Date: Mon, 4 Dec 2000 01:20:04 -0800 (PST) From: Bill Fenner <fenner@research.att.com> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/23254: yacc accepts bad grammer Message-ID: <200012040920.eB49K4o90201@freefall.freebsd.org>
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The following reply was made to PR bin/23254; it has been noted by GNATS.
From: Bill Fenner <fenner@research.att.com>
To: freebsd-gnats-submit@freebsd.org, marka@nominum.com
Cc: fenner@research.att.com
Subject: Re: bin/23254: yacc accepts bad grammer
Date: Mon, 4 Dec 2000 01:14:05 -0800 (PST)
Ugh. Would you believe that yacc's scanner treats semicolons as
whitespace? I wonder if semicolons were added to the input syntax
"late" in the game (like in the mid'80's or so :-) ).
This patch makes semicolons a little more explicitly part of
yacc's input grammar; I'm sure I've missed something since I've
been testing on a relatively unsophisticated grammar, but it's
a start. It parses test/ftp.y and /usr/src/usr.sbin/mrouted/cfparse.y,
at least, and gives a (nonsensical but at least some) error when I
stick in bogus semicolons in various places.
Bill
cvs diff: Diffing .
Index: reader.c
===================================================================
RCS file: /home/ncvs/src/usr.bin/yacc/reader.c,v
retrieving revision 1.6.2.1
diff -u -r1.6.2.1 reader.c
--- reader.c 1999/08/29 15:35:09 1.6.2.1
+++ reader.c 2000/12/04 09:08:12
@@ -255,7 +255,6 @@
case '\r':
case '\v':
case ',':
- case ';':
++s;
break;
@@ -551,7 +550,11 @@
goto loop;
case '}':
- if (--depth == 0)
+ if (--depth < 0) syntax_error(lineno, line, cptr);
+ goto loop;
+
+ case ';':
+ if (depth == 0)
{
fprintf(text_file, " YYSTYPE;\n");
FREE(u_line);
@@ -1198,6 +1201,8 @@
{
register int i;
+ if (!plhs[nrules]) return;
+
if (!last_was_action && plhs[nrules]->tag)
{
for (i = nitems - 1; pitem[i]; --i) continue;
@@ -1259,7 +1264,6 @@
c = nextc();
if (c == ':')
{
- end_rule();
start_rule(bp, s_lineno);
++cptr;
return;
@@ -1569,6 +1573,11 @@
else if (c == '%')
{
if (mark_symbol()) break;
+ }
+ else if (c == ';')
+ {
+ ++cptr;
+ end_rule();
}
else
syntax_error(lineno, line, cptr);
cvs diff: Diffing test
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