https://bugzilla.mozilla.org/show_bug.cgi?id=1176099
Should SIGSYS be delivered to the handler even if blocked? What, if anything, does POSIX say? All I can find is in pthread_sigmask(3p): If any of the SIGFPE, SIGILL, SIGSEGV, or SIGBUS signals are generated while they are blocked, the result is undefined, unless the signal was generated by the action of another process, or by one of the functions kill(), pthread_kill(), raise(), or sigqueue(). It would be easy enough to change our behavior so that we deliver the signal even if it's blocked or to at least add a flag so that users can request that behavior.