macirb: GCD inconsistently copies local variables inside blocks

[ernest.prabhakar@…]

The expectation is that Ruby blocks will have their local variables copied before being passed to GCD, to avoid errors from accessing them after they are destroyed.

However, that does not seem to always happen. For example:

    $ macruby -e 'i=0; Dispatch::Queue.new("i").sync {i = 42}; puts i'

returns '0' as expected. However, this does not:

    $ macirb
    irb(main):001:0> i=0; Dispatch::Queue.new("i").sync {i = 42}; puts i
    42
    => nil

It appears to be copied properly in the block_spec.rb test:

    it "should create const copies of dynamic (local) variables" do
      i = 42
      @q.sync {i = 1}
      i.should == 42
    end

But not in the README.rdoc for the dispatch module (aka dispatch_methods.rb sample):

    n = 0
    job = Dispatch::Job.new { n = 21 }
    job.join
    puts "n (after): #{n} => 0?!?" # [returns 21, not 0]

Any suggestions?

[lsansonetti@…]

I believe this problem only happens inside IRB. I also believe IRB has special code for locals.

[lsansonetti@…]

Adding the 0.7-blocker keyword & assigning to Eloy for comment.

[lsansonetti@…]

Apparently the keyword has been removed. Anyways, it does not seem critical anymore for 0.7. The macirb bug seems minor, and the Dispatch::job bug seems related to the fact that the block is transformed into a Proc then executed separately (again, something minor we can fix later).

[eloy.de.enige@…]

I hang my head in shame, for not being subscribed to the tickets ML and didn't know about this ticket… Anyways, this happens when it’s eval'ed:

% macruby -e 'eval("i=0; Dispatch::Queue.new(\"i\").sync {i = 42}; puts i")'                                
42