[Core][Geometry] Projection constexpr

[tteschemacher]

Dear all,

I am adding here some defined constexpr for the results of the projection functions.

This is the follow up of #6186. It is the same but with clean commits.

Thx!

[tteschemacher]

@loumalouomega @philbucher do you have a glue what is happening with the test in CI? It shouldn't fail due to that change?!

[philbucher]

Well, it fails :)
Can you change the verbosity (I think to TESTS_OUTPUT) to see which test fails?

[philbucher]

that is the error:
corrupted size vs. prev_size

Not sure if related to this PR

[tteschemacher]

Thanks, I hardly think so...

[philbucher]

what is very strange to me is this output:

Test_ConstitutiveLaw_SmallStrainIsotropicDamageTractionOnly3D            OK.

TestnurbsUtilities                                                       OK.

/__w/Kratos/Kratos/bin/Custom/applications//MeshingApplication/tests/test_MeshingApplication.py
Ran 1335 of 1463 test cases in 21.1892s. OK
Running cpp tests
corrupted size vs. prev_size
Aborted (core dumped)

[tteschemacher]

It's coming in all new prs, now

[tteschemacher]

@KratosMultiphysics/technical-committee

I just realized that a quite long time ago we had this PR to avoid the issues which were arising due to misunderstanding return values. By the time we thought by introducing constexpr this would be much easier to understand. Do you think we should proceed with this idea and add the respecive names?

[tteschemacher]

Otherwise, we could close this PR - I am fine with either solution - so - open to discussion.