C compiler issues warnings on wrapper functions

My latest compiler (clang 12) complains about our wrapper codes.

As a frequent pattern, they generate code like this

int res;

if (cond) {
   res = fun();
} else {
   SAC_RuntimeError ( "type error.....");
}

return res;

The compiler complains about res potentially not being initialised.

We have two options ere: either initialise res with some dummy value, or declare SAC_RuntimeError to be non-returning. I would prefer the latter, but I am not sure how to do this in a platform (C compiler) - independent way. My clang compiler allows for:

_Noreturn void SAC_RuntimeError( ...);

This seems to be C++11 standard as well..... but I guess we may have to go through cmake to make this happen.