Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!noao!arizona!rupley
From: rupley@arizona.edu (John Rupley)
Newsgroups: comp.lang.c
Subject: Re: Want a way to strip comments from a
Summary: Lex script still fails (and crashes)
Message-ID: <9888@megaron.arizona.edu>
Date: 26 Mar 89 02:51:19 GMT
References: <7150@siemens.UUCP> <9900010@bradley> <890@m10ux.UUCP> <893@m10ux.UUCP>
Organization: U of Arizona CS Dept, Tucson
Lines: 31


In article <893@m10ux.UUCP>, mnc@m10ux.UUCP (Michael Condict) writes:
> Oops, the previous lex script I posted for deleting comments from
> C source code is incorrect -- it doesn't recognize:  /***...**/
> Here is a better one (simpler, too):
> 
> 	%%
> 	\"([^\\"]*\\(.|\n))*[^\\"]*\"	ECHO;
> 	"/*"([^*]|"*"+[^/*])*"*"*"*/"	;
> 	.				ECHO;

You indeed fixed the /***/ error, but two errors remain.

First, no handling of single-quoted double quotes:

        main() {printf("%c\n", '"');/*gotcha*/printf("%c\n", '"');}

Second, your program crashes when uncommenting a real source file, with
a sizeable change history or whatever inside a comment.  You need at
least one state change, so a comment can be matched line-by-line, and
so not overflow a Lex buffer.  Both previous Lex postings did it
right.  A third state, to handle quoted strings line-by-line, is perhaps
optional, and the previous postings differ here. Apparently you missed
the previous Lex postings, which I will be happy to email you on request.

My argument, that it's difficult to make a logical error in coding this
problem in Lex, has now been demonstrated wrong (sob :-). But at least 
Lex is still outscoring straight C (faint praise :-?).

John Rupley
rupley!local@megaron.arizona.edu