C++
new和delete重载
2012-02-15
23:25:33| 分类： C/C++|举报|字号 订阅
首先，new和delete是运算符，重载new和delete是可能的。这样做的原因是，有时希望使用某种特殊的动态内存分配方法。例如，可能有些分配子程序，他们的堆已耗尽，自动开始把一个磁盘文件当虚存储使用，或者用户希望控制某一片存储空间的分配等。
重载new和delete的格式如下：
void
*operator new (size_t size)
{
.......//完成分配工作
return pointer_to_memory;
}
void
operator delete(void *p)
{
......//释放由p指向的存储空间
}
1.局部重载new和delete（可以使用成员函数和友元函数两种方式重载）
使用new分配某个重载了new的累的对象空间时，先调用new的重载函数，再调用该类的构造函数，如果该类的构造函数有参数要求，则必须给出对应的实参。
使用了delete释放某个重载了delete的累的对象空间时，先调用类的析构函数，然后再调用重载的delete函数。
#include
<iostream>
#include
<stdlib.h>
#include
<string.h>
using namespace std;
class
three_d
{
private:
int
x,y,z;
public:
three_d(int a,int
b,int c);
~three_d()
{
cout << "Destructing\n";
}
void *operator
new(size_t size);
void operator delete(void *p);
friend ostream &
operator <<(ostream &stream,three_d obj);
};
three_d::three_d(int a,int b,int
c)
{
cout <<
"Constructing\n";
x = a;
y = b;
z = c;
}
void
*three_d::operator new(size_t size)
{
cout << "in
threee_d new\n";
return malloc(size);
}
void
three_d::operator delete(void *p)
{
cout << "in
three_d delete\n" ;
free(p);
}
ostream
&operator <<(ostream &os,three_d obj)
{
os << obj.x
<< ",";
os << obj.y << ",";
os << obj.z
<< "\n";
return os;
}
int
main(int argc,char *argv[])
{
three_d *p = new
three_d(1,2,3);
three_d *p1 = new three_d(4,5,6);
if(!p ||
!p1)
{
cout << "Allocation failure" <<
endl;
return 1;
}
cout << *p
<< *p1;
delete p;
delete p1;
int *pnum;
pnum = new int;
*pnum = 0;
cout << "num = " << *pnum << endl;
delete
pnum;
cout << "Application Run Successfully!" << endl;
return
0;
}
2.全局重载new和delete
可以在任何类说明之外重在new和delete，使它们成为全局的。当new和delete被重载为全局时，C++原来的new与delete被忽略，并且重载的运算符用于所有类型（包括标准型和用户定义类型）的分配要求。
#include
<iostream>
#include
<stdlib.h>
#include
<string.h>
using namespace std;
class
three_d
{
private:
int
x,y,z;
public:
three_d(int a,int
b,int c);
~three_d()
{
cout << "Destructing\n";
}
friend ostream &
operator <<(ostream &stream,three_d obj);
};
three_d::three_d(int a,int b,int
c)
{
cout <<
"Constructing\n";
x = a;
y = b;
z = c;
}
void
*operator new(size_t size)
{
cout << "in
threee_d new\n";
return malloc(size);
}
void
operator delete(void *p)
{
cout << "in
three_d delete\n" ;
free(p);
}
ostream
&operator <<(ostream &os,three_d obj)
{
os << obj.x
<< ",";
os << obj.y << ",";
os << obj.z
<< "\n";
return os;
}
int
main(int argc,char *argv[])
{
three_d *p = new
three_d(1,2,3);
three_d *p1 = new three_d(4,5,6);
if(!p ||
!p1)
{
cout << "Allocation failure" <<
endl;
return 1;
}
cout << *p
<< *p1;
delete p;
delete p1;
int *pnum;
pnum = new int;
*pnum = 0;
cout << "num = " << *pnum << endl;
delete
pnum;
cout << "Application Run Successfully!" << endl;
return
0;
}
C++ new和delete重载
原文：http://www.cnblogs.com/jeanschen/p/3538830.html
