heisenbug

jargon /hi:'zen-buhg/ (From Heisenberg's Uncertainty

Principle in quantum physics) A bug that disappears or alters

its behaviour when one attempts to probe or isolate it. (This

usage is not even particularly fanciful; the use of a debugger

sometimes alters a program's operating environment

significantly enough that buggy code, such as that which

relies on the values of uninitialised memory, behaves quite

differently.)

In C, nine out of ten heisenbugs result from uninitialised

auto variables, fandango on core phenomena (especially

lossage related to corruption of the malloc arena) or errors

that smash the stack.

Opposite: Bohr bug. See also mandelbug, schroedinbug.

[Jargon File]

(1995-02-28)