# CheckFortranSourceRuns

Check if given Fortran source compiles and links into an executable and can subsequently be run.

`check_fortran_source_runs`

      check_fortran_source_runs(<code> <resultVar>
          [SRC_EXT <extension>])

  Check that the source supplied in `<code>` can be compiled as a Fortran source file, linked as an executable and then run. The `<code>` must be a Fortran program containing at least an `end` statement–for example:

      check_fortran_source_runs("real :: x[*]; call co_sum(x); end" F2018coarrayOK)

  This command can help avoid costly build processes when a compiler lacks support for a necessary feature, or a particular vendor library is not compatible with the Fortran compiler version being used. Some of these failures only occur at runtime instead of linktime, and a trivial runtime example can catch the issue before the main build process.

  If the `<code>` could be built and run successfully, the internal cache variable specified by `<resultVar>` will be set to 1, otherwise it will be set to an value that evaluates to boolean false (e.g. an empty string or an error message).

  By default, the test source file will be given a `.F90` file extension. The `SRC_EXT` option can be used to override this with `.<extension>` instead.

  The underlying check is performed by the `try_run()` command. The compile and link commands can be influenced by setting any of the following variables prior to calling `check_fortran_source_runs()`:

  `CMAKE_REQUIRED_FLAGS`
    Additional flags to pass to the compiler. Note that the contents of `CMAKE_Fortran_FLAGS` and its associated configuration-specific variable are automatically added to the compiler command before the contents of `CMAKE_REQUIRED_FLAGS`.
  `CMAKE_REQUIRED_DEFINITIONS`
    A ;-list of compiler definitions of the form `-DFOO` or `-DFOO=bar`. A definition for the name specified by `<resultVar>` will also be added automatically.
  `CMAKE_REQUIRED_INCLUDES`
    A ;-list of header search paths to pass to the compiler. These will be the only header search paths used by `try_run()`, i.e. the contents of the `INCLUDE_DIRECTORIES` directory property will be ignored.
  `CMAKE_REQUIRED_LINK_OPTIONS`
    A ;-list of options to add to the link command (see `try_run()` for further details).
  `CMAKE_REQUIRED_LIBRARIES`
    A ;-list of libraries to add to the link command. These can be the name of system libraries or they can be Imported Targets (see `try_run()` for further details).
  `CMAKE_REQUIRED_QUIET`
    If this variable evaluates to a boolean true value, all status messages associated with the check will be suppressed.

  The check is only performed once, with the result cached in the variable named by `<resultVar>`. Every subsequent CMake run will re-use this cached value rather than performing the check again, even if the `<code>` changes. In order to force the check to be re-evaluated, the variable named by `<resultVar>` must be manually removed from the cache.