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- Added intro code block showing how to include this module. - Used "command" instead of "macro". - Added rubric title for variables that affect the check command. - Refactored note about using CheckSymbolExists as a more robust check.
179 lines
5.5 KiB
CMake
179 lines
5.5 KiB
CMake
# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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# file LICENSE.rst or https://cmake.org/licensing for details.
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#[=======================================================================[.rst:
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CheckLibraryExists
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------------------
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This module provides a command to check whether a C library exists.
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Load this module in a CMake project with:
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.. code-block:: cmake
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include(CheckLibraryExists)
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Commands
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^^^^^^^^
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This module provides the following command:
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.. command:: check_library_exists
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Checks once whether a specified library exists and a given C function is
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available:
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.. code-block:: cmake
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check_library_exists(<library> <function> <location> <variable>)
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This command attempts to link a test executable that uses the specified
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C ``<function>`` to verify that it is provided by either a system or
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user-provided ``<library>``.
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The arguments are:
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``<library>``
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The name of the library, a full path to a library file, or an
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:ref:`Imported Target <Imported Targets>`.
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``<function>``
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The name of a function that should be available in the system or
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user-provided library ``<library>``.
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``<location>``
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The directory containing the library file. It is added to the link
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search path during the check. If this is an empty string, only the
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default library search paths are used.
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``<variable>``
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The name of the variable in which to store the check result. This
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variable will be created as an internal cache variable.
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.. note::
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This command is intended for performing basic sanity checks to verify
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that a library provides the expected functionality, or that the correct
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library is being located. However, it only verifies that a function
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symbol can be linked successfully - it does not ensure that the function
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is declared in library headers, nor can it detect functions that are
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inlined or defined as preprocessor macros. For more robust detection
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of function availability, prefer using :module:`CheckSymbolExists` or
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:module:`CheckSourceCompiles`.
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.. rubric:: Variables Affecting the Check
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The following variables may be set before calling this command to modify
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the way the check is run:
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.. include:: /module/include/CMAKE_REQUIRED_FLAGS.rst
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.. include:: /module/include/CMAKE_REQUIRED_DEFINITIONS.rst
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.. include:: /module/include/CMAKE_REQUIRED_LINK_OPTIONS.rst
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.. include:: /module/include/CMAKE_REQUIRED_LIBRARIES.rst
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.. include:: /module/include/CMAKE_REQUIRED_LINK_DIRECTORIES.rst
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.. include:: /module/include/CMAKE_REQUIRED_QUIET.rst
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Examples
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^^^^^^^^
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Checking if the ``curl`` library exists in the default paths and has the
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``curl_easy_perform()`` function:
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.. code-block:: cmake
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include(CheckLibraryExists)
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check_library_exists(curl curl_easy_perform "" HAVE_LIBRARY_CURL)
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To check if library exists in specific non-standard location and has a specified
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function:
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.. code-block:: cmake
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include(CheckLibraryExists)
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check_library_exists(curl curl_easy_perform "/opt/curl/lib" HAVE_LIBRARY_CURL)
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Also :ref:`Imported Targets` (for example, from the ``find_package()`` call)
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can be used:
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.. code-block:: cmake
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find_package(CURL)
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# ...
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if(TARGET CURL::libcurl)
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include(CheckLibraryExists)
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check_library_exists(CURL::libcurl curl_easy_perform "" HAVE_LIBRARY_CURL)
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endif()
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See Also
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^^^^^^^^
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* The :module:`CheckSymbolExists` module to check whether a C symbol exists.
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#]=======================================================================]
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include_guard(GLOBAL)
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macro(CHECK_LIBRARY_EXISTS LIBRARY FUNCTION LOCATION VARIABLE)
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if(NOT DEFINED "${VARIABLE}")
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set(MACRO_CHECK_LIBRARY_EXISTS_DEFINITION
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"-DCHECK_FUNCTION_EXISTS=${FUNCTION} ${CMAKE_REQUIRED_FLAGS}")
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if(NOT CMAKE_REQUIRED_QUIET)
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message(CHECK_START "Looking for ${FUNCTION} in ${LIBRARY}")
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endif()
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set(CHECK_LIBRARY_EXISTS_LINK_OPTIONS)
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if(CMAKE_REQUIRED_LINK_OPTIONS)
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set(CHECK_LIBRARY_EXISTS_LINK_OPTIONS
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LINK_OPTIONS ${CMAKE_REQUIRED_LINK_OPTIONS})
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endif()
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set(CHECK_LIBRARY_EXISTS_LIBRARIES ${LIBRARY})
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if(CMAKE_REQUIRED_LIBRARIES)
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set(CHECK_LIBRARY_EXISTS_LIBRARIES
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${CHECK_LIBRARY_EXISTS_LIBRARIES} ${CMAKE_REQUIRED_LIBRARIES})
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endif()
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if(CMAKE_REQUIRED_LINK_DIRECTORIES)
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set(_CLE_LINK_DIRECTORIES
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"-DLINK_DIRECTORIES:STRING=${LOCATION};${CMAKE_REQUIRED_LINK_DIRECTORIES}")
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else()
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set(_CLE_LINK_DIRECTORIES "-DLINK_DIRECTORIES:STRING=${LOCATION}")
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endif()
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if(CMAKE_C_COMPILER_LOADED)
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set(_cle_source CheckFunctionExists.c)
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elseif(CMAKE_CXX_COMPILER_LOADED)
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set(_cle_source CheckFunctionExists.cxx)
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else()
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message(FATAL_ERROR "CHECK_FUNCTION_EXISTS needs either C or CXX language enabled")
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endif()
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try_compile(${VARIABLE}
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SOURCE_FROM_FILE "${_cle_source}" "${CMAKE_ROOT}/Modules/CheckFunctionExists.c"
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COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
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${CHECK_LIBRARY_EXISTS_LINK_OPTIONS}
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LINK_LIBRARIES ${CHECK_LIBRARY_EXISTS_LIBRARIES}
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CMAKE_FLAGS
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-DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_LIBRARY_EXISTS_DEFINITION}
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"${_CLE_LINK_DIRECTORIES}"
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)
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unset(_cle_source)
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unset(_CLE_LINK_DIRECTORIES)
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if(${VARIABLE})
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if(NOT CMAKE_REQUIRED_QUIET)
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message(CHECK_PASS "found")
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endif()
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set(${VARIABLE} 1 CACHE INTERNAL "Have library ${LIBRARY}")
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else()
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if(NOT CMAKE_REQUIRED_QUIET)
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message(CHECK_FAIL "not found")
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endif()
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set(${VARIABLE} "" CACHE INTERNAL "Have library ${LIBRARY}")
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endif()
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endif()
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endmacro()
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