CMake/Modules/CMakeDetermineCXXCompiler.cmake

# determine the compiler to use for C++ programs
# NOTE, a generator may set CMAKE_CXX_COMPILER before
# loading this file to force a compiler.
# use environment variable CXX first if defined by user, next use 
# the cmake variable CMAKE_GENERATOR_CXX which can be defined by a generator
# as a default compiler

IF(NOT CMAKE_CXX_COMPILER)
  SET(CMAKE_CXX_COMPILER_INIT NOTFOUND)

  # prefer the environment variable CXX
  IF($ENV{CXX} MATCHES ".+")
    GET_FILENAME_COMPONENT(CMAKE_CXX_COMPILER_INIT $ENV{CXX} PROGRAM PROGRAM_ARGS CMAKE_CXX_FLAGS_ENV_INIT)
    IF(CMAKE_CXX_FLAGS_ENV_INIT)
      SET(CMAKE_CXX_COMPILER_ARG1 "${CMAKE_CXX_FLAGS_ENV_INIT}" CACHE STRING "First argument to CXX compiler")
    ENDIF(CMAKE_CXX_FLAGS_ENV_INIT)
    IF(EXISTS ${CMAKE_CXX_COMPILER_INIT})
    ELSE(EXISTS ${CMAKE_CXX_COMPILER_INIT})
      MESSAGE(FATAL_ERROR "Could not find compiler set in environment variable CXX:\n$ENV{CXX}.\n${CMAKE_CXX_COMPILER_INIT}")
    ENDIF(EXISTS ${CMAKE_CXX_COMPILER_INIT})
  ENDIF($ENV{CXX} MATCHES ".+")

  # next prefer the generator specified compiler
  IF(CMAKE_GENERATOR_CXX)
    IF(NOT CMAKE_CXX_COMPILER_INIT)
      SET(CMAKE_CXX_COMPILER_INIT ${CMAKE_GENERATOR_CXX})
    ENDIF(NOT CMAKE_CXX_COMPILER_INIT)
  ENDIF(CMAKE_GENERATOR_CXX)

  # finally list compilers to try
  IF(CMAKE_CXX_COMPILER_INIT)
    SET(CMAKE_CXX_COMPILER_LIST ${CMAKE_CXX_COMPILER_INIT})
  ELSE(CMAKE_CXX_COMPILER_INIT)
    SET(CMAKE_CXX_COMPILER_LIST c++ g++ CC aCC cl bcc xlC)
  ENDIF(CMAKE_CXX_COMPILER_INIT)

  # Find the compiler.
  FIND_PROGRAM(CMAKE_CXX_COMPILER NAMES ${CMAKE_CXX_COMPILER_LIST} DOC "C++ compiler")
  IF(CMAKE_CXX_COMPILER_INIT AND NOT CMAKE_CXX_COMPILER)
    SET(CMAKE_CXX_COMPILER "${CMAKE_CXX_COMPILER_INIT}" CACHE FILEPATH "C++ compiler" FORCE)
  ENDIF(CMAKE_CXX_COMPILER_INIT AND NOT CMAKE_CXX_COMPILER)
ENDIF(NOT CMAKE_CXX_COMPILER)
MARK_AS_ADVANCED(CMAKE_CXX_COMPILER)

GET_FILENAME_COMPONENT(COMPILER_LOCATION "${CMAKE_CXX_COMPILER}" PATH)

FIND_PROGRAM(CMAKE_AR NAMES ar PATHS ${COMPILER_LOCATION})
MARK_AS_ADVANCED(CMAKE_AR)

FIND_PROGRAM(CMAKE_RANLIB NAMES ranlib)
IF(NOT CMAKE_RANLIB)
   SET(CMAKE_RANLIB : CACHE INTERNAL "noop for ranlib")
ENDIF(NOT CMAKE_RANLIB)
MARK_AS_ADVANCED(CMAKE_RANLIB)

# do not test for GNU if the generator is visual studio
IF(${CMAKE_GENERATOR} MATCHES "Visual Studio")
  SET(CMAKE_COMPILER_IS_GNUCXX_RUN 1)
ENDIF(${CMAKE_GENERATOR} MATCHES "Visual Studio")

IF(NOT CMAKE_COMPILER_IS_GNUCXX_RUN)
  # test to see if the cxx compiler is gnu
  SET(CMAKE_COMPILER_IS_GNUCXX_RUN 1)
  EXEC_PROGRAM(${CMAKE_CXX_COMPILER} ARGS -E "\"${CMAKE_ROOT}/Modules/CMakeTestGNU.c\"" OUTPUT_VARIABLE CMAKE_COMPILER_OUTPUT RETURN_VALUE CMAKE_COMPILER_RETURN)
  IF(NOT CMAKE_COMPILER_RETURN)
    IF("${CMAKE_COMPILER_OUTPUT}" MATCHES ".*THIS_IS_GNU.*" )
      SET(CMAKE_COMPILER_IS_GNUCXX 1)
      FILE(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
        "Determining if the C++ compiler is GNU succeeded with "
        "the following output:\n${CMAKE_COMPILER_OUTPUT}\n\n")
    ELSE("${CMAKE_COMPILER_OUTPUT}" MATCHES ".*THIS_IS_GNU.*" )
      FILE(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
        "Determining if the C++ compiler is GNU failed with "
        "the following output:\n${CMAKE_COMPILER_OUTPUT}\n\n")
    ENDIF("${CMAKE_COMPILER_OUTPUT}" MATCHES ".*THIS_IS_GNU.*" ) 
    IF("${CMAKE_COMPILER_OUTPUT}" MATCHES ".*THIS_IS_MINGW.*" )
      SET(CMAKE_COMPILER_IS_MINGW 1)
    ENDIF("${CMAKE_COMPILER_OUTPUT}" MATCHES ".*THIS_IS_MINGW.*" )
    IF("${CMAKE_COMPILER_OUTPUT}" MATCHES ".*THIS_IS_CYGWIN.*" )
      SET(CMAKE_COMPILER_IS_CYGWIN 1)
    ENDIF("${CMAKE_COMPILER_OUTPUT}" MATCHES ".*THIS_IS_CYGWIN.*" )
  ENDIF(NOT CMAKE_COMPILER_RETURN)
ENDIF(NOT CMAKE_COMPILER_IS_GNUCXX_RUN)

# configure all variables set in this file
CONFIGURE_FILE(${CMAKE_ROOT}/Modules/CMakeCXXCompiler.cmake.in 
               ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeCXXCompiler.cmake IMMEDIATE)

SET(CMAKE_CXX_COMPILER_ENV_VAR "CXX")