Fortran: Add support for submodules on Cray

Cray Fortran does not include the enclosing module name as a prefix of submodules. Define CMAKE_Fortran_SUBMODULE_SEP with an empty string to mean that there is no prefix, and set this for Cray.

Also add a default fallback to use the .mod extension when CMAKE_Fortran_SUBMODULE_EXT is not set. This is a better guess than no extension at all.

Issue: #18925
Topic-rename: fortran-submodule-cray

added workflow:wip label

added comp:cray label

changed the description

Thanks for the review @brad.king Would you suggest then that if for any Fortran compiler the CMAKE_Fortran_SUBMODULE_EXT variable is missing, we should throw an exception and state that this variable should be defined?

When removing the code that adds the default .mod extention in this MR, it unexpectedly still works for Cray because of the lines https://gitlab.kitware.com/cmake/cmake/blob/master/Source/cmDependsFortran.cxx#L497-501 that basically re-add the ".mod" extention if no extention is present. So that even if we would print an error message, the build still passes counter-intuitively.

Regarding the right level to check for empty CMAKE_Fortran_SUBMODULE_SEP value: You are right in that you don't want to break all Fortran projects that don't use submodules. The only place that seems to know when submodules are used is during the parsing of the Fortran files in the "rules". So essentially the above routine SModName would be a good place.

added 1 commit

• dd794f5c - Add CMAKE_Fortran_SUBMODULE_{SEP,EXT} to Modules/Compiler/Cray-Fortran.cmake

Compare with previous version

changed title from Fallback for Fortran submodule naming to Fortran: Add support for submodules on Cray

changed the description

changed milestone to %3.16.0

assigned to @brad.king

added 2 commits

• 66feef60 - Fortran: Support compilers using no module prefix on submodule files
• de996c19 - Fortran: Add support for submodules on Cray

Compare with previous version

@wdeconinck1 thanks. I updated your branch to tweak the code, add a comment, and revise the commit messages a bit. Please fetch and reset your checkout (no push needed).

Do: stage

added workflow:nightly-testing label and removed workflow:wip label

added 2 commits

• 4f3a64de - Fortran: Support compilers using no module prefix on submodule files
• 4f6211b5 - Fortran: Add support for submodules on Cray

Compare with previous version

Do: stage

Great, thank you for the quick action. Will this only be available in 3.16.0 or earlier as well?

added 2 commits

• 33de4d27 - Fortran: Support compilers using no module prefix on submodule files
• b0bcd4d7 - Fortran: Add support for submodules on Cray

Compare with previous version

Warnings:

• Eligible for the 3.15.x branch.

The warnings do not need to be fixed, but it is recommended to do so.

changed milestone to %3.15.0

resolved all discussions

Do: merge

removed workflow:nightly-testing label

mentioned in commit 58d10deb

merged

mentioned in commit 1555837c

Hello @brad.king this may be my ignorance in not understanding the workflow. The activity log above shows that the 'fortran-submodule-cray' branch was merged into "release-3.15" branch. But I cannot see it in the current "release" branch, and neither in the just released "3.15-rc4" tag. When and where should it appear?

mentioned in commit 14f69fab

resolved all discussions

mentioned in issue #20220 (closed)