Fix @{*ISA} autovivification

It was not attaching magic to the array, preventing subsequent changes
to the array from updating isa caches.

1 files changed, 3 insertions, 0 deletions

diff --git a/gv.c b/gv.c
index ba8e85ef1f..e0fdc630e9 100644
--- a/gv.c
+++ b/gv.c
@@ -83,6 +83,9 @@ Perl_gv_add_by_type(pTHX_ GV *gv, svtype type)
 
     if (!*where)
 	*where = newSV_type(type);
+    if (type == SVt_PVAV && GvNAMELEN(gv) == 3
+     && strnEQ(GvNAME(gv), "ISA", 3))
+	sv_magic(*where, (SV *)gv, PERL_MAGIC_isa, NULL, 0);
     return gv;
 }