heap corruction after "[] delete"

[jeffreybalala]

#include "stdafx.h"
#include <iostream>
#include "BinarySearchTree.h"
using namespace std;
    // Test program

template <class T>
class storage
{
public:
	T m_data;
	storage( T t ):m_data(t) {};
	
	~storage(){}
 	void print() { cout<<m_data<<endl; }
};
storage<char*>::storage(char* y)
{
	m_data = new char( strlen(y)+10 );
	m_data = strcpy(m_data, y);
	printf("m_data size is %d\n", strlen(m_data) );
}
storage<char*>::~storage()
{
	if( m_data )
		delete m_data;
}


int main( )
{
	storage<int> m(3);
 	m.print();
    
	char *x = new char[20];
	cout<<"input your name"<<endl;
	cin>>x;

	cout<<"output: "<<endl;
	storage<char*> ch(x);
	ch.print();
	return 0;
}

Got Heap Corruption error message after running it. I know it's caused by

storage<char*>::~storage()
{
	if( m_data )
		delete m_data;
}

after this destructor is called at the end of main().

But don't know why... Please help~ Thank you very much!

[firedraco]

m_data = new char( strlen(y)+10 );
m_data = strcpy(m_data, y);

These lines are causing memory corruption. I think you meant:

m_data = new char[ strlen(y)+10 ];
m_data = strcpy(m_data, y);

You will also need to change your destructor to use the correct delete type, but I'll let you go look that up. ;)

[jsmith]

You also need to implement a copy constructor and assignment operator for storage<char*>.

[jeffreybalala]

Firedraco, thank you for pointing this out! I don't know why I made such a silly mistake. For the destructor I need to change to
delete [] m_data;
, right? One further question is: is it always correct to use delete [] ptr? I made the following code

int *p = new int;
*p = 3;
delete [] p;

and it seems to run right.



Jsmith, thanks for your suggestion. Maybe my understanding is not right, but is the following a copy constructor?

storage<char*>::storage(char* y)
{
	m_data = new char( strlen(y)+10 );
	m_data = strcpy(m_data, y);
	printf("m_data size is %d\n", strlen(m_data) );
}

Also I tried to implement a = operator like this:

storage<char*> & storage<char*>::operator=(const char*  &y)
{
	m_data = new char[strlen(y)+1];
	m_data = strcpy(m_data, y);
	printf("m_data size is %d\n", strlen(m_data) );
	return (*this);
}

But there is a compilation error. I think the declaration must be wrong, but I don't know where goes wrong ( I am still a bit confused by the rules of template ). Would you please point it out?

Thank both of you very much!

[firedraco]

A copy constructor would look like this for your class:

storage<char*>::storage(const storage<char*>& other)

What is the error you get on your = operator?

[jsmith]

The assignment operator would have signature

storage<char*>& storage<char*>::operator=( storage<char*> rhs );

[jeffreybalala]

Got it! Thank you both very much!