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//usr/share/cmake/Modules/CheckLibraryExists.cmake

# - Check if the function exists.
# CHECK_LIBRARY_EXISTS (LIBRARY FUNCTION LOCATION VARIABLE)
#
#  LIBRARY  - the name of the library you are looking for
#  FUNCTION - the name of the function
#  LOCATION - location where the library should be found
#  VARIABLE - variable to store the result
#
# 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

#=============================================================================
# Copyright 2002-2009 Kitware, Inc.
#
# Distributed under the OSI-approved BSD License (the "License");
# see accompanying file Copyright.txt for details.
#
# This software is distributed WITHOUT ANY WARRANTY; without even the
# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
# See the License for more information.
#=============================================================================
# (To distribute this file outside of CMake, substitute the full
#  License text for the above reference.)

macro(CHECK_LIBRARY_EXISTS LIBRARY FUNCTION LOCATION VARIABLE)
  if("${VARIABLE}" MATCHES "^${VARIABLE}$")
    set(MACRO_CHECK_LIBRARY_EXISTS_DEFINITION
      "-DCHECK_FUNCTION_EXISTS=${FUNCTION} ${CMAKE_REQUIRED_FLAGS}")
    message(STATUS "Looking for ${FUNCTION} in ${LIBRARY}")
    set(CHECK_LIBRARY_EXISTS_LIBRARIES ${LIBRARY})
    if(CMAKE_REQUIRED_LIBRARIES)
      set(CHECK_LIBRARY_EXISTS_LIBRARIES
        ${CHECK_LIBRARY_EXISTS_LIBRARIES} ${CMAKE_REQUIRED_LIBRARIES})
    endif()
    try_compile(${VARIABLE}
      ${CMAKE_BINARY_DIR}
      ${CMAKE_ROOT}/Modules/CheckFunctionExists.c
      COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
      LINK_LIBRARIES ${CHECK_LIBRARY_EXISTS_LIBRARIES}
      CMAKE_FLAGS
      -DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_LIBRARY_EXISTS_DEFINITION}
      -DLINK_DIRECTORIES:STRING=${LOCATION}
      OUTPUT_VARIABLE OUTPUT)

if(${VARIABLE})
      message(STATUS "Looking for ${FUNCTION} in ${LIBRARY} - found")
      set(${VARIABLE} 1 CACHE INTERNAL "Have library ${LIBRARY}")
      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
        "Determining if the function ${FUNCTION} exists in the ${LIBRARY} "
        "passed with the following output:\n"
        "${OUTPUT}\n\n")
    else()
      message(STATUS "Looking for ${FUNCTION} in ${LIBRARY} - not found")
      set(${VARIABLE} "" CACHE INTERNAL "Have library ${LIBRARY}")
      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
        "Determining if the function ${FUNCTION} exists in the ${LIBRARY} "
        "failed with the following output:\n"
        "${OUTPUT}\n\n")
    endif()
  endif()
endmacro()