I once spent two weeks tracking down a scheduler bug (it would stop scheduling threads and stall forever) to two assembly-language instructions that were in the

I once spent two weeks tracking down a scheduler bug (it would stop scheduling threads and stall forever) to two assembly-language instructions that were in the wrong order, and would cause a timer interrupt to never fire if there was an interrupt between them. Swapping the two instructions fixed the bug. So, not a missing semicolon, but pretty close . . .