wglCreateContextAttribsARB crashes in debug mode, under x64 platform - c++

Question

i have encountered an issue trying to debug my 64 bit application under Visual Studio 2015. When i switch it to debug mode, it crashes during window creation. Which did not happen in 32 bit mode;
Here's redacted window initialization code:
int indexPF;
WNDCLASS WinClass;
WinClass.style = CS_OWNDC | CS_PARENTDC;
WinClass.lpfnWndProc = WndProc;
WinClass.cbClsExtra = 0;
WinClass.cbWndExtra = 0;
WinClass.hInstance = hInstance;
WinClass.hIcon = LoadIcon(NULL, IDC_ICON);
WinClass.hCursor = LoadCursor(NULL, IDC_ARROW);
WinClass.hbrBackground = (HBRUSH)GetStockObject(5);
WinClass.lpszMenuName = NULL;
WinClass.lpszClassName = "N2";
if (!RegisterClass(&WinClass))
{
...report error and terminate...
}
Logger::Inst() << " ~RegisterClass;" << endl;
//CREATE WINDOW
if (fullScreen)
{
if ((hwnd = CreateWindowEx(WS_EX_LEFT, "N2", "N2",
WS_POPUP,
0, 0, width, height,
NULL, NULL, hInstance, NULL)) == 0)
{
...report error and terminate...
}
}
else
{
if ((hwnd = CreateWindowEx(WS_EX_LEFT, "N2", "N2",
WS_OVERLAPPEDWINDOW,
0, 0, width, height,
NULL, NULL, hInstance, NULL)) == 0)
{
...report error and terminate...
}
}
Logger::Inst() << " ~CreateWindow;" << endl;
//PFD SETUP
PIXELFORMATDESCRIPTOR pfd =
{
sizeof(PIXELFORMATDESCRIPTOR),
1,
PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
PFD_TYPE_RGBA,
32,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
24,
8, 0, PFD_MAIN_PLANE, 0, 0, 0x00FF00FF, 0
};
//HDC
if ((hdc = GetDC(hwnd)) == NULL)
{
...report error and terminate...
}
Logger::Inst() << " ~GotHDC;" << endl;
//SET PIXEL FORMAT
indexPF = ChoosePixelFormat(hdc, &pfd);
if (!indexPF)
{
...report error and terminate...
}
if (!SetPixelFormat(hdc, indexPF, &pfd))
{
pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER | PFD_SWAP_EXCHANGE;
indexPF = ChoosePixelFormat(hdc, &pfd);
if (!SetPixelFormat(hdc, indexPF, &pfd))
{
...report error and terminate...
}
}
Logger::Inst() << " ~SetPFD;" << endl;
//TEMP CONTEXT TO ACQUIRE POINTER
HGLRC tempContext = wglCreateContext(hdc);
if (!tempContext) {
...report error and terminate...
}
if (!wglMakeCurrent(hdc, tempContext)) {
...report error and terminate...
}
int major, minor; glGetIntegerv(GL_MAJOR_VERSION, &major); glGetIntegerv(GL_MINOR_VERSION, &minor);
if (major < 4 || minor < 1) {
...report error and terminate...
}
const int attribs[] =
{
WGL_CONTEXT_MAJOR_VERSION_ARB, major,
WGL_CONTEXT_MINOR_VERSION_ARB, minor,
WGL_CONTEXT_PROFILE_MASK_ARB, WGL_CONTEXT_CORE_PROFILE_BIT_ARB,
0, 0
};
PFNWGLCREATEBUFFERREGIONARBPROC wglCreateContextAttribsARB = (PFNWGLCREATEBUFFERREGIONARBPROC)wglGetProcAddress("wglCreateContextAttribsARB");
if (!wglCreateContextAttribsARB) {
...report error and terminate...
}
**!!! CRASH HERE !!!**
if (!(hglrc = (HGLRC)wglCreateContextAttribsARB(hdc, 0, (UINT)attribs))) {
...report error and terminate...
}
Debugger shows it happens exactly at wglCreateContextAttribsARB(nvoglv64.dll!0000000074ccbdfa). That is a complete mystery to me. My only clue is that after switching to x64 it requires attributes passed as "UINT" instead of "const int*", i don't get that part, not even sure how conversion between each other supposed to work, seems fishy. Ideas?

Answer 1

You've got a typo: the type for wglCreateContextAttribsARB is wrong. It should be PFNWGLCREATECONTEXTATTRIBSARBPROC.
The reason it worked when you were targeting 32-bit is because the signature of the two is essentially the same in 32-bit:
wglCreateContextAttribsARB:
typedef HGLRC (WINAPI * PFNWGLCREATECONTEXTATTRIBSARBPROC) (HDC hDC, HGLRC hShareContext, const int *attribList);
wglCreateBufferRegionARB:
typedef HANDLE (WINAPI * PFNWGLCREATEBUFFERREGIONARBPROC) (HDC hDC, int iLayerPlane, UINT uType);
The second and third parameters to wglCreateContextAttribsARB are pointers (an HGLRC is a handle, which is just a pointer) and the second and third parameters to wglCreateBufferRegionARB are integers. In 32-bit, pointers are 32-bit in size, so the signatures are essentially the same.
In 64-bit, pointers are 64-bit in size, but integers are still 32-bit (assuming you're using MSVC) so those two pointers you were passing in were being truncated.