"Stack overflow in regexp"

All, In a couple of places (compilation-mode, message-headers), I get errors about stack overflow in regexp pattern matching. The first one was in compile mode, which builds a looking-at regexp from: mode1\|mode2\|mode3\|...\|mode99. When given a compile line that is very long (lots of -I, ~>1000 chars), I get the error. I had figured that maybe the union of the regexps was too complicated for the regexp engine. However, I got some almost-department-wide email addressed to lots of recipients (~300), and got the error. The header-highlighting was barfing on a find-the-header regexp: highlight-headers.el:215: (looking-at "^\\([^ \t\n:]+[ \t]*:\\) *\\(.*\\(\n[ \t].*\\)*\n\\)") header ws : space field (continued field)* The regexp isn't that complicated, but it caused the highlighting to barf. Questions: a) Is there anyway to make the regexp stack larger? b) Does a larger regexp stack hurt performance? (a little memory isn't that expensive, but I wouldn't want to slow things down) I imagine these might be GNU regexp questions. -Justin vallon(a)mindspring.com