Re: [PATCH 2/2] meson: fix CONFIG_ATOMIC128 check

[Peter Maydell]

On Mon, 28 Feb 2022 at 12:19, <marcandre.lureau@redhat.com> wrote:
>
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> testfile.c: In function 'main':
> testfile.c:5:11: error: incorrect number of arguments to function 
> '__atomic_load'
>     5 |       y = __atomic_load(&x, 0);
>       |           ^~~~~~~~~~~~~
> testfile.c:6:7: error: argument 2 of '__atomic_store' must be a pointer type
>     6 |       __atomic_store(&x, y, 0);
>       |       ^~~~~~~~~~~~~~
> testfile.c:7:7: error: argument 3 of '__atomic_compare_exchange' must be a 
> pointer type
>     7 |       __atomic_compare_exchange(&x, &y, x, 0, 0, 0);
>       |       ^~~~~~~~~~~~~~~~~~~~~~~~~
>
> And it must be linked with -latomic.

As Philippe says, this isn't right. What the configure test
is checking for is "do we have 128-bit atomics which are
handled inline and specifically not via libatomic". The
reason we can't use libatomic is documented in the comment
starting "GCC is a house divided" in include/qemu/atomic128.h.

thanks
-- PMM