# CheckFortranSourceCompiles

Added in version 3.1.

Check if given Fortran source compiles and links into an executable.

check_fortran_source_compiles

      check_fortran_source_compiles(<code> <resultVar>
          [FAIL_REGEX <regex>...]
          [SRC_EXT <extension>]
      )

  Checks that the source supplied in `<code>` can be compiled as a Fortran source file and linked as an executable. The `<code>` must be a Fortran `program`.

      check_fortran_source_compiles("program test
      error stop
      end program"
      HAVE_ERROR_STOP
      SRC_EXT .F90)

  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. This generate-time check may advise the user of such before the main build process. See also the `check_fortran_source_runs()` command to run the compiled code.

  The result will be stored in the internal cache variable `<resultVar>`, with a boolean true value for success and boolean false for failure.

  If `FAIL_REGEX` is provided, then failure is determined by checking if anything in the output matches any of the specified regular expressions.

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

  The check is only performed once, with the result cached in the variable named by `<resultVar>`. Every subsequent CMake run will reuse 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.

  The compile and link commands can be influenced by setting any of the following variables prior to calling `check_fortran_source_compiles()`:

> `CMAKE_REQUIRED_FLAGS`

>   String of additional flags to pass to the compiler. The string must be space-delimited--a ;-list will not work. The contents of `CMAKE_<LANG>_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--the contents of the `INCLUDE_DIRECTORIES` directory property will be ignored.

> `CMAKE_REQUIRED_LINK_OPTIONS`

>   Added in version 3.14.

>   A ;-list of options to add to the link command (see `try_compile()` 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_compile()` for further details).

> `CMAKE_REQUIRED_QUIET`

>   Added in version 3.1.

>   If this variable evaluates to a boolean true value, all status messages associated with the check will be suppressed.