From: v.ondruch@...
Date: 2017-04-03T20:10:27+00:00
Subject: [ruby-core:80550] [Ruby trunk Bug#13397] #object_id should not be	signed

Issue #13397 has been updated by vo.x (Vit Ondruch).


Ok, you want to prevent Bignums, but what is the suggested solution here? Do some pack("l").unpack("L") to get the expected value? Or you can provide object_hexid [ [1] ]. Or provide some %p equivalent formatter?

Because I am afraid that the "inspect" misuse is widespread. Here are some examples, even in Ruby codebase:

https://github.com/ruby/ruby/blob/trunk/lib/rubygems/dependency_list.rb#L107
https://github.com/ruby/ruby/blob/trunk/lib/rubygems/platform.rb#L115
https://github.com/ruby/ruby/blob/trunk/lib/rdoc/attr.rb#L90
https://github.com/ruby-concurrency/concurrent-ruby/blob/master/lib/concurrent/map.rb#L218
https://github.com/rails/rails/blob/master/actionview/lib/action_view/template/resolver.rb#L59

[1]: https://www.ruby-forum.com/topic/208604

----------------------------------------
Bug #13397: #object_id should not be signed
https://bugs.ruby-lang.org/issues/13397#change-64050

* Author: vo.x (Vit Ondruch)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.4.0p0 (2016-12-24 revision 57164) [i386-linux]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
It is surprising that #object_id returns signed value. Let me explain show two examples. Working with 32b Ruby (ruby 2.4.0p0 (2016-12-24 revision 57164) [i386-linux]) to make this issue more apparent.

~~~
$ ruby << \EOR
GC.disable
3_000_000.times { p Object.new.inspect }
EOR
"#<Object:0x57d49a5c>"
"#<Object:0x57d499a8>"
"#<Object:0x57d49930>"
"#<Object:0x57d498b8>"

... snip ...

"#<Object:0x828bf164>"
"#<Object:0x828bf0ec>"
"#<Object:0x828bf074>"
"#<Object:0x828beffc>"
"#<Object:0x828bef84>"
^C-:2:in `p': Interrupt
	from -:2:in `block in <main>'
	from -:2:in `times'
	from -:2:in `<main>'
"#<Object:0x8290b1f4>"
~~~

In this example, the "object_id", which is part of the inspect object is unsigned, since it is printed using C sprintf with %p format. There are other libraries, which tries to mimic the output [ [1] ]. The implementation is approximately following:

~~~
$ ruby << \EOR
GC.disable
class A
  DEFAULT_OBJ_ID_STR_WIDTH = 0.size == 4 ? 7 : 14

  def inspect
    id_str = (object_id << 1).to_s(16).rjust(DEFAULT_OBJ_ID_STR_WIDTH, '0') 
    "#<#{self.class.name}:0x#{id_str}>"
  end
end
3_000_000.times { p A.new.inspect }
EOR

"#<A:0x58585428>"
"#<A:0x585852d4>"
"#<A:0x585851bc>"
"#<A:0x5858507c>"
"#<A:0x58584ec4>"
"#<A:0x58584d5c>"
"#<A:0x58584c1c>"
"#<A:0x58584adc>"

... snip ...

"#<A:0x7fff4888>"
"#<A:0x7fff47c0>"
"#<A:0x7fff46f8>"
"#<A:0x7fff4630>"
"#<A:0x7fff4568>"
"#<A:0x7fff44a0>"
"#<A:0x7fff43d8>"
"#<A:0x7fff4310>"
"#<A:0x7fff4248>"
"#<A:0x7fff4180>"
"#<A:0x7fff40b8>"
"#<A:0x-7fffc034>"
"#<A:0x-7fffc110>"
"#<A:0x-7fffc1ec>"
"#<A:0x-7fffc2c8>"
"#<A:0x-7fffc3a4>"
"#<A:0x-7fffc480>"
"#<A:0x-7fffc55c>"
"#<A:0x-7fffc638>"
^C-:10:in `p': Interrupt
	from -:10:in `block in <main>'
	from -:10:in `times'
	from -:10:in `<main>'
~~~ 

And the output is quite surprising to me. Why the object_id should be signed value? It doesn't make any sense to me. Is this implementation wrong or is Ruby wrong?

[1]: https://github.com/ruby-concurrency/concurrent-ruby/issues/547



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