Bug#966691: emacs-gtk: Segmentation fault with libx11-6 v. 2:1.6.10-1

[Gregory Mounie <Gregory.Mounie@imag.fr>]

Package: emacs-gtk
Version: 1:26.3+1-2
Followup-For: Bug #966691

Dear Maintainer,

Compiling emacs from source produces the same results (26.3 branch or
later, including master). I just send a patch upstream in bug-gnu-emacs
mailing list.

In src/xfns.c in create_frame_xic (line 2551 in upstream 26.3 branch):

The code assume that if the xim pointer is set then the xim_styles pointer is also set.
This is apparently not always true anymore with this X11 update. Hopefully, the patch
seems trivial.

The segfaulting lines are:

xim = FRAME_X_XIM (f);
if (!xim)         <-- should be:  if (!xim || ! FRAME_X_XIM_STYLES (f))
   goto out;

/* Determine XIC Style */
xic_style = best_xim_style (FRAME_X_XIM_STYLES (f)); <-- otherwise SEGFAULT here

 Looking at the bug, may be setting a XIM input is also a possible temporary workaround.
 Grégory Mounié

-- System Information:
Debian Release: bullseye/sid
  APT prefers unstable
  APT policy: (990, 'unstable'), (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.7.0-2-amd64 (SMP w/4 CPU threads)
Kernel taint flags: TAINT_CRAP
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8), LANGUAGE=fr:en_US
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages emacs-gtk depends on:
ii  emacs-bin-common       1:26.3+1-2
ii  emacs-common           1:26.3+1-2
ii  libacl1                2.2.53-8
ii  libasound2             1.2.2-2.3
ii  libc6                  2.31-2
ii  libcairo2              1.16.0-4
ii  libdbus-1-3            1.12.20-1
ii  libfontconfig1         2.13.1-4.2
ii  libfreetype6           2.10.2+dfsg-3
ii  libgdk-pixbuf2.0-0     2.40.0+dfsg-5
ii  libgif7                5.1.9-1
it  libglib2.0-0           2.64.4-1
ii  libgnutls30            3.6.14-2+b1
ii  libgpm2                1.20.7-6
ii  libgtk-3-0             3.24.20-1
ii  libice6                2:1.0.9-2
ii  libjpeg62-turbo        1:2.0.5-1.1
ii  liblcms2-2             2.9-4+b1
ii  libm17n-0              1.8.0-2
ii  libmagickcore-6.q16-6  8:6.9.11.24+dfsg-1
ii  libmagickwand-6.q16-6  8:6.9.11.24+dfsg-1
ii  libotf0                0.9.13-7
ii  libpango-1.0-0         1.44.7-4
ii  libpng16-16            1.6.37-2
ii  librsvg2-2             2.48.7-1
ii  libselinux1            3.1-2
ii  libsm6                 2:1.2.3-1
ii  libsystemd0            245.7-1
ii  libtiff5               4.1.0+git191117-2
ii  libtinfo6              6.2-1
ii  libx11-6               2:1.6.10-1
ii  libxext6               2:1.3.3-1+b2
ii  libxfixes3             1:5.0.3-2
ii  libxft2                2.3.2-2
ii  libxml2                2.9.10+dfsg-5+b1
ii  libxpm4                1:3.5.12-1
ii  libxrender1            1:0.9.10-1
ii  zlib1g                 1:1.2.11.dfsg-2

emacs-gtk recommends no packages.

Versions of packages emacs-gtk suggests:
ii  emacs-common-non-dfsg  1:26.3+1-1

-- no debconf information