c++ - 放置新的连续内存

Question

我在为连续内存使用 placement new 时遇到了一些问题。请指导我，如果有任何其他方法可以做到这一点。
请引用我的代码。

#include <new>  
//================================================
class MyClass
{
 private:
    int ma;
 public:
    MyClass():ma(-1){}      
};
//===========================================

int main()
{
    // I am allocating the memory for holding 10 elements of MyClass on heap
    void* pMyClass = ::operator new(sizeof(MyClass)*10);

    //! Note :: the address of pMyClass1 and pMyClass will now point to same   
    //location after calling placement new  

    MyClass* pMyClass1 = :: new(pMyClass)MyClass();  

    //! Problem with this is that, 
    //! i can only instantiate the constructor for the  base address. That is 
    //!  pMyClass[0]. 
    //! If i have to instantiate it for all the other instances, 
    //! that is pMyClass[1] to pMyClass[9], then how to do it ?
    return 0;
}

Answer 1

你在pMyClass中有内存的开始，步长是sizeof(MyClass)。因此，您需要做的是例如:

MyClass* pMyClass2 = ::new((MyClass*)pMyClass + 1)MyClass();