FOR TESTING ONLY: test windows clang-cl workflow

.github/workflows/ci-windows-installed.yml

@@ -66,18 +66,18 @@ jobs:
     - name: Prepare libavif (cmake)
       run: >
         cmake ${{ steps.vcpkg.outputs.vcpkg-cmake-config }} -G Ninja -S . -B build
-        -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=OFF
+        -DCMAKE_BUILD_TYPE=Release -DBUILD_SHARED_LIBS=ON
         -DAVIF_CODEC_AOM=SYSTEM -DAVIF_CODEC_DAV1D=SYSTEM
         -DAVIF_CODEC_RAV1E=SYSTEM
         -DAVIF_JPEG=SYSTEM -DAVIF_LIBXML2=SYSTEM
         -DAVIF_LIBYUV=SYSTEM -DAVIF_ZLIBPNG=SYSTEM
         -DAVIF_BUILD_EXAMPLES=ON -DAVIF_BUILD_APPS=ON
         -DAVIF_BUILD_TESTS=ON -DAVIF_ENABLE_GTEST=ON -DAVIF_GTEST=LOCAL
         -DAVIF_ENABLE_EXPERIMENTAL_YCGCO_R=ON
-        -DAVIF_ENABLE_EXPERIMENTAL_GAIN_MAP=ON
         -DAVIF_ENABLE_EXPERIMENTAL_METAV1=ON
         -DAVIF_ENABLE_EXPERIMENTAL_SAMPLE_TRANSFORM=ON
         -DAVIF_ENABLE_WERROR=ON $env:AVIF_CMAKE_C_COMPILER $env:AVIF_CMAKE_CXX_COMPILER
+        -DAVIF_ENABLE_NODISCARD=ON
     - name: Build libavif (ninja)
       working-directory: ./build
       run: ninja

CMakeLists.txt

@@ -33,8 +33,14 @@ include(FetchContent)
 include(FindPkgConfig)
 include(AvifExternalProjectUtils)
 
-# Set C99 as the default
-set(CMAKE_C_STANDARD 99)
+option(AVIF_ENABLE_NODISCARD "Add [[nodiscard]] to some functions. CMake must be at least 3.21 to force C23. Best effort." OFF)
+
+if(AVIF_ENABLE_NODISCARD AND CMAKE_VERSION VERSION_GREATER_EQUAL 3.21.0)
+    set(CMAKE_C_STANDARD 23)
+else()
+    # Set C99 as the default
+    set(CMAKE_C_STANDARD 99)
+endif()
 
 # SOVERSION scheme: MAJOR.MINOR.PATCH
 #   If there was an incompatible interface change:
@@ -52,7 +58,6 @@ set(LIBRARY_SOVERSION ${LIBRARY_VERSION_MAJOR})
 option(BUILD_SHARED_LIBS "Build shared avif library" ON)
 
 option(AVIF_ENABLE_WERROR "Treat all compiler warnings as errors" OFF)
-option(AVIF_ENABLE_NODISCARD "Add [[nodiscard]] to some functions. CMake must be at least 3.21 to force C23" OFF)
 
 option(AVIF_ENABLE_EXPERIMENTAL_YCGCO_R "Enable experimental YCgCo-R matrix code" OFF)
 option(AVIF_ENABLE_EXPERIMENTAL_GAIN_MAP
@@ -322,22 +327,6 @@ if(AVIF_ENABLE_WERROR)
     endif()
 endif()
 
-if(AVIF_ENABLE_NODISCARD)
-    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.21.0)
-        set(CMAKE_C_STANDARD 23)
-        set_property(TARGET avif_obj PROPERTY C_STANDARD 23)
-    else()
-        unset(CMAKE_C_STANDARD)
-        set_property(TARGET avif_obj PROPERTY C_STANDARD)
-        if(CMAKE_C_COMPILER_ID MATCHES "Clang" OR CMAKE_C_COMPILER_ID MATCHES "GNU")
-            target_compile_options(avif_obj PUBLIC $<BUILD_INTERFACE:$<$<COMPILE_LANGUAGE:C>:-std=gnu2x>>)
-        elseif(CMAKE_C_COMPILER_ID MATCHES "MSVC")
-            target_compile_options(avif_obj PUBLIC $<BUILD_INTERFACE:$<$<COMPILE_LANGUAGE:C>:/std:clatest>>)
-        endif()
-    endif()
-    target_compile_definitions(avif_obj PUBLIC $<BUILD_INTERFACE:AVIF_ENABLE_NODISCARD=1>)
-endif()
-
 if(AVIF_ENABLE_COVERAGE)
     if(CMAKE_C_COMPILER_ID MATCHES "Clang" OR CMAKE_C_COMPILER_ID MATCHES "GNU")
         message(STATUS "libavif: Enabling coverage for Clang")

include/avif/avif.h

@@ -48,8 +48,7 @@ extern "C" {
 #define AVIF_API
 #endif // defined(AVIF_DLL)
 
-#if defined(AVIF_ENABLE_NODISCARD) || (defined(__cplusplus) && __cplusplus >= 201703L) || \
-    (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202311L)
+#if (defined(__cplusplus) && __cplusplus >= 201703L) || (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 202000L)
 #define AVIF_NODISCARD [[nodiscard]]
 #else
 // Starting with 3.9, clang allows defining the warn_unused_result attribute for enums.