When run in an X window session and with low process memory limits, Emacs 
fails to open and/or syntax highlight some files properly.  To reproduce, 
run:

   bash --noprofile --norc
   ulimit -d 10240
   emacs
     Open treeset-private.hpp [attached]

If things are still going smoothly, try turning on font-lock-mode.  At 
this point, I get the error 'Invalid regexp: "Regular expression too 
big"'.  If the ulimit is set to 8MB instead of 10MB, Emacs encounters this 
error on startup while attempting to load the splash screen.  I have 
encountered similar errors while loading or highlighting this file with 
memory limits up to at least 12MB, if not larger.  Sometimes the file will 
fail to load; sometimes it will load but be improperly highlighted; other 
times it will load but nothing will be highlighted and the modified flag 
will be set.  Behavior is inconsistent; sometimes, simply reissuing the 
open file command or toggling font-lock-mode will fix things.  If you have 
further questions about the bug, contact me at kketcham@cs.hmc.edu.  Thank 
you.

Kwang Ketcham
Harvey Mudd College
CS Department Staff