From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: Another SIGFPE in display code, now in cirrus
Date: Thu, 13 May 2010 09:36:47 +0200
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Cc: Avi Kivity <avi@redhat.com>, Michael Tokarev <mjt@tls.msk.ru>,
	KVM list <kvm@vger.kernel.org>,
	qemu-devel <qemu-devel@nongnu.org>,
	Brian Kress <kressb@moose.net>
To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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On 05/12/2010 05:57 PM, Stefano Stabellini wrote:
> I guess even a src blt pitch of 0 could be useful there, however in
> practice I think the only rop function that was written with this case in
> mind has:
>
> dstpitch -= bltwidth;
> srcpitch -= bltwidth;
>
> if (dstpitch<  0 || srcpitch<  0) {
>      /* is 0 valid? srcpitch == 0 could be useful */
>      return;
> }

Note that here srcpitch == 0 is actually srcpitch == bltwidth, which 
_is_ obviously useful.

The "real" srcpitch == 0 case would result in srcpitch == -bltwidth, and 
it is actually quite useful if you want to stretch a Nx1 bitmap to NxN.

Paolo