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

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Message-ID: <94a0d4530910190815n4cf2c2ebmd288f6e7501b1ba5@mail.gmail.com>
Date:	Mon, 19 Oct 2009 18:15:27 +0300
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	linux-kernel@...r.kernel.org,
	Heiko Carstens <heiko.carstens@...ibm.com>
Subject: Re: [PATCH 2/7] ipc: fix trivial warning

On Mon, Oct 19, 2009 at 5:57 PM, Jiri Kosina <jkosina@...e.cz> wrote:
> On Mon, 19 Oct 2009, Felipe Contreras wrote:
>
>> >> ipc/msg.c: In function ?msgctl_down?:
>> >> ipc/msg.c:415: warning: ?msqid64? may be used uninitialized in this function
>> >>
>> >> Signed-off-by: Felipe Contreras <felipe.contreras@...il.com>
>> >> ---
>> >>  ipc/msg.c |    2 +-
>> >>  1 files changed, 1 insertions(+), 1 deletions(-)
>> >>
>> >> diff --git a/ipc/msg.c b/ipc/msg.c
>> >> index 2ceab7f..085bd58 100644
>> >> --- a/ipc/msg.c
>> >> +++ b/ipc/msg.c
>> >> @@ -412,7 +412,7 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd,
>> >>                      struct msqid_ds __user *buf, int version)
>> >>  {
>> >>       struct kern_ipc_perm *ipcp;
>> >> -     struct msqid64_ds msqid64;
>> >> +     struct msqid64_ds uninitialized_var(msqid64);
>> >>       struct msg_queue *msq;
>> >>       int err;
>> >
>> > What gcc are you using? I am not getting any warning at least with gcc
>> > "(SUSE Linux) 4.3.1 20080507 (prerelease) [gcc-4_3-branch revision
>> > 135036]"
>>
>> gcc (GCC) 4.4.1 20090725 (Red Hat 4.4.1-2)
>>
>> Since I moved to Fedora 11 I get more warnings than other people,
>> possibly because gcc 4.4.
>
> Wouldn't it be better just to report this to gcc developers as a bug
> instead?

If it's a gcc bug, yes.

> I have verified both with 4.1 and 4.3, and it doesn't emit this
> false-positive warning, so there have been gcc versions getting this
> right. Ergo gcc developers should rather fix this "regression" and revert
> to the old behavior, methinks.

The other possibility is that the bug was in gcc 4.1/4.3, and now 4.4
finds an actual problem in the code. I will try to dig deeper to see
what's actually happening... at first glance I don't see who is
initializing msqid64.

-- 
Felipe Contreras
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