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# - Check if the variable exists.
# CHECK_VARIABLE_EXISTS(VAR VARIABLE)
#
# VAR - the name of the variable
# VARIABLE - variable to store the result
#
# 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
MACRO(CHECK_VARIABLE_EXISTS VAR VARIABLE)
IF("${VARIABLE}" MATCHES "^${VARIABLE}$")
SET(MACRO_CHECK_VARIABLE_DEFINITIONS
"-DCHECK_VARIABLE_EXISTS=${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}")
ELSE(CMAKE_REQUIRED_LIBRARIES)
SET(CHECK_VARIABLE_EXISTS_ADD_LIBRARIES)
ENDIF(CMAKE_REQUIRED_LIBRARIES)
TRY_COMPILE(${VARIABLE}
${CMAKE_BINARY_DIR}
${CMAKE_ROOT}/Modules/CheckVariableExists.c
COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
CMAKE_FLAGS -DCOMPILE_DEFINITIONS:STRING=${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 ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/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 ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
"Determining if the variable ${VAR} exists failed with the following output:\n"
"${OUTPUT}\n\n")
ENDIF(${VARIABLE})
ENDIF("${VARIABLE}" MATCHES "^${VARIABLE}$")
ENDMACRO(CHECK_VARIABLE_EXISTS)
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