netdev - Re: [PATCH net-next] net: mvpp2: Initialize link in mvpp2_isr_handle_{xlg,gmac

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Date:   Fri, 11 Sep 2020 09:01:01 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        David Miller <davem@...emloft.net>, andrew@...n.ch,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH net-next] net: mvpp2: Initialize link in
 mvpp2_isr_handle_{xlg,gmac_internal}

On Fri, Sep 11, 2020 at 08:22:36AM -0700, Jakub Kicinski wrote:
> On Fri, 11 Sep 2020 12:11:58 +0100 Russell King - ARM Linux admin wrote:
> > On Thu, Sep 10, 2020 at 05:31:42PM -0700, Nathan Chancellor wrote:
> > > Ah great, that is indeed cleaner, thank you for letting me know!  
> > 
> > Hmm, I'm not sure why gcc didn't find that. Strangely, the 0-day bot
> > seems to have only picked up on it with clang, not gcc.
> 
> May be similar to: https://lkml.org/lkml/2019/2/25/1092
> 
> Recent GCC is so bad at catching uninitialized vars I was considering
> build testing with GCC8 :/

It is even simpler than that, the warning was straight up disabled in
commit 78a5255ffb6a ("Stop the ad-hoc games with -Wno-maybe-initialized").

clang's -Wuninitialized and -Wsometimes-uninitialized are generally more
accurate but can have some false positives because the semantic analysis
phase happens before inlining and dead code elimination.

Cheers,
Nathan