Re: Bug#62339: rc bug

Re: Bug#62339: rc bug

[Decklin Foster]

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Tim Goodwin writes:

> Thanks for the report.  I can reproduce this.
> 
> It's not been reported before, so I don't know what's going on, but I'll
> let you know as soon as I have a fix.

I did send something to to mailing list on Saturday, but it hasn't
gotten through yet. I seem to have figured out the use of m in a List
structure: if there are no metacharacters, NULL, and if there are, we
put a \0 where there's a non-metacharacter in the corresponding part
of n, and a \001 where there is.

Now in lmatch() when we go through looking for '*'s, we have this
loop:

	for (i = 0; p->w[i] != '\0'; i++)
		if (p->w[i] != '*' || p->m[i] != 1) {

Which assumes that m is as big as w (i.e, not NULL). I came up with
this replacement, which works for all the test cases I can think of:

        if (s == NULL) {
                if (p == NULL) /* null matches null */
                        return TRUE; 
                for (; p != NULL; p = p->n) /* one or more stars match null */
                        if (p->w && strspn(p->w, "*") == strlen(p->w) &&
                            p->m && strspn(p->m, "\001") == strlen(p->m))
                                return TRUE;
                return FALSE;
        }

I was also able to get rid of 'okay', which i found hard to follow.
The comment about the null string is gone too, because IMO the null
string fails for the same reason 'foo' fails. There's really no need
for an explicit check.

A patch is attached. Out of curiosity, why was the decision made to
use '\000' and '\001' instead of, say, '0' and '1'? For example in the
old code, we have "p->m[i] != 1", and it wouldn't be that hard to
write "p->m[i] != '1'" instead. I'm sure there's a reason, but I can't
guess it.

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--- glob.c.old	Wed Oct 21 07:01:46 1998
+++ glob.c	Mon Apr 17 15:55:30 2000
@@ -34,23 +34,13 @@
 
 extern bool lmatch(List *s, List *p) {
 	List *q;
-	int i;
-	bool okay;
 	if (s == NULL) {
 		if (p == NULL) /* null matches null */
 			return TRUE;
-		for (; p != NULL; p = p->n) { /* one or more stars match null */
-			if (*p->w != '\0') { /* the null string is a special case; it does *not* match () */
-				okay = TRUE;
-				for (i = 0; p->w[i] != '\0'; i++)
-					if (p->w[i] != '*' || p->m[i] != 1) {
-						okay = FALSE;
-						break;
-					}
-				if (okay)
-					return TRUE;
-			}
-		}
+		for (; p != NULL; p = p->n) /* one or more stars match null */
+			if (p->w && strspn(p->w, "*") == strlen(p->w) &&
+			    p->m && strspn(p->m, "\001") == strlen(p->m))
+				return TRUE;
 		return FALSE;
 	}
 	for (; s != NULL; s = s->n)

oops, let's try that one again

[Decklin Foster]

Decklin Foster writes:

> if (p->w && strspn(p->w, "*") == strlen(p->w) &&
>     p->m && strspn(p->m, "\001") == strlen(p->m))
>         return TRUE;

OK, raise your hand if you can spot the bug here. The test case I came
up with after posting this code, which breaks it, is:

~ () *'*'

(any number of quoted stars will do.) Not a crasher, but still
obviously wrong. Thankfully, the fix involves changing only one
character:

	if (p->w && strspn(p->w, "*") == strlen(p->w) &&
	    p->m && strspn(p->m, "\001") == strlen(p->w))
		return TRUE;

But this of course can be simplified to

	if (p->w && p->m && strspn(p->w, "*") == strspn(p->m, "\001")
					      == strlen(p->w))
		return TRUE;

Which is somewhat more efficient, anyway. If you would like me to stop
thinking aloud, just speak up, but I don't think this list is
suffering from too much traffic ;-)

[Note: my normal style would be to pull "== strlen(p->w))" back to the
first tab stop and then put "return TRUE;" after it on the same line,
but the rc Way seems to be to use

	if (foo)
		bar;

instead of

	if (foo) bar;

which is what I do for short statements. In short, reformat as you see
fit.]

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Written with 100% free software. Please support the following websites:
www.debian.org www.noamazon.com www.gnu.org www.opendvd.org lpf.ai.mit.edu