Re: [PATCH] c++: Fix up __has_extension (cxx_init_captures)

[Jason Merrill <jason@redhat.com>]

On 11/28/23 03:22, Jakub Jelinek wrote:
> On Mon, Nov 27, 2023 at 10:58:04AM +0000, Alex Coplan wrote:
>> Many thanks both for the reviews, this is now pushed (with Jason's
>> above changes implemented) as g:06280a906cb3dc80cf5e07cf3335b758848d488d.
> 
> The new test FAILs everywhere with GXX_TESTSUITE_STDS=98,11,14,17,20,2b
> I'm normally using for testing.
> FAIL: g++.dg/ext/has-feature.C  -std=gnu++11 (test for excess errors)
> Excess errors:
> /home/jakub/src/gcc/gcc/testsuite/g++.dg/ext/has-feature.C:185:2: error: #error
> 
> This is on
> #if __has_extension (cxx_init_captures) != CXX11
> #error
> #endif
> Comparing the values with clang++ on godbolt and with what is actually
> implemented:
> void foo () { auto a = [b = 3]() { return b; }; }
> both clang++ and GCC implement init captures as extension already in C++11
> (and obviously not in C++98 because lambdas aren't implemented there),
> unless -pedantic-errors/-Werror=pedantic, so I think we should change
> the FE to match the test rather than the other way around.
> 
> Tested on x86_64-linux with
> GXX_TESTSUITE_STDS=98,11,14,17,20,23,26 make check-g++ RUNTESTFLAGS="--target_board=unix\{-m32,-m64\} dg.exp='has-feature.C'"
> Ok for trunk?

OK.

> Making __has_extension return __has_feature for -pedantic-errors and not
> for -Werror=pedantic is just weird, 

I think -Werror=pedantic is mostly useless as it doesn't affect pedwarns 
that use other -W options.  Though -pedantic-errors -Wno-error=pedantic 
does seem useful, to error on just the pedwarns that are on by default.

Jason