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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:
CheckLibraryExists
------------------
Check once if the function exists in system or specified library.
.. command:: check_library_exists
.. code-block:: cmake
check_library_exists(<library> <function> <location> <variable>)
Check that the library ``<library>`` exists in the given location
``<location>`` and has the specified ``<function>``. The result is stored in
an internal cache variable ``<variable>``. If ``<location>`` is empty string,
default directories are searched.
Prefer using :module:`CheckSymbolExists` or :module:`CheckSourceCompiles`
instead of this module for more robust detection if a function is available in
a library.
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_LINK_OPTIONS.txt
.. include:: /module/CMAKE_REQUIRED_LIBRARIES.txt
.. include:: /module/CMAKE_REQUIRED_LINK_DIRECTORIES.txt
.. include:: /module/CMAKE_REQUIRED_QUIET.txt
Examples
^^^^^^^^
This module can be useful for performing so-called sanity checks to verify that
the specified library provides the expected functionality and is indeed the
correct one being located.
For example, to check if the ``curl`` library exists in the default paths and
has the ``curl_easy_perform`` function:
.. code-block:: cmake
include(CheckLibraryExists)
check_library_exists(curl curl_easy_perform "" HAVE_LIBRARY_CURL)
To check if library exists in specific non-standard location and has a specified
function:
.. code-block:: cmake
include(CheckLibraryExists)
check_library_exists(curl curl_easy_perform "/opt/curl/lib" HAVE_LIBRARY_CURL)
Also :ref:`IMPORTED library <add_library imported libraries>` (for example,
from the ``find_package()`` call) can be used:
.. code-block:: cmake
find_package(CURL)
# ...
if(TARGET CURL::libcurl)
include(CheckLibraryExists)
check_library_exists(CURL::libcurl curl_easy_perform "" HAVE_LIBRARY_CURL)
endif()
#]=======================================================================]
include_guard(GLOBAL)
macro(CHECK_LIBRARY_EXISTS LIBRARY FUNCTION LOCATION VARIABLE)
if(NOT DEFINED "${VARIABLE}")
set(MACRO_CHECK_LIBRARY_EXISTS_DEFINITION
"-DCHECK_FUNCTION_EXISTS=${FUNCTION} ${CMAKE_REQUIRED_FLAGS}")
if(NOT CMAKE_REQUIRED_QUIET)
message(CHECK_START "Looking for ${FUNCTION} in ${LIBRARY}")
endif()
set(CHECK_LIBRARY_EXISTS_LINK_OPTIONS)
if(CMAKE_REQUIRED_LINK_OPTIONS)
set(CHECK_LIBRARY_EXISTS_LINK_OPTIONS
LINK_OPTIONS ${CMAKE_REQUIRED_LINK_OPTIONS})
endif()
set(CHECK_LIBRARY_EXISTS_LIBRARIES ${LIBRARY})
if(CMAKE_REQUIRED_LIBRARIES)
set(CHECK_LIBRARY_EXISTS_LIBRARIES
${CHECK_LIBRARY_EXISTS_LIBRARIES} ${CMAKE_REQUIRED_LIBRARIES})
endif()
if(CMAKE_REQUIRED_LINK_DIRECTORIES)
set(_CLE_LINK_DIRECTORIES
"-DLINK_DIRECTORIES:STRING=${LOCATION};${CMAKE_REQUIRED_LINK_DIRECTORIES}")
else()
set(_CLE_LINK_DIRECTORIES "-DLINK_DIRECTORIES:STRING=${LOCATION}")
endif()
if(CMAKE_C_COMPILER_LOADED)
set(_cle_source CheckFunctionExists.c)
elseif(CMAKE_CXX_COMPILER_LOADED)
set(_cle_source CheckFunctionExists.cxx)
else()
message(FATAL_ERROR "CHECK_FUNCTION_EXISTS needs either C or CXX language enabled")
endif()
try_compile(${VARIABLE}
SOURCE_FROM_FILE "${_cle_source}" "${CMAKE_ROOT}/Modules/CheckFunctionExists.c"
COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
${CHECK_LIBRARY_EXISTS_LINK_OPTIONS}
LINK_LIBRARIES ${CHECK_LIBRARY_EXISTS_LIBRARIES}
CMAKE_FLAGS
-DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_LIBRARY_EXISTS_DEFINITION}
"${_CLE_LINK_DIRECTORIES}"
)
unset(_cle_source)
unset(_CLE_LINK_DIRECTORIES)
if(${VARIABLE})
if(NOT CMAKE_REQUIRED_QUIET)
message(CHECK_PASS "found")
endif()
set(${VARIABLE} 1 CACHE INTERNAL "Have library ${LIBRARY}")
else()
if(NOT CMAKE_REQUIRED_QUIET)
message(CHECK_FAIL "not found")
endif()
set(${VARIABLE} "" CACHE INTERNAL "Have library ${LIBRARY}")
endif()
endif()
endmacro()
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