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;
}
