[MacRuby-devel] macruby GCD bug?

[Alan Skipp]

I've been continuing with my efforts to implement Fibers using GCD and in the process I think I may have uncovered a Macruby bug - though perhaps it's a bug in my code? Is there anything fundamentally wrong with the code posted below? It consistently results in a EXC_BAD_ACCESS error.

Cheers,
Al

class Fiber
  def initialize &block
    @block = block
    
    @yield_sem = Dispatch::Semaphore.new(0)
    @resume_sem = Dispatch::Semaphore.new(0)
    
    @fiber_queue = Dispatch::Queue.new "fiber"
    @fiber_queue.async {@yield_sem.wait} # immediately suspend @fiber_queue
    
    # the following block will only run after '@yield_sem' is signalled – which happens when 'resume' is called
    @fiber_queue.async do 
      @block.call
      @resume_sem.signal # the block has finished - let the caller resume
    end
  end
  
  def resume
    @yield_sem.signal
    @resume_sem.wait # causes the GCD queue of the caller to suspend
  end
end

array = [1,2,3]
fiber = Fiber.new { array << 4 } # crash when fiber is resumed
fiber.resume
p array # we don't get this far