linux-kernel - Re: [PATCH] TRACING: Fix a copmile warning

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Message-ID: <1311618747.3526.32.camel@gandalf.stny.rr.com>
Date:	Mon, 25 Jul 2011 14:32:27 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	stufever@...il.com
Cc:	linux-kernel@...r.kernel.org,
	Wang Shaoyan <wangshaoyan.pt@...bao.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] TRACING: Fix a copmile warning

On Mon, 2011-07-18 at 17:40 +0800, stufever@...il.com wrote:
> From: Wang Shaoyan <wangshaoyan.pt@...bao.com>
> 
> It's harmless but annyoing.
>   kernel/trace/trace_printk.c: In function 'module_trace_bprintk_format_notify':
>   kernel/trace/trace_printk.c:52: warning: 'fmt' may be used uninitialized in this function

I prefer not to add this patch. Fix gcc. Actually some gcc's do not warn
on this, others do. Here's the code that confuses gcc:

		tb_fmt = kmalloc(sizeof(*tb_fmt), GFP_KERNEL);
		if (tb_fmt)
			fmt = kmalloc(strlen(*iter) + 1, GFP_KERNEL);
		if (tb_fmt && fmt) {
			list_add_tail(&tb_fmt->list, &trace_bprintk_fmt_list);
			strcpy(fmt, *iter);
			tb_fmt->fmt = fmt;
			*iter = tb_fmt->fmt;


fmt will never be looked at if tb_fmt is NULL, and fmt is initialized if
tb_fmt is not NULL.

-- Steve

> 
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Signed-off-by: Wang Shaoyan <wangshaoyan.pt@...bao.com>
> 
> ---
>  kernel/trace/trace_printk.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c
> index 1f06468..1a5fff8 100644
> --- a/kernel/trace/trace_printk.c
> +++ b/kernel/trace/trace_printk.c
> @@ -49,7 +49,7 @@ static
>  void hold_module_trace_bprintk_format(const char **start, const char **end)
>  {
>  	const char **iter;
> -	char *fmt;
> +	char *fmt = NULL;
>  
>  	mutex_lock(&btrace_mutex);
>  	for (iter = start; iter < end; iter++) {


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