Get "Trigger Breakpoint Error at delete" when using template - c++

Question

I'm using visual studio.
I have 3 class.
It's ok when I try to print Rectangle ABCD, but when i push ABCD into Array [rectangle] A and try to print ABCD again, the "wntdll.pdb not loaded" appear and i continue, it's "triggers breakpoint error!!" at delete in ~Rectangle()
I know it's something up to the pointer in class Rectangle but can't firgure out.
`int main(){
Array<Rectangle>A;
Rectangle a;
cout << a; //It's oke
A.PushBack(a); // problem here
cout<<a;
}`
class Point
{
private:
float _x;
float _y;
public:
float GetX() { return _x; }
float GetY() { return _y; }
public:
Point();
Point(float, float);
Point(const Point&);
~Point() {};
public:
string ToString() const;
public:
friend istream& operator>>(istream&, Point*);
friend ostream& operator<<(ostream&, const Point&);
};
Point::Point() {
_x = 1;
_y = 1;
}
Point::Point(float x, float y) {
_x = x;
_y = y;
}
Point::Point(const Point& a) {
_x = a._x;
_y = a._y;
}
string Point::ToString() const{
stringstream out;
out << "( " << _x << "," << _y << " )";
return out.str();
}
istream& operator>>(istream& in, Point* a) {
cout << "Nhap x: ";
in >> a->_x;
cout << "Nhap y: ";
in >> a->_y;
return in;
}
ostream& operator<<(ostream& out, const Point& a)
{
out << a.ToString();
return out;
}
```
class Rectangle
{
private:
Point* _topleft;
Point* _botright;
public:
void Set_topleft(Point tl) { _topleft = &tl; }
Point Get_topleft() { return *_topleft; }
void Set_botright(Point br) { _botright = &br; }
Point Get_botright() { return *_botright; }
public:
Rectangle();
Rectangle(Point*, Point*);
~Rectangle();
public:
string ToString() const;
public:
friend istream& operator>>(istream&, Rectangle&);
friend ostream& operator<<(ostream&, const Rectangle&);
};
Rectangle::Rectangle()
{
_topleft = new Point(0, 2);
_botright = new Point(3, 0);
}
Rectangle::Rectangle(Point* a, Point* b)
{
_topleft = new Point(*a);
_botright = new Point(*b);
}
Rectangle::~Rectangle()
{
delete _topleft;
delete _botright;
}
string Rectangle::ToString() const
{
stringstream out;
out << "A" << *_topleft << "+" << "D" << *_botright;
return out.str();
}
istream& operator>>(istream& in, Rectangle& a)
{
std::cout << "A( x,y ): ";
in >> a._topleft;
std::cout << "D( x,y ): ";
in >> a._botright;
return in;
}
ostream& operator<<(ostream& out, const Rectangle& a)
{
out << a.ToString();
return out;
}
```
template<class T>
class Array
{
private:
T* _a;
int _len;
public:
Array();
~Array();
public:
int length() { return _len; }
void PushBack(T);
T GetAt(int);
};
template<class T>
Array<T>::Array() {
_a = new T[128];
_len = 0;
}
template<class T>
Array<T>::~Array() {
delete[] _a;
_len = 0;
}
template<class T>
void Array<T>::PushBack(T value) {
if (_len >= 128)
{
std::cout << "Array is over size, which is 128\n";
return;
}
_a[_len] = value;
_len++;
}
template<class T>
T Array<T>::GetAt(int pos) {
return _a[pos];
}
```

Answer 1

The problem in your code is that when you PushBack the Rectangle object a into the array, you create copy of this object. This means that you just copy pointers _topleft and _botright. So in this part of code, you have 2 objects with the same pointers, so you're trying to delete twice the same part of memory.
To fix this you need to define own copy constructor, which will create new pointers in the new object.
Remember also to define own move constructors or make it disable for your class.
Rectangle(const Rectangle &other)
{
if(other._topleft)
_topleft= new Point(*other._topleft);
else
_topleft = nullptr;
if(other._botright)
_botright= new Point(*other._botright);
else
_topleft = nullptr;
}
The next problem is because of definition of void Array<T>::PushBack(T value). Please change it to the void Array<T>::PushBack(const T& value).
Also, try Rectangle(Rectangle&& o) = delete;