Re[2]: QNX 6.2 patch

[Pavel Roskin <proski gnu org>]

Hello!

> >> - zombie processes when mcview or mcedit is started

Could you please describe in more details how you create zombies?  I don't
see any zombies with CVS mc and QNX Neutrino 6.2.0.

Even if they are created, I don't like the approach used for SCO.  Waiting
for any process and discarding the exit status is not a good idea.  If I
had access to SCO, I would probably use something safer.

I also wrote a test for popen and pclose (attached), and it works in the
same way on Linux and QNX - waitpid() after pclose() fails.  If waitpid()
is used before pclose() in the signal handler, pclose() returns -1 instead
of the exit status.  This means that pclose() uses waitpid() internally
and doesn't like if the caller gets the exit status itself.

I guess that the SCO pclose was using just one waitpid() for two fork()s
in popen() or something like that.  That's not what I see in QNX.

> Like what ? Making a wrapper function for pclose() or smth like that ?
> I haven't discovered deeply why those zombie processes occure, but
> I'll try to find what happens.

Maybe a wrapper, although waiting for WAIT_ANY and discarding the status
is risky - important events for other processes can be lost.  In
particular, the subshell stops itself to tell mc that it's ready.

I would prefer to identify bogus processes and acknowledge them
explicitly, possibly in the SIGCHLD handler.

-- 
Regards,
Pavel Roskin

#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>
#include <string.h>

void
sigchld_handler (int signum)
{
    int pid, status, serrno;
    serrno = errno;
    while (1) {
	pid = waitpid (-1, &status, WNOHANG | WUNTRACED);
	if (pid < 0) {
	    perror ("waitpid error");
	    break;
	}
	if (pid == 0)
	    break;
	printf ("waitpid returned pid %d, status %d\n", pid, status);
    }
    errno = serrno;
}

int
main ()
{
    int c;
    FILE *file;
    int ret;

#if 0
    signal (SIGCHLD, sigchld_handler);
#endif

    file = popen ("echo 123; exit 1", "r");
    while ((c = getc (file)) != EOF) {
	printf ("%c\n", c);
    }
    ret = pclose (file);
    printf ("pclose returned %d\n", ret);

    printf ("press enter\n");
    getc (stdin);

    printf ("manually calling sigchld_handler\n");
    sigchld_handler (0);

    return 0;
}