Question

I’ve got a function that takes a list of CRuntimeClass pointers in order to setup a view. I’d like to return without doing anything if the function is called with a list of the same classes that are already setup. Saving the pointer values and comparing them on the next call is currently working, but I want to verify that that’s a legal thing to do, and not something that just happens to work. Maybe my doc-search-fu is lacking, but I can’t find anywhere that guarantees the pointer value returned from the RUNTIME_CLASS() macro for a given class will be the same for the life of the program. The closest I could find is in the docs for CObject::GetRuntimeClass():

There is one CRuntimeClass structure for each CObject-derived class.

That implies that the pointer value shouldn’t change, but doesn’t exactly state it. Does anyone have something a bit more concrete on that? Or is there a better way to compare the CRuntimeClasses?

Answer 1

Taking a peek at afx.h plus a little of debugging shows that RUNTIME_CLASS() returns a pointer to a static member: static CRuntimeClass class##class_name (as it can be seen in the definition of DECLARE_DYNAMIC(class_name) macro).

As the member is static, the pointer to it does not change during runtime. In other words static is your guarantee.