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, 9 insertions, 0 deletions

diff --git a/bootstraptest/test_objectspace.rb b/bootstraptest/test_objectspace.rb
index 24a1a0ce2c..63a8d99322 100644
--- a/bootstraptest/test_objectspace.rb
+++ b/bootstraptest/test_objectspace.rb
@@ -44,3 +44,12 @@ assert_normal_exit %q{
     Thread.new {}
   end
 }, '[ruby-core:37858]'
+
+assert_equal 'ok', %q{
+  objects_and_ids = 1000.times.map { o = Object.new; [o, o.object_id] }
+  objects_and_ids.each { |expected, id|
+    actual = ObjectSpace._id2ref(id)
+    raise "expected #{expected.inspect}, got #{actual.inspect}" unless actual.equal?(expected)
+  }
+  'ok'
+}