Re: zsh hangs on IRIX 5.2 / me to: (SunOS4.1.3 + Solaris 2.4)

[Peter Stephenson <pws@hydra.ifh.de>]

leibniz!stucki@leibniz.math.fu-berlin.de wrote:
> - BUT a zsh WAITING FOR A PROCESS TO COMPLETE,
>   RUNS FOREVER READING 'nothing' FROM STDIN
>   IF THE SUBPROCESS VANISHES AND
>   ZSH WAKES UP ON A 'DEAD' TTY.

I've been trying to reproduce this on our IRIX systems but have so far
failed; presumably there's another ingredient I haven't found (I can't
believe zsh's in Dahlem can be *that* different to those in Zeuthen,
or do we have to wait for Berlin-Brandenburg? -:)).

If you enter a sleep command and type more than 20 ^D's while you're
waiting for it to finish, the shell exits, as I would expect given the
current code.  Something funny must be happening when the tty goes
away which I don't understand.  The only things I can think of are (1)
that read() is returning `real' ^D's instead of simply a 0 from read,
which is very unlikely, or (2) that zle is not being used and the
error is somewhere else.  Here's the relevant code from the line
editor, in getkey(), zle_main.c, if anyone can think of anything.
It's been like this for some time.

(N.B.: the 20 maximum here is for ^D's typed while zsh wasn't looking
at input.  The 10 maximum applies if it was; the counter for that is
back in the main loop.)

You can at least see if this is the problem by removing the
`if (isset(IGNOREEOF)...) continue' and seeing if the problem goes
away.  That will have the side-effect that a ^D in typeahead will
cause the shell to exit.


while ((r = read(SHTTY, &cc, 1)) != 1) {
    if (r == 0) {
	/* The test for IGNOREEOF was added to make zsh ignore ^Ds
	   that were typed while commands are running.  Unfortuantely
	   this caused trouble under at least one system (SunOS 4.1).
	   Here shells that lost their xterm (e.g. if it was killed
	   with -9) didn't fail to read from the terminal but instead
	   happily continued to read EOFs, so that the above read
	   returned with 0, and, with IGNOREEOF set, this caused
	   an infinite loop.  The simple way around this was to add
	   the counter (icnt) so that this happens 20 times and than
	   the shell gives up (yes, this is a bit dirty...). */
	if (isset(IGNOREEOF) && icnt++ < 20)
	    continue;
	stopmsg = 1;
	zexit(1);
    }
    icnt = 0;
    if (errno == EINTR) {
	die = 0;
	if (!errflag)
	    continue;
	errflag = 0;
	errno = old_errno;
	return EOF;
    } else if (errno == EWOULDBLOCK) {
	fcntl(0, F_SETFL, 0);
    } else if (errno == EIO && !die) {
	ret = jobbingv;
	jobbingv = OPT_SET;
	attachtty(mypgrp);
	refresh();	/* kludge! */
	jobbingv = ret;
	die = 1;
    } else if (errno != 0) {
	zerr("error on TTY read: %e", NULL, errno);
	stopmsg = 1;
	zexit(1);
    }
}

-- 
Peter Stephenson <pws@ifh.de>       Tel: +49 33762 77366
WWW:  http://www.ifh.de/~pws/       Fax: +49 33762 77330
Deutches Electronen-Synchrotron --- Institut fuer Hochenergiephysik Zeuthen
DESY-IfH, 15735 Zeuthen, Germany.