Re: Some experience with the igc branch

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Thu, 26 Dec 2024 16:12:52 +0000
> Cc: Gerd Möllmann <gerd.moellmann@gmail.com>, 
> 	Eli Zaretskii <eliz@gnu.org>, ofv@wanadoo.es, emacs-devel@gnu.org, eller.helmut@gmail.com, 
> 	acorallo@gnu.org
> 
> Pip Cet <pipcet@protonmail.com> writes:
> 
> > "Stefan Kangas" <stefankangas@gmail.com> writes:
> >
> >> Which parts of C11 help us?
> >
> > stdatomic.h, in this case.
> 
> Thanks for the explanation.
> 
> > IIRC, C99 doesn't have usable memory barriers, not even for signal
> > handler/main thread races such as this one.
> >
> > Of course almost every compiler that supports C99, and certainly all
> > compilers usable for compiling Emacs, provides (or doesn't need, in the
> > case of TinyCC) ways of implementing them.  In the case of GCC, that
> > used to be asm volatile ("" : : : "memory").
> 
> I don't think I understand what this means in practice.
> 
> Can we use stdatomic.h with C99, or do you propose that we require C11?

We will not require C11.  We should see which platforms of those we
care and can use MPS don't have stdatomic.h, and if any do, find
solutions for them.  All that assuming we need atomics, which is not
yet established, AFIU.