# Distributed under the OSI-approved BSD 3-Clause License. See accompanying # file Copyright.txt or https://cmake.org/licensing for details. #[=======================================================================[.rst: CheckSymbolExists ----------------- Provides a macro to check if a symbol exists as a function, variable, or macro in ``C``. .. command:: check_symbol_exists .. code-block:: cmake check_symbol_exists( ) Check that the ```` is available after including given header ```` and store the result in a ````. Specify the list of files in one argument as a semicolon-separated list. ```` will be created as an internal cache variable. If the header files define the symbol as a macro it is considered available and assumed to work. If the header files declare the symbol as a function or variable then the symbol must also be available for linking (so intrinsics may not be detected). If the symbol is a type, enum value, or intrinsic it will not be recognized (consider using :module:`CheckTypeSize` or :module:`CheckSourceCompiles`). If the check needs to be done in C++, consider using :module:`CheckCXXSymbolExists` instead. 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_LINK_DIRECTORIES.txt .. include:: /module/CMAKE_REQUIRED_QUIET.txt For example: .. code-block:: cmake include(CheckSymbolExists) # Check for macro SEEK_SET check_symbol_exists(SEEK_SET "stdio.h" HAVE_SEEK_SET) # Check for function fopen check_symbol_exists(fopen "stdio.h" HAVE_FOPEN) #]=======================================================================] include_guard(GLOBAL) block(SCOPE_FOR POLICIES) cmake_policy(SET CMP0054 NEW) # if() quoted variables not dereferenced macro(CHECK_SYMBOL_EXISTS SYMBOL FILES VARIABLE) if(CMAKE_C_COMPILER_LOADED) __CHECK_SYMBOL_EXISTS_FILTER_FLAGS(C) __CHECK_SYMBOL_EXISTS_IMPL(CheckSymbolExists.c "${SYMBOL}" "${FILES}" "${VARIABLE}" ) __CHECK_SYMBOL_EXISTS_RESTORE_FLAGS(C) elseif(CMAKE_CXX_COMPILER_LOADED) __CHECK_SYMBOL_EXISTS_FILTER_FLAGS(CXX) __CHECK_SYMBOL_EXISTS_IMPL(CheckSymbolExists.cxx "${SYMBOL}" "${FILES}" "${VARIABLE}" ) __CHECK_SYMBOL_EXISTS_RESTORE_FLAGS(CXX) else() message(FATAL_ERROR "CHECK_SYMBOL_EXISTS needs either C or CXX language enabled") endif() endmacro() macro(__CHECK_SYMBOL_EXISTS_FILTER_FLAGS LANG) if(CMAKE_TRY_COMPILE_CONFIGURATION) string(TOUPPER "${CMAKE_TRY_COMPILE_CONFIGURATION}" _tc_config) else() set(_tc_config "DEBUG") endif() foreach(v CMAKE_${LANG}_FLAGS CMAKE_${LANG}_FLAGS_${_tc_config}) set(__${v}_SAVED "${${v}}") string(REGEX REPLACE "(^| )-Werror([= ][^-][^ ]*)?( |$)" " " ${v} "${${v}}") string(REGEX REPLACE "(^| )-pedantic-errors( |$)" " " ${v} "${${v}}") endforeach() endmacro() macro(__CHECK_SYMBOL_EXISTS_RESTORE_FLAGS LANG) if(CMAKE_TRY_COMPILE_CONFIGURATION) string(TOUPPER "${CMAKE_TRY_COMPILE_CONFIGURATION}" _tc_config) else() set(_tc_config "DEBUG") endif() foreach(v CMAKE_${LANG}_FLAGS CMAKE_${LANG}_FLAGS_${_tc_config}) set(${v} "${__${v}_SAVED}") unset(__${v}_SAVED) endforeach() endmacro() macro(__CHECK_SYMBOL_EXISTS_IMPL SOURCEFILE SYMBOL FILES VARIABLE) if(NOT DEFINED "${VARIABLE}" OR "x${${VARIABLE}}" STREQUAL "x${VARIABLE}") set(_CSE_SOURCE "/* */\n") set(MACRO_CHECK_SYMBOL_EXISTS_FLAGS ${CMAKE_REQUIRED_FLAGS}) if(CMAKE_REQUIRED_LINK_OPTIONS) set(CHECK_SYMBOL_EXISTS_LINK_OPTIONS LINK_OPTIONS ${CMAKE_REQUIRED_LINK_OPTIONS}) else() set(CHECK_SYMBOL_EXISTS_LINK_OPTIONS) endif() if(CMAKE_REQUIRED_LIBRARIES) set(CHECK_SYMBOL_EXISTS_LIBS LINK_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES}) else() set(CHECK_SYMBOL_EXISTS_LIBS) endif() if(CMAKE_REQUIRED_INCLUDES) set(CMAKE_SYMBOL_EXISTS_INCLUDES "-DINCLUDE_DIRECTORIES:STRING=${CMAKE_REQUIRED_INCLUDES}") else() set(CMAKE_SYMBOL_EXISTS_INCLUDES) endif() if(CMAKE_REQUIRED_LINK_DIRECTORIES) set(_CSE_LINK_DIRECTORIES "-DLINK_DIRECTORIES:STRING=${CMAKE_REQUIRED_LINK_DIRECTORIES}") else() set(_CSE_LINK_DIRECTORIES) endif() foreach(FILE ${FILES}) string(APPEND _CSE_SOURCE "#include <${FILE}>\n") endforeach() string(APPEND _CSE_SOURCE " int main(int argc, char** argv) { (void)argv;") set(_CSE_CHECK_NON_MACRO "return ((int*)(&${SYMBOL}))[argc];") if("${SYMBOL}" MATCHES "^[a-zA-Z_][a-zA-Z0-9_]*$") # The SYMBOL has a legal macro name. Test whether it exists as a macro. string(APPEND _CSE_SOURCE " #ifndef ${SYMBOL} ${_CSE_CHECK_NON_MACRO} #else (void)argc; return 0; #endif") else() # The SYMBOL cannot be a macro (e.g., a template function). string(APPEND _CSE_SOURCE " ${_CSE_CHECK_NON_MACRO}") endif() string(APPEND _CSE_SOURCE " }\n") unset(_CSE_CHECK_NON_MACRO) if(NOT CMAKE_REQUIRED_QUIET) message(CHECK_START "Looking for ${SYMBOL}") endif() try_compile(${VARIABLE} SOURCE_FROM_VAR "${SOURCEFILE}" _CSE_SOURCE COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS} ${CHECK_SYMBOL_EXISTS_LINK_OPTIONS} ${CHECK_SYMBOL_EXISTS_LIBS} CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_SYMBOL_EXISTS_FLAGS} "${CMAKE_SYMBOL_EXISTS_INCLUDES}" "${_CSE_LINK_DIRECTORIES}" ) unset(_CSE_LINK_DIRECTORIES) if(${VARIABLE}) if(NOT CMAKE_REQUIRED_QUIET) message(CHECK_PASS "found") endif() set(${VARIABLE} 1 CACHE INTERNAL "Have symbol ${SYMBOL}") else() if(NOT CMAKE_REQUIRED_QUIET) message(CHECK_FAIL "not found") endif() set(${VARIABLE} "" CACHE INTERNAL "Have symbol ${SYMBOL}") endif() unset(_CSE_SOURCE) endif() endmacro() endblock()