645409 - ANI: nativegen should emit synthetic C++ classes AS3 interfaces, if possible

Status: RESOLVED FIXED

(Tamarin Graveyard :: Virtual Machine, defect)

Description

[Steven Johnson]

the one hole in synthetic classes are AS3 Interfaces, which reduce to ScriptObject. We should try to emit wrappers for these, too, if possible.

Comment 1

[Steven Johnson]

Attachment: Patch

Generate synthetic C++ classes for interfaces; these will be named with the suffix "Interface" (so AS3 "IFoo" -> C++ "IFooInterface"). 

Note that you can't construct interfaces (duh)... you can, however, obtain them in a couple of ways:

(1) every C++ instance class that implements an interfaces gets cheap methods to cast to the interfaces it implements, e.g.,

    interface IBar { ... }
    class Foo implements IBar { ... }

the C++ will have wrappers like

    GCRef<IBarInterface> FooObject::as_IBarInterface(); // never returns NULL


(2) the ClassManifest provides "Class" objects for each interface; these are really just convenient placeholders to put isType/asType/coerceToType methods. e.g., for the above,

    GCRef<IBarInterface> i = builtinClasses()->get_IBarClass()->coerceToType(someObj);

Comment 2

[Steven Johnson]

This doesn't make a big difference in the avmshell codebase, but in Flash, it adds desired typesafety (where we currently have to declare things "ScriptObject", and it also paves the way for bug 634638 to be implemented more robustly (since we can implement callin wrappers for interface methods while we're here).

Comment 3

[Steven Johnson]

Attachment: Patch v2

Minor modifications to pacify GCC 4.4+

Comment 4

[Jeff Mott]

Will this help make it possible to version interfaces? I'd dearly love to add a method to IEventDispatcher without breaking the world.

Comment 5

[Steven Johnson]

Hmm... offhand, no, I don't think it would make that easier. The best approach would probably to make an IEventDispatcher2 that extends IEventDispatcher.

Comment 6

[Steven Johnson]

pushed to TR in advance of review: 6489:8b8081a5bf83