Re: Linux 6.3-rc3

From: Linus Torvalds <torvalds@linux-foundation.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: dri-devel@lists.freedesktop.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Linux 6.3-rc3
Date: Mon, 20 Mar 2023 11:26:17 -0700	[thread overview]
Message-ID: <CAHk-=wgSqpdkeJBb92M37JNTdRQJRnRUApraHKE8uGHTqQuu2Q@mail.gmail.com> (raw)
In-Reply-To: <20230320180501.GA598084@dev-arch.thelio-3990X>

On Mon, Mar 20, 2023 at 11:05 AM Nathan Chancellor <nathan@kernel.org> wrote:
>
> On the clang front, I am still seeing the following warning turned error
> for arm64 allmodconfig at least:
>
>   drivers/gpu/host1x/dev.c:520:6: error: variable 'syncpt_irq' is uninitialized when used here [-Werror,-Wuninitialized]
>           if (syncpt_irq < 0)
>               ^~~~~~~~~~

Hmm. I do my arm64 allmodconfig builds with gcc, and I'm surprised
that gcc doesn't warn about this.

That syncpt_irq thing isn't written to anywhere, so that's pretty egregious.

We use -Wno-maybe-uninitialized because gcc gets it so wrong, but
that's different from the "-Wuninitialized" thing (without the
"maybe").

I've seen gcc mess this up when there is one single assignment,
because then the SSA format makes it *so* easy to just use that
assignment out-of-order (or unconditionally), but this case looks
unusually clear-cut.

So the fact that gcc doesn't warn about it is outright odd.

> If that does not come to you through other means before -rc4, could you
> just apply it directly so that I can stop applying it to our CI? :)

Bah. I took it now, there's no excuse for that thing.

Do we have any gcc people around that could explain why gcc failed so
miserably at this trivial case?

                   Linus