ActiveX method with variable parameter list?

Question

I have a DLL that provides functions with a variable parameter list that are defined like

my_func(int var,...)

Depending on how my_func() is called it expectes more or less additional parameters.

Now this DLL has to be wrapped by an MFC-based ActiveX-control. For the method definitions I can find many VT_ and VTS_ defines that wrap to a specific, pre-defined type. But is it possible to have a ActiveX-method with such a variable parameter list too?

If yes: how can it be implemented?

Answer 1

Although it is technically possible, by using the vararg keyword in the IDL in combination with an argument specified as SAFEARRAY(VARIANT), there is no support for specifying such a method in an MFC ActiveX project. You can do it with ATL instead, but I think this would be an enormous inconvenience just to get the functionality you describe.

Some better choices (in my opinion) would be:

1. Provide specific methods for each of the use cases of your wrapped function.
2. Provide a single method that exposes all arguments and add a UINT to set flags depending on which arguments should be used.

My choice would be 1.