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SubjectRe: [PATCH 1/3] x86: fix warning of uninitialized variable

* Ingo Molnar <mingo@elte.hu> wrote:

>
> * Jianjun Kong <jianjun@zeuux.org> wrote:
>
> > fix warning of uninitialized 'base' in arch/x86/kernel/scx200_32.c
> >
> > arch/x86/kernel/scx200_32.c: In function ‘scx200_probe’:
> > arch/x86/kernel/scx200_32.c:82: warning: ‘base’ may be used
> > uninitialized in this function
> >
> > Signed-off-by: Jianjun Kong <jianjun@zeuux.org>
> > ---
> > arch/x86/kernel/scx200_32.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
>
> this patch is wrong, and your analysis-free commit log is wrong as
> well!
>
> i fixed this a few weeks ago, and GCC pinpointed a _real_ bug - which
> you hacked around instead of fixing. See the real fix below.

Also, see an example below of the case where GCC is wrong about a
warning, and how it is annotated.

Ingo

------------->
From af4d2994e0e8e6e529b0e87f4e436dad062a9c05 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Tue, 25 Nov 2008 13:14:19 +0100
Subject: [PATCH] fix warning in fs/ocfs2/stack_user.c
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit

this warning:

fs/ocfs2/stack_user.c: In function ‘user_cluster_connect’:
fs/ocfs2/stack_user.c:807: warning: ‘control’ may be used uninitialized in this function

triggers because GCC does not recognize the (correct) error flow
between:

- ocfs2_live_connection_new() and 'control'

Annotate it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
fs/ocfs2/stack_user.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/ocfs2/stack_user.c b/fs/ocfs2/stack_user.c
index faec2d8..55e2cdc 100644
--- a/fs/ocfs2/stack_user.c
+++ b/fs/ocfs2/stack_user.c
@@ -804,7 +804,7 @@ static int fs_protocol_compare(struct ocfs2_protocol_version *existing,
static int user_cluster_connect(struct ocfs2_cluster_connection *conn)
{
dlm_lockspace_t *fsdlm;
- struct ocfs2_live_connection *control;
+ struct ocfs2_live_connection *uninitialized_var(control);
int rc = 0;

BUG_ON(conn == NULL);
--
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