Question

what is size of empty class and difference between union, structure and class in c++ ?

My idea:

if no static members in them, they should be same because all members are allocated on stack.

If they are all empty, they are same.

if they have static members, it depends the relative location of the members inside them.

right ?

thanks

Answer 1

C++ Standard standard specify’s that the size of an Empty class should be Non-Zero.
Usually, it is 1 byte on most systems.

In Bjarne Stroustrup’s words, the size is non-zero “To ensure that the addresses of two different objects will be different.”

The size is 1 on most systems because the alignment rules don’t matter as the entry of the class name is made in symbol table just to obtain an unique address.

For Standerdese fans:
C++03 Standard Section 9: Classes, Para 2:

Complete objects and member subobjects of class type shall have nonzero size.
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