If compiled with -fsanitize=address this showed up when running startlxde:

==11551==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60d000018fbc at pc 0x7f270a9ed57b bp 0x7fff30ef3050 sp 0x7fff30ef2800
READ of size 204 at 0x60d000018fbc thread T0
    #0 0x7f270a9ed57a  (/usr/lib/x86_64-linux-gnu/libasan.so.5+0xb857a)
    #1 0x559dafcd5c93 in FindGlyphRef ../../render/glyph.c:179
    #2 0x559dafcd705d in AddGlyph /work/nx-libs/nx-X11/programs/Xserver/hw/nxagent/NXglyph.c:71
    #3 0x559dafccc0ff in ProcRenderAddGlyphs ../../mi/../render/render.c:1186
    #4 0x559dafcbd5a5 in ProcRenderDispatch /work/nx-libs/nx-X11/programs/Xserver/hw/nxagent/NXrender.c:1689
    #5 0x559dafcbc4ea in Dispatch /work/nx-libs/nx-X11/programs/Xserver/hw/nxagent/NXdispatch.c:476
    #6 0x559dafc4e9b0 in main /work/nx-libs/nx-X11/programs/Xserver/dix/main.c:353
    #7 0x7f2708e1d09a in __libc_start_main ../csu/libc-start.c:308
    #8 0x559dafc4f5d9 in _start (/work/nx-libs/nx-X11/programs/Xserver/nxagent+0x6e5d9)

0x60d000018fbc is located 0 bytes to the right of 140-byte region [0x60d000018f30,0x60d000018fbc)
allocated by thread T0 here:
    #0 0x7f270aa1e330 in __interceptor_malloc (/usr/lib/x86_64-linux-gnu/libasan.so.5+0xe9330)
    #1 0x559dafcd646c in AllocateGlyph ../../render/glyph.c:348

This happens when two glyphs are compared via memcmp and the smaller
one happens to be identical to the beginning of the bigger one.

Newer render implementations use a sha1 hash instead of memcmp so this
patch will (hopefully) be obsolete once render gets updated.