On 2023-09-17 04:58:51+0200, Willy Tarreau wrote:
> On Thu, Sep 14, 2023 at 06:01:18PM +0200, Thomas Weißschuh wrote:
> > The ENOSYS fallback code does not use its functions parameters.
> > This can lead to compiler warnings about unused parameters.
> >
> > Explicitly avoid these warnings.
>
> Just out of curiosity, did you find a valid case for enabling this
> warning or were you trying various combinations ? I'm asking because
> I've never seen it enabled anywhere given that it's probably the most
> useless and unusable warning: as soon as you're dealing with function
> pointers, you start to have multiple functions with a similar
> prototype, some of which just don't need certain arguments, and the
> only way to shut the warning is to significantly uglify the code.
nolibc-test uses it currently and I also used it in some projects.
> If really needed, I'm wondering if instead we shouldn't have an
> "no_syscall*" set of macros, that would have the same signature
> as my_syscall* to just consume all args in the same order and
> return -ENOSYS. E.g, consider the following:
>
> @@ -934,6 +960,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva
> #endif
> return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout);
> #else
> + (void)nfds;
> + (void)rfds;
> + (void)wfds;
> + (void)efds;
> + (void)timeout;
> return -ENOSYS;
> #endif
>
> It would become:
>
> @@ -934,6 +960,11 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva
> #endif
> return my_syscall5(__NR__newselect, nfds, rfds, wfds, efds, timeout);
> #else
> + return no_syscall5(nfds, rfds, wfds, efds, timeout);
> - return -ENOSYS;
> #endif
>
> What do you think ?
The idea sounds good. But "no_syscall5" sounds a bit non-obvious to me.
Maybe the macro-equivalent of this?
static inline int __nolibc_enosys(...)
{
return -ENOSYS;
}
The only-vararg function unfortunately needs C23 so we can't use it.
It's clear to the users that this is about ENOSYS and we don't need a
bunch of new macros similar.
I'll check if it is cleaner to implement a generic macro or a few
numbered ones.
Thomas
