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//usr/share/cmake/Modules/CheckIncludeFile.cmake

# - Check if the include file exists.
# CHECK_INCLUDE_FILE(INCLUDE VARIABLE)
# - macro which checks the include file exists.
#  INCLUDE  - name of include file
#  VARIABLE - variable to return result
#
# an optional third argument is the CFlags to add to the compile line
# or you can use CMAKE_REQUIRED_FLAGS
#
# The following variables may be set before calling this macro to
# modify the way the check is run:
#
#  CMAKE_REQUIRED_FLAGS = string of compile command line flags
#  CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
#  CMAKE_REQUIRED_INCLUDES = list of include directories
#

#=============================================================================
# Copyright 2002-2009 Kitware, Inc.
#
# 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.)

macro(CHECK_INCLUDE_FILE INCLUDE VARIABLE)
  if("${VARIABLE}" MATCHES "^${VARIABLE}$")
    if(CMAKE_REQUIRED_INCLUDES)
      set(CHECK_INCLUDE_FILE_C_INCLUDE_DIRS "-DINCLUDE_DIRECTORIES=${CMAKE_REQUIRED_INCLUDES}")
    else()
      set(CHECK_INCLUDE_FILE_C_INCLUDE_DIRS)
    endif()
    set(MACRO_CHECK_INCLUDE_FILE_FLAGS ${CMAKE_REQUIRED_FLAGS})
    set(CHECK_INCLUDE_FILE_VAR ${INCLUDE})
    configure_file(${CMAKE_ROOT}/Modules/CheckIncludeFile.c.in
      ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckIncludeFile.c IMMEDIATE)
    message(STATUS "Looking for ${INCLUDE}")
    if(${ARGC} EQUAL 3)
      set(CMAKE_C_FLAGS_SAVE ${CMAKE_C_FLAGS})
      set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${ARGV2}")
    endif()

try_compile(${VARIABLE}
      ${CMAKE_BINARY_DIR}
      ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckIncludeFile.c
      COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
      CMAKE_FLAGS
      -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_INCLUDE_FILE_FLAGS}
      "${CHECK_INCLUDE_FILE_C_INCLUDE_DIRS}"
      OUTPUT_VARIABLE OUTPUT)

if(${ARGC} EQUAL 3)
      set(CMAKE_C_FLAGS ${CMAKE_C_FLAGS_SAVE})
    endif()

if(${VARIABLE})
      message(STATUS "Looking for ${INCLUDE} - found")
      set(${VARIABLE} 1 CACHE INTERNAL "Have include ${INCLUDE}")
      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
        "Determining if the include file ${INCLUDE} "
        "exists passed with the following output:\n"
        "${OUTPUT}\n\n")
    else()
      message(STATUS "Looking for ${INCLUDE} - not found")
      set(${VARIABLE} "" CACHE INTERNAL "Have include ${INCLUDE}")
      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
        "Determining if the include file ${INCLUDE} "
        "exists failed with the following output:\n"
        "${OUTPUT}\n\n")
    endif()
  endif()
endmacro()