actually check whether obj is in freelist

Author: Diogo Netto

src/gc.c

@@ -4073,10 +4073,18 @@ JL_DLLEXPORT jl_value_t *jl_gc_internal_obj_base_ptr(void *p)
         // before the freelist pointer was either live during the last
         // sweep or has been allocated since.
         if (gc_page_data(cell) == gc_page_data(pool->freelist)
-            && (char *)cell < (char *)pool->freelist)
+            && (char *)cell < (char *)pool->freelist) {
             goto valid_object;
-        else
-            return NULL;
+        }
+        else {
+            jl_taggedvalue_t *v = pool->freelist;
+            while (v != NULL) {
+                if (v == cell) {
+                    return NULL;
+                }
+                v = v->next;
+            }
+        }
         // Not a freelist entry, therefore a valid object.
     valid_object:
         // We have to treat objects with type `jl_buff_tag` differently,