With virtual inheritance you can prevent a base class from being created more than once. So far I couldnt find a proper way to prevent the assignment/move-assignment operator from being called multiple times on the base. As for C++11 or 14, is there some new feature that makes this possible? If not, whats the best way to handle this? (apart from not putting any data into the base:)) Thanks!

Multiple times in a single invocation?

You have the "dreaded diamond" hierarchy. You have virtual inheritance.

A
| \
|   \
B    C
|   /
| /
D

D d1;    //A`s constructor will be called once. Good
D d2;

d1 = d2; //D will call B`s and C`s operator=, and those both will call A`s. ....so it will be called twice.

Also, with move assignment, ...you are supposed to zero out the data in the source after you`ve copied it. So thats no good.

[edit] I see - scratch my reply. You were talking about virtual inheritance.

@Alvaro - Thanks, I eventually realized that - I was not familiar with virtual inheritance (I seldom use inheritance outside of GUIs and never use multiple inheritance except for the rare case of multiple interfaces)

The only solution I can think of is to override assignment yourself to ensure it does what you want, though you seem to be looking for a built in language feature.

Out of curiosity, do you have a use case for this or is it purely theoretical?

I do have a class: CObjectWithID. If you derive from it:

class CA : public CObjectWithID{ ....

class CB : public CObjectWithID{ ....

...it will automatically generate and maintain ID-s for objects of CA and CB. It uses the constructors, destructor, assignment operatorts for that. I dont wanna go too much into it, but the point is it works as long as you dont do something like this: class CA : public CB, public CObjectWithID{...

I will find a workaround but It made me wonder about this problem with the assignment operators and virtual inheritance.

Just wagering a guess here - but it looks like he has an ID system which gives new IDs to objects upon assignment. In this case 2 IDs would be generated... despite the number of design questions it raises, it's hard to tell with what we've been given if that is problematic or just annoying.