Message queue for two cpp file

/* Unique IDs for Window messages to exchange between the worker and GUI thread. */
#define WM_YOUR_MESSAGE   ( WM_USER + 3 )

   /* Some data structure intended to store the message content. */
typedef struct
{
    int SomeData1;
    int SomeData2;
    int SomeDataN;
} MessageData;


volatile DWORD ThreadID_GUI;

void __cdecl ThreadProc(void* aArg) 
{
    MessageData* data;

    for (;; )
    {
        Sleep(500);

        /* Allocate memory for a new message data structure */
        data = (MessageData*)malloc(sizeof(*data));

        data->SomeData1 = 1234;
        data->SomeData2 = 4567;
        data->SomeDataN = 7894;

        PostThreadMessage(ThreadID_GUI, WM_YOUR_MESSAGE, 0, (LPARAM)data);
    }
}


/************* Main.c ********************/
#include<test.h>
int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
                     _In_opt_ HINSTANCE hPrevInstance,
                     _In_ LPWSTR    lpCmdLine,
                     _In_ int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    // TODO: Place code here.

    ThreadID_GUI = GetCurrentThreadId();

    /* Start some background thread */
    _beginthread(ThreadProc, 0, 0);
#ifdef reg
    // Initialize global strings
    LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
    LoadStringW(hInstance, IDC_TESTMESSAGEQUEUE, szWindowClass, MAX_LOADSTRING);
    MyRegisterClass(hInstance);

    // Perform application initialization:
    if (!InitInstance (hInstance, nCmdShow))
    {
        return FALSE;
    }

    HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_TESTMESSAGEQUEUE));
#endif
    MSG msg;

    // Main message loop:
    while (GetMessage(&msg, NULL, 0, 0))
    {
            /* STEP 3: React on the message sent from the foreign thread */
            if (msg.message == WM_YOUR_MESSAGE)
            {
                MessageData* tmp = (MessageData*)msg.lParam;

                    if (tmp->SomeData1 == 1234) {
                    printf("someData\n");
                }
                /* Free the data structure associated to the message */
                free(tmp);
            }
            TranslateMessage(&msg);
            DispatchMessage(&msg);
    }

    return (int) msg.wParam;
}