Fix double-repossession.

Not completely sure why that can happen just yet, but this should be
enough to make it not be a problem.

Author: jnthn

src/6model/serialization.c

@@ -1695,49 +1695,55 @@ static void repossess(PARROT_INTERP, SerializationReader *reader, INTVAL i) {
         PMC *orig_sc  = locate_sc(interp, reader, read_int32(table_row, 8));
         PMC *orig_obj = SC_get_object(interp, orig_sc, read_int32(table_row, 12));
 
-        /* If we have a reposession conflict, make a copy of the original object
-         * and reference it from the conflicts list. Push the original (about to
-         * be overwritten) object reference too. */
-        if (SC_PMC(orig_obj) != orig_sc) {
-            PMC *backup = REPR(orig_obj)->allocate(interp, STABLE(orig_obj));
-            if (IS_CONCRETE(orig_obj))
-                REPR(orig_obj)->copy_to(interp, STABLE(orig_obj), OBJECT_BODY(orig_obj), OBJECT_BODY(backup));
-            else
-                MARK_AS_TYPE_OBJECT(backup);
-            PARROT_GC_WRITE_BARRIER(interp, backup);
-            VTABLE_push_pmc(interp, reader->repo_conflicts_list, backup);
-            VTABLE_push_pmc(interp, reader->repo_conflicts_list, orig_obj);
-        }
-
-        /* Clear it up, since we'll re-allocate all the bits inside
-         * it on deserialization. */
-        STABLE(orig_obj)->REPR->gc_free(interp, orig_obj);
-        
         /* Put it into objects root set at the apporpriate slot. */
         VTABLE_set_pmc_keyed_int(interp, reader->objects_list,
-            read_int32(table_row, 4), orig_obj);
+        read_int32(table_row, 4), orig_obj);
+        
+        /* Ensure we aren't already trying to repossess the object. */
+        if (PMC_data(orig_obj)) {
+            /* If we have a reposession conflict, make a copy of the original object
+            * and reference it from the conflicts list. Push the original (about to
+            * be overwritten) object reference too. */
+            if (SC_PMC(orig_obj) != orig_sc) {
+                PMC *backup = REPR(orig_obj)->allocate(interp, STABLE(orig_obj));
+                if (IS_CONCRETE(orig_obj))
+                    REPR(orig_obj)->copy_to(interp, STABLE(orig_obj), OBJECT_BODY(orig_obj), OBJECT_BODY(backup));
+                else
+                    MARK_AS_TYPE_OBJECT(backup);
+                PARROT_GC_WRITE_BARRIER(interp, backup);
+                VTABLE_push_pmc(interp, reader->repo_conflicts_list, backup);
+                VTABLE_push_pmc(interp, reader->repo_conflicts_list, orig_obj);
+            }
+    
+            /* Clear it up, since we'll re-allocate all the bits inside
+            * it on deserialization. */
+            STABLE(orig_obj)->REPR->gc_free(interp, orig_obj);
+        }
     }
     else if (repo_type == 1) {
         /* Get STable to repossess. */
         PMC *orig_sc = locate_sc(interp, reader, read_int32(table_row, 8));
         PMC *orig_st = SC_get_stable(interp, orig_sc, read_int32(table_row, 12));
 
-        /* Make sure we don't have a reposession conflict. */
-        if (STABLE_STRUCT(orig_st)->sc != orig_sc)
-            Parrot_ex_throw_from_c_args(interp, NULL, EXCEPTION_INVALID_OPERATION,
-                "STable conflict detected during deserialization.\n"
-                "(Probable attempt to load two modules that cannot be loaded together).");
-        
-        /* Clear it up, since we'll re-allocate all the bits inside
-         * it on deserialization. */
-        if (STABLE_STRUCT(orig_st)->REPR->gc_free_repr_data) {
-            STABLE_STRUCT(orig_st)->REPR->gc_free_repr_data(interp, STABLE_STRUCT(orig_st));
-            STABLE_STRUCT(orig_st)->REPR_data = NULL;
-        }
-        
         /* Put it into STables root set at the apporpriate slot. */
         VTABLE_set_pmc_keyed_int(interp, reader->stables_list,
             read_int32(table_row, 4), orig_st);
+        
+        /* Ensure we aren't already trying to repossess the STable. */
+        if (PMC_data(orig_st)) {
+            /* Make sure we don't have a reposession conflict. */
+            if (STABLE_STRUCT(orig_st)->sc != orig_sc)
+                Parrot_ex_throw_from_c_args(interp, NULL, EXCEPTION_INVALID_OPERATION,
+                    "STable conflict detected during deserialization.\n"
+                    "(Probable attempt to load two modules that cannot be loaded together).");
+            
+            /* Clear it up, since we'll re-allocate all the bits inside
+            * it on deserialization. */
+            if (STABLE_STRUCT(orig_st)->REPR->gc_free_repr_data) {
+                STABLE_STRUCT(orig_st)->REPR->gc_free_repr_data(interp, STABLE_STRUCT(orig_st));
+                STABLE_STRUCT(orig_st)->REPR_data = NULL;
+            }
+        }
     }
     else {
         Parrot_ex_throw_from_c_args(interp, NULL, EXCEPTION_INVALID_OPERATION,