We've had a number of reports of the "PresArena: poison overwritten" assertion (bug 772725, bug 775045) that seem likely to be the result of bad hardware rather than bad software.
Given that bad hardware seems likely to result in things like single bit errors, and bad software seems likely to result in entire words being overwritten, we should make this abort print more information so that we can distinguish the two cases.
Created attachment 655446 [details] [diff] [review]
Print which bits have errors to try to distinguish overwriting from hardware problems. ()
This change came in handy in bug 799091 :)