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RE: [PATCH 2/2] Arm32: tidy the memset() macro
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Wei Chen <Wei.Chen@xxxxxxx>
- Date: Fri, 19 Aug 2022 09:41:50 +0000
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- Cc: Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 19 Aug 2022 09:42:27 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH 2/2] Arm32: tidy the memset() macro
Hi Jan,
> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: 2022年8月19日 16:04
> To: Wei Chen <Wei.Chen@xxxxxxx>
> Cc: Julien Grall <julien@xxxxxxx>; Stefano Stabellini
> <sstabellini@xxxxxxxxxx>; Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>;
> Bertrand Marquis <Bertrand.Marquis@xxxxxxx>; xen-
> devel@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH 2/2] Arm32: tidy the memset() macro
>
> On 19.08.2022 09:59, Wei Chen wrote:
> >> -----Original Message-----
> >> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of
> Jan
> >> Beulich
> >> Sent: 2022年8月19日 15:50
> >>
> >> - add parentheses where they were missing (MISRA)
> >> - make sure to evaluate also v exactly once (MISRA)
> >> - remove excess parentheses
> >> - rename local variables to not have leading underscores
> >> - apply Xen coding style
> >>
> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >> ---
> >> I wonder whether "if ( n_ )" is really helpful: It's extra code in all
> >> callers passing a non-constant size, just to cover a pretty rare case
> >> which memset() is required to deal with correctly anyway, and which
> >
> > What rare case we need to use n_ that can make memset happy?
>
> I'm afraid I don't understand the question.
>
Sorry I didn't describe the problem clearly in the last email. You mentioned
whether if (n_) is useful in your patch comments. I looked at the implementation
of the current memset macro, and I didn't feel it was too useful.
Then in the comments you mentioned that if (n_) is just to cover a very rare
case.
Does the rare case is memset(p, v, 0)? If this is the case, I agree with you,
memset itself should be able to handle with size=0.
Sorry again for confusing you!
Thanks,
Wei Chen
> Jan
>
> > As your
> > comment, I read the code again, but it seems to work fine without n_.
> >
> > Cheers,
> > Wei Chen
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