Question

From some old c++ code im trying to use a com dll, it works fine when the dll is registered, but it crahses if the dll isnt registered.

// Initialize COM. HRESULT hr = CoInitialize(NULL);

IGetTestPtr ptest(__uuidof(tester));

‘Use method from the dll’

// Uninitialize COM. CoUninitialize();

Is it anyway to check if the dll has been registered, before calling IGetTestPtr ptest(__uuidof(tester))?

Or what is the correct way to prevent the crash?

Answer 1

Calling CreateInstance on your object will return an HRESULT that can be tested for success:

IGetTestPtr p = null;  HRESULT hRes = p.CreateInstance( __uuidof(tester) ); bool bSuccess = SUCCEEDED(hRes); 

This assumes you’ve created an interface wrapper around your type library using Visual Studio, where COM Smart Pointers are used in the interface (this gives you the CreateInstance method).