opencv/cmake/OpenCVDetectCXXCompiler.cmake

# Compilers:
# - CV_GCC - GNU compiler (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
# - CV_CLANG - Clang-compatible compiler (CMAKE_CXX_COMPILER_ID MATCHES "Clang" - Clang or AppleClang, see CMP0025)
# - CV_ICC - Intel compiler
# - MSVC - Microsoft Visual Compiler (CMake variable)
# - MSVC64 - additional flag, 64-bit
# - MINGW / CYGWIN / CMAKE_COMPILER_IS_MINGW / CMAKE_COMPILER_IS_CYGWIN (CMake original variables)
# - MINGW64 - 64-bit
#
# CPU Platforms:
# - X86 / X86_64
# - ARM - ARM CPU, not defined for AArch64
# - AARCH64 - ARMv8+ (64-bit)
# - PPC64 / PPC64LE - PowerPC
#
# OS:
# - WIN32 - Windows | MINGW
# - UNIX - Linux | MacOSX | ANDROID
# - ANDROID
# - IOS
# - APPLE - MacOSX | iOS
# ----------------------------------------------------------------------------

if(CMAKE_CL_64)
    set(MSVC64 1)
endif()

if(NOT DEFINED CV_GCC AND CMAKE_CXX_COMPILER_ID MATCHES "GNU")
  set(CV_GCC 1)
endif()
if(NOT DEFINED CV_CLANG AND CMAKE_CXX_COMPILER_ID MATCHES "Clang")  # Clang or AppleClang (see CMP0025)
  set(CV_CLANG 1)
  set(CMAKE_COMPILER_IS_CLANGCXX 1)  # TODO next release: remove this
  set(CMAKE_COMPILER_IS_CLANGCC 1)   # TODO next release: remove this
endif()

function(access_CMAKE_COMPILER_IS_CLANGCXX)
  if(NOT OPENCV_SUPPRESS_DEPRECATIONS)
    message(WARNING "DEPRECATED: CMAKE_COMPILER_IS_CLANGCXX support is deprecated in OpenCV.
    Consider using:
    - CV_GCC    # GCC
    - CV_CLANG  # Clang or AppleClang (see CMP0025)
")
  endif()
endfunction()
variable_watch(CMAKE_COMPILER_IS_CLANGCXX access_CMAKE_COMPILER_IS_CLANGCXX)
variable_watch(CMAKE_COMPILER_IS_CLANGCC access_CMAKE_COMPILER_IS_CLANGCXX)


# ----------------------------------------------------------------------------
# Detect Intel ICC compiler
# ----------------------------------------------------------------------------
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|icl")
  set(CV_ICC   __INTEL_COMPILER_FOR_WINDOWS)
endif()

if(NOT DEFINED CMAKE_CXX_COMPILER_VERSION)
  message(WARNING "Compiler version is not available: CMAKE_CXX_COMPILER_VERSION is not set")
endif()

if(WIN32 AND CV_GCC)
  execute_process(COMMAND ${CMAKE_CXX_COMPILER} -dumpmachine
                  OUTPUT_VARIABLE OPENCV_GCC_TARGET_MACHINE
                  OUTPUT_STRIP_TRAILING_WHITESPACE)
  if(OPENCV_GCC_TARGET_MACHINE MATCHES "amd64|x86_64|AMD64")
    set(MINGW64 1)
  endif()
endif()

if(MSVC64 OR MINGW64)
  set(X86_64 1)
elseif(MINGW OR (MSVC AND NOT CMAKE_CROSSCOMPILING))
  set(X86 1)
elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "amd64.*|x86_64.*|AMD64.*")
  set(X86_64 1)
elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "i686.*|i386.*|x86.*|amd64.*|AMD64.*")
  set(X86 1)
elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(arm.*|ARM.*)")
  set(ARM 1)
elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64.*|AARCH64.*)")
  set(AARCH64 1)
elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(powerpc|ppc)64le")
  set(PPC64LE 1)
elseif(CMAKE_SYSTEM_PROCESSOR MATCHES "^(powerpc|ppc)64")
  set(PPC64 1)
endif()

# Workaround for 32-bit operating systems on 64-bit x86_64 processor
if(X86_64 AND CMAKE_SIZEOF_VOID_P EQUAL 4 AND NOT FORCE_X86_64)
  message(STATUS "sizeof(void) = 4 on x86 / x86_64 processor. Assume 32-bit compilation mode (X86=1)")
  unset(X86_64)
  set(X86 1)
endif()

# Similar code exists in OpenCVConfig.cmake
if(NOT DEFINED OpenCV_STATIC)
  # look for global setting
  if(NOT DEFINED BUILD_SHARED_LIBS OR BUILD_SHARED_LIBS)
    set(OpenCV_STATIC OFF)
  else()
    set(OpenCV_STATIC ON)
  endif()
endif()

if(DEFINED OpenCV_ARCH AND DEFINED OpenCV_RUNTIME)
  # custom overridden values
elseif(MSVC)
  if(CMAKE_CL_64)
    set(OpenCV_ARCH x64)
  elseif((CMAKE_GENERATOR MATCHES "ARM") OR ("${arch_hint}" STREQUAL "ARM") OR (CMAKE_VS_EFFECTIVE_PLATFORMS MATCHES "ARM|arm"))
    # see Modules/CmakeGenericSystem.cmake
    set(OpenCV_ARCH ARM)
  else()
    set(OpenCV_ARCH x86)
  endif()
  if(MSVC_VERSION EQUAL 1400)
    set(OpenCV_RUNTIME vc8)
  elseif(MSVC_VERSION EQUAL 1500)
    set(OpenCV_RUNTIME vc9)
  elseif(MSVC_VERSION EQUAL 1600)
    set(OpenCV_RUNTIME vc10)
  elseif(MSVC_VERSION EQUAL 1700)
    set(OpenCV_RUNTIME vc11)
  elseif(MSVC_VERSION EQUAL 1800)
    set(OpenCV_RUNTIME vc12)
  elseif(MSVC_VERSION EQUAL 1900)
    set(OpenCV_RUNTIME vc14)
  elseif(MSVC_VERSION MATCHES "^191[0-9]$")
    set(OpenCV_RUNTIME vc15)
  else()
    message(WARNING "OpenCV does not recognize MSVC_VERSION \"${MSVC_VERSION}\". Cannot set OpenCV_RUNTIME")
  endif()
elseif(MINGW)
  set(OpenCV_RUNTIME mingw)

  if(MINGW64)
    set(OpenCV_ARCH x64)
  else()
    set(OpenCV_ARCH x86)
  endif()
endif()

# Fix handling of duplicated files in the same static library:
# https://public.kitware.com/Bug/view.php?id=14874
if(CMAKE_VERSION VERSION_LESS "3.1")
  foreach(var CMAKE_C_ARCHIVE_APPEND CMAKE_CXX_ARCHIVE_APPEND)
    if(${var} MATCHES "^<CMAKE_AR> r")
      string(REPLACE "<CMAKE_AR> r" "<CMAKE_AR> q" ${var} "${${var}}")
    endif()
  endforeach()
endif()

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
set(CMAKE_CXX_EXTENSIONS OFF) # use -std=c++11 instead of -std=gnu++11
if(CMAKE_CXX11_COMPILE_FEATURES)
  set(HAVE_CXX11 ON)
endif()
if(NOT HAVE_CXX11)
  ocv_check_compiler_flag(CXX "" HAVE_CXX11 "${OpenCV_SOURCE_DIR}/cmake/checks/cxx11.cpp")
  if(NOT HAVE_CXX11 AND ENABLE_CXX11)
    ocv_check_compiler_flag(CXX "-std=c++11" HAVE_STD_CXX11 "${OpenCV_SOURCE_DIR}/cmake/checks/cxx11.cpp")
    if(HAVE_STD_CXX11)
      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
      set(HAVE_CXX11 ON)
    endif()
  endif()
endif()
if(NOT HAVE_CXX11)
  message(FATAL_ERROR "OpenCV 4.x requires C++11")
endif()