002_n.rb

q_default = Dispatch::Queue.concurrent
q_sum = Dispatch::Queue.new("com.example.sum")

sum = 0
q_default.apply(10) do |i|
  puts("i: #{i}")
  sleep(1)
  x = i + 1
  q_sum.dispatch(false, &lambda {
    puts("x: #{x}")
    sum += x
  })
end
q_sum.dispatch(true) do
  puts("sum: #{sum}")
end

gistfile1.txt

run on gdb

(gdb) r 002_n.rb
Starting program: /usr/local/bin/macruby 002_n.rb
i: 0i: 1

i: 2
x: 2
x: 1
i: 3
i: 4x: 3

i: 5
x: 4
i: 6
x: 5
i: 7
x: 6
i: 8
x: 7
x: 8
i: 9
x: 9
x: 10
sum: 55

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: KERN_INVALID_ADDRESS at address: 0x0000001000000017
rb_vm_keep_vars (uses=<value temporarily unavailable, due to optimizations>, lvars_size=3) at vm.cpp:2622
2622			    locals_to_replace = binding->locals;

backtrace:
#0  rb_vm_keep_vars (uses=<value temporarily unavailable, due to optimizations>, lvars_size=3) at vm.cpp:2622
#1  0x0000000101110389 in ?? ()
#2  0x000000010003f939 in ruby_run_node (n=0x4) at eval.c:198
#3  0x0000000100000dd8 in main (argc=2, argv=0x100f1c330, envp=<value temporarily unavailable, due to optimizations>) at main.cpp:42


#0  rb_vm_keep_vars (uses=<value temporarily unavailable, due to optimizations>, lvars_size=3) at vm.cpp:2622
2622			    locals_to_replace = binding->locals;
Current language:  auto; currently c++
(gdb) l
2617	
2618			    locals_to_replace = block->locals;
2619			}
2620			else { // VM_LVAR_USE_TYPE_BINDING
2621			    rb_vm_binding_t *binding = (rb_vm_binding_t *)use;
2622			    locals_to_replace = binding->locals;
2623			}
2624	
2625			for (rb_vm_local_t *l = locals_to_replace; l != NULL; l = l->next) {
2626			    for (int lvar_index = 0; lvar_index < lvars_size; ++lvar_index) {

#1  0x0000000101110389 in ?? ()
(gdb) l
2627				if (l->value == locals[lvar_index].stack_address) {
2628				    GC_WB(&l->value, locals[lvar_index].new_address);
2629				    break;
2630				}
2631			    }
2632			}
2633	
2634			// indicate to the GC that we do not have a reference here anymore
2635			rb_gc_assign_weak_ref(NULL, &current->uses[use_index]);
2636		    }

#2  0x000000010003f939 in ruby_run_node (n=0x4) at eval.c:198
198	    rb_vm_run(RSTRING_PTR(rb_progname), (NODE *)n, NULL, false);
Current language:  auto; currently c
(gdb) l
193		return EXIT_FAILURE;
194	    }
195	    else if (FIXNUM_P(n)) {
196		return FIX2INT(n);
197	    }
198	    rb_vm_run(RSTRING_PTR(rb_progname), (NODE *)n, NULL, false);
199	    return ruby_cleanup(0);
200	}
201	
202	/*

#3  0x0000000100000dd8 in main (argc=2, argv=0x100f1c330, envp=<value temporarily unavailable, due to optimizations>) at main.cpp:42
42		    rb_exit(ruby_run_node(node));
Current language:  auto; currently c++
(gdb) l
37		if (ruby_aot_compile) {
38		    rb_vm_aot_compile((NODE *)node);
39		    rb_exit(0);
40		}
41		else {	
42		    rb_exit(ruby_run_node(node));
43		}
44	    }
45	    catch (...) {
46		rb_vm_print_current_exception();