# Distributed under the OSI-approved BSD 3-Clause License. See accompanying # file Copyright.txt or https://cmake.org/licensing for details. #.rst: # CheckVariableExists # ------------------- # # Check if the variable exists. # # :: # # CHECK_VARIABLE_EXISTS(VAR VARIABLE) # # # # :: # # VAR - the name of the variable # VARIABLE - variable to store the result # Will be created as an internal cache variable. # # # This macro is only for C variables. # # 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_LIBRARIES = list of libraries to link # CMAKE_REQUIRED_QUIET = execute quietly without messages macro(CHECK_VARIABLE_EXISTS VAR VARIABLE) if(NOT DEFINED "${VARIABLE}") set(MACRO_CHECK_VARIABLE_DEFINITIONS "-DCHECK_VARIABLE_EXISTS=${VAR} ${CMAKE_REQUIRED_FLAGS}") if(NOT CMAKE_REQUIRED_QUIET) message(STATUS "Looking for ${VAR}") endif() if(CMAKE_REQUIRED_LIBRARIES) set(CHECK_VARIABLE_EXISTS_ADD_LIBRARIES LINK_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES}) else() set(CHECK_VARIABLE_EXISTS_ADD_LIBRARIES) endif() try_compile(${VARIABLE} ${CMAKE_BINARY_DIR} ${CMAKE_ROOT}/Modules/CheckVariableExists.c COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS} ${CHECK_VARIABLE_EXISTS_ADD_LIBRARIES} CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_VARIABLE_DEFINITIONS} OUTPUT_VARIABLE OUTPUT) if(${VARIABLE}) set(${VARIABLE} 1 CACHE INTERNAL "Have variable ${VAR}") if(NOT CMAKE_REQUIRED_QUIET) message(STATUS "Looking for ${VAR} - found") endif() file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log "Determining if the variable ${VAR} exists passed with the following output:\n" "${OUTPUT}\n\n") else() set(${VARIABLE} "" CACHE INTERNAL "Have variable ${VAR}") if(NOT CMAKE_REQUIRED_QUIET) message(STATUS "Looking for ${VAR} - not found") endif() file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log "Determining if the variable ${VAR} exists failed with the following output:\n" "${OUTPUT}\n\n") endif() endif() endmacro()