Fix for the IO::Scalar bug (I think).

At tie time break the loop but in a different place:
 A. Increment REFCNT of the RV involved in the self-tie
 B. Decrement REFCNT of the thing RV points to (e.g. the GV)
At mg_free time
 Break the connection between the RV and its referent
 so that we do not try and free it (again).

p4raw-id: //depot/perlio@16808

1 files changed, 11 insertions, 2 deletions

diff --git a/mg.c b/mg.c
index 63de61249f..299d1bbb11 100644
--- a/mg.c
+++ b/mg.c
@@ -359,8 +359,17 @@ Perl_mg_free(pTHX_ SV *sv)
 	    else if (mg->mg_len == HEf_SVKEY)
 		SvREFCNT_dec((SV*)mg->mg_ptr);
 	}
-	if (mg->mg_flags & MGf_REFCOUNTED)
-	    SvREFCNT_dec(mg->mg_obj);
+	if (mg->mg_flags & MGf_REFCOUNTED) {
+	    SV *obj = mg->mg_obj;
+	    if (mg->mg_type == PERL_MAGIC_tiedscalar && SvROK(obj) &&
+		(SvRV(obj) == sv || GvIO(SvRV(obj)) == (IO *) sv)) {
+		/* We are already free'ing the self-tied thing
+		   so SvREFCNT_dec must not.
+		 */
+		SvROK_off(obj);
+	    }
+	    SvREFCNT_dec(obj);
+	}
 	Safefree(mg);
     }
     SvMAGIC(sv) = 0;