Re: [C PATCH] Do not drop qualifiers for _Atomic in typeof

["Uecker, Martin" <Martin.Uecker@med.uni-goettingen.de>]

Am Montag, den 23.11.2020, 20:21 +0000 schrieb Joseph Myers:
> On Mon, 23 Nov 2020, Uecker, Martin wrote:
> 
> > Joseph,
> > 
> > here is the patch to not drop qualifiers for _Atomic in
> > typeof. I am not sure whether this is appropriate in
> > stage3, but I wanted to leave it here for you to comment
> > and so that it does not lost.
> > 
> > First, I noticed that the change to drop qualifiers
> > in lvalue conversion also implies that __auto_type now
> > always uses the non-qualified type. I think this is more
> > correct, and also what other compilers and C++'s auto do.
> > The first change here in c-parser would remove the now
> > redundant code to drop qualifiers for _Atomic types.
> > 
> > The second change would remove the code to drop qualifiers
> > for _Atomic types for typeof. I would then use the
> > comma operator for stdatomic to remove all qualifiers.
> > Here, the question is whether this may have same
> > unintended side effects.
> 
> This is OK, with references to bugs 65455 and 92935 as I think it fixes 
> those.
> 
> Any change to qualifiers for typeof risks breaking something relying on 
> the details of when the result is or is not qualified, but given that in 
> previous GCC versions that was poorly defined and inconsistent, making 
> these changes to make it more consistent seems reasonable.
> 
> It is probably still the case that _Typeof as proposed for ISO C would 
> need special handling of function and function pointer types for the same 
> reason as _Generic has such handling (_Noreturn not being part of the 
> function type as defined by ISO C).

So OK to apply with the following Changelog?



    C: Do not drop qualifiers in typeof for _Atomic types. [PR65455,PR92935]
    
    2020-11-25  Martin Uecker  <muecker@gwdg.de>

    gcc/c/
            * c-parsers.c (c_parser_declaration_or_fndef): Remove redundant code
	    to drop qualifiers of _Atomic types for __auto_type.
	    (c_parser_typeof_specifier): Do not drop qualifiers of _Atomic
	    types for __typeof__.

    gcc/ginclude/
	    * ginclude/stdatomic.h: Use comma operator to drop qualifiers.
 
    gcc/testsuite/
	    * gcc.dg/typeof-2.c: Adapt test.