The hardest bug I had to track down exhibited different behavior on different systems. On one system, it only took an hour or two for the program (a daemon) to

The hardest bug I had to track down exhibited different behavior on different systems. On one system, it only took an hour or two for the program (a daemon) to crash; on another system, several days could pass before a crash. I was able to track it down once I realized that signal handlers were, technically speaking, another thread of execution in a special context ...