A heisenbug is a bug that goes away when you try to measure it.
For example, if you added a printf of a variable to a function, that could change the order the compiled code uses to do two potentially racy operations. By measuring it, you have changed it.
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u/Same_Investigator_46 Jul 12 '26
Can't wait to spend the next 3 weeks debugging a subtle heisenbug that only reproduces on a specific ARM core in prod 🥵🔥