I installed NotoSansJavanese-Regular.ttf and when I type `C-h h' to view
the Javanese script, Emacs immediately crashes.  It also crashes when I
just try to insert a character from that script, e.g. `C-x 8 RET #xa9b2
RET'.  I've attached the backtrace from gdb produced from the latter.
Emacs also crashes when trying to display a character from the Balinese
script with NotoSansBalinese-Regular.ttf installed.  The crashes do not
happen in emacs-27 built without cairo, but characters from the Javanese
and Balinese scripts are displayed there as tofu, as they are in Firefox
(e.g. https://en.wikipedia.org/wiki/Javanese_script), so maybe the fonts
are buggy; and indeed, when I uninstall them Emacs built with cairo does
not crash and the characters are displayed as tofu.  But it would be
better for Emacs with cairo not to crash with a buggy font, if possible.
If desired, I can send the fonts.

In GNU Emacs 28.0.50 (build 37, x86_64-pc-linux-gnu, GTK+ Version 3.24.17, cairo version 1.17.3)
 of 2020-10-20 built on strobe-jhalfs
Repository revision: 39271ed108380494667ab680fc71b800f9ea5097
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12008000
System Description: Linux From Scratch SVN-20200401

Configured using:
 'configure --with-xwidgets 'CFLAGS=-Og -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG CAIRO SOUND DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL GNUTLS LIBXML2 FREETYPE HARFBUZZ ZLIB TOOLKIT_SCROLL_BARS
GTK3 X11 XDBE XIM MODULES THREADS XWIDGETS LIBSYSTEMD PDUMPER LCMS2

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