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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 2.8.12+
     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_${VAR})
     25     set(HAVE_${VAR} 1 PARENT_SCOPE)
     26     add_definitions(-DHAVE_${VAR})
     27     return()
     28   endif()
     29 
     30   message("-- Performing Test ${FEATURE}")
     31   if(CMAKE_CROSSCOMPILING)
     32     try_compile(COMPILE_${FEATURE}
     33             ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
     34             CMAKE_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS}
     35             LINK_LIBRARIES ${BENCHMARK_CXX_LIBRARIES})
     36     if(COMPILE_${FEATURE})
     37       message(WARNING
     38             "If you see build failures due to cross compilation, try setting HAVE_${VAR} to 0")
     39       set(RUN_${FEATURE} 0)
     40     else()
     41       set(RUN_${FEATURE} 1)
     42     endif()
     43   else()
     44     message("-- Performing Test ${FEATURE}")
     45     try_run(RUN_${FEATURE} COMPILE_${FEATURE}
     46             ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
     47             CMAKE_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS}
     48             LINK_LIBRARIES ${BENCHMARK_CXX_LIBRARIES})
     49   endif()
     50 
     51   if(RUN_${FEATURE} EQUAL 0)
     52     message("-- Performing Test ${FEATURE} -- success")
     53     set(HAVE_${VAR} 1 PARENT_SCOPE)
     54     add_definitions(-DHAVE_${VAR})
     55   else()
     56     if(NOT COMPILE_${FEATURE})
     57       message("-- Performing Test ${FEATURE} -- failed to compile")
     58     else()
     59       message("-- Performing Test ${FEATURE} -- compiled but failed to run")
     60     endif()
     61   endif()
     62 endfunction()
     63