIC=YES \
+	  -D FMT_MODULE=1 -D FMT_IMPORT_STD=0 -D CMAKE_CXX_STANDARD=20 \
 	  -D CMAKE_EXPERIMENTAL_CXX_IMPORT_STD=f35a9ac6-8463-4d38-8eec-5d6008153e7d
 	ln -fs build/compile_commands.json .
 
 find-package-test: install
 	cmake -G Ninja -S test/find-package-test -B build/find-package-build --fresh \
-	  -D FMT_MODULE=1 -D FMT_IMPORT_STD=1 -D CMAKE_CXX_STANDARD=23 \
+	  -D FMT_MODULE=1 -D FMT_IMPORT_STD=0 -D CMAKE_CXX_STANDARD=20 \
 	  -D CMAKE_EXPERIMENTAL_CXX_IMPORT_STD=f35a9ac6-8463-4d38-8eec-5d6008153e7d
 	ninja -C build/find-package-build -v
 	ninja -C build/find-package-build -t deps CMakeFiles/module-test.dir/main.cc.o
 	./build/find-package-build/module-test build/find-package-build/*-test
-	
 
 clean:
 	rm -rf build .cache compile_commands.json
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 28d143d4..4e05da80 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -184,6 +184,8 @@ if (FMT_PEDANTIC
     "-DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}"
     "-DCMAKE_CXX_FLAGS=${CMAKE_CXX_FLAGS}"
     "-DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD}"
+    "-DFMT_IMPORT_STD=${FMT_IMPORT_STD}"
+    "-DCMAKE_EXPERIMENTAL_CXX_IMPORT_STD=${CMAKE_EXPERIMENTAL_CXX_IMPORT_STD}"
     "-DFMT_DIR=${PROJECT_BINARY_DIR}"
     "-DPEDANTIC_COMPILE_FLAGS=${PEDANTIC_COMPILE_FLAGS}"
     "-DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}")
diff --git a/test/find-package-test/CMakeLists.txt b/test/find-package-test/CMakeLists.txt
index 27171c72..1372c8c1 100644
--- a/test/find-package-test/CMakeLists.txt
+++ b/test/find-package-test/CMakeLists.txt
@@ -9,13 +9,11 @@ set(PEDANTIC_COMPILE_FLAGS)
 add_executable(library-test main.cc)
 target_link_libraries(library-test fmt::fmt)
 target_compile_options(library-test PRIVATE ${PEDANTIC_COMPILE_FLAGS})
-target_include_directories(library-test PUBLIC SYSTEM .)
 
 if (TARGET fmt::fmt-header-only)
   add_executable(header-only-test main.cc)
   target_link_libraries(header-only-test fmt::fmt-header-only)
   target_compile_options(header-only-test PRIVATE ${PEDANTIC_COMPILE_FLAGS})
-  target_include_directories(header-only-test PUBLIC SYSTEM .)
 endif ()
 
 if (TARGET fmt::fmt-module)
@@ -26,5 +24,4 @@ if (TARGET fmt::fmt-module)
     target_compile_features(module-test PRIVATE cxx_std_23)
     set_target_properties(module-test PROPERTIES CXX_MODULE_STD 1)
   endif ()
-  target_include_directories(module-test PUBLIC SYSTEM .)
 endif ()