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      1 # - Compile and run code to check for C++ features
      2 #
      3 # This functions compiles a source file under the `cmake` folder
      4 # and adds the corresponding `HAVE_[FILENAME]` flag to the CMake
      5 # environment
      6 #
      7 #  cxx_feature_check(<FLAG> [<VARIANT>])
      8 #
      9 # - Example
     10 #
     11 # include(CXXFeatureCheck)
     12 # cxx_feature_check(STD_REGEX)
     13 # Requires CMake 2.6+
     14 
     15 if(__cxx_feature_check)
     16   return()
     17 endif()
     18 set(__cxx_feature_check INCLUDED)
     19 
     20 function(cxx_feature_check FILE)
     21   string(TOLOWER ${FILE} FILE)
     22   string(TOUPPER ${FILE} VAR)
     23   string(TOUPPER "HAVE_${VAR}" FEATURE)
     24   if (DEFINED HAVE_${VAR})
     25     return()
     26   endif()
     27   message("-- Performing Test ${FEATURE}")
     28   try_run(RUN_${FEATURE} COMPILE_${FEATURE}
     29           ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
     30           CMAKE_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS}
     31           LINK_LIBRARIES ${BENCHMARK_CXX_LIBRARIES})
     32   if(RUN_${FEATURE} EQUAL 0)
     33     message("-- Performing Test ${FEATURE} -- success")
     34     set(HAVE_${VAR} 1 CACHE INTERNAL "Feature test for ${FILE}" PARENT_SCOPE)
     35     add_definitions(-DHAVE_${VAR})
     36   else()
     37     if(NOT COMPILE_${FEATURE})
     38       message("-- Performing Test ${FEATURE} -- failed to compile")
     39     else()
     40       message("-- Performing Test ${FEATURE} -- compiled but failed to run")
     41     endif()
     42   endif()
     43 endfunction()
     44 
     45