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//usr/share/cmake/Modules/CheckIncludeFiles.cmake

# - Check if the files can be included
#
# CHECK_INCLUDE_FILES(INCLUDE VARIABLE)
#
#  INCLUDE  - list of files to include
#  VARIABLE - variable to return result
#
# 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 2003-2012 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_FILES INCLUDE VARIABLE)
  if("${VARIABLE}" MATCHES "^${VARIABLE}$")
    set(CMAKE_CONFIGURABLE_FILE_CONTENT "/* */\n")
    if(CMAKE_REQUIRED_INCLUDES)
      set(CHECK_INCLUDE_FILES_INCLUDE_DIRS "-DINCLUDE_DIRECTORIES=${CMAKE_REQUIRED_INCLUDES}")
    else()
      set(CHECK_INCLUDE_FILES_INCLUDE_DIRS)
    endif()
    set(CHECK_INCLUDE_FILES_CONTENT "/* */\n")
    set(MACRO_CHECK_INCLUDE_FILES_FLAGS ${CMAKE_REQUIRED_FLAGS})
    foreach(FILE ${INCLUDE})
      set(CMAKE_CONFIGURABLE_FILE_CONTENT
        "${CMAKE_CONFIGURABLE_FILE_CONTENT}#include <${FILE}>\n")
    endforeach()
    set(CMAKE_CONFIGURABLE_FILE_CONTENT
      "${CMAKE_CONFIGURABLE_FILE_CONTENT}\n\nint main(){return 0;}\n")
    configure_file("${CMAKE_ROOT}/Modules/CMakeConfigurableFile.in"
      "${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckIncludeFiles.c" @ONLY IMMEDIATE)

set(_INCLUDE ${INCLUDE}) # remove empty elements
    if("${_INCLUDE}" MATCHES "^([^;]+);.+;([^;]+)$")
      list(LENGTH _INCLUDE _INCLUDE_LEN)
      set(_description "${_INCLUDE_LEN} include files ${CMAKE_MATCH_1}, ..., ${CMAKE_MATCH_2}")
    elseif("${_INCLUDE}" MATCHES "^([^;]+);([^;]+)$")
      set(_description "include files ${CMAKE_MATCH_1}, ${CMAKE_MATCH_2}")
    else()
      set(_description "include file ${_INCLUDE}")
    endif()

message(STATUS "Looking for ${_description}")
    try_compile(${VARIABLE}
      ${CMAKE_BINARY_DIR}
      ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckIncludeFiles.c
      COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
      CMAKE_FLAGS
      -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_INCLUDE_FILES_FLAGS}
      "${CHECK_INCLUDE_FILES_INCLUDE_DIRS}"
      OUTPUT_VARIABLE OUTPUT)
    if(${VARIABLE})
      message(STATUS "Looking for ${_description} - found")
      set(${VARIABLE} 1 CACHE INTERNAL "Have include ${INCLUDE}")
      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
        "Determining if files ${INCLUDE} "
        "exist passed with the following output:\n"
        "${OUTPUT}\n\n")
    else()
      message(STATUS "Looking for ${_description} - not found")
      set(${VARIABLE} "" CACHE INTERNAL "Have includes ${INCLUDE}")
      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
        "Determining if files ${INCLUDE} "
        "exist failed with the following output:\n"
        "${OUTPUT}\nSource:\n${CMAKE_CONFIGURABLE_FILE_CONTENT}\n")
    endif()
  endif()
endmacro()