Interfacing with XPCOM

[John Reimer]

Hello Walter,

> John Reimer wrote:
> 
>> It would be nice if extern(C++) were still ported to D 1.0, but the
>> other alternative of enabling extern(System) in COM support (instead
>> of extern(Windows) ) will also work.
>> 
> Unfortunately, extern(C++), even if ported to D1, will not work for
> COM objects. COM objects, to be compatible with Windows, need to be
> the Windows calling convention.
> 


Er... Yes, actually my statement above was meant to emphasize the potential 
usefulness of extern(C++) for XPCOM support on Linux among many things.

That said, I'm guessing that even extern(C++) would work fine for COM support 
on windows if one directly declares the interface methods with extern(Windows) 
attribute.  Similar to COM, C++ XPCOM on win32 seems to do this as well: 
it applies stdcall to the XPCOM class (interface) methods.

In D (windows) it would look like so (assuming you have done away with the 
compilers internal detection of COM interfaces):

extern(C++) interface IUnknown:
{
     extern(Windows):
         int QueryInterface(nsIID* uuid, void **result);
         int AddRef();
         int Release();
}

I bet it would work fine and would be a good way to avoid the special-cased 
interfaces providing COM support in D.  Instead we've special-cased for C++, 
which is, at least, a more general case. ;-)

-JJR