Re: C2x features status

[Florian Weimer <fweimer@redhat.com>]

* Joseph Myers:

> I'm working on adding various C2x features to the C front end (and 
> elsewhere in GCC as applicable).
>
> I suspect I won't get all the C2x features done for GCC 13.  If anyone 
> else is interested in adding C2x features, I'd encourage looking at some 
> of the following, which I may well not get to for GCC 13 (and posting here 
> to avoid duplication of effort if working on such a feature):
>
> * Bit-precise integer types (_BitInt) (see bug 102989) (integrated version 
> based on N2763, plus literal suffixes from N2775 and bit-fields from 
> N2969).  Would require working with back-end maintainers and upstream ABI 
> groups, where available, to get ABIs defined for as many architectures as 
> possible, as well as some default ABI choice in GCC for architectures that 
> haven't defined the ABI for these types.
>
> * [[unsequenced]] and [[reproducible]] attributes for function types.  See 
> N2956.  These are supposed to be similar to const and pure attributes, at 
> least in the absence of pointer and array function parameters (but note 
> they never affect type compatibility).
>
> * Tag compatibility (N3037, alternative wording).  Martin Uecker might 
> have patches for a draft version of this?
>
> * Preprocessor #embed (N3017) (see bug 105863).

Do you have a list of C2X features that are likely to impact autoconf
tests?  Or planned changes in the GCC 13 and 14 default language modes
that reject constructs previous accepted as an extension?

I'm asking because I'm working on the implicit function declaration
problem once more, and other things could be piggybacked on the tool
support over time.  See the parallel “C89isms in the test suite” thread.

I wonder if anything went into the default C2X language mode already
that could be similarly disruptive as the removal of implicit ints?  In
that case, I should probably backport that change into my GCC test
version.  (To avoid chasing ghosts, it's based off GCC 12, I've decided
to decouple it from our planned switch to GCC 13.)

Thanks,
Florian