c++ - Performances of Structs vs Classes

Question

I wonder if there are performance comparisons of classes and C style structs in C++ with g++ -O3 option. Is there any benchmark or comparison about this. I've always thought C++ classes as heavier and possibly slower as well than the structs (compile time isn't very important for me, run time is more crucial). I'm going to implement a B-tree, should I implement it with classes or with structs for the sake of performance.

Answer 1

On runtime level there is no difference between structs and classes in C++ at all. So it doesn't make any performance difference whether you use struct A or class A in your code.

Other thing, is using some features -- like, constructors, destructors and virtual functions, -- could have some performance penalties (but if you use them you probably need them anyway). But you can with equal success use them both inside your class or struct.

In this document you can read about other performance-related subtleties of C++.