Tales of Science-Fiction Bugs: The Thing That Killed Talos

Have you ever encountered one of these bugs? One in which every single line of your code is correct, in which every type-check passes, every single unit test succeeds, the specifications are fulfilled but somehow, for no reason that can be explained rationally, it just does not work? I call them Science-Fiction Bugs. I am sure that you have met some of them. For some reason, the Mozilla Performance Team seems to stumble upon such bugs rather often, perhaps because we spend so much time refactoring other team’s code long after the original authors have moved on to other features, and combining their code with undertested libraries and technologies. Truly, this is life on the Frontier.

Today, I would like to tell you the tale of one of these Science-Fiction Bugs: The Thing That Killed Talos.