Bug 764192 was pretty successful. Even if it didn't find bug 709860, it immediately pointed us to a double-free.
There are some additional assertions in jemalloc which I didn't enable because they're not related to bug 709860. But given how useful the assertions we've turned on have been, I think we might as well enable some more. I doubt there will be any measurable performance implications here.
Created attachment 634547 [details] [diff] [review]
Part 1: Enable more release-time jemalloc assertions.
Created attachment 634548 [details] [diff] [review]
Part 2: Split MOZ_TEMP_INVESTIGATION into MOZ_TEMP_INVESTIGATION and MOZ_JEMALLOC_HARD_ASSERTS.
MOZ_TEMP_INVESTIGATION is temporary, but I'm thinking now that MOZ_JEMALLOC_HARD_ASSERTS should not be.