Bug #9622: Extra method arguments are magically swallowed after first successful call, possible method cache bug

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: 2.0.0
• Backport: 1.9.3: REQUIRED, 2.0.0: DONE, 2.1: DONE

[byroot (Jean Boussier)]

The following code behaviour totally change since ruby 2.0.0

class Foo

  def bar(*args)
    attribute(:bar, *args)
  end

  def attribute(name)
    puts name
  end

end

foo = Foo.new

begin
  foo.bar(100)
rescue => e
  puts e.class.name
end

foo.bar # legit

5.times do
  foo.bar(100)
end

puts 'No errors??? WTF???'

ruby < 2.0 output:

ArgumentError
bar
(eval):3:in `attribute': wrong number of arguments (2 for 1) (ArgumentError)
    from (eval):3:in `bar'
    from foo.rb:28
    from foo.rb:27:in `times'
    from foo.rb:27

Which is expected.

But ruby >= 2.0 output

ArgumentError
bar
bar
bar
bar
bar
bar
No errors??? WTF???

In short, after the first successful call, the extra arguments are just ignored. I have no idea of what is going on here, but it look like a broken optimization.

All rubies >= 2.0 are affected. 1.8.7 and 1.9.3 are fine.

Regards.

A gist describing the issue: https://gist.github.com/byroot/9495455

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed
• % Done changed from 0 to 100

Applied in changeset r45321.

---

vm_insnhelper.c: disable fastpath if splat

• vm_insnhelper.c (vm_callee_setup_arg): disable fastpath if splat
  argument, since argc may differ for each calls.
  [ruby-core:61422] [Bug #9622]

[nobu (Nobuyoshi Nakada)]

• Priority changed from 5 to Normal
• Backport changed from 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN to 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

just for memorandum. r45320 is also required to be backported.

[usa (Usaku NAKAMURA)]

• Backport changed from 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: REQUIRED to 1.9.3: REQUIRED, 2.0.0: DONE, 2.1: REQUIRED

backported into ruby_2_0_0 at r45748.

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 1.9.3: REQUIRED, 2.0.0: DONE, 2.1: REQUIRED to 1.9.3: REQUIRED, 2.0.0: DONE, 2.1: DONE

Backported into ruby_2_1 at r46302.

[marcandre (Marc-Andre Lafortune)]

• Has duplicate Bug #10291: Strange behaviour of splat in Ruby 2.0.0 added

[nobu (Nobuyoshi Nakada)]

• Has duplicate Bug #10353: weird behavior when dynamically adding method using instance_eval added