linux-kernel - Re: [PATCH 2/7] ipc: fix trivial warning

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Message-ID: <alpine.LSU.2.00.0910200047200.8582@wotan.suse.de>
Date:	Tue, 20 Oct 2009 00:50:03 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Felipe Contreras <felipe.contreras@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH 2/7] ipc: fix trivial warning

On Mon, 19 Oct 2009, Felipe Contreras wrote:

> > This statement of your makes me wonder why you have submitted the patch in
> > the first place, as you are apparently not sure whether adding
> > uninitialized_var() is a valid thing to do or not.
[ ... ]
> In any case, if the patch is not correct, then somebody should point
> that out, which is what the patch review process is for. Alternatively
> I could have sent an email asking what is happening here, but from my
> point of view this patch serves exactly the same purpose, and has the
> advantage that it might turn out to be correct.
>
> It's not as if I didn't do any homework while writing this patch.

Sorry if it sounded to offensive, I have probably been a little bit too 
tired ysterday.

> > The gcc warning in this case is actually bogus, as msqid64 is touched only
> > iff cmd == IPC_SET, and in such case, copy_msqid_from_user() initializes
> > it properly.
> 
> Yes, but it's used by ipcctl_pre_down, which from what I can see is
> only using those arguments when cmd == IPC_SET, so everything is ok.
> But still, I don't think the compiler _should_ know what
> ipcctl_pre_down is going to do, if you look _only_ at msgctl_down,
> then uninitialized_var is OK.

Well at least older compilers were able to see this, only 4.4 seems to be 
warning here ... I have applied the patch for now, but I am really not 
fully convinced about it yet, we should probably report it to gcc folks 
anyway.

Thanks,

-- 
Jiri Kosina
SUSE Labs, Novell Inc.
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