[MacRuby-devel] [MacRuby] #795: GCD inconsistently copies local variables inside blocks

15 Jul 2010

      #795: GCD inconsistently copies local variables inside blocks
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 Reporter:  ernest.prabhakar@…          |       Owner:  lsansonetti@…        
     Type:  defect                      |      Status:  new                  
 Priority:  critical                    |   Milestone:                       
Component:  MacRuby                     |    Keywords:                       
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 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?

-- 
Ticket URL: <http://www.macruby.org/trac/ticket/795>
MacRuby <http://macruby.org/>