Re: [PATCH] io_uring/net: fix build warning for !CONFIG_COMPAT

[Pavel Begunkov]

On 2/27/25 13:58, Arnd Bergmann wrote:
> On Thu, Feb 27, 2025, at 14:49, Pavel Begunkov wrote:
> > On 2/27/25 13:20, Arnd Bergmann wrote:
> > >         |                      ^~~
> > >
> > > Since io_is_compat() turns into a compile-time 'false', the #ifdef
> > > here is completely unnecessary, and removing it avoids the warning.
> >
> > I don't think __get_compat_msghdr() and other helpers are
> > compiled for !COMPAT.
>
> They are not defined without CONFIG_COMPAT. My point in the
> message is that io_is_compat() turning into a compile-time
> 'false' value means that they also don't get called, because
> compilers are really good at this type of dead code elimination.
>
> > I'd just silence it like:
> >
> > if (io_is_compat(req->ctx)) {
> > 	ret = -EFAULT;
> > #ifdef CONFIG_COMPAT
> > 	...
> > #endif CONFIG_COMPAT
> > }
>
> That seems even less readable. If you want to be explicit
> about it, you could use
>
>       if (IS_ENABLED(CONFIG_COMPAT) && io_is_compat(req->ctx)) {
>
> to replace the #ifdef, but as I wrote in the patch
> description, the compile-time check is really redundant
> because io_is_compat() is meant to do exactly that.

I do like getting rid of #ifdef, just a bit surprised that we're
relying on dead code elimination, even though it's what any
reasonable compiler must do.

Btw, sth went wrong with the reply: (delivered after 24733 seconds)

--
Pavel Begunkov