[committed] libstdc++: Define std::numeric_limits<_FloatNN> before C++23

[Pranav Kant]

I have reverted the change upstream (
https://github.com/llvm/llvm-project/commit/7d21086d0ca4a680e96e0f4cd3e2597ebe027a48
).

On Wed, Oct 4, 2023 at 10:00 AM Pranav Kant <prka@google.com> wrote:

> I will revert the commit while I work on this. Thanks for the pointers.
>
> On Wed, Oct 4, 2023 at 9:57 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
>> On Wed, Oct 04, 2023 at 09:47:34AM -0700, Pranav Kant wrote:
>> > Thanks for bringing this to my attention. I am working on a fix. Will
>> keep
>> > this thread posted.
>> >
>> > Clang *does* define this macro only when float128 type is available. But
>> > the problem seems to be that clang doesn't define _Float128 alias type
>> > which is what's being used here. It only defines __float128 type.
>> Should be
>> > easy to fix.
>>
>> _Float128 (and other _FloatNN types) are standard C23 and C++23 types,
>> they certainly can't be simple aliases to __float128 or other similar
>> types.
>> In C++ they mangle differently, have significantly different behavior in
>> lots of different language details.
>> So, you need to implement the https://wg21.link/P1467R9 paper, rather
>> than
>> doing quick hacks.
>>
>>         Jakub
>>
>>
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