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War story: the hardest bug I ever debugged

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462 points jakevoytko | 2 comments | 24 Mar 25 14:37 UTC | HN request time: 0.001s | source
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BobbyTables2 ◴[27 Mar 25 03:27 UTC] No.43490119[source]▶
Interesting writeup, but 2 days to debug “the hardest bug ever”, while accurate, seems a bit overdone.

Though abs() returning negative numbers is hilarious.. “You had one job…”

To me, the hardest bugs are nearly irreproducible “Heisenbugs” that vanish when instrumentation is added.

I’m not just talking about concurrency issues either…

The kind of bug where a reproduction attempt takes a week, not parallelizable due to HW constraints, and logging instrumentation makes it go away or fail differently.

2 days is cute though.

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1. lukan ◴[27 Mar 25 09:45 UTC] No.43491823[source]▶
"To me, the hardest bugs are nearly irreproducible “Heisenbugs” that vanish when instrumentation is added."

My favourite are bugs, that not only don't appear in the debugger - but also don't reproduce anymore on normal settings after I took a closer look in the debugger (Only to come back later at a random time). Feels like chasing ghosts.

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2. btschaegg ◴[27 Mar 25 12:28 UTC] No.43492875[source]▶
Terminology proposal: "Gremlins" :)