> What I should have said is that the address space layout is a source of non-determinism that would otherwise need to be accounted for in the recording of a program.

Ah yes, it needs to be deterministic in the context of a time-traveling debugger, I was thinking about the general case, sorry.

> Further, I hold to the view that given a program, knowledge of the thread execution schedule/scheduler and the results of external calls, a program's execution should be deterministic.

Surely it is, if you precisely know all timings and IO and can replay them there's nowhere for non-determinism to creep in.

That's not really an acceptable scale of required knowledge for a time-traveling debugger though.