When do we break binary compatibility

Question

I was under the impression that whenever you do one of these:

• Add a new public virtual method virtual void aMethod();
• Add a new public non-vi

Answer 1

C++ doesn't say.

Visual Studio generally follows COM rules, allowing you to add virtual methods to the end of your most derived class unless they are overloads.

Any non-static data member will change the binary layout as well.

Non-virtual functions don't affect binary compatibility.

Templates make a huge mess because of name mangling.

Your best bet to retain binary compatibility is to use both the pimpl idiom and the nvi idiom quite liberally.