Thanks to Nelson H.F. Beebe's machines I've reproduced Bug#17072 on IRIX 
and have verified that the attached gawk patch fixes it.  This patch is 
almost identical to the gawk patch I submitted in 
<http://bugs.gnu.org/17157#44>.  It improves on the earlier patch only 
by changing gawk's dfa.c to look more like grep's dfa.c in one more way: 
include "dfa.h" before all other include files (except config.h).

I'll CC: this to Bug#17157 so that the patch is visible there too.  No 
further change should be needed to grep for this.