bug report: gitk crashes on git commit with emoji (utf-8)

[Tomek Mrugalski <tomasz.mrugalski@gmail.com>]

Hi there,

I'd like to report a bug in gitk. gitk crashes when trying to view a
repository that has utf-8 chars in the commit comments.

System: Ubuntu 20.04
Tested gitk versions:
- 2.25 (the default in ubuntu 20.04),
- 2.28 (installed from ppa:git-core/ppa),
- latest (next branch, commit fdf196b9972337a0285dae59f904f62f989fbca8)

Steps to reproduce the issue:

I've isolated the commit in our repo that causes this problem and pushed
it here: https://github.com/tomaszmrugalski/gitk-bug-emoji
The repo is small (only 3 commits). The offending commit that seems to
trigger this bug seems to be 3ad99781c449da3b1b42a098c4a820455050eb44.

git clone https://github.com/tomaszmrugalski/gitk-bug-emoji
cd gitk-bug-emoji
gitk

Actual behavior:

$ ~/devel-ssd/git/gitk-git/gitk
X Error of failed request:  BadLength (poly request too large or
internal Xlib length error)
  Major opcode of failed request:  139 (RENDER)
  Minor opcode of failed request:  20 (RenderAddGlyphs)
  Serial number of failed request:  3065
  Current serial number in output stream:  3148

There is a window showing up for a split second (too fast to even
notice its content), then it disappears and the aforementioned
X Error is shown in the console.

I've tried removing ~/.config/git/gitk, but that didn't help.

Expected behavior:

gitk should not crash. The window should show the git history.

It's very much ok if gitk doesn't show the emoji, but it shouldn't
crash. I've tried to look for existing bug reports, but couldn't find
anything useful.

System info (as produced by git bugreport)
git version:
git version 2.28.0.1022.gfdf196b997
cpu: x86_64
built from commit: fdf196b9972337a0285dae59f904f62f989fbca8
sizeof-long: 8
sizeof-size_t: 8
shell-path: /bin/sh
uname: Linux 5.4.0-48-generic #52-Ubuntu SMP Thu Sep 10 10:58:49 UTC
2020 x86_64
compiler info: gnuc: 9.3
libc info: glibc: 2.31
$SHELL (typically, interactive shell): /bin/bash

The same error happens on earlier versions 2.25 and 2.28. Here's output
from 2.28:

git version:
git version 2.28.0
cpu: x86_64
no commit associated with this build
sizeof-long: 8
sizeof-size_t: 8
shell-path: /bin/sh
uname: Linux 5.4.0-48-generic #52-Ubuntu SMP Thu Sep 10 10:58:49 UTC
2020 x86_64
compiler info: gnuc: 9.3
libc info: glibc: 2.31
$SHELL (typically, interactive shell): /bin/bash

Is there a workaround I could try?

I'm willing to help with debugging the problem or testing patches.
I'm not sure how long I'll be able to remain subscribed to this list
due to the traffic volume.

Other than that, gitk has been rock solid stable for me and I've been
using it for years. Thanks a lot for providing this great tool.

Tomek Mrugalski