linux-kernel - Re: [PATCH] x86, dumpstack: Fix unused variable warning.

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Message-ID: <25439.1290658067@localhost>
Date:	Wed, 24 Nov 2010 23:07:47 -0500
From:	Valdis.Kletnieks@...edu
To:	Jesper Juhl <jj@...osbits.net>
Cc:	Rakib Mullick <rakib.mullick@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org
Subject: Re: [PATCH] x86, dumpstack: Fix unused variable warning.

On Wed, 24 Nov 2010 10:57:10 +0100, Jesper Juhl said:

> On Wed, 24 Nov 2010, Rakib Mullick wrote:

> > diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
> > index 8474c99..fc5a253 100644
> > --- a/arch/x86/kernel/dumpstack.c
> > +++ b/arch/x86/kernel/dumpstack.c
> > @@ -197,10 +197,10 @@ void show_stack(struct task_struct *task,
> > unsigned long *sp)
> >   */
> >  void dump_stack(void)
> >  {
> > -	unsigned long bp = 0;
> >  	unsigned long stack;
> > 
> >  #ifdef CONFIG_FRAME_POINTER
> > +	unsigned long bp = 0;
> >  	if (!bp)
> >  		get_bp(bp);
> >  #endif
> 
> So, now the bp variable does not exist at all if CONFIG_FRAME_POINTER is 
> not defined.
> That's going to make this line :
> 
>           show_trace(NULL, NULL, &stack, bp);
> 
> found further down in the dump_stack() function, quite unhappy.

OK, I'll bite.  Why does the original say 'unsigned long bp = 0;' and then turns
around and has an 'if (!bp)' check?  Why is the conditional there?

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