Auto_ptr

Smart pointer that deletes the instance it points to when going out of scope

View version details

Contents

Definition
Description
Member Functions
Page Comments

Key Facts

Gyroscopic Couple: The rate of change of angular momentum ( $\inline \tau$ ) = $\inline I\omega\Omega$ (In the limit).

$\inline I$ = Moment of Inertia.
$\inline \omega$ = Angular velocity
$\inline \Omega$ = Angular velocity of precession.

Blaise Pascal (1623-1662) was a French mathematician, physicist, inventor, writer and Catholic philosopher.

Leonhard Euler (1707-1783) was a pioneering Swiss mathematician and physicist.

Definition

The auto_ptr class template is defined in the standard header <memory>, and in the nonstandard backward-compatibility header <memory.h>.

template <class Type>
class auto_ptr

Parameter	Description
`Type`	The type of object for which storage is being allocated or deallocated

Description

The auto_ptr is provided by the C++ standard library as a kind of a smart pointer that helps to avoid resource leaks when exceptions are thrown.

It manages an object obtained via new and deletes that object when auto_ptr itself is destroyed. It may be used to provide exception safety for dynamically-allocated objects, for passing ownership of dynamically-allocated objects into functions and for returning dynamically-allocated objects from functions.

NOTE:

Copying an auto_ptr changes the object being copied by setting the contents to NULL
auto_ptr objects are not guaranteed to work correctly with the STL containers

Member Functions

Function	Description
(constructor)	Creates a new auto_ptr object
(destructor)	Destroys an auto_ptr and the managed object
get	Obtains a pointer to the managed object
operator*	Dereference object (accesses the managed object)
operator->	Dereference object member (accesses the managed object)
release	Releases ownership of the managed object
reset	Deallocate object pointed and set new value
(conversion operators)	Conversion operators

References:

Example:

Example - Reset auto_ptr

Problem

The following example of program illustrates how to reset an auto_ptr.

Workings

#include <iostream>
#include <memory>
 
struct Resetter
{
  Resetter() { std::cout << "Constructor" << std::endl; }
  ~Resetter() { std::cout << "Destructor" << std::endl; }
};
 
int main()
{
  std::auto_ptr<Resetter> pReset(new Resetter);
  pReset.reset(new Resetter);
}

Solution

Output:

Constructor
Constructor
Destructor
Destructor

References

http://www.richelbilderbeek.nl/