Pfthb

My problem I think that is due to the fact that I try to bind a class member function (not static) as a callback to the SetWindowsHookEx function. I've tried debugging but I was unable to get any other useful info except the callback binding which I'm not aware of any other way of doing so.
Therefore, at the first call of the GetMessage function I receive the following exception: An unhandled exception was encountered during a user callback. .

My question is, if the cause of the exception is the way I'm binding the HookLowLevel::KeyboardProc function so I can pass it as a callback, what's the right way of doing so? If not, what do you think may be the cause of the exception being thrown?

The function inside which I'm doing the callback binding and where the GetMessage function that throws the exception is found:

void HookLowLevel::attachHook()

 printf("Hooking the keyboardn");
 auto callback = std::bind(&HookLowLevel::KeyboardProc, this);
 hook_ = SetWindowsHookEx(WH_KEYBOARD_LL, (HOOKPROC)(&callback), 0, 0);
 printf("%Xn", hook_);
 MSG msg 0 ;
 try
 
 while (GetMessage(&msg, NULL, 0, 0) != 0 && !windowChanged_)
 
 TranslateMessage(&msg);
 DispatchMessage(&msg);
 
 
 catch (const std::runtime_error& re)
 
 std::cerr << "Runtime error: " << re.what() << std::endl;
 
 catch (const std::exception &e)
 
 std::cerr << "exception: " << e.what();
 

And this is how the definition of the KeyboardProc looks like:

LRESULT CALLBACK HookLowLevel::KeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)

The Windows API is strictly exposed as a C interface. You cannot pass pointers to non-static class members as callbacks to any Windows API (or function objects as returned by std::bind). The compiler told you about this already, which probably resulted in you silencing the compiler by adding an (invalid) cast.

Remove the cast and the compiler will let you know, whether you passed a function pointer with the correct signature. You can also safely remove your try/catch handlers. The Windows API will not ever throw a C++ exception (see first paragraph).