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From: tom@flood.com (Tom Chatt)
Newsgroups: comp.unix.internals
Subject: Re: two (or more) lex's/yacc's in one executable
Message-ID: <1990Dec9.211732.1917@flood.com>
Date: 9 Dec 90 21:17:32 GMT
References: <1990Dec6.200753.12694@cs.columbia.edu>
Sender: root@flood.com (Operator)
Organization: The Flood Group, Inc.  Lawndale, Ca.
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I have an several occasions used more than one lex/yacc thing
in one executable. I used a kludge that is similar in concept
to yours, but perhaps a bit more reliable. Rather than creating
a header file to redefine all of the yy_symbols to something
else (which requires you to know all of the yy_symbols), I would
run a "sed" on the generated code to do a global replace on the
"yy" prefix. For example, to make two separate yaccs:
	    yacc zzparse.y
	    sed -e s/yy/zz/g y.tab.c > zzparse.c
	    yacc xxparse.y
	    sed -e s/yy/xx/g y.tab.c > xxparse.c
If you are willing to follow some fairly reasonable naming
conventions with regard to your lex and yacc source files, the
above sort of filtering can be implemented in a couple of
general ".y.o" and ".l.o" rules in your makefile. This solves
the general case, rather than having to deal (e.g., create a
header file) for each specific case, which is surely tedious.

With regard to using calls out of the lex library (which are not
available for you to rename -- not easily, anyway), I believe that
most of the calls in the lex (and yacc) libraries provide "default
action" routines which a user may want to customize. (This explains
why the implementers did *not* make these routines static globals.
It would have defeated the purpose.) For instance, the lex library
even provides a "main()" routine, so that you could create a lex
executable without having to provide your own "main()". Of course,
providing your own "main()" is not precluded. Likewise for "yywrap()",
and (if I remember right) everything else in there. It is possible
(and not even hard) to create a lex source which does not need any
of these default routines, by providing your own versions. Your
own versions may perform the same default actions, but this gives
you the opportunity to do your global rename on the prefixes.

I can provide more specific info if you e-mail me (though I'm out
of the office a lot recently and can't guarantee quick turnaround).
Good luck.

-- 
Tom Chatt                        \   Don't take offense, take action.
Internet: tom@flood.com           \    Speak up. When we remain silent,
UUCP: ...!uunet!flood!tom        / \     we oppress ourselves.