Instant replay: Debugging C and C++ programs with rr (Red Hat Developer)

rr should show you the exact correct values in `info registers` at any time, yet that does not require storing that much information. The basic idea of rr is that most instructions in a program are deterministic, the only non-determinism is localized at relatively few points in the program's execution (typically: I/O). So in order to allow you to rewind back to any point and show the correct values in `info registers`, rr only needs to state from those relatively few non-determinism sources, rewind back to there, then re-play forward from there.

rr replay reproduces the exact memory and register contents* of the recording at every point during program execution.

* There are some very small exceptions in our accelerated syscall interception machinery that are irrelevant in practice.