memcpy overlap: quickly detect, diagnose, work around

Gregory Maxwell gmaxwell at
Mon Nov 29 23:47:03 UTC 2010

On Mon, Nov 29, 2010 at 6:35 PM, John Reiser <jreiser at> wrote:
> While the details of inlining are subject
> to change, copying in ascending address order is the order that is
> assumed by all violators of the no-overlap requirement.

All violators? Citation needed.

I'm sure lurking somewhere there are ovelap copies which have no
'assumption' at all— some bad luck with arithmetic makes it ovelap
during some rare alignment of the stars... though cases like that
aren't going to be the ones that get inlined by GCC.

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