opencv/cmake/OpenCVDetectCXXCompiler.cmake

# ----------------------------------------------------------------------------
# Detect Microsoft compiler:
# ----------------------------------------------------------------------------
if(CMAKE_CL_64)
    set(MSVC64 1)
endif()

if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
  set(CMAKE_COMPILER_IS_GNUCXX 1)
  set(CMAKE_COMPILER_IS_CLANGCXX 1)
endif()
if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
  set(CMAKE_COMPILER_IS_GNUCC 1)
  set(CMAKE_COMPILER_IS_CLANGCC 1)
endif()

if((CMAKE_COMPILER_IS_CLANGCXX OR CMAKE_COMPILER_IS_CLANGCC) AND NOT CMAKE_GENERATOR MATCHES "Xcode")
  set(ENABLE_PRECOMPILED_HEADERS OFF CACHE BOOL "" FORCE)
endif()

# ----------------------------------------------------------------------------
# Detect Intel ICC compiler -- for -fPIC in 3rdparty ( UNIX ONLY ):
#  see  include/opencv/cxtypes.h file for related   ICC & CV_ICC defines.
# NOTE: The system needs to determine if the '-fPIC' option needs to be added
#  for the 3rdparty static libs being compiled.  The CMakeLists.txt files
#  in 3rdparty use the CV_ICC definition being set here to determine if
#  the -fPIC flag should be used.
# ----------------------------------------------------------------------------
if(UNIX)
    if  (__ICL)
        set(CV_ICC   __ICL)
    elseif(__ICC)
        set(CV_ICC   __ICC)
    elseif(__ECL)
        set(CV_ICC   __ECL)
    elseif(__ECC)
        set(CV_ICC   __ECC)
    elseif(__INTEL_COMPILER)
        set(CV_ICC   __INTEL_COMPILER)
    elseif(CMAKE_C_COMPILER MATCHES "icc")
        set(CV_ICC   icc_matches_c_compiler)
    endif()
endif()

if(MSVC AND CMAKE_C_COMPILER MATCHES "icc")
    set(CV_ICC   __INTEL_COMPILER_FOR_WINDOWS)
endif()

# ----------------------------------------------------------------------------
# Detect GNU version:
# ----------------------------------------------------------------------------
if(CMAKE_COMPILER_IS_CLANGCXX)
  set(CMAKE_GCC_REGEX_VERSION "4.2.1")
  set(CMAKE_OPENCV_GCC_VERSION_MAJOR 4)
  set(CMAKE_OPENCV_GCC_VERSION_MINOR 2)
  set(CMAKE_OPENCV_GCC_VERSION 42)
  set(CMAKE_OPENCV_GCC_VERSION_NUM 402)

  execute_process(COMMAND ${CMAKE_CXX_COMPILER} ${CMAKE_CXX_COMPILER_ARG1} -v
                  ERROR_VARIABLE CMAKE_OPENCV_CLANG_VERSION_FULL
                  ERROR_STRIP_TRAILING_WHITESPACE)

  string(REGEX MATCH "version.*$" CMAKE_OPENCV_CLANG_VERSION_FULL "${CMAKE_OPENCV_CLANG_VERSION_FULL}")
  string(REGEX MATCH "[0-9]+\\.[0-9]+" CMAKE_CLANG_REGEX_VERSION "${CMAKE_OPENCV_CLANG_VERSION_FULL}")

elseif(CMAKE_COMPILER_IS_GNUCXX)
    execute_process(COMMAND ${CMAKE_CXX_COMPILER} ${CMAKE_CXX_COMPILER_ARG1} -dumpversion
                  OUTPUT_VARIABLE CMAKE_OPENCV_GCC_VERSION_FULL
                  OUTPUT_STRIP_TRAILING_WHITESPACE)

    execute_process(COMMAND ${CMAKE_CXX_COMPILER} ${CMAKE_CXX_COMPILER_ARG1} -v
                  ERROR_VARIABLE CMAKE_OPENCV_GCC_INFO_FULL
                  OUTPUT_STRIP_TRAILING_WHITESPACE)

    # Typical output in CMAKE_OPENCV_GCC_VERSION_FULL: "c+//0 (whatever) 4.2.3 (...)"
    # Look for the version number
    string(REGEX MATCH "[0-9]+\\.[0-9]+\\.[0-9]+" CMAKE_GCC_REGEX_VERSION "${CMAKE_OPENCV_GCC_VERSION_FULL}")
    if(NOT CMAKE_GCC_REGEX_VERSION)
      string(REGEX MATCH "[0-9]+\\.[0-9]+" CMAKE_GCC_REGEX_VERSION "${CMAKE_OPENCV_GCC_VERSION_FULL}")
    endif()

    # Split the three parts:
    string(REGEX MATCHALL "[0-9]+" CMAKE_OPENCV_GCC_VERSIONS "${CMAKE_GCC_REGEX_VERSION}")

    list(GET CMAKE_OPENCV_GCC_VERSIONS 0 CMAKE_OPENCV_GCC_VERSION_MAJOR)
    list(GET CMAKE_OPENCV_GCC_VERSIONS 1 CMAKE_OPENCV_GCC_VERSION_MINOR)

    set(CMAKE_OPENCV_GCC_VERSION ${CMAKE_OPENCV_GCC_VERSION_MAJOR}${CMAKE_OPENCV_GCC_VERSION_MINOR})
    math(EXPR CMAKE_OPENCV_GCC_VERSION_NUM "${CMAKE_OPENCV_GCC_VERSION_MAJOR}*100 + ${CMAKE_OPENCV_GCC_VERSION_MINOR}")
    message(STATUS "Detected version of GNU GCC: ${CMAKE_OPENCV_GCC_VERSION} (${CMAKE_OPENCV_GCC_VERSION_NUM})")

    if(WIN32)
        execute_process(COMMAND ${CMAKE_CXX_COMPILER} -dumpmachine
                  OUTPUT_VARIABLE CMAKE_OPENCV_GCC_TARGET_MACHINE
                  OUTPUT_STRIP_TRAILING_WHITESPACE)
        if(CMAKE_OPENCV_GCC_TARGET_MACHINE MATCHES "64")
            set(MINGW64 1)
        endif()
    endif()
endif()

if(CMAKE_SYSTEM_PROCESSOR MATCHES "amd64.*|x86_64.*|AMD64.*" OR CMAKE_GENERATOR MATCHES "Visual Studio.*Win64")
    set(X86_64 1)
elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "i686.*|i386.*|x86.*|amd64.*|AMD64.*")
    set(X86 1)
endif()