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# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file LICENSE.rst or https://cmake.org/licensing for details.
#[=======================================================================[.rst:
CheckIncludeFile
----------------
This module provides a command to check C header file.
Load this module in a CMake project with:
.. code-block:: cmake
include(CheckIncludeFile)
Commands
^^^^^^^^
This module provides the following command:
.. command:: check_include_file
Checks once whether a header file can be included in C code:
.. code-block:: cmake
check_include_file(<include> <variable> [<flags>])
This command checks once whether the given ``<include>`` header file
exists and can be included in a C source file. The result of the check
is stored in an internal cache variable named ``<variable>``. The
optional third argument may be used to add additional compilation flags
to the check (or use the ``CMAKE_REQUIRED_FLAGS`` variable below).
.. rubric:: Variables Affecting the Check
The following variables may be set before calling this command to modify
the way the check is run:
.. include:: /module/include/CMAKE_REQUIRED_FLAGS.rst
.. include:: /module/include/CMAKE_REQUIRED_DEFINITIONS.rst
.. include:: /module/include/CMAKE_REQUIRED_INCLUDES.rst
.. include:: /module/include/CMAKE_REQUIRED_LINK_OPTIONS.rst
.. include:: /module/include/CMAKE_REQUIRED_LIBRARIES.rst
.. include:: /module/include/CMAKE_REQUIRED_LINK_DIRECTORIES.rst
.. include:: /module/include/CMAKE_REQUIRED_QUIET.rst
.. versionadded:: 3.12
The ``CMAKE_REQUIRED_LIBRARIES`` variable, if policy :policy:`CMP0075` is
set to ``NEW``.
Examples
^^^^^^^^
Example: Checking C Header
""""""""""""""""""""""""""
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)
Example: Isolated Check
"""""""""""""""""""""""
In the following example, this module is used in combination with the
:module:`CMakePushCheckState` module to temporarily modify the required
compile definitions (via ``CMAKE_REQUIRED_DEFINITIONS``) and verify whether
the C header ``ucontext.h`` is available. The result is stored
in the internal cache variable ``HAVE_UCONTEXT_H``.
For example, on macOS, the ``ucontext`` API is deprecated, and headers may
be hidden unless certain feature macros are defined. In particular,
defining ``_XOPEN_SOURCE`` (without a value) can expose the necessary
symbols without enabling broader POSIX or SUS (Single Unix Specification)
features (values 500 or greater).
.. code-block:: cmake
include(CheckIncludeFile)
include(CMakePushCheckState)
cmake_push_check_state(RESET)
if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
set(CMAKE_REQUIRED_DEFINITIONS -D_XOPEN_SOURCE)
endif()
check_include_files(ucontext.h HAVE_UCONTEXT_H)
cmake_pop_check_state()
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()
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