# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.

#[=======================================================================[.rst:
CheckFortranFunctionExists
--------------------------

Check if a Fortran function exists.

.. command:: CHECK_FORTRAN_FUNCTION_EXISTS

  .. code-block:: cmake

    CHECK_FORTRAN_FUNCTION_EXISTS(<function> <result>)

  where

  ``<function>``
    the name of the Fortran function
  ``<result>``
    variable to store the result; will be created as an internal cache variable.

The following variables may be set before calling this macro to modify
the way the check is run:

``CMAKE_REQUIRED_LINK_OPTIONS``
  A :ref:`;-list <CMake Language Lists>` of options to add to the link
  command (see :command:`try_compile` for further details).

``CMAKE_REQUIRED_LIBRARIES``
  A :ref:`;-list <CMake Language Lists>` of libraries to add to the link
  command. These can be the name of system libraries or they can be
  :ref:`Imported Targets <Imported Targets>` (see :command:`try_compile` for
  further details).
#]=======================================================================]

include_guard(GLOBAL)

macro(CHECK_FORTRAN_FUNCTION_EXISTS FUNCTION VARIABLE)
  if(NOT DEFINED ${VARIABLE})
    message(STATUS "Looking for Fortran ${FUNCTION}")
    if(CMAKE_REQUIRED_LINK_OPTIONS)
      set(CHECK_FUNCTION_EXISTS_ADD_LINK_OPTIONS
        LINK_OPTIONS ${CMAKE_REQUIRED_LINK_OPTIONS})
    else()
      set(CHECK_FUNCTION_EXISTS_ADD_LINK_OPTIONS)
    endif()
    if(CMAKE_REQUIRED_LIBRARIES)
      set(CHECK_FUNCTION_EXISTS_ADD_LIBRARIES
        LINK_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
    else()
      set(CHECK_FUNCTION_EXISTS_ADD_LIBRARIES)
    endif()
    file(WRITE
    ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/testFortranCompiler.f
    "
      program TESTFortran
      external ${FUNCTION}
      call ${FUNCTION}()
      end program TESTFortran
    "
    )
    try_compile(${VARIABLE}
    ${CMAKE_BINARY_DIR}
    ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/testFortranCompiler.f
    ${CHECK_FUNCTION_EXISTS_ADD_LINK_OPTIONS}
    ${CHECK_FUNCTION_EXISTS_ADD_LIBRARIES}
    OUTPUT_VARIABLE OUTPUT
    )
#    message(STATUS "${OUTPUT}")
    if(${VARIABLE})
      set(${VARIABLE} 1 CACHE INTERNAL "Have Fortran function ${FUNCTION}")
      message(STATUS "Looking for Fortran ${FUNCTION} - found")
      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
        "Determining if the Fortran ${FUNCTION} exists passed with the following output:\n"
        "${OUTPUT}\n\n")
    else()
      message(STATUS "Looking for Fortran ${FUNCTION} - not found")
      set(${VARIABLE} "" CACHE INTERNAL "Have Fortran function ${FUNCTION}")
      file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
        "Determining if the Fortran ${FUNCTION} exists failed with the following output:\n"
        "${OUTPUT}\n\n")
    endif()
  endif()
endmacro()