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
#
MACRO(CHECK_VARIABLE_EXISTS VAR VARIABLE)
SET(MACRO_CHECK_VARIABLE_DEFINITIONS -DCHECK_VARIABLE_EXISTS=${VAR})
TRY_COMPILE(${VARIABLE}
${PROJECT_BINARY_DIR}
${CMAKE_ROOT}/Modules/CheckVariableExists.c
CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_VARIABLE_DEFINITIONS}
OUTPUT_VARIABLE OUTPUT)
IF(${VARIABLE})
SET(${VARIABLE} 1 CACHE INTERNAL "Have variable ${VAR}")
ELSE(${VARIABLE})
SET(${VARIABLE} "" CACHE INTERNAL "Have variable ${VAR}")
WRITE_FILE(${PROJECT_BINARY_DIR}/CMakeError.log
"Determining if the variable ${VAR} exists failed with the following output:\n"
"${OUTPUT}\n" APPEND)
ENDIF(${VARIABLE})
ENDMACRO(CHECK_VARIABLE_EXISTS)