A bug so cool that the development team was reluctant to fix it

Raymond Chen


Long ago, there was a big filed against Outlook that was titled “Outlook crashes when used violently.”

Well that’s an interesting title.

The bug was also interesting: What you had to do was create a Note and then drag it around the screen continuously for several minutes. Eventually, Outlook crashed.

What was happening was that each time the Note window moved, even just one pixel, Outlook created an entry in its Undo history. Drag the window around long enough, and the Undo history fills up with remembered Note positions, until eventually you run out of memory and crash.

If you stopped before you ran out of memory, then you could use this bug as a parlor trick: Press and hold the Undo hotkey Ctrl+Z, and the Note will zoom around the screen, retracing its steps.

This bug was so cool that the development team was reluctant to fix it.

They did fix it, but it was accompanied by a twinge of regret.

Raymond Chen
Raymond Chen

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Simon Clarkstone 2019-06-03 09:56:39
Do you know who found this bug? (Quite possibly not, given that it was "long ago".) Could it have been a testing tool that gives random inputs? An end-user mucking around? Someone making a deduction from the fact that so much undo history is stored?
Ji Luo 2019-06-03 10:09:06
“there was a big field ...” => “there was a bug filed...” I was thinking “I had seen this somewhere else, but where?” until I scrolled down to the One Dev Question video.
"Fleet Command" 2019-06-04 01:27:06
"Long ago, there was a big filed" s/big/bug
Neil Rashbrook 2019-06-04 04:11:14
I wish I could undo every accidental window move or resize. (If my mouse button is still down then I press Escape to try to cancel it, but that doesn't work everywhere.)
Lex Mitchell 2019-06-05 03:01:33
I remember this bug/feature, we used to do it at school! Was a fun little trick making a note loop the loop around the screen as if by magic for people. Never caused a crash, but I guess people pushed it as far as it could go.