Interfacing with XPCOM

[Sergey Gromov]

Tue, 02 Dec 2008 22:32:33 -0800, Walter Bright wrote:

> John Reimer wrote:
>> Is there a ClassInfo flag indicating no-gc-collection for extern(C++) 
>> interfaces too?
> 
> No. The COM object is special because part of its interface is to do its 
> own memory management, that isn't true in general for C++ interfaces.

But what's the typical use case for extern(C++) objects ?  I think it's
something like this:

  extern(C++) class CppInterfaceClass { ... }

  extern(C++) CppInterfaceClass create()
  {
    return new CppInterfaceClass(...);
  }

  extern(C++) void destroy(CppInterfaceClass obj)
  {
    delete obj;
  }

Here, there are no references left in D code to the created interface
object and GC is free to collect it even though it's still being used
from within C++ code.  I'll have to manage a list of created interface
object simply to keep them alive, getting another multi-threading
headache, or add them as GC roots.  I think it's better to assume manual
memory management for extern(C++) objects.