Re: Unexpected pointer behavior with unpack

Hi,

At Sat, 15 Jul 2006 00:36:37 +0900,
Justin Bailey wrote in [ruby-core:08223]:
>   puts outer.unpack("P4").first.unpack("P3") # ArgumentError - no associated
> pointer
> 
> I get an error. Now, I think I understand why this happens - pointers have
> to be associated with variables. It would be dangerous to unpack to treat
> any string as a pointer. However, I do think the above is surprising
> behavior. It took me awhile to understand why my nested structures didn't
> seem to work.

Since the result string will be tainted, so the original string
also will be tainted implicitly.  But now I about to think it
should be tainted too.


Index: pack.c
===================================================================
RCS file: /cvs/ruby/src/ruby/pack.c,v
retrieving revision 1.84
diff -p -U 2 -r1.84 pack.c
--- pack.c	9 Jun 2006 21:20:12 -0000	1.84
+++ pack.c	14 Jul 2006 16:16:48 -0000
@@ -1875,6 +1875,10 @@ pack_unpack(VALUE str, VALUE fmt)
 		    while (p < pend) {
 			if (TYPE(*p) == T_STRING && RSTRING(*p)->ptr == t) {
-			    if (len > RSTRING(*p)->len) {
-				len = RSTRING(*p)->len;
+			    rb_obj_taint(*p);
+			    if (len < RSTRING(*p)->len) {
+				tmp = rb_tainted_str_new(t, len);
+			    }
+			    else {
+				tmp = *p;
 			    }
 			    break;
@@ -1885,5 +1889,4 @@ pack_unpack(VALUE str, VALUE fmt)
 			rb_raise(rb_eArgError, "non associated pointer");
 		    }
-		    tmp = rb_tainted_str_new(t, len);
 		}
 		else {


-- 
Nobu Nakada