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2 stories about impossible bugs

I was working in a job running the campus email system some years ago when I got a call from the chairman of the statistics department.

"We're having a problem sending email out of the department."
"What's the problem?" I asked.
"We can't send mail more than 500 miles," the chairman explained.

I choked on my latte.  "Come again?"

"We can't send mail farther than 500 miles from here," he repeated. "A little bit more, actually.  Call it 520 miles.  But no farther."


And another one:

Evgeny Goldin
Tuesday, December 24, 2002


Great stories.

All of my bugs now seem too easy to exterminate. The last hard bug I had: everything was fine but the frame displaced itself in a strange way. It took me quite long to figure out that I accidentally overrode the setLocation() method so everytime the object (subclassed Frame) changed the location of something else, the position of the frame changed too. I now know it's stupid, but for an inexperienced programmer learning Java back then, how would I know every method signatures of the Component class?


No matter what that radar jam thing is, will it really affect the server, but not the other devices like watches, etc.? Even if it does, is it so sensitive that moving up or down by a couple of feet will change the power?

I admit that I have no idea how much tide changes the water level and how the radar jam thing works.

Tuesday, December 24, 2002

Remember the story (back in 1994) about Dr. Thomas Nicely, the guy who found the bug in the Intel processor?  He was calculating prime numbers on his PC, and noticed some incorrect results.  Eventually, he figured out that it was a hardware problem with the Pentium.

J. D. Trollinger
Tuesday, December 24, 2002

I read one of my favorite "impossible bugs" stories many years ago, and no longer remember many of the details. It may have happened at Bell Labs.

The bug report was, "I can log into my terminal when I'm sitting down, but not when I'm standing up."

What it eventually turned out to be was that his keyboard had been cleaned a short time before, and some of the relevant keycaps had been replaced in the wrong locations. Sitting down, the user was a touch-typist, and hit the correct keys without looking. Standing up, he did hunt-and-peck typing, and got the wrong password.

Steve Wheeler
Tuesday, December 24, 2002

Don't forget the one about the guy who stopped for ice cream, but his car would only start if he bought vanilla.

Matt Foley
Tuesday, December 24, 2002

Not entirely in the same vein, but nevertheless interesting:

A Story About Magic:

Mike Swieton
Wednesday, December 25, 2002

wow... =)

Wednesday, December 25, 2002

I think most people that have built any kind of electronics or electrical circuit have come across the 'finger' effect.  It works, or conversely doesn't work, if a finger is placed just ------>

The broadcast version is the critical listening position to an FM radio when you have a poor signal.

Tracy Kidder in 'The Soul of a New Machine' described how the Eagle worked fine when its boards were pulled out with all the circuit probes in, but failed when pushed back together as a product.

And then the software versions: 'it works if I use the Debugger' and other Heisenbugs.

They are all of the same class of problem, the thing is almost broken unless something smears over the top of it; like the conductance of a finger, the performance of the body as noise filter, shorts in one layer of a circuit board annealed by the steel runners and debuggers that massage the stack to be larger in order to work with their probes.

Simon Lucy
Thursday, December 26, 2002

My initial hypothesis for the 500 mile email bug was that a different network route was used for "long distance" email and that network link got backhoed. :)

Friday, December 27, 2002

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