CMake/Modules/CheckCXXCompilerFlag.cmake

# - Check whether the CXX compiler supports a given flag.
# CHECK_CXX_COMPILER_FLAG(<flag> <var>)
#  <flag> - the compiler flag
#  <var>  - variable to store the result
# This internally calls the check_cxx_source_compiles macro and
# sets CMAKE_REQUIRED_DEFINITIONS to <flag>.
# See help for CheckCXXSourceCompiles for a listing of variables
# that can otherwise modify the build.
# The result only tells that the compiler does not give an error message when
# it encounters the flag. If the flag has any effect or even a specific one is
# beyond the scope of this module.

#=============================================================================
# Copyright 2006-2010 Kitware, Inc.
# Copyright 2006 Alexander Neundorf <neundorf@kde.org>
# Copyright 2011 Matthias Kretz <kretz@kde.org>
#
# Distributed under the OSI-approved BSD License (the "License");
# see accompanying file Copyright.txt for details.
#
# This software is distributed WITHOUT ANY WARRANTY; without even the
# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the License for more information.
#=============================================================================
# (To distribute this file outside of CMake, substitute the full
#  License text for the above reference.)

include(CheckCXXSourceCompiles)
include(CMakeCheckCompilerFlagCommonPatterns)

macro (CHECK_CXX_COMPILER_FLAG _FLAG _RESULT)
   set(SAFE_CMAKE_REQUIRED_DEFINITIONS "${CMAKE_REQUIRED_DEFINITIONS}")
   set(CMAKE_REQUIRED_DEFINITIONS "${_FLAG}")

   # Normalize locale during test compilation.
   set(_CheckCXXCompilerFlag_LOCALE_VARS LC_ALL LC_MESSAGES LANG)
   foreach(v ${_CheckCXXCompilerFlag_LOCALE_VARS})
     set(_CheckCXXCompilerFlag_SAVED_${v} "$ENV{${v}}")
     set(ENV{${v}} C)
   endforeach()
   CHECK_COMPILER_FLAG_COMMON_PATTERNS(_CheckCXXCompilerFlag_COMMON_PATTERNS)
   CHECK_CXX_SOURCE_COMPILES("int main() { return 0; }" ${_RESULT}
     # Some compilers do not fail with a bad flag
     FAIL_REGEX "command line option .* is valid for .* but not for C\\\\+\\\\+" # GNU
     ${_CheckCXXCompilerFlag_COMMON_PATTERNS}
     )
   foreach(v ${_CheckCXXCompilerFlag_LOCALE_VARS})
     set(ENV{${v}} ${_CheckCXXCompilerFlag_SAVED_${v}})
     unset(_CheckCXXCompilerFlag_SAVED_${v})
   endforeach()
   unset(_CheckCXXCompilerFlag_LOCALE_VARS)
   unset(_CheckCXXCompilerFlag_COMMON_PATTERNS)

   set (CMAKE_REQUIRED_DEFINITIONS "${SAFE_CMAKE_REQUIRED_DEFINITIONS}")
endmacro ()