linux-kernel - Re: Linux 6.3-rc3

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Message-ID: <CAHk-=wgSqpdkeJBb92M37JNTdRQJRnRUApraHKE8uGHTqQuu2Q@mail.gmail.com>
Date:   Mon, 20 Mar 2023 11:26:17 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org
Subject: Re: Linux 6.3-rc3

On Mon, Mar 20, 2023 at 11:05 AM Nathan Chancellor <nathan@...nel.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