Re: [PATCH v2] c: Silently ignore pragma region [PR85487]

[Austin Morton <austinpmorton@gmail.com>]

> But in that case the pragma shouldn't be ignored, but instead checked
> against the various requirements.  E.g. that region is followed by a single
> optional name (are there any requirements on what name can be, can it be
> just a single token, can it be C/C++ keyword, etc.), guess ignore all the
> tokens after endregion if it is all a comment, and verify nesting
> (all region/endregion are properly paired up).

I cannot speak to the internals of the MSVC compiler, but I can say
definitively that
clang does not do any of this.  The clang handling of #pragma region
is a no-op, as
can be seen here:
https://github.com/llvm/llvm-project/blob/48b510c4bc0fe090e635ee0440e46fc176527d7e/clang/lib/Lex/Pragma.cpp#L1847

Additionally, the MSVC implementation appears to do no validation (or
at least doesn't
emit warnings that indicate that it does). https://godbolt.org/z/3zTbnn

#pragma region is purely designed for editors to assist in
code-folding (primarily
visual studio and visual studio code, although I am sure others support it).

The goal of this patch is to make GCC compatible with both clang and
MSVC handling of this
pragma, not to introduce novel functionality.