Re: [Linux-ia64] Re: memcpy failure

From: Christian Cotte-Barrot <Christian.Cotte-Barrot_at_bull.net>
Date: 2002-11-15 21:32:10
"Chen, Kenneth W" wrote:
> 
> > >On Thu, Nov 14, 2002 at 10:01:44AM +0100, Christian Cotte-Barrot wrote:
> > > But memcpy from memcpy.S is returning a pointer to dest area.
> > > That would lead to quasi non-portable code when the return from memcopy
> > > is correctly checked depending on which memcopy function is addressed.
> > > But BTW, is it meaningful to take into account a return code
> > > that is always the same and which value is known in advance ?
> > > Does memcpy suppose to failed in some cases ?
> 
> > no, memcpy cannot fail (you get a SIGSEGV in userspace or an MCA in
> > kernel space).  checking the return value is meaningless.
> 
> That's what I feel as well that it is kind of silly to return something that the caller already has. BUt then, I'm not here to judge the specification ;-)
> 
> Anyhow, the fix is fairly easy and won't affect the code size as well as the copy throughput, I should have a patch ready shortly to make everyone happy!
>

That's too much noise for a thing with slight importance.
It's not a matter of making everyone happy but to provide reliable code.
For e.g. if a device driver checks a return as it must because the
the function is suppose to provide one, the return code in question
must be consistent.
On bad return from memcpy the concerned device driver loggs warning
in /var/log/messages and the system administrator may have some doubt
about the good working of the device.

Thanks for the patch Ken.
Received on Fri Nov 15 02:32:09 2002

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