C++中的::operator new, ::operator delete

一般在使用new  和 delete的时候,做了两件事情,一是空间的配置( new 是分配,delete是回收),而是调用对象的析构函数

但是也有办法将这两个过程分开

那就是显式的调用::operator new, ::operator delete,它们只进行空间配置,并不调用对象的析构函数

具体的可以参看下面这个例子:

// operator new[] example
#include <iostream> // std::cout
#include <new> // ::operator new[] struct MyClass {
int data;
MyClass() {std::cout << '*';} // print an asterisk for each construction
}; int main () {
std::cout << "constructions (1): ";
// allocates and constructs five objects:
MyClass * p1 = new MyClass[5];
std::cout << '\n'; std::cout << "constructions (2): ";
// allocates and constructs five objects (nothrow):
MyClass * p2 = new (std::nothrow) MyClass[5];
std::cout << '\n'; std::cout << "constructions (3): ";
// allocates storage for five objects, but does not construct them:
MyClass * p3 = static_cast<MyClass*> (::operator new (sizeof(MyClass[5])));
std::cout << '\n'; std::cout << "constructions (4): ";
// constructs five objects at p3, but does not allocate:
new (p3) MyClass[5];
std::cout << '\n'; delete[] p3;
delete[] p2;
delete[] p1; return 0;
}
 
 

关于operator delete和operator new  ,可以参看这里的原型定义:

http://en.cppreference.com/w/cpp/memory/new/operator_delete

http://en.cppreference.com/w/cpp/memory/new/operator_new

可以看到,都是void*型的指针,跟C语言里面的malloc  free机制差不多了。

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