Hi Matt,

I'm reviving an old thread...

Matthew wrote:

6. Allow interface_cast_addref<>() to accept interface_ptr arguments
instead of just bare pointers.
This would allow more readable code.


This is something that I actually achieved a couple of years ago, and never
got round to releasing. (I'd planned to discuss this as part of a series on
smart pointers for the Smart Pointers column, but that dragged its feet, and
...)

As it stands, it supports code such as the following:

 {
  LPSTREAM  pstm;
  HRESULT   hr = ::CreateStreamOnHGlobal(NULL, true, &pstm);

  IStream_ptr  p(pstm, false);

  IUnknown_ptr punk = comstl2::interface_cast<IUnknown>(p);

  IMalloc_ptr  pstm2 = comstl2::interface_cast<IMalloc>(punk);
 }

I think you'll agree that this is rather good stuff. I will make it a
priority to have this in 1.9.1.

Has this actually been done?

I'm having problems using this.
Here's my working code:

//... stlsoft::ref_ptr<IGraphBuilder> pGraph; stlsoft::ref_ptr<IMediaControl> pMediaControl; //... if(SUCCEEDED(co_create_instance(CLSID_FilterGraph, pGraph))) { pMediaControl.set(interface_cast_addref<IMediaControl*>(pGraph.get()), false); //...

When I remove the .get() the whole thing blows up:

pMediaControl.set(interface_cast_addref<IMediaControl*>(pGraph), false);

The compilation errors are really weird:

--------------------Configuration: ConsoleApp - Win32 Debug-------------------- Compiling... SequenceProcessor.cpp h:\adish\dev\stlsoft\include\comstl\conversion\interface_cast.hpp(351) : error C2784: 'I *__cdecl stlsoft::comstl_project::simple_interface_cast(I *)' : could not deduce template argument for ' *' from 'class stlsoft::ref_ptr<struct IGraphBuilder,st ruct IGraphBuilder,struct IGraphBuilder>' h:\adish\dev\stlsoft\include\comstl\conversion\interface_cast.hpp(566) : see reference to function template instantiation '__thiscall stlsoft::comstl_project::interface_cast_base<struct IMediaControl *,struct stlsoft::comstl_project::addref_ release<struct IMediaControl *>,struct stlsoft::comstl_project::ignore_interface_cast_exception>::stlsoft::comstl_project::interface_cast_base<struct IMediaControl *,struct stlsoft::comstl_project::addref_release<struct IMediaControl *>,struct stlso ft::comstl_project::ignore_interface_cast_exception>(class stlsoft::ref_ptr<struct IGraphBuilder,struct IGraphBuilder,struct IGraphBuilder> &,enum stlsoft::comstl_project::interface_cast_base<struct IMediaControl *,struct stlsoft::comstl_project::ad dref_release<struct IMediaControl *>,struct stlsoft::comstl_project::ignore_interface_cast_exception>::NullThrowPermission)' being compiled h:\adish\dev\stlsoft\include\comstl\conversion\interface_cast.hpp(353) : fatal error C1903: unable to recover from previous error(s); stopping compilation h:\adish\dev\stlsoft\include\comstl\conversion\interface_cast.hpp(566) : see reference to function template instantiation '__thiscall stlsoft::comstl_project::interface_cast_base<struct IMediaControl *,struct stlsoft::comstl_project::addref_ release<struct IMediaControl *>,struct stlsoft::comstl_project::ignore_interface_cast_exception>::stlsoft::comstl_project::interface_cast_base<struct IMediaControl *,struct stlsoft::comstl_project::addref_release<struct IMediaControl *>,struct stlso ft::comstl_project::ignore_interface_cast_exception>(class stlsoft::ref_ptr<struct IGraphBuilder,struct IGraphBuilder,struct IGraphBuilder> &,enum stlsoft::comstl_project::interface_cast_base<struct IMediaControl *,struct stlsoft::comstl_project::ad dref_release<struct IMediaControl *>,struct stlsoft::comstl_project::ignore_interface_cast_exception>::NullThrowPermission)' being compiled Error executing cl.exe.

I suspect it has something to do with MSVC6.
Any thought?

Thanks,
Adi