Re: <sys/membarrier.h>

On Thu, Jul 9, 2026 at 7:44 PM Arsen Arsenović <[email protected]> wrote:
>
> Florian Weimer <[email protected]> writes:
>
> >> yeah, "all the choices suck". varargs has caused android (and android
> >> developers) pain in the past too, so i'm tempted to go for three
> >> arguments, but then callers are going to need an #if to support musl,
> >> at which point everyone may as well have stuck with syscall() :-(
> >
> > We can provide C++ overloads for two and three arguments.  With GCC, we
> > can use __builtin_va_arg_pack and __builtin_va_arg_pack_len to emulate
> > that in C.  It's not supported by Clang.
>
> That may not be, but
> https://clang.llvm.org/docs/AttributeReference.html#overloadable is.

yeah, bionic uses that to get round the unsigned/signed conversion
warnings with ioctl() so we could use it to have two membarrier()s
(it's also used throughout the clang fortify implementation, but
that's unrelated). i suppose we could even do something like the
fortify check for open() with O_CREAT or O_TMPFILE but no mode. that's
by far the most verbose way we could possible write membarrier() in
the headers, but maybe the best option?

> --
> Arsen Arsenović