Re: Fixing MSVC's inability to detect elog(ERROR) does not return

On Wed, 3 Sept 2025 at 23:32, Peter Eisentraut <peter(at)eisentraut(dot)org> wrote:
> The variant using _Generic is not a full replacement for
> __builtin_constant_p(), because it only detects integer constant
> expressions. So for example, it wouldn't work in the use in
> src/include/utils/memutils.h, which checks for constant strings. So I
> think we need to be careful here to maintain the difference.

Makes sense.

> I think what we could do is make a separate macro for detecting integer
> constant expressions (like ICE_P() in the reddit thread) and define that
> to __builtin_constant_p if available, else using _Generic. (We can't
> use _Generic on all platforms yet, that's a separate undertaking, but I
> think all platforms support either __builtin_constant_p or _Generic.)
> And then use that one for ereport.

Done

> It would also be nice to provide a comment with some explanation and/or
> a link and credit for the _Generic expression.

I've added a link to the stackoverflow thread in the comment above the
macro's definition.

> Btw., I think we should stick to the *_p() naming (for "predicate", I
> think) for compiler-intrinsic-affiliated functions/macros that report
> boolean results.

I didn't know what the _p suffix was meant to indicate. Do you have a
link which states that it's for "predicate"? The other things I had
in mind were "pointer" and "proprocessor", neither of which makes much
sense to me. Looking through [1], the only other intrinsic function I
see ending in _p is __builtin_types_compatible_p(). I don't see what
these both have in common with each other.

I've modified the patch to include the _p, however, I'd personally
rather leave this out as if someone asks me what it's for, I've got no
answer for them, other than Peter said.

> The __STDC_VERSION__ comparison can be dropped, since that is the
> minimum now required. (But you need to keep defined(__STDC_VERSION__),
> since this won't work in C++.)

Done.

Updated patch attached. Thanks for the review.

David

[1] https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html