Programming

Hi Everybody,

Can anybody give me an pratical example where we can use SA_ONSTACK flag in sigaction() system call ?

Please explain me the significance of having an alternate signal stack in UNIX for signal handling.


Regards
Dinesh-Ahuja

Here is one example...a process has a limit on the size of the stack. If a process exceeds that limit it will get a signal, often SIGSEGV, but it can vary from os to os. Now, how can you catch that signal? Without an alternate stack, the signal handler could never run.

I had this exact situation once. A process was dying from a blown stack but its current directory was in a filesystem that was too small to hold a core dump. My handler needed to catch the signal, cd to a large filesystem, set the signal action back to default, and resend the signal to itself. I could not have done that without an alternate stack.

That was the only time that I needed an alternate stack.

Thanks for your reply.

Regards
Dinesh