# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
# file LICENSE.rst or https://cmake.org/licensing for details.

#[=======================================================================[.rst:
CheckIncludeFile
----------------

Provides a macro to check if a header file can be included in ``C``.

.. command:: check_include_file

  .. code-block:: cmake

    check_include_file(<include> <variable> [<flags>])

  Check if the given ``<include>`` file may be included in a ``C``
  source file and store the result in an internal cache entry named
  ``<variable>``.  The optional third argument may be used to add
  compilation flags to the check (or use ``CMAKE_REQUIRED_FLAGS`` below).

The following variables may be set before calling this macro to modify
the way the check is run:

.. include:: /module/CMAKE_REQUIRED_FLAGS.txt

.. include:: /module/CMAKE_REQUIRED_DEFINITIONS.txt

.. include:: /module/CMAKE_REQUIRED_INCLUDES.txt

.. include:: /module/CMAKE_REQUIRED_LINK_OPTIONS.txt

.. include:: /module/CMAKE_REQUIRED_LIBRARIES.txt

.. include:: /module/CMAKE_REQUIRED_LINK_DIRECTORIES.txt

.. include:: /module/CMAKE_REQUIRED_QUIET.txt

Examples
^^^^^^^^

Checking whether the ``C`` header ``<unistd.h>`` exists and storing the check
result in the ``HAVE_UNISTD_H`` cache variable:

.. code-block:: cmake

  include(CheckIncludeFile)

  check_include_file(unistd.h HAVE_UNISTD_H)

See Also
^^^^^^^^

* The :module:`CheckIncludeFileCXX` module to check for single ``C++`` header.
* The :module:`CheckIncludeFiles` module to check for one or more ``C`` or
  ``C++`` headers at once.
#]=======================================================================]

include_guard(GLOBAL)

macro(CHECK_INCLUDE_FILE INCLUDE VARIABLE)
  if(NOT DEFINED "${VARIABLE}")
    if(CMAKE_REQUIRED_INCLUDES)
      set(CHECK_INCLUDE_FILE_C_INCLUDE_DIRS "-DINCLUDE_DIRECTORIES=${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})
    file(READ ${CMAKE_ROOT}/Modules/CheckIncludeFile.c.in _CIF_SOURCE_CONTENT)
    string(CONFIGURE "${_CIF_SOURCE_CONTENT}" _CIF_SOURCE_CONTENT)
    if(NOT CMAKE_REQUIRED_QUIET)
      message(CHECK_START "Looking for ${INCLUDE}")
    endif()
    if(${ARGC} EQUAL 3)
      set(CMAKE_C_FLAGS_SAVE ${CMAKE_C_FLAGS})
      string(APPEND CMAKE_C_FLAGS " ${ARGV2}")
    endif()

    set(_CIF_LINK_OPTIONS)
    if(CMAKE_REQUIRED_LINK_OPTIONS)
      set(_CIF_LINK_OPTIONS LINK_OPTIONS ${CMAKE_REQUIRED_LINK_OPTIONS})
    endif()

    set(_CIF_LINK_LIBRARIES "")
    if(CMAKE_REQUIRED_LIBRARIES)
      cmake_policy(GET CMP0075 _CIF_CMP0075
        PARENT_SCOPE # undocumented, do not use outside of CMake
        )
      if("x${_CIF_CMP0075}x" STREQUAL "xNEWx")
        set(_CIF_LINK_LIBRARIES LINK_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
      elseif("x${_CIF_CMP0075}x" STREQUAL "xOLDx")
      elseif(NOT _CIF_CMP0075_WARNED)
        set(_CIF_CMP0075_WARNED 1)
        message(AUTHOR_WARNING
          "Policy CMP0075 is not set: Include file check macros honor CMAKE_REQUIRED_LIBRARIES.  "
          "Run \"cmake --help-policy CMP0075\" for policy details.  "
          "Use the cmake_policy command to set the policy and suppress this warning."
          "\n"
          "CMAKE_REQUIRED_LIBRARIES is set to:\n"
          "  ${CMAKE_REQUIRED_LIBRARIES}\n"
          "For compatibility with CMake 3.11 and below this check is ignoring it."
          )
      endif()
      unset(_CIF_CMP0075)
    endif()

    if(CMAKE_REQUIRED_LINK_DIRECTORIES)
      set(_CIF_LINK_DIRECTORIES
        "-DLINK_DIRECTORIES:STRING=${CMAKE_REQUIRED_LINK_DIRECTORIES}")
    else()
      set(_CIF_LINK_DIRECTORIES)
    endif()

    try_compile(${VARIABLE}
      SOURCE_FROM_VAR CheckIncludeFile.c _CIF_SOURCE_CONTENT
      COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
      ${_CIF_LINK_OPTIONS}
      ${_CIF_LINK_LIBRARIES}
      CMAKE_FLAGS
      -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_INCLUDE_FILE_FLAGS}
      "${CHECK_INCLUDE_FILE_C_INCLUDE_DIRS}"
      "${_CIF_LINK_DIRECTORIES}"
      )
    unset(_CIF_LINK_OPTIONS)
    unset(_CIF_LINK_LIBRARIES)
    unset(_CIF_LINK_DIRECTORIES)

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

    if(${VARIABLE})
      if(NOT CMAKE_REQUIRED_QUIET)
        message(CHECK_PASS "found")
      endif()
      set(${VARIABLE} 1 CACHE INTERNAL "Have include ${INCLUDE}")
    else()
      if(NOT CMAKE_REQUIRED_QUIET)
        message(CHECK_FAIL "not found")
      endif()
      set(${VARIABLE} "" CACHE INTERNAL "Have include ${INCLUDE}")
    endif()
  endif()
endmacro()