Created attachment 98331 [details]
backtrace of segfault

Hello all,

when using a Firefox compiled against cairo 1.12.16 I get a segfault
when visiting some webpages, eg when scrolling an expose on
www.immobilienscout24.de.

debugging the problem with gdb led me to line 3125 of
cairo-xcb-surface-render.c:

_cairo_clip_path_destroy (clip->path);

where on that webpage for reasons I don't know clip->path = NULL

I changed the line to

if (clip->path != NULL) _cairo_clip_path_destroy (clip->path);

which fixes the segfault.

a Backtrace is attached.