> Please describe exactly what actions triggered the bug > and the precise symptoms of the bug:
A user of the emacs-based mail client, Notmuch [*], found that attempting to display a particular message would consistently causes a segmentation fault in emacs. I tracked this down to calling `json-read-string' with a very long string, (roughly 1 million characters). Rather than including that enormous string in this message, here's a little snippet of emacs lisp that creates and reads such a string. So, if evaluated, this code should trigger the segmentation fault, (assuming a copy of GPLv3 exists at /usr/share/emacs/23.1/etc/COPYING---adjust the filename if necessary). ;; Caution: Evaluating the block below has been known to crash emacs (with-temp-buffer (require 'json) ;; First we just need a lot of text. 32 copies of GPLv3 seems to do it (dotimes (i 32) (insert-file "/usr/share/emacs/23.1/etc/COPYING")) ;; Now create a buffer with a json-encoded version of the text (let ((json-string (json-encode-string (buffer-string)))) (with-temp-buffer (insert json-string) (goto-char (point-min)) ;; And try to read the string. This triggers the segfault. (json-read-string)))) > If Emacs crashed, and you have the Emacs process in the gdb debugger, > please include the output from the following gdb commands: > `bt full' and `xbacktrace'. I haven't attempted to debug this within gdb yet, (I'll have to get my hands on a build of emacs with debugging symbols first). But I wanted to share things right away, so that perhaps someone else could do further debugging and follow up. In the meantime, notmuch folks, if you've got a good idea for modifying notmuch to avoid this bug I'd be glad to hear it. Adjust followups to include the notmuch list and not the gnu.org bug address as appropriate. -Carl [*] http://notmuchmail.org PS. Here are some of the details provided by `report-emacs-bug': In GNU Emacs 23.1.1 (i486-pc-linux-gnu, GTK+ Version 2.18.2) of 2010-01-26 on raven, modified by Debian Windowing system distributor `The X.Org Foundation', version 11.0.10799001 configured using `configure '--build=i486-linux-gnu' '--host=i486-linux-gnu' '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib' '--localstatedir=/var/lib' '--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-pop=yes' '--enable-locallisppath=/etc/emacs23:/etc/emacs:/usr/local/share/emacs/23.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/23.1/site-lisp:/usr/share/emacs/site-lisp:/usr/share/emacs/23.1/leim' '--with-x=yes' '--with-x-toolkit=gtk' '--with-toolkit-scroll-bars' 'build_alias=i486-linux-gnu' 'host_alias=i486-linux-gnu' 'CFLAGS=-DDEBIAN -g -O2' 'LDFLAGS=-g' 'CPPFLAGS='' Important settings: value of $LC_ALL: nil value of $LC_COLLATE: nil value of $LC_CTYPE: nil value of $LC_MESSAGES: nil value of $LC_MONETARY: nil value of $LC_NUMERIC: nil value of $LC_TIME: nil value of $LANG: en_US.UTF-8 value of $XMODIFIERS: nil locale-coding-system: utf-8-unix default-enable-multibyte-characters: t -- carl.d.worth at intel.com