在编写堆栈实现C ++时遇到问题

Question

I am building a programming language interpreter, and I am currently working on writing the stack code. Write now the stack will only hold byte values, but it will be extended to hold other bytes as well. At the moment I am having trouble with casting between 'BaseObject' that all my stack objects extend and my jbyte class. Here is my current test code.

#include "stdafx.h"
#include <string>
#include <stack>
#include <iostream>
#include <Windows.h>
#include <stack>

using namespace std;

class BaseObject
{
public:
    virtual string getIdentifier(){return "Not Implemented";}
};

class Stack
{
    class jbyte : public BaseObject
    {
    private:
        INT8 byteValue;

    public: 
        jbyte(INT8 value)
        {
            byteValue = value;
        }

        INT8 getValue()
        {
            return byteValue;
        }
    };

private:
    stack<BaseObject> objectStack;

public:
    void pushByte(INT8 byteValue)
    {
        jbyte toPush(byteValue);
        objectStack.push(toPush);
    }

    INT8 popByte()
    {
        if(objectStack.size() == 0)
        {
            cout<<"ERROR: Trying To Pop Value From Empty Stack\nPress Any Key To Continue...";
            _gettch();
            exit(1);
        }
        else
        {
            BaseObject& bo = objectStack.top();
            jbyte& b = dynamic_cast<jbyte&>(bo);
        }
    }
};

int main()
{
    Stack stack;
    stack.pushByte(9);
    stack.popByte();
    while(true);
}

When I try to run this however, I get an Unhandled exception at at 0x75C4C41F in StackTests.exe: Microsoft C++ exception: std::bad_cast at memory location 0x0034F858.

I would like to know how to fix this problem, or if that is difficult, how I could rewrite the stack to work successfully.

Answer 1

When you objectStack.push(toPush) , the jbyte part of toPush is sliced off and only the BaseObject part remains. That's why casting the BaseObject back to jbyte is no longer possible.