Bug #16297: calling undefined allocator by `Class.instance_method(:allocate)`

• Status: Closed
• Assignee: -
• Target version: -
• Backport: 2.5: REQUIRED, 2.6: DONE

[nobu (Nobuyoshi Nakada)]

For instance, Rational.allocate is undefined.

Rational.allocate #=> undefined method `allocate' for Rational:Class (NoMethodError)

But it can be called by Class.instance_method(:allocate).

Class.instance_method(:allocate).bind_call(Rational) #=> (0/1)
Class.instance_method(:allocate).bind(Rational).call #=> (0/1)

These allocators are defined for Marshal, and undefined as methods.

[usa (Usaku NAKAMURA)]

• Backport changed from 2.5: REQUIRED, 2.6: REQUIRED to 2.5: REQUIRED, 2.6: DONE

ruby_2_6 r67896 merged revision(s) f72dc407.

[usa (Usaku NAKAMURA)]

usa (Usaku NAKAMURA) wrote in #note-1:

ruby_2_6 r67896 merged revision(s) f72dc407.

note that ruby_2_6 does not have UnboundMethod#bind_call.

[jhawthorn (John Hawthorn)]

I'm not sure if there's a deeper problem this causes, but it is still possible after this patch to call the allocator on a Rational through defining an arbitrary allocate method.

>> def Rational.allocate; end
=> :allocate
>> Class.instance_method(:allocate).bind_call(Rational)
=> (0/1)