为什么`ObjectSpace._id2ref`在Ruby1.9和Ruby2.0上提供不同的输出？

Question

为什么ObjectSpace._id2ref在Ruby1.9和Ruby2.0上提供不同的输出？

Ruby1.9.3p392 i 386-mingw32

class Foo ; end

Foo.object_id                     #=> 17569464
ObjectSpace._id2ref(17569464)     #=> Foo

Foo.new.singleton_class.object_id #=> 17075124
ObjectSpace._id2ref(17075124)     #=> "\x00"

Ruby2.0.0p0i 386-mingw32

class Foo ; end

Foo.object_id                     #=> 17197176
ObjectSpace._id2ref(17197176)     #=> Foo

Foo.new.singleton_class.object_id #=> 19181436
ObjectSpace._id2ref(19181436)     #=> RangeError: 0x124af7c is recycled object

Foo.new.singleton_class.object_id #=> 17454324
ObjectSpace._id2ref(17454324)     #=> RangeError: 0x10a54f4 is not id value

Foo.new.singleton_class.object_id #=> 17139816
ObjectSpace._id2ref(17139816)     #=> "c"

Answer 1

仅仅是因为在2.0中垃圾收集器很容易出错。

# RangeError: 0x124af7c is recycled object

对象的状态已经被GC‘编辑了。

UPD:我们可以使用Mutex来处理请求的行为

2.0.0 (main):0 > Mutex.new.synchronize {
2.0.0 (main):0 *   class Foo ; end
2.0.0 (main):0 *   id = Foo.new.singleton_class.object_id
2.0.0 (main):0 *   puts id
2.0.0 (main):0 *   puts ObjectSpace._id2ref(id)
2.0.0 (main):0 * }  
# 23172260
# <Class:#<Foo:0x00000002c32970>>