Re: [Vala] async method and delegate

[Nor Jaidi Tuah <norjaidi tuah ubd edu bn>]

On Mon, 2011-06-20 at 17:37 -0700, Jim Nelson wrote:
> With async, the delegate *is* copied, you just don't see it in the
> Vala code.  With an async method, when the thread of execution yields,
> the state of the function at that point is stored (copied or ref'd) in
> a context structure.  When the thread of execution resumes later, the
> state is pulled back out and the function resumes.

Has that any bearing on the bug I mentioned in
my earlier email?
        
>         I also get segmentation fault trying to pass
>         a closure accessing local variables. The closure
>         works if it doesn't access local vars.
>         
>         e.g.,
>           var f = etc;
>           async_func ( () => { fn (f);} );
>         
>         will crash trying to access f. Apparently
>         the closure isn't properly constructed.


In the following example, the closure bug doesn't
lead to a crash. But it is apparent in the output.

Expected output:
        hello
        hello
        hello
        bye
        
Actual output:
        hello
        hello
        (null)
        bye

The code:

        public class Foo : Object {
            public delegate void DelegateType ();
        
            async void f3 (DelegateType d) {
                d ();
            }
        
            async void f2 (DelegateType d) {
                d ();
                yield f3 (d);
                d ();      // <----- x local to f1 has gone
                stdout.printf ("bye\n");
            }
        
            void f1 () {
                var x = "hello";
                f2 (() => {stdout.printf ("%s\n", x);});
            }
        
            public static int main(string[] args) {
                var foo = new Foo ();
                foo.f1 ();
                new MainLoop (null, false).run ();
                return 0;
            }
        }

hand
Nor Jaidi Tuah