Uli's 4:53 PM Law

When your Lex/YACC (aka FLex/BISON)-parser gives you several tokens (e.g. "15 + 4") for the text of one, you very likely assumed yytext was valid beyond the end of yylex() or yy_scan_string(). Inconveniently, it isn't. Use strdup() or some other convenient API call to make a copy of yytext to be able to keep it around.

Apologies for posting a law during daytime. I, too, wish I'd found this bug last night ;-)