Interesting. I would have expected that these methods were implemented like other module methods, with two copies of the method in two method tables, but I suppose in MRI the instance method just dispatches to the class method. That's not a difficult change to make.

I expect this affects 1.7 too.

Humm... it's interesting, according to this, you are right, it should.

I tried patching the Kernel.timeout, even:

extend Timeout::Extensions

and, if I see load it in the console, it's overwritten:

[1] pry(main)> require 'timeout/extensions'                            
=> true                                                                
[2] pry(main)> method(:timeout).source_location                        
=> ["/home/timeout-extensions/lib/timeout/extensions.rb", 16] 
[3] pry(main)>                                                         

But then, in a script, doing something inside TCPSocket class from Celluloid (using debugger):

irb(#<Celluloid::IO::TCPSocket:0x13dac87a>):002:0> method(:timeout).source_location     
=> nil

this call to timeout jumps to the jruby implementation, according to the backtrace I receive:

        /home/sem-celluloid/lib/sem/celluloid/net/ssh.rb:35:in `block in available_for_read?'           
        org/jruby/ext/timeout/Timeout.java:123:in `timeout'                                                      
        org/jruby/ext/timeout/Timeout.java:92:in `timeout'                                                       
        /home/sem-celluloid/lib/sem/celluloid/net/ssh.rb:34:in `available_for_read?'                    
        /home/sem-celluloid/lib/sem/celluloid/net/ssh.rb:47:in `next_packet'                            

(the available_for_read? method calls the timeout method, should have jumped to the timeout-extensions method).

Maybe has to do with alias_method?

I figured the issue out. In MRI, where timeout is pure Ruby, the top-level timeout method is defined like this:

# Identical to:
#
#   Timeout::timeout(n, e, &block).
#
# This method is deprecated and provided only for backwards compatibility.
# You should use Timeout#timeout instead.
def timeout(n, e = nil, &block)
  Timeout::timeout(n, e, &block)
end

Note the deprecation.

In JRuby, it's defined as a direct static call in Java to the actual implementation. The Timeout::timeout method is defined as a normal module method in both MRI and JRuby, though, so that part's ok.

I'll have a fix for this momentarily. Thanks for the report!

No mention, glad to help 👍