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Stop enabling C++26 reflection by default

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Don't inject -freflection when building the module, so it isn't forced onto
the module or its importers. Build enum-test unconditionally (it is a no-op
without reflection) and drop the now-unneeded reflection detection. Enable
reflection explicitly in the g++-16 C++26 CI job.
This commit is contained in:
Victor Zverovich 2026-08-29 16:28:09 -07:00
parent 9375eb3792
commit bb1bcede25
3 changed files with 2 additions and 62 deletions
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1
.github/workflows/linux.yml vendored
View File

@ -50,6 +50,7 @@ jobs:
build_type: Debug
std: 26
os: ubuntu-24.04
cxxflags: -freflection
install: sudo apt install g++-16
- cxx: clang++-3.6
- cxx: clang++-11

32
CMakeLists.txt
View File

@ -409,41 +409,9 @@ function (add_module_library name)
target_sources(${name} PRIVATE ${sources})
endfunction ()
# Code that compiles only if C++26 reflection, required by fmt/enum.h, is
# available. Also used by test/CMakeLists.txt.
set(FMT_REFLECTION_TEST_CODE
"
#include <fmt/enum.h>
enum class [[=fmt::as_identifiers]] color { red };
static_assert(fmt::is_formattable<color>::value, \"\");
int main() {}
")
if (FMT_MODULE)
# Unlike with headers, whether fmt/enum.h provides anything is decided when
# the module is compiled, so detect reflection with the configured standard
# and enable it if possible. Reflection needs C++26 and, in some compilers
# such as GCC, an extra flag.
if (NOT MSVC AND CMAKE_CXX_STANDARD GREATER_EQUAL 26)
include(CheckCXXSourceCompiles)
set(CMAKE_REQUIRED_INCLUDES ${PROJECT_SOURCE_DIR}/include)
check_cxx_source_compiles("${FMT_REFLECTION_TEST_CODE}"
FMT_MODULE_HAVE_REFLECTION)
if (NOT FMT_MODULE_HAVE_REFLECTION)
set(CMAKE_REQUIRED_FLAGS -freflection)
check_cxx_source_compiles("${FMT_REFLECTION_TEST_CODE}"
FMT_MODULE_HAVE_REFLECTION_FLAG)
unset(CMAKE_REQUIRED_FLAGS)
endif ()
unset(CMAKE_REQUIRED_INCLUDES)
endif ()
add_module_library(fmt-module src/fmt.cc USE_CMAKE_MODULES
${FMT_USE_CMAKE_MODULES})
if (FMT_MODULE_HAVE_REFLECTION_FLAG)
# PUBLIC because importers need the flag to use annotations.
target_compile_options(fmt-module PUBLIC -freflection)
endif ()
setup_target(fmt-module PUBLIC)
endif ()

31
test/CMakeLists.txt
View File

@ -45,6 +45,7 @@ add_fmt_test(base-test)
add_fmt_test(assert-test)
add_fmt_test(chrono-test)
add_fmt_test(color-test)
add_fmt_test(enum-test)
add_fmt_test(gtest-extra-test)
add_fmt_test(format-test mock-allocator.h)
if (MSVC)
@ -77,36 +78,6 @@ add_fmt_test(enforce-checks-test)
target_compile_definitions(enforce-checks-test
PRIVATE -DFMT_ENFORCE_COMPILE_STRING)
# Enum formatting requires C++26 reflection, which needs compiler support and,
# in some compilers such as GCC, an extra flag to enable it.
if (NOT MSVC)
include(CheckCXXSourceCompiles)
set(CMAKE_REQUIRED_INCLUDES ${PROJECT_SOURCE_DIR}/include)
set(CMAKE_REQUIRED_FLAGS "-std=c++26")
check_cxx_source_compiles("${FMT_REFLECTION_TEST_CODE}" FMT_HAVE_REFLECTION)
if (NOT FMT_HAVE_REFLECTION)
set(CMAKE_REQUIRED_FLAGS "-std=c++26 -freflection")
check_cxx_source_compiles("${FMT_REFLECTION_TEST_CODE}"
FMT_HAVE_REFLECTION_FLAG)
endif ()
unset(CMAKE_REQUIRED_FLAGS)
unset(CMAKE_REQUIRED_INCLUDES)
if (FMT_HAVE_REFLECTION OR FMT_HAVE_REFLECTION_FLAG)
add_fmt_test(enum-test)
set_target_properties(
enum-test
PROPERTIES CXX_STANDARD 26
CXX_STANDARD_REQUIRED ON
CXX_EXTENSIONS OFF)
if (FMT_HAVE_REFLECTION_FLAG)
target_compile_options(enum-test PRIVATE -freflection)
endif ()
else ()
message(STATUS "Reflection is not supported, skipping enum-test.")
endif ()
endif ()
add_executable(perf-sanity perf-sanity.cc)
target_link_libraries(perf-sanity fmt::fmt)