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 the internal cmake variable _CMAKE_TOOLCHAIN_PREFIX is set, this is used 
# as prefix for the tools (e.g. arm-elf-g++, arm-elf-ar etc.)
# It also tries to detect a MS crosscompiler and find out its 
# suffix (clarm.exe), which will be stored in _CMAKE_TOOLCHAIN_SUFFIX and
# reused for the C compiler.
#
# Sets the following variables:
#   CMAKE_CXX_COMPILER
#   CMAKE_COMPILER_IS_GNUCXX
#   CMAKE_AR
#   CMAKE_RANLIB
#
# If not already set before, it also sets
#   _CMAKE_TOOLCHAIN_PREFIX
#   _CMAKE_TOOLCHAIN_SUFFIX

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(NOT 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(NOT 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 ${_CMAKE_TOOLCHAIN_PREFIX}c++ ${_CMAKE_TOOLCHAIN_PREFIX}g++ CC aCC cl${_CMAKE_TOOLCHAIN_SUFFIX} bcc xlC)
  ENDIF(CMAKE_CXX_COMPILER_INIT)

  # Find the compiler.
  IF (_CMAKE_USER_C_COMPILER_PATH)
    FIND_PROGRAM(CMAKE_CXX_COMPILER NAMES ${CMAKE_CXX_COMPILER_LIST} PATHS ${_CMAKE_USER_C_COMPILER_PATH} DOC "C++ compiler" NO_DEFAULT_PATH)
  ENDIF (_CMAKE_USER_C_COMPILER_PATH)
  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)
ELSE(NOT CMAKE_CXX_COMPILER)

# we only get here if CMAKE_CXX_COMPILER was specified using -D or a pre-made CMakeCache.txt
# (e.g. via ctest) or set in CMAKE_TOOLCHAIN_FILE
#
# if a compiler was specified by the user but without path, 
# now try to find it with the full path
# if it is found, force it into the cache, 
# if not, don't overwrite the setting (which was given by the user) with "NOTFOUND"
# if the CXX compiler already had a path, reuse it for searching the C compiler
  GET_FILENAME_COMPONENT(_CMAKE_USER_CXX_COMPILER_PATH "${CMAKE_CXX_COMPILER}" PATH)
  IF(NOT _CMAKE_USER_CXX_COMPILER_PATH)
    FIND_PROGRAM(CMAKE_CXX_COMPILER_WITH_PATH NAMES ${CMAKE_CXX_COMPILER})
    MARK_AS_ADVANCED(CMAKE_CXX_COMPILER_WITH_PATH)
    IF(CMAKE_CXX_COMPILER_WITH_PATH)
      SET(CMAKE_CXX_COMPILER ${CMAKE_CXX_COMPILER_WITH_PATH} CACHE FILEPATH "CXX compiler" FORCE)
    ENDIF(CMAKE_CXX_COMPILER_WITH_PATH)
  ENDIF(NOT _CMAKE_USER_CXX_COMPILER_PATH)
ENDIF(NOT CMAKE_CXX_COMPILER)
MARK_AS_ADVANCED(CMAKE_CXX_COMPILER)

IF (NOT _CMAKE_TOOLCHAIN_LOCATION)
  GET_FILENAME_COMPONENT(_CMAKE_TOOLCHAIN_LOCATION "${CMAKE_CXX_COMPILER}" PATH)
ENDIF (NOT _CMAKE_TOOLCHAIN_LOCATION)

# if we have a g++ cross compiler, they have usually some prefix, like 
# e.g. powerpc-linux-g++, arm-elf-g++ or i586-mingw32msvc-g++
# the other tools of the toolchain usually have the same prefix
IF (NOT _CMAKE_TOOLCHAIN_PREFIX)
  GET_FILENAME_COMPONENT(COMPILER_BASENAME "${CMAKE_CXX_COMPILER}" NAME_WE)
  IF (COMPILER_BASENAME MATCHES "^(.+-)[gc]\\+\\+")
    STRING(REGEX REPLACE "^(.+-)[gc]\\+\\+"  "\\1" _CMAKE_TOOLCHAIN_PREFIX "${COMPILER_BASENAME}")
  ENDIF (COMPILER_BASENAME MATCHES "^(.+-)[gc]\\+\\+")
ENDIF (NOT _CMAKE_TOOLCHAIN_PREFIX)

# if we have a MS cross compiler, it usually has a suffix, like 
# e.g. clarm.exe or clmips.exe. Use this suffix for the CXX compiler too.
IF (NOT _CMAKE_TOOLCHAIN_SUFFIX)
  GET_FILENAME_COMPONENT(COMPILER_BASENAME "${CMAKE_CXX_COMPILER}" NAME)
  IF (COMPILER_BASENAME MATCHES "^cl(.+)\\.exe$")
    STRING(REGEX REPLACE "^cl(.+)\\.exe$"  "\\1" _CMAKE_TOOLCHAIN_SUFFIX "${COMPILER_BASENAME}")
  ENDIF (COMPILER_BASENAME MATCHES "^cl(.+)\\.exe$")
ENDIF (NOT _CMAKE_TOOLCHAIN_SUFFIX)


# some exotic compilers have different extensions (e.g. sdcc uses .rel)
# so don't overwrite it if it has been already defined by the user
IF(NOT CMAKE_CXX_OUTPUT_EXTENSION)
  IF(UNIX)
    SET(CMAKE_CXX_OUTPUT_EXTENSION .o)
  ELSE(UNIX)
    SET(CMAKE_CXX_OUTPUT_EXTENSION .obj)
  ENDIF(UNIX)
ENDIF(NOT CMAKE_CXX_OUTPUT_EXTENSION)


# This block was used before the compiler was identified by building a
# source file.  Unless g++ crashes when building a small C++
# executable this should no longer be needed.
#
# The g++ that comes with BeOS 5 segfaults if you run "g++ -E"
#  ("gcc -E" is fine), which throws up a system dialog box that hangs cmake
#  until the user clicks "OK"...so for now, we just assume it's g++.
# IF(BEOS)
#   SET(CMAKE_COMPILER_IS_GNUCXX 1)
#   SET(CMAKE_COMPILER_IS_GNUCXX_RUN 1)
# ENDIF(BEOS)

# Build a small source file to identify the compiler.
IF(${CMAKE_GENERATOR} MATCHES "Visual Studio")
  SET(CMAKE_CXX_COMPILER_ID_RUN 1)
  SET(CMAKE_CXX_PLATFORM_ID "Windows")

  # TODO: Set the compiler id.  It is probably MSVC but
  # the user may be using an integrated Intel compiler.
  # SET(CMAKE_CXX_COMPILER_ID "MSVC")
ENDIF(${CMAKE_GENERATOR} MATCHES "Visual Studio")
IF(NOT CMAKE_CXX_COMPILER_ID_RUN)
  SET(CMAKE_CXX_COMPILER_ID_RUN 1)

  # Try to identify the compiler.
  SET(CMAKE_CXX_COMPILER_ID)
  INCLUDE(${CMAKE_ROOT}/Modules/CMakeDetermineCompilerId.cmake)
  CMAKE_DETERMINE_COMPILER_ID(CXX CXXFLAGS ${CMAKE_ROOT}/Modules/CMakeCXXCompilerId.cpp)

  # Set old compiler and platform id variables.
  IF("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
    SET(CMAKE_COMPILER_IS_GNUCXX 1)
  ENDIF("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU")
  IF("${CMAKE_CXX_PLATFORM_ID}" MATCHES "MinGW")
    SET(CMAKE_COMPILER_IS_MINGW 1)
  ELSEIF("${CMAKE_CXX_PLATFORM_ID}" MATCHES "Cygwin")
    SET(CMAKE_COMPILER_IS_CYGWIN 1)
  ENDIF("${CMAKE_CXX_PLATFORM_ID}" MATCHES "MinGW")
ENDIF(NOT CMAKE_CXX_COMPILER_ID_RUN)

INCLUDE(CMakeFindBinUtils)

# 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")