Allow internal pointers to point to the end of an object

Cargo.toml

@@ -231,6 +231,12 @@ no_mmap_annotation = []
 # only be used if you understand how VO bit works internally. Use at your own risk.
 vo_bit_access = []
 
+# When a pointer points to the end of an object, it is not pointing inside an object and is usually not considered as an internal pointer.
+# However, some languages may have 0-size fields such as unit ().
+# When such fields appear as the last field of an object, an internal pointer to it would point directly to the end of the object,
+# and still needs to be considered as an internal pointer.
+object_end_internal_pointer = []
+
 # Do not modify the following line - ci-common.sh matches it
 # -- Mutally exclusive features --
 # Only one feature from each group can be provided. Otherwise build will fail.

src/util/metadata/vo_bit/mod.rs

@@ -211,7 +211,11 @@ pub(crate) fn get_object_ref_for_vo_addr(vo_addr: Address) -> ObjectReference {
 fn is_internal_ptr<VM: VMBinding>(obj: ObjectReference, internal_ptr: Address) -> bool {
     let obj_start = obj.to_object_start::<VM>();
     let obj_size = VM::VMObjectModel::get_current_size(obj);
-    internal_ptr < obj_start + obj_size
+    if cfg!(feature = "object_end_internal_pointer") {
+        internal_ptr <= obj_start + obj_size
+    } else {
+        internal_ptr < obj_start + obj_size
+    }
 }
 
 /// Check if the address could be an internal pointer based on where VO bit is set.