linux-kernel - Re: Question on compiler warning

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Message-ID: <52C2A2E5.3020100@ilande.co.uk>
Date:	Tue, 31 Dec 2013 10:56:37 +0000
From:	Mark Cave-Ayland <mark.cave-ayland@...nde.co.uk>
To:	Larry Finger <Larry.Finger@...inger.net>
CC:	linux-wireless <linux-wireless@...r.kernel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Question on compiler warning

On 31/12/13 01:24, Larry Finger wrote:

> In his regular article entitled Build regressions/improvements in
> v3.13-rc6"
> (http://lkml.indiana.edu/hypermail/linux/kernel/1312.3/01550.html),
> Geert Uytterhoeven reports the following warning regression:
>
> + /scratch/kisskb/src/drivers/net/wireless/b43/phy_n.c: warning:
> 'val_addr' may be used uninitialized in this function [-Wuninitialized]:
> => 178:21
>
> This warning does not show up on any of my compilers, and it should not
> as the initialization and usage of that variable both take place in
> conditional branches that are testing exactly the same pointer.

Hi Larry,

Could it be that you don't see the issue the locally because you've got 
different compiler optimisation settings? I've seen a similar bug 
recently on another project where the "may be used uninitialized" 
warning appears with -O0 and -O1 but magically disappears with the 
default -O2 setting (presumably because the optimiser performs some kind 
of inlining/reordering that makes the issue go away).


HTH,

Mark.
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