WinDbg Time Travelling Debugger is Amazing Magic
This week I learned that WinDbg has a Time Travelling Debugger. I had no idea this existed, and I suspect I'm not alone! This tool is kinda mind blowing and it feels like more people should know it exists.
What is a time travelling debugger (TTD)? Normal debuggers allow you to set breakpoints and step forward through code. A TTD debugger allows you to step backwards. They allow you to freely move forward and backwards in time.
Imagine you have a bug where your program gets into a bad state. A normal debugger will let you inspect the current state. This will merely confirm what you already know! The real question is how did you get into this bad state. A TTD debugger will allow you to work backwards to root cause the bad logic that caused the bad state.
What I do know is that WinDbg's TTD works at the instruction level and requires zero instrumentation. It is, somehow, deterministic even when threading is involved!? 🤯
