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# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.
#[=======================================================================[.rst:
CheckFunctionExists
-------------------
Check if a C function can be linked
.. command:: check_function_exists
.. code-block:: cmake
check_function_exists(<function> <variable>)
Checks that the ``<function>`` is provided by libraries on the system and store
the result in a ``<variable>``, which will be created as an internal
cache variable.
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_QUIET.txt
.. note::
Prefer using :Module:`CheckSymbolExists` instead of this module,
for the following reasons:
* ``check_function_exists()`` can't detect functions that are inlined
in headers or specified as a macro.
* ``check_function_exists()`` can't detect anything in the 32-bit
versions of the Win32 API, because of a mismatch in calling conventions.
* ``check_function_exists()`` only verifies linking, it does not verify
that the function is declared in system headers.
#]=======================================================================]
include_guard(GLOBAL)
macro(CHECK_FUNCTION_EXISTS FUNCTION VARIABLE)
if(NOT DEFINED "${VARIABLE}" OR "x${${VARIABLE}}" STREQUAL "x${VARIABLE}")
set(MACRO_CHECK_FUNCTION_DEFINITIONS
"-DCHECK_FUNCTION_EXISTS=${FUNCTION} ${CMAKE_REQUIRED_FLAGS}")
if(NOT CMAKE_REQUIRED_QUIET)
message(CHECK_START "Looking for ${FUNCTION}")
endif()
if(CMAKE_REQUIRED_LINK_OPTIONS)
set(CHECK_FUNCTION_EXISTS_ADD_LINK_OPTIONS
LINK_OPTIONS ${CMAKE_REQUIRED_LINK_OPTIONS})
else()
set(CHECK_FUNCTION_EXISTS_ADD_LINK_OPTIONS)
endif()
if(CMAKE_REQUIRED_LIBRARIES)
set(CHECK_FUNCTION_EXISTS_ADD_LIBRARIES
LINK_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
else()
set(CHECK_FUNCTION_EXISTS_ADD_LIBRARIES)
endif()
if(CMAKE_REQUIRED_INCLUDES)
set(CHECK_FUNCTION_EXISTS_ADD_INCLUDES
"-DINCLUDE_DIRECTORIES:STRING=${CMAKE_REQUIRED_INCLUDES}")
else()
set(CHECK_FUNCTION_EXISTS_ADD_INCLUDES)
endif()
if(CMAKE_C_COMPILER_LOADED)
set(_cfe_source CheckFunctionExists.c)
elseif(CMAKE_CXX_COMPILER_LOADED)
set(_cfe_source CheckFunctionExists.cxx)
else()
message(FATAL_ERROR "CHECK_FUNCTION_EXISTS needs either C or CXX language enabled")
endif()
try_compile(${VARIABLE}
SOURCE_FROM_FILE "${_cfe_source}" "${CMAKE_ROOT}/Modules/CheckFunctionExists.c"
COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
${CHECK_FUNCTION_EXISTS_ADD_LINK_OPTIONS}
${CHECK_FUNCTION_EXISTS_ADD_LIBRARIES}
CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_FUNCTION_DEFINITIONS}
"${CHECK_FUNCTION_EXISTS_ADD_INCLUDES}"
)
unset(_cfe_source)
if(${VARIABLE})
set(${VARIABLE} 1 CACHE INTERNAL "Have function ${FUNCTION}")
if(NOT CMAKE_REQUIRED_QUIET)
message(CHECK_PASS "found")
endif()
else()
if(NOT CMAKE_REQUIRED_QUIET)
message(CHECK_FAIL "not found")
endif()
set(${VARIABLE} "" CACHE INTERNAL "Have function ${FUNCTION}")
endif()
endif()
endmacro()
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