[cmake-developers] Fortran detection, issue 9220

[Brad King]

On 02/11/2015 09:26 AM, Ben Boeckel wrote:
> A sketch for anyone interested (probably still not complete, but it's
> things to look for):
> 
>   - change cmGlobalGenerator::EnableLanguage to return a bool;
>   - add CMAKE_<LANG>_FOUND variables to indicate support for a language
>     is available;

We already guarantee that CMAKE_<LANG>_COMPILER is set, so we could indicate
failure simply by having it not set.

Also one would need to decide what determines whether an optional language
is not available.  If a compiler is available but cannot compile binaries,
should that be an error or tolerated as "not available"?  As a user I would
expect setting FC=/path/to/gfortran in my environment before calling CMake
to cause Fortran to be enabled if the project wants it or else an error.

>   - trigger an error when build rules for an unsupported language are
>     encountered.

We already treat unknown extensions like .txt files in most cases, so
this would have to be specific to languages that were OPTIONAL and failed
to be enabled.

-Brad