Remove compiler ID from include directrory

[yurivict]

It adds the compiler ID to the include directory: include/mctc-lib/GNU-11.3.0/

This is very unconventional and unnecessary.

With this patch it now installs headers into include/mctc-lib which aligns with the way how most projects install their headers.

[awvwgk]

The exact directory doesn't matter, since the user of the library should always query it with pkg-config. Putting the module files in just $CMAKE_INSTALL_INCLUDEDIR/$PROJECT_NAME will result in problems for projects which provide C headers in the same directory because you can now use the header with either $PROJECT_NAME/something.h or something.h.

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Codecov Report

Merging #55 (8d84a92) into main (05caf6c) will not change coverage. The diff coverage is n/a.

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[yurivict]

Putting the module files in just $CMAKE_INSTALL_INCLUDEDIR/$PROJECT_NAME will result in problems for projects which provide C headers in the same directory because you can now use the header with either $PROJECT_NAME/something.h or something.h.

This doesn't cause any real problems because projects both would still resolve to the same header. Projects usually define how their headers are included: #include <project-name/header.h> or #include <header.h>.

[awvwgk]

Projects usually define how their headers are included: #include <project-name/header.h> or #include <header.h>.

If the latter becomes possible due to the module install location, it might get used by accident due to pkg-config adding the location to --cflags and result in unexpected breakage. $CMAKE_INSTALL_INCLUDEDIR/$PROJECT_NAME and $CMAKE_INSTALL_INCLUDEDIR are both not a good place to install Fortran module files.

I think Fedora is installing them in $CMAKE_INSTALL_LIBDIR/.../ including at least the build triple and finclude in the path, which might be an alternative.

[yurivict]

But almost no other projects install headers this way and they are all fine.

What is special about mctc-lib that requires its headers to include compiler ID?

[awvwgk]

What is special about mctc-lib that requires its headers to include compiler ID?

It does not, it only requires to not install the module files in a directory which might contain C headers. This project does not have C headers, but other projects which use a similar structure have and would probably be the next to receive a similar patch.

If the compiler ID is the problem, any other subdirectory name can be used, the actual path doesn't matter. With the module files being a build time requirement I wonder why the compiler ID is causing problems in the first place?

But almost no other projects install headers this way and they are all fine.

Packages installing modulefiles into $CMAKE_INSTALL_INCLUDEDIR are usually broken when installed in a system prefix like /usr. NetCDF for example does this, making the pkg-config file unusable for Fortran projects, which is why they provide nc-config as a workaround.

[yurivict]

If the compiler ID is the problem, any other subdirectory name can be used [...]

Fortran headers are already in a subdirectory. This is sufficient.

What other projects would install headers into include/mctc-lib? This is a dedicated directory for this project. Even if someone else would install C/C++ headers there - this would be totally fine.

[awvwgk]

We can split the differences here. I'm happy to accept this patch for installing modules in include/mctc-lib/modules.

[yurivict]

Ok, I updated the PR.