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# 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
#]=======================================================================]
include_guard(GLOBAL)
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()
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