CMake/Modules/CheckVariableExists.cmake

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#
# Check if the variable exists.
# # CHECK_VARIABLE_EXISTS - macro which checks if the variable exists
# VAR - the name of the variable
# VARIABLE - variable to store the result
#
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# If CMAKE_REQUIRED_FLAGS is set then those flags will be passed into the
# compile of the program likewise if CMAKE_REQUIRED_LIBRARIES is set then
# those libraries will be linked against the test program
#
# only for C variables
#
MACRO(CHECK_VARIABLE_EXISTS VAR VARIABLE)
IF("${VARIABLE}" MATCHES "^${VARIABLE}$")
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SET(MACRO_CHECK_VARIABLE_DEFINITIONS
"-DCHECK_VARIABLE_EXISTS=${VAR} ${CMAKE_REQUIRED_FLAGS}")
MESSAGE(STATUS "Looking for ${VAR}")
IF(CMAKE_REQUIRED_LIBRARIES)
SET(CHECK_VARIABLE_EXISTS_ADD_LIBRARIES
"-DLINK_LIBRARIES:STRING=${CMAKE_REQUIRED_LIBRARIES}")
ENDIF(CMAKE_REQUIRED_LIBRARIES)
TRY_COMPILE(${VARIABLE}
${CMAKE_BINARY_DIR}
${CMAKE_ROOT}/Modules/CheckVariableExists.c
CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_VARIABLE_DEFINITIONS}
"${CHECK_VARIABLE_EXISTS_ADD_LIBRARIES}"
OUTPUT_VARIABLE OUTPUT)
IF(${VARIABLE})
SET(${VARIABLE} 1 CACHE INTERNAL "Have variable ${VAR}")
MESSAGE(STATUS "Looking for ${VAR} - found")
FILE(APPEND ${CMAKE_BINARY_DIR}/CMakeFiles/CMakeOutput.log
"Determining if the variable ${VAR} exists passed with the following output:\n"
"${OUTPUT}\n\n")
ELSE(${VARIABLE})
SET(${VARIABLE} "" CACHE INTERNAL "Have variable ${VAR}")
MESSAGE(STATUS "Looking for ${VAR} - not found")
FILE(APPEND ${CMAKE_BINARY_DIR}/CMakeFiles/CMakeError.log
"Determining if the variable ${VAR} exists failed with the following output:\n"
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"${OUTPUT}\n\n")
ENDIF(${VARIABLE})
ENDIF("${VARIABLE}" MATCHES "^${VARIABLE}$")
ENDMACRO(CHECK_VARIABLE_EXISTS)