Cplus Overolad new and delete Operator

Posted 2020-10-26

思考:在C++类中,通过设计类的构造和析构函数,就已经把复杂的内存管理起来了. 及时是简单的结构体,也是有构造和析构函数的,而下面这种情况,可以在非结构中使用.

/** Operator Overload new and delete */

#include <iostream>
#include <cstdlib>
#include <new>

using namespace std;

class MyClass{
public:
    MyClass(){ x = y = 0; }
    MyClass(int lg, int lt) {
        x = lg;
        y = lt;
    }
    void show(){
        cout << x << " ";
        cout << y << endl;
    }

    void *operator new(size_t size);
    void operator delete(void *p);
    void *operator new[](size_t size);
    void operator delete[](void *p);

private:
    int x, y;
};

/** overloaded new operator */
void *MyClass::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 operator overloaded */
void MyClass::operator delete(void *p){
    cout << "In overloaded delete.\n";
    free(p);
}

/** new operator overloaded for arrays. */
void *MyClass::operator new[](size_t size){
    void *p;
    cout << "Using overload new[].\n";
    p = malloc(size);
    if(!p){
        bad_alloc ba;
        throw ba;
    }
    return p;
}

/** delete operator overloaded for arrays. */
void MyClass::operator delete[](void *p)
{
    cout << "Freeing array using overloaded delete[]\n";
    free(p);
}

int main()
{
    MyClass *objectPointer1, *objectPointer2;
    int i;

    try{
        objectPointer1 = new MyClass (10, 20);
    }catch (bad_alloc xa){
        cout << "Allocation error for objectPointer1.\n";
        return 1;;
    }

    try{
        objectPointer2 = new MyClass [10];
    } catch (bad_alloc xa) {
        cout << "Allocation error for objectPointer2.\n";
        return 1;
    }

    objectPointer1->show();
    for( i = 0; i < 10; i++){
        objectPointer2[i].show();
    }

    delete objectPointer1;
    delete [] objectPointer2;

    return 0;
}

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