Debugging Elusive Bugs

This cluster focuses on experiences with hard-to-track-down software bugs, such as Heisenbugs, that take significant time to diagnose but often have simple fixes, including anecdotes from production and open-source code.

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#1962
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Keywords

OP LLM STL OSS NetHack FPGA nethackwiki.com github.com wikipedia.org bug bugs code codebase probability fixing defect fix catch introducing

Sample Comments

UncleMeat Sep 27, 2019 View on HN

You've never had a bug in your code that seemed insane after the fact?

aussieguy1234 Sep 22, 2020 View on HN

It's not surprising. As a software engineer I've seen bugs that took days to track down which were fixed with a single line of code.

scotty79 Jan 9, 2010 View on HN

In practice annoying bugs can be caused by few easily understandable lines that no one bothered to look into so far.

chris_wot May 3, 2012 View on HN

There's nothing like spending hours tracking down a bug that shouldn't occur in normal practice.

jbotz Apr 12, 2022 View on HN

The Heisenbug: a software bug that seems to disappear or alter its behavior when one attempts to study it.[0] They're rare, but they do happen.[0] https://en.wikipedia.org/wiki/Heisenbug

gobdovan Sep 11, 2025 View on HN

Doubt accepted. A spot-the-bug challenge on real OSS/prod code would be fun.

parasti Apr 28, 2023 View on HN

Finding bugs must be unpleasant.

fc417fc802 Jan 7, 2026 View on HN

How do you avoid sinking time into chasing illusory bugs?

myself248 Feb 21, 2023 View on HN

This is brilliant. Is it based on a real bug you found in your company's own code?

willsmith72 Nov 17, 2024 View on HN

There's always a bug, you just haven't found it yet