Item 6: Explicitly Disallow the Use of Compiler-Generated Functions You Do Not Want

Declare (but don’t define) what you don’t want and compiler won’t generate it (default constructor, copy constructor, copy assignment operator, and destructor).

For example, you want to disallow assignment:

class Foo {
 private:
  Foo(const Foo&);  // Declare but don't define it!
  Foo& operator=(const Foo&);
};

Or define a uncopyable base class:

class Uncopyable {
 protected:
  Uncopyable() {}
  ~Uncopyable() {}  // Note it's not virtual!
 private:
  Uncopyable(const Uncopyable&);
  Uncopyable& operator=(const Uncopyable&);
};

// Use private inheritance.
class Foo : private Uncopyable { ... };

• Note that Uncopyable’s destructor needs not to be virtual.
• The empty base class optimization might not work in the presence of multiple inheritance, but in general you should not worry about this (and other C++ subtleties).
• Boost has it and calls it noncopyable.