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Date: Mon, 19 Oct 2009 17:29:20 +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: > >> >> 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; [ ... snip ... ] > > 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. 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. 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. -- Jiri Kosina SUSE Labs, Novell Inc.
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