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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Date: Thu, 17 Mar 2011 07:05:19 +1100
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Subject: [Qemu-devel] Re: [PATCH 21/26] Implement TCE translation for sPAPR
	VIO
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To: Alexander Graf <agraf@suse.de>
Cc: paulus@samba.org, qemu-devel@nongnu.org, anton@samba.org, David Gibson <david@gibson.dropbear.id.au>

On Wed, 2011-03-16 at 17:03 +0100, Alexander Graf wrote:
> 
> > +int spapr_tce_dma_zero(VIOsPAPRDevice *dev, uint64_t taddr,
> uint32_t size)
> > +{
> > +    uint8_t *zeroes;
> > +
> > +#ifdef DEBUG_TCE
> > +    fprintf(stderr, "spapr_tce_dma_zero taddr=0x%llx size=0x%x\n",
> > +            (unsigned long long)taddr, size);
> > +#endif
> > +
> > +    /* FIXME: do this better... */
> > +    zeroes = alloca(size);
> > +    memset(zeroes, 0, size);
> 
> You sure that zeroes is still alive during the call? If I were a 
> compiler, I'd probably optimize the return away so that it'd end up 
> being a simple branch to spapr_tce_dma_write - coincidentally 
> invalidating the stack that zeroes is on.

Ugh ? How would this ever be legal for a compiler to do that ?

Ben.