Thread: Destructor Issue

I'm having problems with a destructor. It says my heap is corrupted and after debugging I'm assuming that this is the problem. It is after a certain function so here's that function:

Code:

#include "stdafx.h"
#include <string>
#include <iostream>
#include <fstream>
#include <stdlib.h>
#include "string.h"

#define NULL "\0"


extern std::ofstream csis;

//Default Ctor

String::String()
{
	m_buf = new char[1];
	m_length = 1;
	m_buf[0] = '\0';
	
	m_name = "";
}

//Ctor with string literal param
String::String(char* s)
{
	int inputString = strlen(s);
	inputString++;

	m_length = inputString;

	m_buf = new char[inputString];

	strcpy_s(m_buf, m_length, s);
	
	m_name = "";
}

//Ctor with single char as param
String::String(char c)
{
	m_buf = new char[2];

	m_buf[0] = c;
	m_buf[1] = '\0';

	int inputString = strlen(m_buf);

	m_length = inputString;
	
	m_name = "";
}

String::String(int x)
{
	m_buf = new char[sizeof(x)];

	_itoa(x, m_buf, 10);

	m_length = strlen(m_buf);

	m_name = "";
}

//Ctor with pointer to data member
String::String(const String& s)
{
	m_length = s.m_length;
	m_length;
	m_buf = new char[m_length];

	strcpy_s(m_buf, m_length, s.m_buf);

	m_name = "";
}


//Ctor with repeating char
String::String(char c, int x)
{
	m_buf = new char[x];
	
	for(int i =0; i < x; i++)
	{
		m_buf[i] = c;
	}

	m_buf[x] = '\0';

	m_length = strlen(m_buf);

	m_name = "";
}

//Destructor
String::~String()
{
	if(m_name)
		delete[]m_name;
	if(m_buf)
		delete[]m_buf;

}
......

The error occurs after the last constructor function and at delet[]m_buf in the destructor. The actual error is: Heap corruption detected.....detected that the program wrote to the memory after the end of heap buffer....

Any thoughts please and thank you?

This is probably it:

Code:

m_buf = new char[x];
	
// loop through m_buf

m_buf[x] = '\0';

m_buf has x characters, but x isn't a safe index. It's one past the memory you asked for.

that one is wrong

Code:

String::String(int x) {
	m_buf = new char[sizeof(x)];
	_itoa(x, m_buf, 10);
	m_length = strlen(m_buf);
	m_name = "";
}

sizeof(x) doesn't tell you how many chars are needed to represent an int as string.
that one as well

Code:

String::String(char c, int x) {
	m_buf = new char[x];
	for(int i =0; i < x; i++) {
		m_buf[i] = c;
	}
	m_buf[x] = '\0';
	m_length = strlen(m_buf);
	m_name = "";
}

you allocate only x chars but then you assigne '\0' to the n+1 char.

same thing with the copy constructor. the buffer is too small.

also you have to implement an assignement operator. the compiler generated one will create memory-leaks and double deletes in the destructor.
Kurt

I fixed the x char issue..... I debugged again and at my assignment operator is where i"m having the problem I guess. I have something assigns a string to two others to String s7, t7, u7....then String s7("whatever")....then s7 = t7 = u7; Then when my destructor is called at m_buf it says there is writing past the heap buffer. Here's that assignment operator and my destructor again:

Code:

String& String::operator=(const String& rhs)
{
	m_length = rhs.m_length;

	strcpy_s(m_buf, m_length, rhs.m_buf);
	
	return *this;
}

//Destructor
String::~String()
{
	delete[]m_buf;
	delete[]m_name;

}

try something like this

Code:

String& String::operator=(const String& rhs) {
        // we don't want self assignement
        if ( this != &rhs ) {
            // free old buffer
            delete [] m_buf;
	    m_length = rhs.m_length;
            // need space for '\0'
	    m_buf = new char[m_length + 1];
            // don't know that one. looks strange
	    strcpy_s(m_buf, m_length, rhs.m_buf);
  	   // what about m_name ?
	}
	return *this;
}

Kurt