Direct2D COM calls returning 64-bit structs and C++Builder 2010 - com

Question

I'm trying to get the size of a Direct2D Bitmap and getting an immediate crash.
// props and target etc all set up beforehand.
CComPtr<ID2D1Bitmap> &b;
target->CreateBitmap(D2D1::SizeU(1024,1024), frame.p_data, 1024* 4, &props, &b));
D2D_SIZE_U sz = b->GetPixelSize(); // Crashes here.
All other operations using the bitmap (including drawing it) work correctly. It's just returning the size that seems to be the problem.
Based on a articles like this by Rudy V, my suspicion is that it's some incompatibility with C++Builder 2010 and how COM functions return 64-bit structures. http://rvelthuis.de/articles/articles-convert.html
The Delphi declaration of GetPixelSize looks like this: (from D2D1.pas)
// Returns the size of the bitmap in resolution dependent units, (pixels).
procedure GetPixelSize(out pixelSize: TD2D1SizeU); stdcall;
... and in D2D1.h it's
//
// Returns the size of the bitmap in resolution dependent units, (pixels).
//
STDMETHOD_(D2D1_SIZE_U, GetPixelSize)(
) CONST PURE;
Can I fix this without rewriting the D2D headers?
All suggestions welcome - except upgrading from C++Builder 2010 which is more of a task than I'm ready for at the moment.

Answer 1

„getInfo“ is a function derived from Delphi code, which can work around.
void getInfo(void* itfc, void* info, int vmtofs)
{
asm {
push info // pass pointer to return result
mov eax,itfc // eax poionts to interface
push eax // pass pointer to interface
mov eax,[eax] // eax points to VMT
add eax,vmtofs // eax points rto address of virtual function
call dword ptr [eax] // call function
}
}
Disassembly of code generated by CBuilder, which results in a crash:
Graphics.cpp.162: size = bmp->GetSize();
00401C10 8B4508 mov eax,[ebp+$08]
00401C13 FF7004 push dword ptr [eax+$04]
00401C16 8D55DC lea edx,[ebp-$24]
00401C19 52 push edx
00401C1A 8B4D08 mov ecx,[ebp+$08]
00401C1D 8B4104 mov eax,[ecx+$04]
00401C20 8B10 mov edx,[eax]
00401C22 FF5210 call dword ptr [edx+$10]
00401C25 8B4DDC mov ecx,[ebp-$24]
00401C28 894DF8 mov [ebp-$08],ecx
00401C2B 8B4DE0 mov ecx,[ebp-$20]
00401C2E 894DFC mov [ebp-$04],ecx
„bmp“ is declared as
ID2D1Bitmap* bmp;
Code to call „getInfo“:
D2D1_SIZE_F size;
getInfo(bmp,&pf,0x10);
You get 0x10 (vmtofs) from disassembly line „call dword ptr [edx+$10]“
You can call „GetPixelSize“, „GetPixelFormat“ and others by calling „getInfo“
D2D1_SIZE_U ps;// = bmp->GetPixelSize();
getInfo(bmp,&ps,0x14);
D2D1_PIXEL_FORMAT pf;// = bmp->GetPixelFormat();
getInfo(bmp,&pf,0x18);
„getInfo“ works with methods „STDMETHOD_ ... CONST PURE;“, which return a result.
STDMETHOD_(D2D1_SIZE_F, GetSize)(
) CONST PURE;
For this method CBuilder generates malfunctional code.
In case of
STDMETHOD_(void, GetDpi)(
__out FLOAT *dpiX,
__out FLOAT *dpiY
) CONST PURE;
the CBuilder code works fine, „getDpi“ results void.