Virtual destructor for CustomVertex in DIRECTX9 - c++

Question

This is my first question on stackoverflow, so forgive me if my question is dumb.
I am trying to simply render a triangle in DirectX9 in Visual Studio 2012 following this: www.directxtutorial.com/Lesson.aspx?lessonid=9-4-4.
When I create a CUSTOMVERTEX class with a non-virtual destructor it renders the triangle without any problem. Whereas if I make the destructor virtual the triangle is not rendered.
Here is the code with the virtual destructor:
// include the basic windows header files and the Direct3D header file
#include <windows.h>
#include <windowsx.h>
#include <d3d9.h>
// define the screen resolution
#define SCREEN_WIDTH 800
#define SCREEN_HEIGHT 600
// include the Direct3D Library file
#pragma comment (lib, "d3d9.lib")
#define CUSTOMFVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE)
// global declarations
LPDIRECT3D9 d3d; // the pointer to our Direct3D interface
LPDIRECT3DDEVICE9 d3ddev; // the pointer to the device class
LPDIRECT3DVERTEXBUFFER9 v_buffer = NULL; // the pointer to the vertex buffer
// function prototypes
void initD3D(HWND hWnd); // sets up and initializes Direct3D
void render_frame(void); // renders a single frame
void cleanD3D(void); // closes Direct3D and releases memory
void init_graphics(void); // 3D declarations
// the WindowProc function prototype
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
//************CUSTOMVERTEX CLASS**********/
class CUSTOMVERTEX {
public:
CUSTOMVERTEX( float _X, float _Y, float _Z, float _RHW, DWORD _COLOR )
: X(_X), Y(_Y), Z(_Z), RHW(_RHW), COLOR(_COLOR)
{}
virtual ~CUSTOMVERTEX(){
OutputDebugString("Destructed!!!\n");
}
float X, Y, Z, RHW;
DWORD COLOR;
};
// the entry point for any Windows program
int WINAPI WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
HWND hWnd;
WNDCLASSEX wc;
ZeroMemory(&wc, sizeof(WNDCLASSEX));
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = WindowProc;
wc.hInstance = hInstance;
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.lpszClassName = "WindowClass";
RegisterClassEx(&wc);
hWnd = CreateWindowEx(NULL,
"WindowClass",
"Our Direct3D Program",
WS_OVERLAPPEDWINDOW,
0, 0,
SCREEN_WIDTH, SCREEN_HEIGHT,
NULL,
NULL,
hInstance,
NULL);
ShowWindow(hWnd, nCmdShow);
// set up and initialize Direct3D
initD3D(hWnd);
// enter the main loop:
MSG msg;
while(TRUE)
{
while(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
if(msg.message == WM_QUIT)
break;
render_frame();
}
// clean up DirectX and COM
cleanD3D();
return msg.wParam;
}
// this is the main message handler for the program
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch(message)
{
case WM_DESTROY:
{
PostQuitMessage(0);
return 0;
} break;
}
return DefWindowProc (hWnd, message, wParam, lParam);
}
// this function initializes and prepares Direct3D for use
void initD3D(HWND hWnd)
{
d3d = Direct3DCreate9(D3D_SDK_VERSION);
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory(&d3dpp, sizeof(d3dpp));
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.hDeviceWindow = hWnd;
d3dpp.BackBufferFormat = D3DFMT_X8R8G8B8;
d3dpp.BackBufferWidth = SCREEN_WIDTH;
d3dpp.BackBufferHeight = SCREEN_HEIGHT;
// create a device class using this information and the info from the d3dpp struct
d3d->CreateDevice(D3DADAPTER_DEFAULT,
D3DDEVTYPE_HAL,
hWnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&d3dpp,
&d3ddev);
init_graphics(); // call the function to initialize the triangle
}
// this is the function used to render a single frame
void render_frame(void)
{
d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 0), 1.0f, 0);
d3ddev->BeginScene();
// select which vertex format we are using
d3ddev->SetFVF(CUSTOMFVF);
// select the vertex buffer to display
d3ddev->SetStreamSource(0, v_buffer, 0, sizeof(CUSTOMVERTEX));
// copy the vertex buffer to the back buffer
d3ddev->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 1);
d3ddev->EndScene();
d3ddev->Present(NULL, NULL, NULL, NULL);
}
// this is the function that cleans up Direct3D and COM
void cleanD3D(void)
{
v_buffer->Release(); // close and release the vertex buffer
d3ddev->Release(); // close and release the 3D device
d3d->Release(); // close and release Direct3D
}
// this is the function that puts the 3D models into video RAM
void init_graphics(void)
{
// create the vertices using the CUSTOMVERTEX class
CUSTOMVERTEX vertices[] =
{
CUSTOMVERTEX(400.0f, 62.5f, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 0, 255)),
CUSTOMVERTEX(650.0f, 500.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 255, 0)),
CUSTOMVERTEX(150.0f, 500.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 0, 0)),
};
// create a vertex buffer interface called v_buffer
d3ddev->CreateVertexBuffer(3*sizeof(CUSTOMVERTEX),
0,
CUSTOMFVF,
D3DPOOL_MANAGED,
&v_buffer,
NULL);
VOID* pVoid; // a void pointer
// lock v_buffer and load the vertices into it
v_buffer->Lock(0, 0, (void**)&pVoid, 0);
memcpy(pVoid, vertices, sizeof(vertices));
v_buffer->Unlock();
}
Rendered triangle:Rendered Triangle
The code without virtual destructor:
// include the basic windows header files and the Direct3D header file
#include <windows.h>
#include <windowsx.h>
#include <d3d9.h>
// define the screen resolution
#define SCREEN_WIDTH 800
#define SCREEN_HEIGHT 600
// include the Direct3D Library file
#pragma comment (lib, "d3d9.lib")
#define CUSTOMFVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE)
// global declarations
LPDIRECT3D9 d3d; // the pointer to our Direct3D interface
LPDIRECT3DDEVICE9 d3ddev; // the pointer to the device class
LPDIRECT3DVERTEXBUFFER9 v_buffer = NULL; // the pointer to the vertex buffer
// function prototypes
void initD3D(HWND hWnd); // sets up and initializes Direct3D
void render_frame(void); // renders a single frame
void cleanD3D(void); // closes Direct3D and releases memory
void init_graphics(void); // 3D declarations
// the WindowProc function prototype
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
//************CUSTOMVERTEX CLASS**********/
class CUSTOMVERTEX {
public:
CUSTOMVERTEX( float _X, float _Y, float _Z, float _RHW, DWORD _COLOR )
: X(_X), Y(_Y), Z(_Z), RHW(_RHW), COLOR(_COLOR)
{}
~CUSTOMVERTEX(){
OutputDebugString("Destructed!!!\n");
}
float X, Y, Z, RHW;
DWORD COLOR;
};
// the entry point for any Windows program
int WINAPI WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
HWND hWnd;
WNDCLASSEX wc;
ZeroMemory(&wc, sizeof(WNDCLASSEX));
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = WindowProc;
wc.hInstance = hInstance;
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.lpszClassName = "WindowClass";
RegisterClassEx(&wc);
hWnd = CreateWindowEx(NULL,
"WindowClass",
"Our Direct3D Program",
WS_OVERLAPPEDWINDOW,
0, 0,
SCREEN_WIDTH, SCREEN_HEIGHT,
NULL,
NULL,
hInstance,
NULL);
ShowWindow(hWnd, nCmdShow);
// set up and initialize Direct3D
initD3D(hWnd);
// enter the main loop:
MSG msg;
while(TRUE)
{
while(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
if(msg.message == WM_QUIT)
break;
render_frame();
}
// clean up DirectX and COM
cleanD3D();
return msg.wParam;
}
// this is the main message handler for the program
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch(message)
{
case WM_DESTROY:
{
PostQuitMessage(0);
return 0;
} break;
}
return DefWindowProc (hWnd, message, wParam, lParam);
}
// this function initializes and prepares Direct3D for use
void initD3D(HWND hWnd)
{
d3d = Direct3DCreate9(D3D_SDK_VERSION);
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory(&d3dpp, sizeof(d3dpp));
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.hDeviceWindow = hWnd;
d3dpp.BackBufferFormat = D3DFMT_X8R8G8B8;
d3dpp.BackBufferWidth = SCREEN_WIDTH;
d3dpp.BackBufferHeight = SCREEN_HEIGHT;
// create a device class using this information and the info from the d3dpp struct
d3d->CreateDevice(D3DADAPTER_DEFAULT,
D3DDEVTYPE_HAL,
hWnd,
D3DCREATE_SOFTWARE_VERTEXPROCESSING,
&d3dpp,
&d3ddev);
init_graphics(); // call the function to initialize the triangle
}
// this is the function used to render a single frame
void render_frame(void)
{
d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 0), 1.0f, 0);
d3ddev->BeginScene();
// select which vertex format we are using
d3ddev->SetFVF(CUSTOMFVF);
// select the vertex buffer to display
d3ddev->SetStreamSource(0, v_buffer, 0, sizeof(CUSTOMVERTEX));
// copy the vertex buffer to the back buffer
d3ddev->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 1);
d3ddev->EndScene();
d3ddev->Present(NULL, NULL, NULL, NULL);
}
// this is the function that cleans up Direct3D and COM
void cleanD3D(void)
{
v_buffer->Release(); // close and release the vertex buffer
d3ddev->Release(); // close and release the 3D device
d3d->Release(); // close and release Direct3D
}
// this is the function that puts the 3D models into video RAM
void init_graphics(void)
{
// create the vertices using the CUSTOMVERTEX class
CUSTOMVERTEX vertices[] =
{
CUSTOMVERTEX(400.0f, 62.5f, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 0, 255)),
CUSTOMVERTEX(650.0f, 500.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(0, 255, 0)),
CUSTOMVERTEX(150.0f, 500.0f, 0.5f, 1.0f, D3DCOLOR_XRGB(255, 0, 0)),
};
// create a vertex buffer interface called v_buffer
d3ddev->CreateVertexBuffer(3*sizeof(CUSTOMVERTEX),
0,
CUSTOMFVF,
D3DPOOL_MANAGED,
&v_buffer,
NULL);
VOID* pVoid; // a void pointer
// lock v_buffer and load the vertices into it
v_buffer->Lock(0, 0, (void**)&pVoid, 0);
memcpy(pVoid, vertices, sizeof(vertices));
v_buffer->Unlock();
}
Rendered without any triangle: without any triangle
Can anyone please explain to me why this is happening?

Answer 1

In short: Adding the virtual changes the memory layout of the structure, meaning your data is no longer in the correct place for the Vertex Declaration you provided:
struct CUSTOMVERTEX {
CUSTOMVERTEX( float _X, float _Y, float _Z, float _RHW, DWORD _COLOR )
: X(_X), Y(_Y), Z(_Z), RHW(_RHW), COLOR(_COLOR)
{}
float X, Y, Z, RHW;
DWORD COLOR;
};
The size of this structure is 20 bytes.
class CUSTOMVERTEX {
public:
CUSTOMVERTEX( float _X, float _Y, float _Z, float _RHW, DWORD _COLOR )
: X(_X), Y(_Y), Z(_Z), RHW(_RHW), COLOR(_COLOR)
{}
virtual ~CUSTOMVERTEX(){
OutputDebugString("Destructed!!!\n");
}
float X, Y, Z, RHW;
DWORD COLOR;
};
The size of this structure is 24 bytes for x86 (Win32) and 32 bytes for x64 native. This is because there's a pointer to the vtable added at the start of the structure (and on x64 the additional padding pushes it out a little more than 8 bytes).
Furthermore, since you are using the type through a Direct3D Vertex Buffer, it's never going to have it's constructor or destructor executed. It's just allocated from the heap as a "plain old data type". The only time constructors or destructors are invoked for heap-allocated memory is via new, new [], delete, and/or delete []. Internally Direct3D Vertex Buffer is doing something more akin to malloc.
Your constructor is being invoked by the C++ compiler when you create the initialized array vertices, and the destructor is invoked when vertices goes out of scope.
In other words: This doesn't do what you think it does. Don't use virtual in your vertex data structures.
Note that you should consider making using of a smart pointer like Microsoft::WRL::ComPtr for managing the lifetime of your Direct3D COM objects. This takes advantage of the C++ scoping rules for ctors/destructors to properly call Release automatically. Of course, you should also not be spending a lot of time learning legacy Direc3D 9 either.