Use a monotonically increasing number for object_id

This changes object_id from being based on the objects location in
memory (or a nearby memory location in the case of a conflict) to be
based on an always increasing number.

This number is a Ruby Integer which allows it to overflow the size of a
pointer without issue (very unlikely to happen in real programs
especially on 64-bit, but a nice guarantee).

This changes obj_to_id_tbl and id_to_obj_tbl to both be maps of Ruby
objects to Ruby objects (previously they were Ruby object to C integer)
which simplifies updating them after compaction as we can run them
through gc_update_table_refs.

Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/hash.c b/hash.c
index 0f5d418534..a5de9fde07 100644
--- a/hash.c
+++ b/hash.c
@@ -273,10 +273,14 @@ rb_objid_hash(st_index_t index)
 static st_index_t
 objid_hash(VALUE obj)
 {
+    VALUE object_id = rb_obj_id(obj);
+    if (!FIXNUM_P(object_id))
+        object_id = rb_big_hash(object_id);
+
 #if SIZEOF_LONG == SIZEOF_VOIDP
-    return (st_index_t)st_index_hash((st_index_t)NUM2LONG(rb_obj_id(obj)));
+    return (st_index_t)st_index_hash((st_index_t)NUM2LONG(object_id));
 #elif SIZEOF_LONG_LONG == SIZEOF_VOIDP
-    return (st_index_t)st_index_hash((st_index_t)NUM2LL(rb_obj_id(obj)));
+    return (st_index_t)st_index_hash((st_index_t)NUM2LL(object_id));
 #endif
 }