GNU bug report logs - #30762
27.0.50; Apparent regression in process.c caused by checking pty_flag before calling setsid

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#30762: closed (27.0.50; Apparent regression in process.c
 caused by checking pty_flag before calling setsid)
Date: Sun, 11 Mar 2018 02:34:01 +0000

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Your message dated Sat, 10 Mar 2018 18:33:05 -0800
with message-id <b1e85b66-ed49-aa96-8da0-4b65d1f607be <at> cs.ucla.edu>
and subject line Re: bug#30762: 27.0.50; Apparent regression in process.c caused by checking pty_flag before calling setsid
has caused the debbugs.gnu.org bug report #30762,
regarding 27.0.50; Apparent regression in process.c caused by checking pty_flag before calling setsid
to be marked as done.

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From: Thomas Fitzsimmons <fitzsim <at> fitzsim.org>
To: bug-gnu-emacs <at> gnu.org
Cc: Paul Eggert <eggert <at> cs.ucla.edu>
Subject: 27.0.50;
 Apparent regression in process.c caused by checking pty_flag before
 calling setsid
Date: Fri, 09 Mar 2018 23:18:51 -0500

Hi,

On x86_64, CentOS 7.3.1611, I noticed that on master tip (I tested
461e6818...), eudc-expand-inline was hanging.  It calls the ldapsearch
command line utility (by way of ldap-search-internal) using
start-process, and waits for a password prompt:

  (let* ((process-connection-type nil)
	 (proc-args (append arglist ldap-ldapsearch-args
			    filter))
	 (proc (apply #'start-process "ldapsearch" buf
		      ldap-ldapsearch-prog
		      proc-args)))
    (while (null (progn
		   (goto-char (point-min))
		   (re-search-forward
		    ldap-ldapsearch-password-prompt-regexp
		    (point-max) t)))
      (accept-process-output proc 1))
      [...])

master tip gets stuck in that while loop, whereas Emacs 25.1 is fine.

If I print the contents of the buffer within the loop, it shows:

Process ldapsearch stopped (tty output)

I isolated the working-to-non-working transition to this commit:

commit 8e5a769965313a7a1c42b5992ed24e8b0ea71ead
Author: Paul Eggert <eggert <at> cs.ucla.edu>
Date:   Tue Dec 6 23:41:45 2016 -0800

    Clean out some IRIX cruft
    
    * etc/MACHINES: Remove obsolete discussion of IRIX.
    * src/process.c (allocate_pty) [__sgi]: Remove SGI-specific code.
    (create_process) [HAVE_PTYS]: Don't worry about IRIX.
    * src/syntax.c (scan_sexps_forward): Remove obsolete comment.
    * src/unexelf.c [__sgi]: Don't include <syms.h>.
    (unexec) [__sgi]: Remove SGI-specific code.

and specifically the addition of this check in src/process.c:

-      /* We tried doing setsid only if pty_flag, but it caused
-	 process_set_signal to fail on SGI when using a pipe.  */
-      setsid ();
+      if (pty_flag)
+	setsid ();

If I remove the if (pty_flag) line, then eudc-expand-inline works again.

It may be that ldap-search-internal should change how it's invoking
ldapsearch, but I thought I would report the change in process.c
behavior anyway.

Thomas

[Message part 3 (message/rfc822, inline)]

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Eli Zaretskii <eliz <at> gnu.org>, Thomas Fitzsimmons <fitzsim <at> fitzsim.org>
Cc: 30762-done <at> debbugs.gnu.org
Subject: Re: bug#30762: 27.0.50; Apparent regression in process.c caused by
 checking pty_flag before calling setsid
Date: Sat, 10 Mar 2018 18:33:05 -0800

Eli Zaretskii wrote:
> This change is on the emacs-26 branch as well, so if we want to
> restore previous code, we should do it on emacs-26, not only on
> master.

I installed the fix into emacs-26 and merged it into master. Thanks, Thomas, for 
reporting it and for tracking down the fix.

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