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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::
#
# check_function_exists(<function> <variable>)
#
# Check that the ``<function>`` is provided by libraries on the system and store
# the result in a ``<variable>``. ``<variable>`` 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:
#
# ::
#
# 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
# CMAKE_REQUIRED_LIBRARIES = list of libraries to link
# CMAKE_REQUIRED_QUIET = execute quietly without messages
#
# .. 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(STATUS "Looking for ${FUNCTION}")
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 ${CMAKE_ROOT}/Modules/CheckFunctionExists.c)
elseif(CMAKE_CXX_COMPILER_LOADED)
set(_cfe_source ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CheckFunctionExists/CheckFunctionExists.cxx)
configure_file(${CMAKE_ROOT}/Modules/CheckFunctionExists.c "${_cfe_source}" COPYONLY)
else()
message(FATAL_ERROR "CHECK_FUNCTION_EXISTS needs either C or CXX language enabled")
endif()
try_compile(${VARIABLE}
${CMAKE_BINARY_DIR}
${_cfe_source}
COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
${CHECK_FUNCTION_EXISTS_ADD_LIBRARIES}
CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_FUNCTION_DEFINITIONS}
"${CHECK_FUNCTION_EXISTS_ADD_INCLUDES}"
OUTPUT_VARIABLE OUTPUT)
unset(_cfe_source)
if(${VARIABLE})
set(${VARIABLE} 1 CACHE INTERNAL "Have function ${FUNCTION}")
if(NOT CMAKE_REQUIRED_QUIET)
message(STATUS "Looking for ${FUNCTION} - found")
endif()
file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
"Determining if the function ${FUNCTION} exists passed with the following output:\n"
"${OUTPUT}\n\n")
else()
if(NOT CMAKE_REQUIRED_QUIET)
message(STATUS "Looking for ${FUNCTION} - not found")
endif()
set(${VARIABLE} "" CACHE INTERNAL "Have function ${FUNCTION}")
file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
"Determining if the function ${FUNCTION} exists failed with the following output:\n"
"${OUTPUT}\n\n")
endif()
endif()
endmacro()
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