Replay divergence with VMWare Fusion 8

Jan de Mooij jdemooij at
Wed Mar 2 19:54:24 UTC 2016

On Wed, Mar 2, 2016 at 8:37 PM, Robert O'Callahan <robert at>

> One question is: are the divergence failures in Firefox clustered in one
> phase of startup or shutdown, or are they uniformly distributed?

It's hard to say. The failures are not entirely random/non-deterministic
though; sometimes replays fail at exactly the same number of ticks and I
very often see the divergence while executing the following tight loops
(this is a Firefox debug build):

Not sure if that's just because we execute a lot of branches there, or if
there's another reason.

Sometimes I also get this failure: Assertion `!use_breakpoint_optimization'
failed to hold. Is that related?

Knowing more about the test failure could be useful.

Tomorrow or so I'll run the test suite again and log all output.

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