Grep bug

[utzoo!decvax!watmath!kwlalonde]

Grep recognises syntactically incorrect patterns, such as '[', and
prints a diagnostic.  It then goes ahead and tries to execute its compiled
pattern on the input, resulting in infinite loops and other uglies.
A fix is to exit after the diagnostic.
	
	diff oldgrep.c newgrep.c
	186a187
	> 	exit(2);
						Ken Lalonde