[perl #87664] Don’t autovivify stashes when anonymising CVs

This commit stops CV anonymisation from autovivifying stashes to point
to (unless the stash is %__ANON__::).

If a stash has been deleted from its original position in the symbol
table, then its HvNAME will no longer indicate where to find it.

S_anonymise_cv_maybe in sv.c was using the HvNAME to look up (and
autovivify) the *__ANON__ glob in the stash, without taking into
account that it might not actually be looking in the right spot.

So now, after checking that the stash still has a name (HvNAME), it
uses the HvENAME to find it. If the HvENAME is null, which indicates
that the stash has been detached altogether, then %__ANON__:: is used,
as happens when HvNAME is null.

This solves a Class::Monadic failure introduced by commit 2d0d1eccfc
([perl #79208] %stash:: = () anonymises CVs), which was included
in 5.13.7.

Basically, it can be reduced to this:

1 files changed, 2 insertions, 1 deletions

diff --git a/sv.c b/sv.c
index 9ea0b50c3f..447c2bc5ef 100644
--- a/sv.c
+++ b/sv.c
@@ -5991,7 +5991,8 @@ S_anonymise_cv_maybe(pTHX_ GV *gv, CV* cv)
     }
 
     /* if not, anonymise: */
-    stash  = GvSTASH(gv) ? HvNAME(GvSTASH(gv)) : NULL;
+    stash  = GvSTASH(gv) && HvNAME(GvSTASH(gv))
+              ? HvENAME(GvSTASH(gv)) : NULL;
     gvname = Perl_newSVpvf(aTHX_ "%s::__ANON__",
 					stash ? stash : "__ANON__");
     anongv = gv_fetchsv(gvname, GV_ADDMULTI, SVt_PVCV);