Switch the core MRO code over to HvENAME

This has the side-effect of fixing these one-liners:

$ perl5.13.5 -le' my $glob = \*foo::ISA; delete $::{"foo::"}; *$glob = *a'
Bus error
$ perl5.13.5 -le' my $glob = \*foo::ISA; delete $::{"foo::"}; *$glob = []'
Bus error
$ perl5.13.6 -le'sub baz; my $glob = \*foo::bar; delete $::{"foo::"}; *$glob = *baz;'
Bus error
$ perl5.13.6 -le'sub foo::bar; my $glob = \*foo::bar; delete $::{"foo::"}; *$glob = *baz;'
Bus error

In the first two cases the crash was inadvertently fixed (isn’t it
nice when that happens?) in 5.13.6 (by 6f86b615fa7), but there was
still a fatal error:
Can't call mro_isa_changed_in() on anonymous symbol table at -e line 1.

Because sv_clear calls ->DESTROY, if an object’s stash has been
detached from the symbol table, mro_get_linear_isa can be called on a
hash with no HvENAME. So HvNAME is used as a fallback for those cases.

1 files changed, 2 insertions, 2 deletions

diff --git a/pp.c b/pp.c
index c99d6978ed..45f536e1d0 100644
--- a/pp.c
+++ b/pp.c
@@ -854,11 +854,11 @@ PP(pp_undef)
             HV *stash;
 
             /* undef *Foo:: */
-            if((stash = GvHV((const GV *)sv)) && HvNAME_get(stash))
+            if((stash = GvHV((const GV *)sv)) && HvENAME_get(stash))
                 mro_isa_changed_in(stash);
             /* undef *Pkg::meth_name ... */
             else if(GvCVu((const GV *)sv) && (stash = GvSTASH((const GV *)sv))
-		    && HvNAME_get(stash))
+		    && HvENAME_get(stash))
                 mro_method_changed_in(stash);
 
 	    gp_free(MUTABLE_GV(sv));