bug#29506: find-composition segfaults

bug#29506: find-composition segfaults

[Edgard Bikelis]

Hi!

I was testing decomposing some characters in malayalam, and by evaluating this:

(find-composition 0 1 "ദേ")

emacs segfaults when it’s in gui mode, but not when it’s on the
console, with the -nw option. I have asked on #emacs on freenode, and
other people had the same effect on version 25.2 and 26. It seems to
happen with unicode past some high number, it doesn’t happen with "á"
for instance, with a+ combining acute above, but it does happen in
Arabic also, like with "ڜ".

Thanks,

Edgard

In GNU Emacs 27.0.50 (build 2, x86_64-pc-linux-gnu, GNU/LessTif
Version 2.1 Release 0.95.2)
 of 2017-11-28 built on svar
Repository revision: c816e647ebf128eccc9df6ce3d64ebc5a5554aec
Windowing system distributor 'The X.Org Foundation', version 11.0.11704000
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --with-x-toolkit=motif'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
ACL GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS
MOTIF X11 LIBSYSTEMD LCMS2

Important settings:
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS:
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Major mode: Lisp Interaction

Minor modes in effect:
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  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

Load-path shadows:
None found.

Features:
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Memory information:
((conses 16 94775 7532)
 (symbols 48 20346 1)
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 (strings 32 29096 1253)
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bug#29506: find-composition segfaults

[Andreas Schwab]

On Nov 30 2017, Edgard Bikelis <bikelis@gmail.com> wrote:

> I was testing decomposing some characters in malayalam, and by evaluating this:
>
> (find-composition 0 1 "ദേ")
>
> emacs segfaults when it’s in gui mode, but not when it’s on the
> console, with the -nw option.

That looks like a very old bug, probably since commit 90b3fe91253.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

bug#29506: find-composition segfaults

[Eli Zaretskii]

> From: Edgard Bikelis <bikelis@gmail.com>
> Date: Thu, 30 Nov 2017 03:52:57 -0200
> 
> I was testing decomposing some characters in malayalam, and by evaluating this:
> 
> (find-composition 0 1 "ദേ")
> 
> emacs segfaults when it’s in gui mode, but not when it’s on the
> console, with the -nw option. I have asked on #emacs on freenode, and
> other people had the same effect on version 25.2 and 26. It seems to
> happen with unicode past some high number, it doesn’t happen with "á"
> for instance, with a+ combining acute above, but it does happen in
> Arabic also, like with "ڜ".

More accurately, it aborts or segfaults for any string with characters
that are not supported by the default face's font.  On a TTY, fonts
are never an issue, so it never crashes there.

I fixed this now for Emacs 26, thanks for reporting this issue.