GNU bug report logs - #24911
25.1; Emacs hangs or crashes on use of read syntax for circular objects in IELM

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Gemini Lasswell <gazally <at> runbox.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 25.1;
 Emacs hangs or crashes on use of read syntax for circular objects in
 IELM
Date: Wed, 09 Nov 2016 12:03:47 -0800

[Message part 1 (text/plain, inline)]

Typing an example from the "Read Syntax for Circular Objects" section of
the manual into IELM can cause Emacs to hang or crash. I can reproduce
this fairly consistently with an Emacs built from master on my machine. It
took me several tries, but I was also able to reproduce it with the Emacs
25.1 installed by homebrew. Here are the steps:

emacs -Q
M-x ielm RET
#1=(a #1#) RET
C-p C-p RET

Result: (on OS X) rainbow spinning mouse cursor, unresponsive Emacs

There may be something timing-related going on, because these steps
don't work every time and they seem to work more consistently if I enter
the sequence of keystrokes quickly. If it doesn't happen the first time,
navigating again to a previous line and editing it by adding a quote
somewhere or another symbol and pressing RET again may cause it to
happen.

When I encountered this bug, I was working on one of my own branches
based on commit eb610f2 in master, and Emacs crashed and gave me a stack
trace, which I've attached. Since then I have not been able to reproduce
the crash, just the hang.

[emacs-crash.txt (text/plain, attachment)]

[Message part 3 (text/plain, inline)]

In GNU Emacs 25.1.1 (x86_64-apple-darwin15.6.0, NS appkit-1404.47 Version 10.11.6 (Build 15G1004))
 of 2016-10-09 built on rainbow.local
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
 'configure --disable-dependency-tracking --disable-silent-rules
 --enable-locallisppath=/usr/local/share/emacs/site-lisp
 --infodir=/usr/local/Cellar/emacs/25.1/share/info/emacs
 --prefix=/usr/local/Cellar/emacs/25.1 --without-x --with-xml2
 --without-dbus --with-gnutls --with-imagemagick --with-rsvg --with-ns
 --disable-ns-self-contained'

Configured features:
JPEG RSVG IMAGEMAGICK NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS
NS

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message dired format-spec rfc822 mml
mml-sec password-cache epg epg-config gnus-util mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util help-fns help-mode easymenu
cl-loaddefs pcase cl-lib mail-prsvr mail-utils time-date mule-util
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel ns-win ucs-normalize term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cl-generic cham
georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese charscript case-table epa-hook
jka-cmpr-hook help simple abbrev minibuffer cl-preloaded nadvice
loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote kqueue cocoa ns multi-tty
make-network-process emacs)

Memory information:
((conses 16 195998 6534)
 (symbols 48 19735 0)
 (miscs 40 50 176)
 (strings 32 15069 5856)
 (string-bytes 1 433667)
 (vectors 16 32908)
 (vector-slots 8 653890 4234)
 (floats 8 158 12)
 (intervals 56 213 0)
 (buffers 976 18))

Message #8 received at 24911 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Gemini Lasswell <gazally <at> runbox.com>
Cc: 24911 <at> debbugs.gnu.org
Subject: Re: bug#24911: 25.1;
 Emacs hangs or crashes on use of read syntax for circular objects in
 IELM
Date: Thu, 10 Nov 2016 18:30:53 +0200

> From: Gemini Lasswell <gazally <at> runbox.com>
> Date: Wed, 09 Nov 2016 12:03:47 -0800
> 
> Typing an example from the "Read Syntax for Circular Objects" section of
> the manual into IELM can cause Emacs to hang or crash. I can reproduce
> this fairly consistently with an Emacs built from master on my machine. It
> took me several tries, but I was also able to reproduce it with the Emacs
> 25.1 installed by homebrew. Here are the steps:
> 
> emacs -Q
> M-x ielm RET
> #1=(a #1#) RET
> C-p C-p RET
> 
> Result: (on OS X) rainbow spinning mouse cursor, unresponsive Emacs

I get an error when I type the first line at IELM prompt:

  *** Eval error ***  Symbol’s function definition is void: a

Message #11 received at 24911 <at> debbugs.gnu.org (full text, mbox):

From: Gemini Lasswell <gazally <at> runbox.com>
To: Eli Zaretskii <eliz <at> gnu.org>, 24911 <at> debbugs.gnu.org
Subject: Re: bug#24911: 25.1;
 Emacs hangs or crashes on use of read syntax for circular objects in
 IELM
Date: Thu, 10 Nov 2016 09:02:13 -0800

Eli Zaretskii <eliz <at> gnu.org> writes:

>
> I get an error when I type the first line at IELM prompt:
>
>   *** Eval error ***  Symbol’s function definition is void: a

Yes, so do I. The hang happens when I navigate back to the first line
after receiving the error message and either edit it and press RET, or
press RET again without editing it.

Message #14 received at 24911 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Gemini Lasswell <gazally <at> runbox.com>
Cc: 24911 <at> debbugs.gnu.org
Subject: Re: bug#24911: 25.1;
 Emacs hangs or crashes on use of read syntax for circular objects in
 IELM
Date: Thu, 10 Nov 2016 19:26:00 +0200

> From: Gemini Lasswell <gazally <at> runbox.com>
> Cc: 
> Date: Thu, 10 Nov 2016 09:02:13 -0800
> 
> > I get an error when I type the first line at IELM prompt:
> >
> >   *** Eval error ***  Symbol’s function definition is void: a
> 
> Yes, so do I. The hang happens when I navigate back to the first line
> after receiving the error message and either edit it and press RET, or
> press RET again without editing it.

When I do that, I get "end of file during parsing".

Message #17 received at 24911 <at> debbugs.gnu.org (full text, mbox):

From: Gemini Lasswell <gazally <at> runbox.com>
To: Eli Zaretskii <eliz <at> gnu.org>, 24911 <at> debbugs.gnu.org
Subject: Re: bug#24911: 25.1;
 Emacs hangs or crashes on use of read syntax for circular objects in
 IELM
Date: Thu, 10 Nov 2016 10:08:05 -0800

Eli Zaretskii <eliz <at> gnu.org> writes:

>> > I get an error when I type the first line at IELM prompt:
>> >
>> >   *** Eval error ***  Symbol’s function definition is void: a
>> 
>> Yes, so do I. The hang happens when I navigate back to the first line
>> after receiving the error message and either edit it and press RET, or
>> press RET again without editing it.
>
> When I do that, I get "end of file during parsing".

Yes, I've seen that too. Is that the correct behavior? Shouldn't it
repeat the same error message as before?

Message #20 received at 24911 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Gemini Lasswell <gazally <at> runbox.com>
Cc: 24911 <at> debbugs.gnu.org
Subject: Re: bug#24911: 25.1;
 Emacs hangs or crashes on use of read syntax for circular objects in
 IELM
Date: Thu, 10 Nov 2016 20:52:12 +0200

> From: Gemini Lasswell <gazally <at> runbox.com>
> Cc: 
> Date: Thu, 10 Nov 2016 10:08:05 -0800
> 
> Eli Zaretskii <eliz <at> gnu.org> writes:
> 
> >> > I get an error when I type the first line at IELM prompt:
> >> >
> >> >   *** Eval error ***  Symbol’s function definition is void: a
> >> 
> >> Yes, so do I. The hang happens when I navigate back to the first line
> >> after receiving the error message and either edit it and press RET, or
> >> press RET again without editing it.
> >
> > When I do that, I get "end of file during parsing".
> 
> Yes, I've seen that too. Is that the correct behavior? Shouldn't it
> repeat the same error message as before?

I don't know, but it's hardly fatal.  I'd like to focus on the hangs
and crashes first, if they can be reproduced.

Thanks.

Message #23 received at 24911 <at> debbugs.gnu.org (full text, mbox):

From: Gemini Lasswell <gazally <at> runbox.com>
To: Eli Zaretskii <eliz <at> gnu.org>, 24911 <at> debbugs.gnu.org
Subject: Re: bug#24911: 25.1;
 Emacs hangs or crashes on use of read syntax for circular objects in
 IELM
Date: Thu, 10 Nov 2016 11:25:52 -0800

[Message part 1 (text/plain, inline)]

Eli Zaretskii <eliz <at> gnu.org> writes:
>
> I don't know, but it's hardly fatal.  I'd like to focus on the hangs
> and crashes first, if they can be reproduced.
>

I have just made it happen under gdb, with a breakpoint on
handle_sigsegv. Here is the output of 'bt full'. It tells me
'xbacktrace' is an undefined command. This is my first time working with
gdb.

[btfull (text/plain, attachment)]

Message #28 received at 24911 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Gemini Lasswell <gazally <at> runbox.com>
Cc: 24911 <at> debbugs.gnu.org
Subject: Re: bug#24911: 25.1;
 Emacs hangs or crashes on use of read syntax for circular objects in
 IELM
Date: Thu, 10 Nov 2016 22:06:38 +0200

forcemerge 24640 24911
thanks

> From: Gemini Lasswell <gazally <at> runbox.com>
> Cc: 
> Date: Thu, 10 Nov 2016 11:25:52 -0800
> 
> I have just made it happen under gdb, with a breakpoint on
> handle_sigsegv. Here is the output of 'bt full'. It tells me
> 'xbacktrace' is an undefined command. This is my first time working with
> gdb.
> 
> (gdb) bt full
> #0  0x000000010023ca45 in mark_object (arg=...) at alloc.c:6501
>         obj = {i = 4287568137794125953}
>         po = 0x3b8080813b808080
>         cdr_count = 0
> #1  0x000000010023cca1 in mark_object (arg=...) at alloc.c:6552
>         ptr = 0x7fff5fbf8288
>         obj = {i = 140734799774347}
>         po = 0x7fff5fbf8288
>         cdr_count = 1
> #2  0x000000010023b8fb in garbage_collect_1 (end=0x7fff5fbf69a8) at alloc.c:5760
>         nextb = 0x0
>         stack_top_variable = 0 '\000'
>         i = 201
          ^^^^^^^
This is bug#24640, already fixed on the emacs-25 branch.

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