Re: PATCH: coprocess descriptor and error messages

[Bart Schaefer <schaefer@brasslantern.com>]

On Sep 17,  7:41am, Bart Schaefer wrote:
}
} Aside:  Should an interactive shell ever exit on SIGPIPE?  Or maybe
} a better question is, should a print to the coprocess ever cause an
} un-trapped SIGPIPE?

Experimenting with pdksh seems to indicate that the equivalent of
zsh's coprocout descriptor is closed in the child-exited handler
when the coprocess terminates.  I don't recall enough about (and
didn't yet delve back into) the zsh job table to know if we have
enough information to identify the coprocess job at that point.

The coprocin descriptor remains open until EOF, as in zsh.

} In looking further, the coprocess descriptor is reset to -1 only (and
} immediately) by "read -p" detecting EOF on the coprocess output.  So
} in the "read" case, the invalid descriptor has always served as an
} EOF flag.  What should happen if the parent attempts to read after
} an EOF has been seen?  I would tend to think it should just get EOF
} again, not produce a diagnostic, which is the current behavior. 
} 
} However, ksh (at least pdksh) disagrees with me:

Here's a patch that duplicates the pdksh behavior, except for the part
about exiting on SIGPIPE if an extra print occurs before all output
has been read.  Apply this *instead* of the previous patch.

Index: builtin.c
===================================================================
RCS file: /extra/cvsroot/zsh/zsh-4.0/Src/builtin.c,v
retrieving revision 1.48
diff -c -r1.48 builtin.c
--- builtin.c	17 Apr 2009 18:57:22 -0000	1.48
+++ builtin.c	17 Sep 2010 15:59:06 -0000
@@ -3677,13 +3720,21 @@
     if (OPT_HASARG(ops,'u') || OPT_ISSET(ops,'p')) {
 	int fd;
 
-	if (OPT_ISSET(ops, 'p'))
+	if (OPT_ISSET(ops, 'p')) {
 	    fd = coprocout;
-	else {
+	    if (fd < 0) {
+		zwarnnam(name, "-p: no coprocess");
+		return 1;
+	    }
+	} else {
 	    char *argptr = OPT_ARG(ops,'u'), *eptr;
 	    /* Handle undocumented feature that -up worked */
 	    if (!strcmp(argptr, "p")) {
 		fd = coprocout;
+		if (fd < 0) {
+		    zwarnnam(name, "-p: no coprocess");
+		    return 1;
+		}
 	    } else {
 		fd = (int)zstrtol(argptr, &eptr, 10);
 		if (*eptr) {
@@ -5038,6 +5099,10 @@
 	/* The old code handled -up, but that was never documented. Still...*/
 	if (!strcmp(argptr, "p")) {
 	    readfd = coprocin;
+	    if (readfd < 0) {
+		zwarnnam(name, "-p: no coprocess");
+		return 1;
+	    }
 	} else {
 	    readfd = (int)zstrtol(argptr, &eptr, 10);
 	    if (*eptr) {
@@ -5052,6 +5117,10 @@
 	izle = 0;
     } else if (OPT_ISSET(ops,'p')) {
 	readfd = coprocin;
+	if (readfd < 0) {
+	    zwarnnam(name, "-p: no coprocess");
+	    return 1;
+	}
 	izle = 0;
     } else
 	readfd = izle = 0;