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; }

Edit & Run

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。