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CMake/Modules/Internal/FeatureTesting.cmake

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project: Add infrastructure for recording CXX compiler features Add a feature test using the compiler macros and the preprocessor to determine available features. Add a CMAKE_CXX_COMPILE_FEATURES variable which contains all features known to the loaded compiler, and a CMAKE_CXX_KNOWN_FEATURES variable containing all features known to CMake. Add language standard specific variables for internal use to determine the standard-specific compile flags to use. This will be extended to other languages in the future. Follow-up commits will add features which will be recorded by the feature test.
2013-10-17 13:47:29 +04:00
macro(record_compiler_features lang compile_flags feature_list)
include("${CMAKE_ROOT}/Modules/Compiler/${CMAKE_${lang}_COMPILER_ID}-${lang}-FeatureTests.cmake" OPTIONAL)
string(TOLOWER ${lang} lang_lc)
file(REMOVE "${CMAKE_BINARY_DIR}/CMakeFiles/feature_tests.bin")
file(WRITE "${CMAKE_BINARY_DIR}/CMakeFiles/feature_tests.${lang_lc}" "
Features: Extract strings from test binary more reliably (#15736) Since commit v3.1.0-rc1~635^2~7 (project: Add infrastructure for recording CXX compiler features, 2013-10-17) we compile a test source to a binary and then extract "<LANG>_FEATURES:..." strings from the binary with the file(STRINGS) command. Add a newline at the beginning of the string literal to be sure file(STRINGS) can extract the first entry as a string independent of whatever else the compiler may put before the storage it allocates for the literal within the binary.
2015-09-10 21:37:20 +03:00
const char features[] = {\"\\n\"\n")
Features: Make CMAKE_CXX_KNOWN_FEATURES a property. As a 'built-in' variable it imposes a cost on all variable lookups and it is expected to be rarely used.
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get_property(known_features GLOBAL PROPERTY CMAKE_${lang}_KNOWN_FEATURES)
foreach(feature ${known_features})
project: Add infrastructure for recording CXX compiler features Add a feature test using the compiler macros and the preprocessor to determine available features. Add a CMAKE_CXX_COMPILE_FEATURES variable which contains all features known to the loaded compiler, and a CMAKE_CXX_KNOWN_FEATURES variable containing all features known to CMake. Add language standard specific variables for internal use to determine the standard-specific compile flags to use. This will be extended to other languages in the future. Follow-up commits will add features which will be recorded by the feature test.
2013-10-17 13:47:29 +04:00
if (_cmake_feature_test_${feature})
if (${_cmake_feature_test_${feature}} STREQUAL 1)
set(_feature_condition "\"1\" ")
else()
set(_feature_condition "#if ${_cmake_feature_test_${feature}}\n\"1\"\n#else\n\"0\"\n#endif\n")
endif()
file(APPEND "${CMAKE_BINARY_DIR}/CMakeFiles/feature_tests.${lang_lc}" "\"${lang}_FEATURE:\"\n${_feature_condition}\"${feature}\\n\"\n")
endif()
endforeach()
file(APPEND "${CMAKE_BINARY_DIR}/CMakeFiles/feature_tests.${lang_lc}"
Features: Use the features symbol in the feature-test compile. Clang discards the entire string if it is not used, removing the ability to read the features from the compiled binary. That is prevented by using the symbol. GNU with -O3 also discards the string, so use the string in a way which is determined by a runtime value (argc) to prevent it being discarded.
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"\n};\n\nint main(int argc, char** argv) { (void)argv; return features[argc]; }\n")
project: Add infrastructure for recording CXX compiler features Add a feature test using the compiler macros and the preprocessor to determine available features. Add a CMAKE_CXX_COMPILE_FEATURES variable which contains all features known to the loaded compiler, and a CMAKE_CXX_KNOWN_FEATURES variable containing all features known to CMake. Add language standard specific variables for internal use to determine the standard-specific compile flags to use. This will be extended to other languages in the future. Follow-up commits will add features which will be recorded by the feature test.
2013-10-17 13:47:29 +04:00
try_compile(CMAKE_${lang}_FEATURE_TEST
${CMAKE_BINARY_DIR} "${CMAKE_BINARY_DIR}/CMakeFiles/feature_tests.${lang_lc}"
COMPILE_DEFINITIONS "${compile_flags}"
OUTPUT_VARIABLE _output
COPY_FILE "${CMAKE_BINARY_DIR}/CMakeFiles/feature_tests.bin"
COPY_FILE_ERROR _copy_error
)
if(CMAKE_${lang}_FEATURE_TEST AND NOT _copy_error)
set(_result 0)
else()
set(_result 255)
endif()
unset(CMAKE_${lang}_FEATURE_TEST CACHE)
if (_result EQUAL 0)
file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
"\n\nDetecting ${lang} [${compile_flags}] compiler features compiled with the following output:\n${_output}\n\n")
if(EXISTS "${CMAKE_BINARY_DIR}/CMakeFiles/feature_tests.bin")
file(STRINGS "${CMAKE_BINARY_DIR}/CMakeFiles/feature_tests.bin"
features REGEX "${lang}_FEATURE:.*")
foreach(info ${features})
file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
" Feature record: ${info}\n")
string(REPLACE "${lang}_FEATURE:" "" info ${info})
string(SUBSTRING ${info} 0 1 has_feature)
if(has_feature)
string(REGEX REPLACE "^1" "" feature ${info})
list(APPEND ${feature_list} ${feature})
endif()
endforeach()
endif()
else()
file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
"Detecting ${lang} [${compile_flags}] compiler features failed to compile with the following output:\n${_output}\n${_copy_error}\n\n")
endif()
endmacro()