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Sep 1st, 2009

Does this programme have any memory Leaks?

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C++ Syntax (Toggle Plain Text)
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <string>
 
using namespace std;
 
void RandomArrayFill(int* array, int size)
{
	//int* array = new int[size];
 
	cout << "Creating and filling the array with integers..." << endl;
	for(int i = 0; i< size; ++i)
	{
		array[i] = rand() % 101;
	}
 
 
	cout << "Array = {";
 
	for(int i = 0; i < size; ++i)
	{
		cout << array[i] << " ";  
	}
	cout << "}" << endl;
 
 
}
 
int main()
{
 
	srand((unsigned)time(0));
 
	int size;
	cout << "Enter Size: ";
	cin >> size;
	int* newArray = new int[size];
	RandomArrayFill(newArray, size);
 
	delete[] newArray;
	newArray = 0;
}
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <string>

using namespace std;

void RandomArrayFill(int* array, int size)
{
	//int* array = new int[size];
	
	cout << "Creating and filling the array with integers..." << endl;
	for(int i = 0; i< size; ++i)
	{
		array[i] = rand() % 101;
	}
	
	
	cout << "Array = {";

	for(int i = 0; i < size; ++i)
	{
		cout << array[i] << " ";  
	}
	cout << "}" << endl;
	
	
}

int main()
{

	srand((unsigned)time(0));
	
	int size;
	cout << "Enter Size: ";
	cin >> size;
	int* newArray = new int[size];
	RandomArrayFill(newArray, size);

	delete[] newArray;
	newArray = 0;
}

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invisi

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Sep 1st, 2009

Re: Does this programme have any memory Leaks?

This is the same programme but done using a vector. Alsthough it works it still comes up with this warning twice:

Warning 1 warning C4018: '<' : signed/unsigned mismatch Line 15

Why is that anyone know?

C++ Syntax (Toggle Plain Text)
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <vector>
#include <string>
#include <cmath>
 
using namespace std;
 
 
void RandomArrayFill(std::vector<int>& vec)
{
 
	cout << "Creating and filling the array with integers..." << endl;
	for(int i = 0; i< vec.size(); ++i)
	{
		vec[i] = rand() % 101;
	}
 
 
	cout << "Array = {";
 
	for(int i = 0; i < vec.size(); ++i)
	{
		cout << vec[i] << " ";  
	}
	cout << "}" << endl;	
}
 
 
int main()
{
 
	srand((unsigned)time(0));
 
	int size = 0;
 
	vector<int> intVector;
 
	cout << "New Size: " ;
	cin >> size;
 
	intVector.resize(size);
 
	RandomArrayFill(intVector);
 
	cout << endl;
}
#include <iostream>
#include <cstdlib>
#include <ctime>
#include <vector>
#include <string>
#include <cmath>

using namespace std;


void RandomArrayFill(std::vector<int>& vec)
{

	cout << "Creating and filling the array with integers..." << endl;
	for(int i = 0; i< vec.size(); ++i)
	{
		vec[i] = rand() % 101;
	}
	
	
	cout << "Array = {";

	for(int i = 0; i < vec.size(); ++i)
	{
		cout << vec[i] << " ";  
	}
	cout << "}" << endl;	
}


int main()
{
	
	srand((unsigned)time(0));

	int size = 0;

	vector<int> intVector;
	
	cout << "New Size: " ;
	cin >> size;
	
	intVector.resize(size);
	
	RandomArrayFill(intVector);

	cout << endl;
}

invisi

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Sep 1st, 2009

Re: Does this programme have any memory Leaks?

vector sizes are always in unsigned integers, so change the for-iterator i into an unsigned int.

Topi Ojala

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Sep 1st, 2009

Re: Does this programme have any memory Leaks?

also in the first program there is no memory leak.

NathanOliver

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Sep 1st, 2009

Re: Does this programme have any memory Leaks?

If you are using UNIX, you can use valgrind to check for memory leaks. You need to add --tool=memcheck on the command line to check for leaks.

GDICommander

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Sep 2nd, 2009

Re: Does this programme have any memory Leaks?

Click to Expand / Collapse Quote originally posted by NathanOliver ...

also in the first program there is no memory leak.

Are you sure. His program is tricky in a sense that there is a memory
leak. His function is definitely not doing what he thinks its doing.

One way to tell if you have memory leak is to see if every new
is matched with delete. In your function, you allocate new memory for the array
that is passed, which already has been allocated memory. So when
inside the function, the arrays thats passed is located in whatever
memory address that was reserved inside the function. When he
exits out that functions, that memory is no longer in play. Inside
main he has already the array pointing at a specific address.

So the memory inside the function has a leak. Also you use
2 instances of new but only 1 delete. Does that give you a hint?

Last edited by firstPerson; Sep 2nd, 2009 at 2:53 am.

firstPerson

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Sep 2nd, 2009

Re: Does this programme have any memory Leaks?

Quote ...

vector sizes are always in unsigned integers, so change the for-iterator i into an unsigned int.

The type might not be unsigned int . It is safer to use the actual type that is typedef'd in the vector class:

C++ Syntax (Toggle Plain Text)
void RandomArrayFill(vector<int>& vec)
{
    cout << "Creating and filling the array with integers..." << endl;
 
    for (vector<int>::size_type i = 0; i < vec.size(); ++i)
    {
        vec[i] = rand() % 101;
    }
 
    cout << "Array = {";
 
    for (vector<int>::size_type i = 0; i < vec.size(); ++i)
    {
        cout << vec[i] << " ";  
    }
 
    cout << "}" << endl;	
}
void RandomArrayFill(vector<int>& vec)
{
    cout << "Creating and filling the array with integers..." << endl;

    for (vector<int>::size_type i = 0; i < vec.size(); ++i)
    {
        vec[i] = rand() % 101;
    }

    cout << "Array = {";

    for (vector<int>::size_type i = 0; i < vec.size(); ++i)
    {
        cout << vec[i] << " ";  
    }

    cout << "}" << endl;	
}

Quote ...

Quote ...

also in the first program there is no memory leak.

Are you sure.

I am. The allocation in the function is commented and will not run. If you uncomment it, there will be a compiler error because array is redefined.

Tom Gunn

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Sep 2nd, 2009

Re: Does this programme have any memory Leaks?

>In your function, you allocate new memory for the array
>that is passed, which already has been allocated memory.

I suppose he has commented that line.
Hence technically, there are no memory leaks in the first program.

OP>Why is that anyone know?
That is because the .size() member function of the std::vector returns a size_t and not a int. size_t is usually a unsigned int defined by your implementation. Hence it is actually safe to do for(size_t i = 0; i< vec.size(); ++i)

By the way, in your second program, rather than first creating a vector and then resizing, it would have been better if you could have constructed a vector of the given size before hand.
Anyways, it wont matter here for the problem in hand.

Edit: I replied a bit slow.

Last edited by siddhant3s; Sep 2nd, 2009 at 10:42 am.

siddhant3s

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Sep 2nd, 2009

Re: Does this programme have any memory Leaks?

Click to Expand / Collapse Quote originally posted by siddhant3s ...

>In your function, you allocate new memory for the array
>that is passed, which already has been allocated memory.

I suppose he has commented that line.
Hence technically, there are no memory leaks in the first program.

I guess it was late. Didn't see the backlashes.

firstPerson

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Sep 2nd, 2009

Re: Does this programme have any memory Leaks?

Click to Expand / Collapse Quote originally posted by firstPerson ...

Are you sure. His program is tricky in a sense that there is a memory
leak. His function is definitely not doing what he thinks its doing.

One way to tell if you have memory leak is to see if every new
is matched with delete. In your function, you allocate new memory for the array
that is passed, which already has been allocated memory. So when
inside the function, the arrays thats passed is located in whatever
memory address that was reserved inside the function. When he
exits out that functions, that memory is no longer in play. Inside
main he has already the array pointing at a specific address.

So the memory inside the function has a leak. Also you use
2 instances of new but only 1 delete. Does that give you a hint?

Actually the second instance of new in the function is a comment.

Anyway for those you said I didn't have any memory leaks, thanks thats what I though, just wanted to make sure

Thanks Tom Gunn, the vector<int>::size_type, actually worked

Last edited by invisi; Sep 2nd, 2009 at 3:10 pm.

invisi

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