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

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Date:	Thu, 4 Dec 2008 11:10:23 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jianjun Kong <jianjun@...ux.org>
Cc:	mingo@...hat.com,
	Linux-Kernel-Mailing-List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] x86: fix warning of uninitialized variable


* Jianjun Kong <jianjun@...ux.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@...ux.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@...e.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@...e.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");

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