[Vm-dev] BitBltSimulation buffer overrun

tim Rowledge tim at rowledge.org
Wed Sep 4 18:16:01 UTC 2019

> On 2019-09-04, at 11:00 AM, Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com> wrote:
> tim
> Do we ever use the extra word that we read? I don't think so, we don't generate funny artefacts.
> But we could try and test that now that we know how to trigger it (statistically).

We certainly shouldn't use that extra word. 

Unless something has gone horribly wrong, the only time this is an issue is on the last fetch of the last row of a BLT. So we *could* consider splitting out the last row and only for that last row include a check for the last word, and only for that word include a 'stick 0 in'. 

Since this is an assert for the debug, perhaps the smart thing to do is make the assert test more thoughtful in some manner. The typical case simply doesn't matter, since all we do is load a wasted word. Where things do need some care is at the end of object memory and page boundaries etc.

tim Rowledge; tim at rowledge.org; http://www.rowledge.org/tim
No single raindrop believes it is to blame for the flood

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