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# - Compile and run code to check for C++ features
#
# This functions compiles a source file under the `cmake` folder
# and adds the corresponding `HAVE_[FILENAME]` flag to the CMake
# environment
#
# cxx_feature_check(<FLAG> [<VARIANT>])
#
# - Example
#
# include(CXXFeatureCheck)
# cxx_feature_check(STD_REGEX)
# Requires CMake 3.13+
if(__cxx_feature_check)
return()
endif()
set(__cxx_feature_check INCLUDED)
option(CXXFEATURECHECK_DEBUG OFF "Enable debug messages for CXX feature checks")
function(cxx_feature_check_print log)
if(CXXFEATURECHECK_DEBUG)
message(STATUS "${log}")
endif()
endfunction()
function(cxx_feature_check FEATURE)
string(TOLOWER ${FEATURE} FILE)
string(TOUPPER HAVE_${FEATURE} VAR)
# Check if the variable is already defined to a true or false for a quick return.
# This allows users to predefine the variable to skip the check.
# Or, if the variable is already defined by a previous check, we skip the costly check.
if (DEFINED ${VAR})
if (${VAR})
cxx_feature_check_print("Feature ${FEATURE} already enabled.")
add_compile_definitions(${VAR})
else()
cxx_feature_check_print("Feature ${FEATURE} already disabled.")
endif()
return()
endif()
set(FEATURE_CHECK_CMAKE_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS})
if (ARGC GREATER 1)
message(STATUS "Enabling additional flags: ${ARGV1}")
list(APPEND FEATURE_CHECK_CMAKE_FLAGS ${ARGV1})
endif()
if(CMAKE_CROSSCOMPILING)
cxx_feature_check_print("Cross-compiling to test ${FEATURE}")
try_compile(
COMPILE_STATUS
${CMAKE_BINARY_DIR}
${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
CXX_STANDARD 17
CXX_STANDARD_REQUIRED ON
CMAKE_FLAGS "${FEATURE_CHECK_CMAKE_FLAGS}"
LINK_LIBRARIES "${BENCHMARK_CXX_LIBRARIES}"
OUTPUT_VARIABLE COMPILE_OUTPUT_VAR
)
if(COMPILE_STATUS)
set(RUN_STATUS 0)
message(WARNING
"If you see build failures due to cross compilation, try setting ${VAR} to 0")
endif()
else()
cxx_feature_check_print("Compiling and running to test ${FEATURE}")
try_run(
RUN_STATUS
COMPILE_STATUS
${CMAKE_BINARY_DIR}
${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
CXX_STANDARD 17
CXX_STANDARD_REQUIRED ON
CMAKE_FLAGS "${FEATURE_CHECK_CMAKE_FLAGS}"
LINK_LIBRARIES "${BENCHMARK_CXX_LIBRARIES}"
COMPILE_OUTPUT_VARIABLE COMPILE_OUTPUT
RUN_OUTPUT_VARIABLE RUN_OUTPUT
)
endif()
if(COMPILE_STATUS AND RUN_STATUS EQUAL 0)
message(STATUS "Performing Test ${FEATURE} -- success")
set(${VAR} TRUE CACHE BOOL "" FORCE)
add_compile_definitions(${VAR})
return()
endif()
set(${VAR} FALSE CACHE BOOL "" FORCE)
message(STATUS "Performing Test ${FEATURE} -- failed")
if(NOT COMPILE_STATUS)
cxx_feature_check_print("Compile Output: ${COMPILE_OUTPUT}")
else()
cxx_feature_check_print("Run Output: ${RUN_OUTPUT}")
endif()
endfunction()
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