Crash on boot when proxying D3D12.dll

[techiew]

Not sure why this happens. I've noticed some weird behavior with D3D12 though. Here is an extremely simple example D3D12 proxy DLL which illustrates said weird behavior:

#include <Windows.h>
 
FARPROC p[3];
void* pp = &p[0];
 
extern "C" {
    void RunAsm();
    HMODULE originalDll = 0;
    FARPROC funcAddr = NULL;
    
    // This works. Using individual FARPROC variables also works.
    void Proxy_D3D12CreateDevice() { funcAddr = *((FARPROC*)pp + 0); RunAsm(); }
    void Proxy_D3D12GetDebugInterface() { funcAddr = *((FARPROC*)pp + 1); RunAsm(); }
    void Proxy_D3D12SerializeRootSignature() { funcAddr = *((FARPROC*)pp + 2); RunAsm(); }
 
    // Declaring the functions like this does not work and causes an instant crash, seems to be unique to proxying D3D12...
    // No popups when crashing, crash cause is an access violation when checking with debugger
    // Game in question only imports these 3 functions, proxying everything does not make a difference.
    void Proxy_D3D12CreateDevice() { funcAddr = p[0]; RunAsm(); }
    void Proxy_D3D12GetDebugInterface() { funcAddr = p[1]; RunAsm(); }
    void Proxy_D3D12SerializeRootSignature() { funcAddr = p[2]; RunAsm(); }
}
 
BOOL APIENTRY DllMain(HMODULE hModule, DWORD ul_reason_for_call, LPVOID lpReserved)
{
    if (ul_reason_for_call == DLL_PROCESS_ATTACH)
    {
        originalDll = LoadLibraryEx(L".\\d3d12.dll", NULL, LOAD_LIBRARY_SEARCH_SYSTEM32);
        p[0] = GetProcAddress(originalDll, "D3D12CreateDevice");
        p[1] = GetProcAddress(originalDll, "D3D12GetDebugInterface");
        p[2] = GetProcAddress(originalDll, "D3D12SerializeRootSignature");
    }
    return TRUE;
}

This weird behavior may or may not be related to the crashing.

[techiew]

Added a workaround using the newly discovered macro method. Using this method means callbacks when proxying D3D12.dll do not work.