CODEWITHSUNDEEP
c++stack
kingcong3
kingcong3

Reputation: 193

"Assertion Failed" on destructor

does anyone know whats wrong with this ?? it keeps giving me an "Assertion Failed" _BLOCK_TYPE_IS_VAILD(pHead->nBlockUse) when it tries to use the detructor on a non empty stack EDIT:MORE CODES:

class stack
{
private:
   struct StackNode
   {
      int x;
      int y;
      StackNode *next;  
   };

   StackNode *top;     

public:

   stack()
      {  top = NULL; }

   ~stack();

 stack::~stack()
    {
        StackNode *nodePtr,*nextNode;
            nodePtr=top;
            while (nodePtr!=NULL) 
            { 
                nextNode=nodePtr->next;
                delete nodePtr;
                nodePtr=nextNode;
            }   
    }

main.cpp

mouse_position.push(mouse_x,mouse_y);
print_stack(mouse_position);

void print_stack(stack m)
{
    int tempx=0;
    int tempy=0;
//  while(!m.isEmpty()){
//      m.pop(tempx,tempy);
    cout<<tempx<<tempy<<endl;
//  }

}

Upvotes: 1

Views: 1378

Answers (3)

Pablo
Pablo

Reputation: 8644

From the code you posted, it seems the problem is the missing copy constructor. Consider the following code:

stack mouse_position;
// fill mouse_position
print_stack(mouse_position);

When you call print_stack, you make a bitwise copy of mouse_position. When print_stack exits, that copy (namely m) is destroyed, calling delete on its top member, which is exactly the same top of mouse_position. When mouse_position is deleted, you're deleting its top twice.

Then again, there could be more bugs lurking in the code you haven't posted yet.

Upvotes: 4

Mark B
Mark B

Reputation: 96241

You copy your stack when passed into print_stack and didn't follow the rule of three What is The Rule of Three? which results in a double deletion and your problem.

Unless you're doing this as an exercise, use std::stack instead - it's been tested and debugged for years.

Upvotes: 2

Thomas Matthews
Thomas Matthews

Reputation: 57688

Some things to look at:

  1. StackNode has no destructor.
  2. There are two definitions of stack destructor.
  3. Missing closing brace for class stack.
  4. Consider moving StackNode outside of the class.
  5. Prefer using std::stack and std::list.

Edit your post to show more context for more detailed help.

Upvotes: 2

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