linux-kernel - Re: [PATCH -mm] drivers/md/: Shut up uninitialized variable warnings

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Date:	Sun, 02 Sep 2007 16:34:36 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Satyam Sharma <satyam@...radead.org>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alasdair G Kergon <agk@...hat.com>, dm-devel@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH -mm] drivers/md/: Shut up uninitialized variable warnings

Satyam Sharma wrote:
> drivers/md/dm-exception-store.c: In function ‘persistent_read_metadata’:
> drivers/md/dm-exception-store.c:452: warning: ‘new_snapshot’ may be used uninitialized in this function
> 
> drivers/md/dm-ioctl.c: In function ‘ctl_ioctl’:
> drivers/md/dm-ioctl.c:1407: warning: ‘param’ may be used uninitialized in this function
> 
> [ For these, I'd like to especially add -- shame on you, gcc! ]
> 
> drivers/md/dm-table.c: In function ‘dm_get_device’:
> drivers/md/dm-table.c:472: warning: ‘dev’ may be used uninitialized in this function
> 
> are all verified to be bogus warnings. Let's shut them up.
> 
> ---
> 
>  drivers/md/dm-exception-store.c |    3 ++-
>  drivers/md/dm-ioctl.c |    2 +-
>  drivers/md/dm-table.c |    2 +-
>  3 file changed, 4 insertions(+), 3 deletion(-)

same comment as with the last uninit'd var patch:  these markers should 
be used sparingly.  Try it on multiple compiler versions, see if it's a 
new behavior.

Quite realistically, you might actually be finding gcc bugs, implying 
the proper path is to file a gcc bug report (and they are _very_ 
diligent about handling these, its impressive) rather than to patch the 
Linux kernel.

Overall, for any uninitialized_var() patch, we need more info on 
platform/compiler version/analysis methods/etc.

	Jeff



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