Re: [PATCH] Implement "P0631R4 Math Constants" for C++20

[Jakub Jelinek <jakub at redhat dot com>]

On Wed, Jul 31, 2019 at 07:58:55PM +0100, Jonathan Wakely wrote:
> > Perhaps add __extension__ before the literals too?
> 
> Does that do anything for Q literals? I thought I'd tried it
> previously and decided it didn't. I'm happy to add it though.

You're right, it works well that way only in C, not in C++, on say:
long double x = 1.234Q;
long double y = __extension__ 1.234Q;
This is pedwarned not when actually parsing the number, but
when tokenizing it, which for C++ we do before parsing for all tokens.

We could add a hack for it, say don't emit the pedwarn if the previous token
is RID_EXTENSION, but it wouldn't be anything close to how we handle
__extension__ during parsing (where pedantic is disabled while parsing the
whole cast expression after it).

	Jakub