delta

Delta debugging is not new: https://en.wikipedia.org/wiki/Delta_debugging My implementation of delta debugging, "delta" is 19+ years old: https://github.com/dsw/delta I released it as Open Source because Microsoft Research sent someone to my office to ask me to, back when Microsoft was calling Open Source a "cancer". The LLVM introduction by Latner refers to the "standard delta debugging tool", so it is rather well-known: https://aosabook.org/en/v1/llvm.html 'unlike the standard "delta" command line tool.'

Comby looks nice, I miss the "tops" tool from the old MacOSX ecosystem. For a decade or so I've been using the "delta" tool for this[1,2], although it sometimes requires manual intervention to get an extremely small testcase because it has very little understanding of the source language's syntax. On the other hand, that genericness can be an advantage for custom languages and it's usually pretty fast at getting to the nut of the matter anyway. (On the other hand, I don't have any evidence to suggest that a compiler bug report with a 5-line testcase gets looked at any sooner than one with a 1000-line testcase.) Aside from "minimization" or "reduction" this technique is also sometimes called "delta debugging"[3]. [1] https://github.com/dsw/delta [2] https://tracker.debian.org/pkg/delta [3] https://en.wikipedia.org/wiki/Delta_debugging