Subject: Re: [Suggestion] powerpc: xmon: about 'longjmp' related warning.

From: Chen Gang <[email-masked]>
Date: Wed, 24 Jul 2013 08:38:21 +0800

On 07/23/2013 09:58 PM, Michael Ellerman wrote:
> On Mon, Jul 22, 2013 at 03:02:53PM +0800, Chen Gang wrote:
>> Hello Maintainers:
>>
>> With allmodconfig and EXTRA_CFLAGS=-W", it reports warnings below:
> 
>>
>> arch/powerpc/xmon/xmon.c:3027:6: warning: variable ‘i’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
>> arch/powerpc/xmon/xmon.c:3068:6: warning: variable ‘i’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
> 
> In both these cases we are inside the body of a for loop and we do a
> if (setjmp) / else block. Although looking at the source the value of i
> is not modified by the setjmp, I guess it's possible that the compiler
> might reorder the increment of i inside the setjmp and loose the value
> when we longjmp.
> 

I should continue to confirm the details based on your valuable
information, thanks.

>> arch/powerpc/xmon/xmon.c:352:48: warning: argument ‘fromipi’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
> 
> This one I can't see, but I assume it's a similar case.
> 

OK, I should continue for it.

>> Excuse me, I am not quite sure about it whether can cause issue or not.
> 
> I've never seen it get stuck in those loops or anything, but I guess
> it's possible.
> 

OK, I should make the confirmation.

> The first thing to do would be to analyse the generated assembler code
> to determine if there really is any possiblity of the value being
> clobbered, or if it's just a theoretical bug.
>

Thank you for your valuable information again.

Excuse me, I have to do another things within this month, so I should
provide the confirmation within next month (2013-08-31), is it OK (no
reply means OK).

Welcome any suggestions or completions.

Thanks.
-- 
Chen Gang