Value Semantics

Lengthy articles are written about value semantics. Now it's my turn and I will try to be short.

First, what is a value? A value is the content of an object. There are different types of values, depending on the usage.

Value semantics in C++ is defined by passing objects by value (in contrast to by pointer or by reference) and this requirement recursively holds for all data members. It has a direct relation to functional style of programming (add to that immutability).

The greatest benefit of value semantics is avoding dynamic memory allocation.

By the way, even if you use pointers in your data, you still can maintain value semantics for them. Here is a wrapper over a pointer that provides value-like behavior:

template<class T0> struct value_wrapper {

    value_wrapper( T0* data_ ) : data{ data_ } {}

    value_wrapper() : data{ new T0{} } {}

    value_wrapper( const value_wrapper& other ) : value_wrapper{} {
        *data = *other.data;
    }

    value_wrapper& operator=( const value_wrapper& other ) { 
        //could've used copy-and-swap
        *data = *other.data;
    }

    ~value_wrapper() {
        delete data;
    }

    //move construction and assigment
    //other operators, member functions

    T0* data;

};

Ideone