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Use a monotonically increasing number for object_id

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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>
This commit is contained in:
John Hawthorn 2019-10-31 17:21:01 -07:00 • committed by Aaron Patterson
parent d62abc47c8
commit b99833baec
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5 changed files with 90 additions and 151 deletions
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8
hash.c
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@ -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
}