Copy semantics

An object keeps state information in its data members, which can themselves be of POD-types or class types. If you do not define a copy constructor for your class, then the compiler implicitly defines one for you. This implicitly-defined copy constructor copies each member in turn, invoking the copy constructor of members of class type and performing a bitwise copy of POD-type members. The same is true of the assignment operator. The compiler generates one if you do not define your own, and it performs member-wise assignment, invoking the assignment operators of member objects of class-type, and performing bitwise copies of POD-type members.

The following example illustrates this:

Listing A.2: Implicit destructor, copy constructor, and assignment operator

 1 #include <iostream>
 2
 3 class Foo {
 4 public:
 5   Foo() {}
 6
 7   Foo(const Foo&) {
 8     std::cout << "Foo(const Foo&)\n";
 9   }
10
11   ~Foo() {
12     std::cout << "~Foo...