Restoring signals before os.exec

Source

A short note. As both the signal module doc and the subprocess module doc (almost at the end, when it finally goes around to talk about the restore_signals parameter), Python3 disables the following signals, so it can properly report them as exceptions:

  • SIGPIPE
  • SIGXFZ
  • SIGXFSZ
  • SIGINT

But if you're executing processes with any of the os.exec*() functions, you have to restore them by hand. Of course, the option is to use subprocess, which is best for most cases; not for ayrton.

I spent a long time analyzing the process-which-didn't-die-on-SIGPIPE's source code and wondering what was all this about. The I compared the same pipeline under bash and ayrton with strace to find the real culprit.