linux-kernel - Re: [git patches 2/2] warnings: use uninitialized

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Message-ID: <20070718113011.GI3801@stusta.de>
Date:	Wed, 18 Jul 2007 13:30:11 +0200
From:	Adrian Bunk <bunk@...sta.de>
To:	Jeff Garzik <jgarzik@...hat.com>
Cc:	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	chas@....nrl.navy.mil, rolandd@...co.com, dwmw2@...radead.org,
	gregkh@...e.de
Subject: Re: [git patches 2/2] warnings: use uninitialized_var()

On Tue, Jul 17, 2007 at 05:49:52PM -0400, Jeff Garzik wrote:
> 
> For many months, I have maintained a hand-verified list of bogus "may be
> used uninitialized" warning fixes, in misc-2.6.git#gccbug.  Andrew urged
> me to head these upstream.
> 
> I have gone through and re-analyzed each warning, and verified that
> these variables are indeed initialized properly, and gcc is making
> needless noise.
>...

Some notes:
- if gcc can prove a variable gets used uninitialized it gives
  a different warning
- gcc says it may be used uninitialized - there can always be false
  positives when the correctness of the code is due to some higher
  level logic
- I've seen cases in the kernel where it was technically impossible
  for the compiler to verify a variable always gets initialized

So if we want these warnings we'll always need to silence the ones that 
are verified as being correct code like your patches do - and that's not 
gcc's fault.

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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