Rare 1% bugs practically require prints debugging because they are only going to appear only 6 times if you run the test 600 times. So you just run the test 600 times all at once, look at the logs of the 6 failed tests, and fix the bug. You don’t want to run the debugger 600 times in sequence.

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roca 5 days ago | parent | next [-]

Record-and-replay debuggers like rr and UndoDB are designed for exactly this scenario. In fact it's way better than logging; with logging, in practice, you usually don't have the logs you need the first time, so you have to iterate "add logs, rerun 600 times" several times. With rr and UndoDB you just have to reproduce once and then you'll be able to figure it out.

	▲	seanmcdirmid 4 days ago \| parent \| next [-]
		I'm not going to manually execute the bug in a test once if it is 1% (or .1%, which I often have to deal with also). I'm going to run it 600, 1200, or maybe even 1800 times, and then pick bug exhibitors to dissect them. I can imagine that these could all be running under a time travel debugger that just then stops and lets me interact when the bug is found, but that sounds way more complicated than just adding log messages and and picking thru the logs of failures.
	▲	adgjlsfhk1 4 days ago \| parent \| prev [-]
		rr has the one downside of being often useless for multithreading bugs since it serializes execution

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pjmlp 5 days ago | parent | prev | next [-]

Trace points do exist.

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binary132 4 days ago | parent | prev [-]

conditional breakpoints, watches, …

	▲	tharkun__ 4 days ago \| parent [-]
		... will sometimes make the race condition not occur because things are too slow. Like the bugs "that disappear in a debug build but happen in the production build all the time".