当我的堆栈加倍时，它会给我临界区错误!_ctrlvalidHeappointer

我写了一个类Stack，它的两边都被使用，即两个堆栈在一起。一个从[0]到[someplace - 1]，一个从[capacity-1]到[someplace +1]。

一切都很好，但我有一些问题，加倍内存当我的数组是满的。我的代码一开始可以翻倍，但是当它需要再翻倍时，它给了我一些奇怪的错误。

_ctrlvalidHeappointer

临界区错误

这是我的代码。代码中也有一些解释。当我在堆栈中压入太多元素时，它会失败。

    string firstname = "asasasasasaasasasasassasasasaasas";
    string secondname= "asasdasfregeasasasasasgergergererg";
        for (int i = 0; i < firstname.length(); i++)
        {
            a.push_at_first(firstname.at(i));
        }
        for (int i = 0; i < secondname.length(); i++)
        {
            a.push_from_end(secondname.at(i));
        }

这是我的班

using namespace std;
template <class T>
class Stack{
public:
    Stack();
    ~Stack();
    Stack(const Stack<T>& ob);
    void double_size();
    void push_at_first(T mydata);
    void push_from_end(T mydata);
    T & operator = (Stack<T> ob);
private:
    int top;
    int top2;
    T * stack;
    int capacity;
};
template <class T>
T& Stack<T>::operator = (Stack<T> ob)
{
    if(capacity == ob.capacity){
        top = ob.top;
        top2 = ob.top2;
        for (int i = 0; i < capacity; i++)
        {
            stack[i] = ob.stack[i];
        }
        return *this;}
    else
    {
        capacity = ob.capacity;
        stack = new T[capacity];
        for (int i = 0; i < capacity; i++)
        {
            stack[i] = ob.stack[i];
        }
    }
}

template <class T>
Stack<T>::Stack (const Stack<T>& ob) :capacity(ob.capacity)
{
    
    stack = new T[capacity];
    top = ob.top;
    top2=ob.top2;
    for (int i = 0; i < capacity; i++)
    {
        stack[i] = ob.stack[i];
    }
}
template <class T>
 Stack<T>::~Stack()
  {
delete [] stack;
   }
template <class T>
Stack<T>::Stack()
{
    capacity = 17;
    top = 0;
    top2 = capacity-1;
    stack = new T[capacity];
}
template <class T>
void Stack<T>::push_at_first(T mydata)
{
    if ( (top + 1) == (top2 -1) ) //  1 : because I want to Be a Empty Space between Two Stack so i can tell the difference
        double_size();
    stack[++top] = mydata;
}
template <class T>
void Stack<T>::push_from_end(T mydata)
{
    if( (top + 1) == (top2 -1) ) //  1 : because I want to Be a Empty Space between Two Stack so i can tell the difference
        double_size();
    stack[--top2] = mydata;
}
    
template <class T>
void Stack<T>::double_size()
{
Stack<T> temp(*this);
capacity *= 2;
stack = new T[capacity];
top = temp.top;
top2 = capacity - (temp.capacity - temp.top2);// capacity - number of data in stack of temp ;
// if we have something in first stack then copy 0 to top elements of temp.stack to stack
if(top > 0)
{
    for (int i = 0; i <= top ; i++)
    {
        stack[i] = temp.stack[i];
    }
}
// There is Something Wrong Down here ! i can't figure out what !
if(top2 < capacity - 1)
{
    for (int i = capacity-1; i >= top2; i--)
    {
        stack[i] = temp.stack[i-(temp.capacity)];
    }
}

}