Help with undefined behavior of signal system call!!!

tuxfood · 07-14-2005, 02:45 AM

hi....

I read abt a method to make a parent process wait() for all its children to exit before it can exit using the signal system call...

It involved setting the action for the SIGCHLD signal to SIG_IGN (ignore)

So what i did was

Code:

    signal(SIGCHLD,SIG_IGN);
     
     /****  The forking stuff ****/


    ret = wait(&wait_val) ;

As per the book what should happen is that the signal SIGCHLD should be ignored and so on recieving the signal the parent just ignores the signal and continues to wait... until all the children have exited... .. When there are no more processes the wait system call returns

But as per the man page signal(2) tells that behavior of SIGCHLD signal with SIG_IGN set is undefined

Is there any way to rectify this???

tuxfood

Hko · 07-14-2005, 06:48 AM

To me it makes more sense, to do it the other way around:
Leave the SIGCHLD as it is.
Call wait() in a loop until it returns -1 with errno == ECHILD.
Then the process will not have any child-processes anymore.

(errno ECHILD means: The calling process does not have any unwaited-for children.)

tuxfood · 07-15-2005, 11:31 PM

hi...

i actually did it as u have said before i read abt the method....

thnks anyway.... any idea why this behavior has been kept undefined???