On Fri, Aug 1, 2014 at 1:57 AM, Eli Zaretskii <eliz@gnu.org> wrote:

Sounds like some code called clear_face_cache, for some reason. Is f
at all the same frame where you were typing? If not, the crash could
have nothing to do with what you typed, but with some background
activity on another frame.

I just ran Emacs a while under gdb, and it called clear_face_cache while I wasn't doing anything interesting, just typing into a buffer. It happened from in redisplay_internal when clear_face_cache_count reached 501. Its documentation says it's used to "clear the face cache every once in a while".