typed vtable

[Jarrett Billingsley]

On Tue, Nov 18, 2008 at 9:17 AM, Michel Fortin
<michel.fortin at michelf.com> wrote:
> On 2008-11-17 13:56:55 -0500, Harry Vennik <htvennik at zonnet.nl> said:
>
>> Hi,
>>
>> One of the things D claims is that it eliminates the need for IDL. And
>> yeah, it does a lot in that direction, but I found something that's missing
>> while trying to actually implement some sense of RPC...
>>
>> To get a good view of an interface that can be used to construct the
>> necessary stub code, you need to have a typed vtable. And D almost provides
>> it... You can get the untyped vtable, you can get a typed list of virtual
>> function overloads by name, and you can get the names of all interface
>> members... So you can get all what's needed, except that there is no way to
>> know the vtable index of a member function!!!
>>
>> My proposal to fix this is to allow an expression like:
>>
>> __traits(getVirtualFunctions, T)           // no second argument!
>>
>> where T is an interface or class type (or an expression of such a type).
>> Such an expression should then return all virtual member functions in vtable
>> order, thus making it possible to relate the function itself to its vtable
>> index.
>
> Personally, I had to work around the same problem in the D/Objective-C
> bridge and thus I could probably simplify a few things by having this,
> except that what I need in my case is always the vtable index of a
> particular function. I guess it could be implemented from the above __traits
> syntax, but I'd wish for a simpler solution to my problem, such as:
>
>        __traits(getVTableIndex, T.foo);
>
> along with a way to check if a function is virtual, possibly by checking
> they're not final:
>
>        static if (is(T.foo == final)) ...;
>
> This way I could build a pointer template-struct to a virtual member
> function (without knowing the target object in advance as with delegates).

A pointer template-struct to a virtual member function without knowing
the target object in advance?

Something like this: http://codepad.org/SXIP2jBL ?