Просмотр исходного текста страницы C++ Tutorial/Operator Overloading/overload new operator

==An example of overloading new and delete globally==


   
<source lang="cpp">#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
   
class loc {
int longitude, latitude;
public:
  loc() {}
  loc(int lg, int lt) {
    longitude = lg;
    latitude = lt;
  }
   
  void show() {
    cout << longitude << " ";
    cout << latitude << "\n";
  }
};
   
// Global new
void *operator new(size_t size)
{
  void *p;
   
  p =  malloc(size);
  if(!p) {
    bad_alloc ba;
    throw ba;
  }
  return p;
}
   
// Global delete
void operator delete(void *p)
{
  free(p);
}
   
int main()
{
  loc *p1, *p2;
  float *f;
   
  try {
    p1 = new loc (10, 20);
  } catch (bad_alloc xa) {
    cout << "Allocation error for p1.\n";
    return 1;;
  }
   
  try {
    p2 = new loc (-10, -20);
  } catch (bad_alloc xa) {
    cout << "Allocation error for p2.\n";
    return 1;;
  }
   
  try {
    f = new float; // uses overloaded new, too
  } catch (bad_alloc xa) {
    cout << "Allocation error for f.\n";
    return 1;;
  }
   
  *f = 10.10F;
  cout << *f << "\n";
   
  p1->show();
  p2->show();
   
  delete p1;
  delete p2;
  delete f;
   
  return 0;
}</source>

==Overloaded "new" operator relative to Point==


   
<source lang="cpp">#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
class Point {
  int x, y;
public:
  Point() {}
  Point(int px, int py) {
    x = px;
    y = py;
  }
  void show() {
    cout << x << " ";
    cout << y << "\n";
  }
  void *operator new(size_t size);
  void operator delete(void *p);
};
// new overloaded relative to Point.
void *Point::operator new(size_t size)
{
  void *p;
  cout << "In overloaded new.\n";
  p =  malloc(size);
  if(!p) {
    bad_alloc ba;
    throw ba;
  }
  return p;
}
// delete overloaded relative to Point.
void Point::operator delete(void *p)
{
  cout << "In overloaded delete.\n";
  free(p);
}
int main()
{
  Point *p1, *p2;
  try {
    p1 = new Point (10, 20);
  } catch (bad_alloc xa) {
    cout << "Allocation error for p1.\n";
    return 1;
  }
  try {
    p2 = new Point (-10, -20);
  } catch (bad_alloc xa) {
    cout << "Allocation error for p2.\n";
    return 1;;
  }
  p1->show();
  p2->show();
  delete p1;
  delete p2;
  return 0;
}</source>
<pre class=codeResult>In overloaded new.
In overloaded new.
10 20
-10 -20
In overloaded delete.
In overloaded delete.</pre>

==Overloading new and delete==


   
<source lang="cpp">#include <iostream>
#include <cstdlib>
#include <new>
using namespace std;
   
class loc {
  int longitude, latitude;
public:
  loc() {}
  loc(int lg, int lt) {
    longitude = lg;
    latitude = lt;
  }
   
  void show() {
    cout << longitude << " ";
    cout << latitude << "\n";
  }
   
  void *operator new(size_t size);
  void operator delete(void *p);
};
   
// new overloaded relative to loc.
void *loc::operator new(size_t size)
{
  void *p;
   
  cout << "In overloaded new.\n";
  p =  malloc(size);
  if(!p) {
    bad_alloc ba;
    throw ba;
  }
  return p;
}
   
// delete overloaded relative to loc.
void loc::operator delete(void *p)
{
  cout << "In overloaded delete.\n";
  free(p);
}
   
int main()
{
  loc *p1, *p2;
   
  try {
    p1 = new loc (10, 20);
  } catch (bad_alloc xa) {
    cout << "Allocation error for p1.\n";
    return 1;
  }
   
  try {
    p2 = new loc (-10, -20);
  } catch (bad_alloc xa) {
    cout << "Allocation error for p2.\n";
    return 1;;
  }
   
  p1->show();
  p2->show();
   
  delete p1;
  delete p2;
   
  return 0;
}</source>