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

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

[Jianjun Kong]

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(-)

diff --git a/arch/x86/kernel/scx200_32.c b/arch/x86/kernel/scx200_32.c
index 7e004ac..e9e3a24 100644
--- a/arch/x86/kernel/scx200_32.c
+++ b/arch/x86/kernel/scx200_32.c
@@ -58,7 +58,7 @@ static void __devinit scx200_init_shadow(void)
 
 static int __devinit scx200_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 {
-	unsigned base;
+	unsigned base = 0;
 
 	if (pdev->device == PCI_DEVICE_ID_NS_SCx200_BRIDGE ||
 	    pdev->device == PCI_DEVICE_ID_NS_SC1100_BRIDGE) {
-- 
1.5.6.3

-- 
Jianjun Kong | Happy Hacking
HOMEPAGE: http://kongove.cn/
GTALK: kongjianjun@gmail.com

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

[Ingo Molnar]

* 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.

	Ingo

---------------------->
>From 6f9fecb3d70400c5f99c1a1d09ffcce84483f611 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Sat, 18 Oct 2008 17:37:39 +0200
Subject: [PATCH] fix warning in arch/x86/kernel/scx200_32.c
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit

fix this warning:

  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

gcc is right: pci_read_config_dword() can fail, and this code did not
handle it.

Add proper error handling.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/kernel/scx200_32.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/scx200_32.c b/arch/x86/kernel/scx200_32.c
index 7e004ac..1b6e3d1 100644
--- a/arch/x86/kernel/scx200_32.c
+++ b/arch/x86/kernel/scx200_32.c
@@ -78,8 +78,10 @@ static int __devinit scx200_probe(struct pci_dev *pdev, const struct pci_device_
 		if (scx200_cb_probe(SCx200_CB_BASE_FIXED)) {
 			scx200_cb_base = SCx200_CB_BASE_FIXED;
 		} else {
-			pci_read_config_dword(pdev, SCx200_CBA_SCRATCH, &base);
-			if (scx200_cb_probe(base)) {
+			int err;
+
+			err = pci_read_config_dword(pdev, SCx200_CBA_SCRATCH, &base);
+			if (!err && scx200_cb_probe(base)) {
 				scx200_cb_base = base;
 			} else {
 				printk(KERN_WARNING NAME ": Configuration Block not found\n");

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

[Ingo Molnar]

* 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);