C++ Tutorial/Operator Overloading/overload new operator

An example of overloading new and delete globally

<source lang="cpp">#include <iostream>

1. include <cstdlib>
2. 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>

1. include <cstdlib>
2. 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>

In overloaded new.
In overloaded new.
10 20
-10 -20
In overloaded delete.
In overloaded delete.

Overloading new and delete

<source lang="cpp">#include <iostream>

1. include <cstdlib>
2. 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>