Volume 7A: XView Programming Manual

notify_perror() prints the string str, followed by a colon, and followed by a string

that describes notify_errno to stderr.

20.14 Issues

Here are some additional issues surrounding the Notifier:

• The layer over the UNIX signal mechanism is not complete. Signal blocking (sigblock

(2)) can still be done safely in the flow of control of a client to protect critical portions of

code as long as the previous signal mask is restored before returning to the Notifier.

Signal pausing (sigpause (2)) is essentially done by the Notifier. Signal masking

(sigmask (2)) can be accomplished via multiple notify_set_ signal_func()

calls. Setting up a process signal stack (sigstack (2)) can still be done. Setting the

signal catcher mask and on-signal-stack flag (sigvec (2)) could be done by reaching

around the Notifier, but this is not supported.

• Not all process resources are multiplexed (e.g., rlimit (2), setjmp (2), umask

(2), setquota (2), and setpriority (2)), only ones that have to do with flow

of control multiplexing. Thus, some level of cooperation and understanding needs to

exist among packages in the single process.

• One might intercept

close (2) and dup (2) calls so that the Notifier is not waiting on

invalid or incorrect file descriptors if a client forgets to remove its conditions from the

Notifier before making these calls.

• One might intercept signal (3) and sigvec (2) calls so that the Notifier does not get ...