When should you use a class vs a struct in C++?

Question

In what scenarios is it better to use a struct vs a class in C++?

Answer 1

As others have pointed out

• both are equivalent apart from default visibility
• there may be reasons to be forced to use the one or the other for whatever reason

There's a clear recommendation about when to use which from Stroustrup/Sutter:

Use class if the class has an invariant; use struct if the data members can vary independently

However, keep in mind that it is not wise to forward declare sth. as a class (class X;) and define it as struct (struct X { ... }). It may work on some linkers (e.g., g++) and may fail on others (e.g., MSVC), so you will find yourself in developer hell.