C / C++ / MFC

__declspec(dllexport) void public_func_taking_callback(callback_t evHnd)
{
 //   evHnd(333);//value just for testing // this was causing your problem
    callback_t = evHnd; // save the callback address for funcA. //this line doesn't compile
}

typedef void (__stdcall* callback_t) (unsigned int halfbeast);
static callback_t s_user_function = nullptr; // variable used to store the user function address

extern "C" __declspec(dllexport) void funcA(const unsigned long long a, const unsigned long long b);
//following function should be the callback, triggering an assigned function in the main application
extern "C"
{
    __declspec(dllexport) void public_func_taking_callback(callback_t evHnd)
    {
        s_user_function = evHnd; // store the passed user function address
    }
}


void funcA(
    const unsigned long long a,
    const unsigned long long b)
{
    //some code here... do things with a and b
   if(a>10 && s_user_function != nullptr)                       //trigger the event in the main application
       s_user_function(333); // call the user function
}

CPallini wrote:

a bit confused

static HANDLE gDoneEvent;
static HANDLE hTimer = NULL;
static HANDLE hTimerQueue = NULL;
int arg = 123; //will be passed to callback of timer


VOID CALLBACK TimerRoutine(PVOID lpParam, BOOLEAN TimerOrWaitFired)
{
    if (lpParam == NULL)
    {
        //do some error handling her
        return;
    }
    else
    {
        if(s_user_function!=nullptr)
            s_user_function(12);
    }
    //SetEvent(gDoneEvent);   //for periodic calls, don't set gDoneEvent
}

char timer_init(void)
{   
    // Use an event object to track the TimerRoutine execution
    gDoneEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
    if (NULL == gDoneEvent)
    {
        return 1;
    }
    // Create the timer queue.
    hTimerQueue = CreateTimerQueue();
    if (NULL == hTimerQueue)
    {
        return 2;
    }
    CreateTimerQueueTimer(&hTimer, hTimerQueue, (WAITORTIMERCALLBACK)TimerRoutine, &arg, 3000, 10000, 0);

    WaitForSingleObject(gDoneEvent, INFINITE); //if we don't wait it crashes although handles are stored globally?
        
    //the handles should be closed and deleted only after timer had occured. 

    ////CloseHandle(gDoneEvent);
    ////// Delete all timers in the timer queue.
    ////if (!DeleteTimerQueue(hTimerQueue))
    ////    printf("DeleteTimerQueue failed (%d)\n", GetLastError());
}

Bodo2407 wrote:

I need the dll running, not waiting inside a fucntion for a timer..

Quote:

EACCES The given path is a directory, or the file is read-only, but an open-for-writing operation was attempted.

using RetType = std::typename invoke_result_t<Func, Args...>;

using RetType = std::typename invoke_result_t<Func, Args...>;

using RetType = typename std::invoke_result_t<Func, Args...>;

using RetType = typename std::invoke_result_t<Func, Args...>;