c++ - 如何防止通过 'new' 运算符分配类？ (我想确保我的 RAII 类始终分配在堆栈上。)

Question

我想确保我的 RAII 类始终分配在堆栈上。

如何防止通过“new”运算符分配类？

Answer 1

您需要做的就是将类的新运算符声明为私有(private):

class X
{
    private: 
      // Prevent heap allocation
      void * operator new   (size_t);
      void * operator new[] (size_t);
      void   operator delete   (void *);
      void   operator delete[] (void*);

    // ...
    // The rest of the implementation for X
    // ...
};  

将“operator new”设为私有(private)可以有效地防止类外的代码使用“new”来创建 X 的实例。

要完成事情，您应该隐藏“运算符删除”和两个运算符的数组版本。

从 C++11 开始，您还可以显式删除函数:

class X
{
// public, protected, private ... does not matter
    static void *operator new     (size_t) = delete;
    static void *operator new[]   (size_t) = delete;
    static void  operator delete  (void*)  = delete;
    static void  operator delete[](void*)  = delete;
};

相关问题: Is it possible to prevent stack allocation of an object and only allow it to be instiated with ‘new’?