Specify C standard

[maxaehle]

Proposed Changes

In SU2/meson.build, specify the version of the C standard used when compiling SU2, as C99. It must be at least C99 because of the for loop initial declarations in externals/cgns/cgnslib.c. (One could probably use a newer C standard as well.)

This change was necessary to compile SU2 on a system where cc is the GCC 4.8.5 (from 2015), which used -std=gnu89 by default.

Related Work

The change was not necessary in v7.1.0. I suppose it has something to do with the recent CGNS updates (#1500, #1507, ...).

PR Checklist

Put an X by all that apply. You can fill this out after submitting the PR. If you have any questions, don't hesitate to ask! We want to help. These are a guide for you to know what the reviewers will be looking for in your contribution.

• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with the '-Wall -Wextra -Wno-unused-parameter -Wno-empty-body' compiler flags, or simply --warnlevel=2 when using meson).
• My contribution is commented and consistent with SU2 style.
• I have added a test case that demonstrates my contribution, if necessary.
• I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp) , if necessary.

[TobiKattmann]

On Elwetritsch I guess... I didn't notice because I build with -Denable-cgns=false as I never really deal with CGNS meshes
💐

[maxaehle]

On Elwetritsch I guess...

Yes ;-)

[thomasdick]

Yes, it is an issue on the Elwetritsch cluster. I tested this and the solution works.

[TobiKattmann]

Don't mind the failing parallel_regression.py, that is due to su2code/TestCases#91 . The correct residuals will be pushed with #1530. It is the 3D streamwise periodic case where I changed a wrong NDIME in the mesh

But I guess merging is blocked as parallel_regression.py is required 😬