Is there a memory leak? - c++

Question

I have tried to write my own String class in C++ using Microsoft Visual Studio 2015. I wrote the class like this;
#include<string.h>
class myString {
private:
char* content;
public:
int size;
myString();
myString(char*);
~myString();
bool operator== (const myString &) const;
bool operator!= (const myString &) const;
myString operator= (const myString &);
myString operator+ (const myString &) const;
myString operator+= (const myString &);
friend std::ostream& operator<< (std::ostream &os, const myString &);
char operator[] (int &) const;
};
std::ostream& operator<<(std::ostream &os, const myString &string) {
os << string.content;
return os;
}
myString::myString() {
size = 0;
content = "\0";
}
myString::myString(char* newContent) {
size = strlen(newContent);
content = new char[size+1];
strcpy(content, newContent);
}
myString::~myString() {
delete[] content;
}
myString myString::operator= (const myString &string) {
if (size != string.size) {
delete[] content;
size = string.size;
content = new char[size+1];
}
strcpy(content, string.content);
return *this;
}
bool myString::operator== (const myString &string) const {
if (size != string.size)
return false;
if (strcmp(content, string.content))
return false;
return true;
}
bool myString::operator!= (const myString &string) const {
if (*this == string)
return false;
return true;
}
myString myString::operator+ (const myString &string) const {
int newSize = size + string.size;
char* newContent = new char[newSize];
strcpy(newContent, content);
strcat(newContent, string.content);
return myString(newContent);
}
myString myString::operator+= (const myString &string) {
*this = *this + string;
return *this;
}
char myString::operator[] (int &index) const {
return content[index];
}
It works fine when I tried to do this;
#include<iostream>
#include "MyString.h"
using namespace std;
int main() {
myString s("my new");
cout << s+" string" << endl;
}
But I am not sure if there is any memory leak in operator+ function in the line char* newContent = new char[newSize]; I am allocating new space from the memory and I need it in the return statement return myString(newContent);.
So I can not deallocate it before this line and I can not deallocate it after the return statement. Am I correct, is there a memory leak? If so, how can I fix this?
EDIT 1 :
I've changed the operator+ function as follows with the help of Prince Dhaliwal;
myString myString::operator+ (const myString &string) const {
myString temp;
int newSize = size + string.size;
char* newContent = new char[newSize + 1];
temp.size = newSize;
strcpy(newContent, content);
strcat(newContent, string.content);
temp.content = newContent;
return temp;
}
But since I created the temp locally it calls its destructor before returning it and gives error. I supposed I should allocate memory for temp too. And I changed the function as follows;
myString myString::operator+ (const myString &string) const {
myString* temp= new myString;
int newSize = size + string.size;
char* newContent = new char[newSize+1];
temp->size = newSize;
strcpy(newContent, content);
strcat(newContent, string.content);
temp->content = newContent;
return *temp;
}
It works fine now, but I believe there is still memory leak because of the temp variable. If there is a memory leak, how to fix this?
EDIT 2 :
I've fixed it simply by creating a Copy Constructor

Answer 1

There is actually a memory leak in your code. When you are using the + operator in s + " string". In your operator+() definition i.e.
myString myString::operator+ (const myString &string) const {
int newSize = size + string.size;
char* newContent = new char[newSize];
strcpy(newContent, content);
strcat(newContent, string.content);
return myString(newContent);
}
You are allocating the new string here char* newContent = new char[newSize];, copying the older and new part to the new string. And again you are allocating the new string in the constructor return myString(newContent);. But where are you deleting your old string? Its nowhere in your code. So you have to delete the string newContent.
You can do this
myString myString::operator+ (const myString &string) const {
myString temp;
int newSize = size + string.size;
char* newContent = new char[newSize + 1];
temp.size = newSize;
strcpy(newContent, content);
strcat(newContent, string.content);
temp.content = newContent;
return temp;
}
UPDATE
You have to create a copy constructor.
myString(const myString &rhs) :
size(rhs.size) {
content = new char[size + 1];
strcpy(content, rhs.content);
}