Thread: problems with overloaded '+' again

Ok look , i have a simple string class with overloaded '+=' , '=' and '+'. The '+=' and '=' work just fine when i use them with object. But the friggin '+' sign is still causing troubles !!!

I spent like 1 hour on this crap and i still can't figure out how to get around this "Debug Assertion Failed" error (vc++). I tracked execution and found that the problem occurs when one of the objects (don't know which) tries to delete it's sPtr space.

anyway , the following are my .h , .cpp and main.cpp files. The problem is probably in the operator+ function (hilihgted in blue) , i posted the whole code just incase you need to take a look at something else :

mystr.h

Code:

#ifndef MYSTR_H
#define MYSTR_H

class mystr
{
public :
	mystr(const char * = "");
	~mystr();
	
	const mystr &operator+=(const mystr &);
	const mystr &operator=(const mystr &);

	mystr operator+(const mystr &);

	void print();

private :
	int length;
	char *sPtr;
};

#endif

mystr.cpp

Code:

#include <iostream>
using std::cout;
using std::endl;

#include <cstring>
#include "mystr.h"

mystr::mystr(const char *s) // default constructor
{
	length = strlen(s);
	sPtr = new char[ length + 10 ];

	strcpy(sPtr, s);
}


mystr::~mystr()   // destructor
{
	delete [] sPtr;
}


const mystr &mystr::operator +=(const mystr &right)
{
	size_t newLength = length + right.length;

	char *tempPtr = new char[newLength + 1];

	strcpy(tempPtr, sPtr);
	strcpy(tempPtr + length, right.sPtr);
	
	delete [] sPtr;

	sPtr = tempPtr;
	length = newLength;

	return *this;
}


mystr mystr::operator+(const mystr &right)
{
	mystr temp(sPtr);

	temp += right;

	return temp;

}


const mystr &mystr::operator=(const mystr &right)
{
	if( &right != this)
	{
		delete [] sPtr;

		sPtr = new char[right.length + 1];

		strcpy(sPtr, right.sPtr);
	}

	return *this;
}



void mystr::print()
{
	cout << sPtr << endl;
}

main.cpp

Code:

#include "mystr.h"

int main(void)
{
	mystr a("hello"), b("world\n"), c;

	a.print();

	b.print();

	c = a + b;

	c.print();

	return 0;
}

it only displays :

hello
world

then shows an error. I hope someone can help before i tear the rest of my hair out.

p.s : please don't give examples , just show me how to fix my my code.