COM ABI Infodump

• Returned C struct FFI
  • The oracle always tells the truth, even when it is wrong: COM method calls with a user-defined type as a return value (The Old New Thing)
  • midl /cstruct_out switch (microsoft.com)
  • https://github.com/microsoft/DirectX-Graphics-Samples/issues/622#issuecomment-850898100
  • See #[fixme]s in winapi
• Misc. COM ABI
  • winapi-rs#523: Overloaded methods in COM have wrong vtable order
  • Interface Definition Language (IDL) ([C706] section 4.)
    • "[C706] is the primary specification for DCE/RPC 1.1."
    • "DCE/RPC is an implementation of the Remote Procedure Call technology developed by the Open Group as part of the Distributed Computing Environment. DCE/RPC is most commonly used to interact with Windows network services."
• XFG
  • How the MSVC Compiler Generates XFG Function Prototype Hashes

C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\um\d3d12.h

// line 45
#ifndef DECLSPEC_XFGVIRT
#if defined(_CONTROL_FLOW_GUARD_XFG)
#define DECLSPEC_XFGVIRT(base, func) __declspec(xfg_virtual(base, func))
#else
#define DECLSPEC_XFGVIRT(base, func)
#endif
#endif

// line 4380
        DECLSPEC_XFGVIRT(ID3D12Heap, GetDesc)
        D3D12_HEAP_DESC *( STDMETHODCALLTYPE *GetDesc )( 
            ID3D12Heap * This,
            D3D12_HEAP_DESC * RetVal);

// line 4426
#define ID3D12Heap_GetDesc(This,RetVal)	\
    ( (This)->lpVtbl -> GetDesc(This,RetVal) ) 

C:\Program Files (x86)\Windows Kits\10\Include\10.0.17134.0\um\d3d12.h

// line 3870
        D3D12_HEAP_DESC ( STDMETHODCALLTYPE *GetDesc )( 
            ID3D12Heap * This);

// line 3914
#define ID3D12Heap_GetDesc(This)	\
    ( (This)->lpVtbl -> GetDesc(This) )