Clear method caches when unwinding local *foo=sub{}

local *foo=sub{} is done in two stages:

• First the local *foo localises the GP (the glob pointer, or list of
  slots), setting a flag on the GV.
• Then scalar assignment sees the flag on the GV on the LHS and loca-
  lises a single slot.

The slot localisation only stores on the savestack a pointer into the
GP struct and the old value.  There is no reference to the GV.

To restore a method properly, we have to have a reference to the GV
when the slot localisation is undone.

So in this commit I have added a new save type, SAVEt_GVSLOT.  It is
like SAVEt_GENERIC_SV, except it pushes the GV as well.  Currently
it is used only for CVs, but I will need it for HVs and maybe
AVs as well.

It is possible for the unwinding of the slot localisation to affect
only a GV other than the one that is pushed, if glob assignments have
taken place since the local *foo.  So we have to check whether the
pointer is inside the GP and use PL_sub_generation++ if it is not.

1 files changed, 17 insertions, 0 deletions

diff --git a/scope.c b/scope.c
index f96aa45ad3..3d50932bee 100644
--- a/scope.c
+++ b/scope.c
@@ -783,6 +783,23 @@ Perl_leave_scope(pTHX_ I32 base)
 	    SvREFCNT_dec(sv);
 	    SvREFCNT_dec(value);
 	    break;
+	case SAVEt_GVSLOT:			/* any slot in GV */
+	    value = MUTABLE_SV(SSPOPPTR);
+	    ptr = SSPOPPTR;
+	    gv = MUTABLE_GV(SSPOPPTR);
+	    hv = GvSTASH(gv);
+	    if (hv && HvENAME(hv) && (
+		    (value && SvTYPE(value) == SVt_PVCV)
+		 || (*(SV **)ptr && SvTYPE(*(SV**)ptr) == SVt_PVCV)
+	       ))
+	    {
+		if ((char *)ptr < (char *)GvGP(gv)
+		 || (char *)ptr > (char *)GvGP(gv) + sizeof(struct gp)
+		 || GvREFCNT(gv) > 1)
+		    PL_sub_generation++;
+		else mro_method_changed_in(hv);
+	    }
+	    goto restore_svp;
 	case SAVEt_AV:				/* array reference */
 	    av = MUTABLE_AV(SSPOPPTR);
 	    gv = MUTABLE_GV(SSPOPPTR);