C++ Compilation problem with creating an array of struct from the heap

I'm getting a compilation error and warning when I compile this.

#include <iostream>


struct {
    uint8_t m_data;
    int size;
    
} BufferCustom;


class MyClass
{
private:
    int x, y;
    const int CONST_BUFFER_SIZE = 10;
    struct BufferCustom *m_BufferPtr;
public:
    MyClass(int xx, int yy) : x(xx), y(yy)
    {
        m_BufferPtr = new struct BufferCustom[CONST_BUFFER_SIZE];
        
    }
    
    virtual ~MyClass() {
        if (m_BufferPtr){
            delete [] m_BufferPtr;
            m_BufferPtr = nullptr;
        }
    }
    
    // user defined copy constructor
    MyClass(const MyClass& rhs)
        : x{ rhs.x }, y{ rhs.y } // initialize members with other object's // members
    {
        std::cout << "User defined copy constructor invoked.";
        //m_BufferPtr = new struct B
    }
    MyClass& operator=(const MyClass &rhs)
    {
        std::cout << "Assignment operator called\n";
        return *this;
    }
};
int main()
{
    MyClass o1{ 1, 2 };
    MyClass o2 = o1; // user defined copy constructor invoked
    o2 = o1;
}

The error(s) are in these lines:

1. Ctor

  MyClass(int xx, int yy) : x(xx), y(yy)
    {
        m_BufferPtr = new struct BufferCustom[CONST_BUFFER_SIZE];
        
    }

compilation error being Allocation of incomplete type struct BufferCustom

2. The second warning is in the dtor

if (m_BufferPtr){
            delete [] m_BufferPtr;
            m_BufferPtr = nullptr;
}

saying that Deleting pointer to incomplete type 'struct BufferCustom' may cause undefined behavior

I am perplexed as to why this is an error!

This:

struct {
    uint8_t m_data;
    int size;
    
} BufferCustom;

...defines a struct with an anonymous type, then defines one instance of that type named BufferCustom. So BufferCustom is a single variable of a type that doesn't have a name.

But your later code attempts to use BufferCustom as if it were the name of a type. I'd guess what you intended was something like this instead:

struct BufferCustom {
    uint8_t m_data;
    int size;   
};

This defines BufferCustom as the name of the type, so you can later allocate objects of type BufferCustom.