It's nice to say that catching bugs earlier is better. But what if that time is long gone? Lately, I've used Pernosco to debug my changes to a multi-process-re

It's nice to say that catching bugs earlier is better. But what if that time is long gone? Lately, I've used Pernosco to debug my changes to a multi-process-relevant decade-old part of two-decade-old codebase, which was single-process when written, only later became multi-process-relevant, and recently became even multier-process. (And there are test cases, but there's a huge mass of them and they depend on decade-old comments not actually being true the interesting situations.) Pernosco is very useful for debugging multi-process interaction in cases that would be very hard to debug even with rr.