A pointer is a type that holds an address.

When a pointer is uninitialized, it should point to NULL. You initialize a pointer using new, which reserves free space for the dynamically allocated instance and returns the address to it.

C++ does not free this memory on its own. Therefore, you have to call delete to do so.

Reading/writing from/to an uninitialized pointer results in an access violation.

Prefer using a smart pointer over a plain pointer [1-3], e.g. use an std::auto_ptr or boost::shared_ptr. Use 0 rather than NULL [4].

Avoid non-trivial pointer arithmetic [5].

Example with plain pointer


struct MyClass { /* some class definition */ };



int main()

{

  MyClass * pClass = new MyClass;

  pClass->doStuff();

  delete pClass

}

Example with std::auto_ptr


#include <memory>



struct MyClass { /* some class definition */ };



int main()

{

  const std::auto_ptr<MyClass> pClass(new MyClass);

  pClass->doStuff(); //Hey, the same way of accessing the pointed instance!

  //Done, std::auto_ptr deletes itself when going out of scope

}

References

Scott Meyers. Effective C++ (3rd edition). ISBN: 0-321-33487-6. Item 13: 'Use objects to manage resources'.
Scott Meyers. Effective C++ (3rd edition). ISBN: 0-321-33487-6. Item 17: 'Store newed objects in smart pointers in standalone statements'
Herb Sutter, Andrei Alexandrescu. C++ coding standards: 101 rules, guidelines, and best practices. 2005. ISBN: 0-32-111358-6. Chapter 13: 'Ensure resources are owned by objects. Use explicit RAII and smart pointers.
Bjarne Stroustrup. The C++ Programming Language (3rd edition). 1997. ISBN: 0-201-88954-4. Section 5.8.3: 'Use 0 rather than NULL'.
Bjarne Stroustrup. The C++ Programming Language (3rd edition). 1997. ISBN: 0-201-88954-4. Section 5.8.1: 'Avoid non-trivial pointer arithmetic'.

Go back to Richel Bilderbeek's C++ page.

Go back to Richel Bilderbeek's homepage.

(C++) pointer

Example with plain pointer

Example with std::auto_ptr

References