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cxxmodules: Scan only targets that explicitly enable C++ 20

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Previously we scanned any targets for which C++ 20 is enabled,
even if enabled only by the compiler's default, such as when
`CXXFLAGS=-std=c++20`.
This commit is contained in:
Brad King
2023-10-04 15:48:36 -04:00
parent 68fca3eafe
commit b8ead378de
4 changed files with 23 additions and 7 deletions
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12
Source/cmGeneratorTarget.cxx
View File

@@ -9142,13 +9142,11 @@ cmGeneratorTarget::Cxx20SupportLevel cmGeneratorTarget::HaveCxxModuleSupport(
}
cmStandardLevelResolver standardResolver(this->Makefile);
if (!standardResolver.HaveStandardAvailable(this, "CXX", config,
"cxx_std_20") ||
// During the ABI detection step we do not know the compiler's features.
// HaveStandardAvailable may return true as a fallback, but in this code
// path we do not want to assume C++ 20 is available.
this->Makefile->GetDefinition("CMAKE_CXX20_COMPILE_FEATURES")
.IsEmpty()) {
cmStandardLevel const cxxStd20 =
*standardResolver.LanguageStandardLevel("CXX", "20");
cm::optional<cmStandardLevel> explicitLevel =
this->GetExplicitStandardLevel("CXX", config);
if (!explicitLevel || *explicitLevel < cxxStd20) {
return Cxx20SupportLevel::NoCxx20;
}

13
Tests/RunCMake/CXXModules/ImplicitCXX20.cmake Normal file
View File

@@ -0,0 +1,13 @@
# Enable scanning by default for targets that explicitly use C++ 20.
cmake_policy(SET CMP0155 NEW)
# Force CMAKE_CXX_STANDARD_DEFAULT to be C++ 20.
set(ENV{CXXFLAGS} "$ENV{CXXFLAGS} ${CMAKE_CXX20_STANDARD_COMPILE_OPTION}")
enable_language(CXX)
# Hide any real scanning rule that may be available.
unset(CMAKE_CXX_SCANDEP_SOURCE)
# Create a target that does not explicitly use C++ 20 to verify it works
# without any scanning rule available.
add_executable(cmp0155-new sources/module-use.cxx)

2
Tests/RunCMake/CXXModules/Inspect.cmake
View File

@@ -23,6 +23,8 @@ set(forced_cxx_standard \"${forced_cxx_standard}\")
set(CMAKE_CXX_COMPILER_VERSION \"${CMAKE_CXX_COMPILER_VERSION}\")
set(CMAKE_CXX_OUTPUT_EXTENSION \"${CMAKE_CXX_OUTPUT_EXTENSION}\")
set(CXXModules_default_build_type \"${CMAKE_BUILD_TYPE}\")
set(CMAKE_CXX_STANDARD_DEFAULT \"${CMAKE_CXX_STANDARD_DEFAULT}\")
set(CMAKE_CXX20_STANDARD_COMPILE_OPTION \"${CMAKE_CXX20_STANDARD_COMPILE_OPTION}\")
")
file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/info.cmake" "${info}")

3
Tests/RunCMake/CXXModules/RunCMakeTest.cmake
View File

@@ -13,6 +13,9 @@ if ("cxx_std_20" IN_LIST CMAKE_CXX_COMPILE_FEATURES)
# standard. If the compiler forces a standard to be used, skip it.
if (NOT forced_cxx_standard)
run_cmake(NoCXX20)
if(CMAKE_CXX_STANDARD_DEFAULT AND CMAKE_CXX20_STANDARD_COMPILE_OPTION)
run_cmake_with_options(ImplicitCXX20 -DCMAKE_CXX20_STANDARD_COMPILE_OPTION=${CMAKE_CXX20_STANDARD_COMPILE_OPTION})
endif()
endif ()
run_cmake(NoScanningSourceFileProperty)