rsync 2.5.5, HPUX, getting unexplained error at main.c(578)

[Paul Haas]

On Wed, 29 May 2002, Allen D. Winter wrote:

> I finally found that in the wait_process() function in main.c, the status
> value returned from WEXITSTATUS() was apparently returning
> the pid of the child instead of the exit status of the child... or something
> like that.

Or something not like that, since the manpage for waitpid() says the
value of status is undefined if waitpd() returns  (pid_t)-1.

Here's the current version of the function, note how it isn't checking for
-1:

void wait_process(pid_t pid, int *status)
{
        while (waitpid(pid, status, WNOHANG) == 0) {
                msleep(20);
                io_flush();
        }

        /* TODO: If the child exited on a signal, then log an
         * appropriate error message.  Perhaps we should also accept a
         * message describing the purpose of the child.  Also indicate
         * this to the caller so that thhey know something went
         * wrong.  */
        *status = WEXITSTATUS(*status);
}

Elsewhere in the HP UX manpage for waitpid() it says that
WEXITSTATUS(*status) is only valid if WIFEXITED(*status) is nonzero.

So an HP-UX user could try the following code and see what lands in
standard error.

void wait_process(pid_t pid, int *status)
{
        int notdone = 1;
        int waitPidRet;
        while ( notdone ) {
                waitPidRet = waitpid(pid, status, WNOHANG);
                if ( waitPidRet == 0 ||
                    ( waitPidRet == (pid_t)-1 && errno == EINTR ) ) {
                        msleep(20);
                        io_flush();
                        if ( waitPidRet == (pid_t)-1 ) {
                                 fprintf(stderr,
                                  "A mysterious failure averted.\n");
                        }
                } else if ( waitPidRet == (pid_t) -1 ) {
                        perror("waitpid() did something I don't understand.");
                        exit(1);
                }
                if ( WIFEXITED(*status) ){
                        *status = WEXITSTATUS(*status);
                        notdone = 0;
                } else {
                        fprintf(stderr,"Now what should I do?\n");
                        exit(2);
                }
        }
}

The EINTR case doesn't make sense with WNOHANG, but HP-UX doesn't always
do things that make sense.  If you get the "Now what should I do?"
message, then add code to check WIFSIGNALED(), WIFSTOPPED() and
WIFCONTINUED() and do something appropriate.  If you reach the perror(),
hopefully the text there will offer some clues.

I don't have an HP-UX 11.11 system, I'm looking at the manpages on
an HP-UX 11.00 system.

--
Paul Haas
Just because I sometimes use HP-UX, doesn't mean I like it.