Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Subscribe: <mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive: <http://sources.redhat.com/ml/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-help AT cygwin DOT com>, <http://sources.redhat.com/ml/#faqs>
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Delivered-To: mailing list cygwin AT cygwin DOT com
Date: Sat, 18 Oct 2003 01:58:36 -0400
From: Christopher Faylor <cgf-rcm AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: cygpath hangings: A fix - bash patch enclosed -- bash maintainer please note!
Message-ID: <20031018055836.GA28155@redhat.com>
Reply-To: cygwin AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
References: <D721826DEE793D49BC49582C121EDD3E3F55C3 AT exchange DOT perwill DOT com> <20031015184328 DOT GD28402 AT redhat DOT com> <Pine DOT GSO DOT 4 DOT 56 DOT 0310151404100 DOT 823 AT eos> <20031015203012 DOT GA9255 AT redhat DOT com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20031015203012.GA9255@redhat.com>
User-Agent: Mutt/1.4.1i
Note-from-DJ: This may be spam

On Wed, Oct 15, 2003 at 04:30:12PM -0400, Christopher Faylor wrote:
>I just managed to duplicate the problem on my system at work.
>
>Stay tuned.

I managed to duplicate it at home by booting into W2K, too.  That meant
I didn't have to feel guilty about working on this at work.  :-)

This should fix the problem.  Bash wasn't closing the read end of a pipe
in some situations.  I'm not sure why that would cause some programs to
hang but the following patch fixes the problem.  I think it provides
more robust code than what was in bash previously, too.

Ronald, if you agree with this patch, could you release a new version of
bash, ASAP?  If you don't agree with the patch, then please let me
(aka the cygwin list) know soon since I'm going to be submitting it
upstream ASAP.

cgf

2003-10-18  Christopher Faylor  <cgf AT redhat DOT com>

	* subst.c (command_substitute): Guard against opening a pipe handle in
	stdin/stdout/stderr since they may be closed and keeping the pipe
	handle open in a subprocess will cause hangs.

--- subst.c.orig	2003-10-15 15:09:01.000000000 -0400
+++ subst.c	2003-10-18 01:47:49.737056307 -0400
@@ -3716,6 +3716,7 @@ command_substitute (string, quoted)
   pid_t pid, old_pid, old_pipeline_pgrp;
   char *istring;
   int result, fildes[2], function_value;
+  int i, closeit[3];
 
   istring = (char *)NULL;
 
@@ -3742,6 +3743,16 @@ command_substitute (string, quoted)
   if (subst_assign_varlist == 0 || garglist == 0)
     maybe_make_export_env ();	/* XXX */
 
+
+  for (i = 0; i <= 2; i++)
+    if (fcntl (i, F_GETFD, &result) != -1)
+      closeit[i] = 0;
+    else
+      {
+	open ("/dev/null", O_RDONLY);
+	closeit[i] = 1;
+      }
+
   /* Pipe the output of executing STRING into the current shell. */
   if (pipe (fildes) < 0)
     {
@@ -3749,6 +3760,10 @@ command_substitute (string, quoted)
       goto error_exit;
     }
 
+  for (i = 0; i <= 2; i++)
+    if (closeit[i])
+      close (i);
+
   old_pid = last_made_pid;
 #if defined (JOB_CONTROL)
   old_pipeline_pgrp = pipeline_pgrp;
@@ -3793,21 +3808,8 @@ command_substitute (string, quoted)
 	  exit (EXECUTION_FAILURE);
 	}
 
-      /* If standard output is closed in the parent shell
-	 (such as after `exec >&-'), file descriptor 1 will be
-	 the lowest available file descriptor, and end up in
-	 fildes[0].  This can happen for stdin and stderr as well,
-	 but stdout is more important -- it will cause no output
-	 to be generated from this command. */
-      if ((fildes[1] != fileno (stdin)) &&
-	  (fildes[1] != fileno (stdout)) &&
-	  (fildes[1] != fileno (stderr)))
-	close (fildes[1]);
-
-      if ((fildes[0] != fileno (stdin)) &&
-	  (fildes[0] != fileno (stdout)) &&
-	  (fildes[0] != fileno (stderr)))
-	close (fildes[0]);
+      close (fildes[1]);
+      close (fildes[0]);
 
       /* The currently executing shell is not interactive. */
       interactive = 0;

--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/