Efficient C++ Performance Programming Techniques

Return by Value

Another path that leads to temporary object creation is function return value. If you code a function that returns an object by value (as opposed to a reference or pointer), you can easily end up with a temporary. Consider f() as a simple example:

string f()
{
    string s;
    ... // Compute "s"
    return s;
}

The return value of f() is an object of type string. A temporary is generated to hold that return value. For example:

String p;
...
p = f();

The temporary object holding f()'s return value is then assigned to the left-hand side object p. For a more concrete example consider the string operator+. This operator will implement the intuitive interpretation of string "+" operation. It takes two input string objects and returns a new ...