Re: [PATCH 0/12] GCC _BitInt support [PR102989]

[Richard Biener <rguenther@suse.de>]

On Wed, 9 Aug 2023, Joseph Myers wrote:

> On Wed, 9 Aug 2023, Jakub Jelinek via Gcc-patches wrote:
> 
> > - _Complex _BitInt(N) isn't supported; again mainly because none of the psABIs
> >   mention how those should be passed/returned; in a limited way they are
> >   supported internally because the internal functions into which
> >   __builtin_{add,sub,mul}_overflow{,_p} is lowered return COMPLEX_TYPE as a
> >   hack to return 2 values without using references/pointers
> 
> What happens when the usual arithmetic conversions are applied to 
> operands, one of which is a complex integer type and the other of which is 
> a wider _BitInt type?  I don't see anything in the code to disallow this 
> case (which would produce an expression with a _Complex _BitInt type), or 
> any testcases for it.
> 
> Other testcases I think should be present (along with any corresponding 
> changes needed to the code itself):
> 
> * Verifying that the new integer constant suffix is rejected for C++.
> 
> * Verifying appropriate pedwarn-if-pedantic for the new constant suffix 
> for versions of C before C2x (and probably for use of _BitInt type 
> specifiers before C2x as well) - along with the expected -Wc11-c2x-compat 
> handling (in C2x mode) / -pedantic -Wno-c11-c2x-compat in older modes.

Can we go as far as deprecating our _Complex int extension for
C17 and make it unavailable for C2x, side-stepping the issue?
Or maybe at least considering that for C2x?

Richard.