This may be caused by a bug in "giza". Someone please tell the giza developers.
The segfault happens when _giza_parse_string tries to return. The return address on the stack was corrupted by this call to cairo_get_current_point: https://sources.debian.org/src/giza/1.0.0-1/src/lex.yy.c/#L2285 If you add this assertion just before that line you should see the assertion fail: assert(0 <= nGlyph && nGlyph < lenstr);
