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Mar 23rd, 2005

The definiton of "Memory leaks"

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Could anyone define "Memory leaks" well ?
'cause pretty hard for me to understand with C++ books.

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tenoran

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Mar 23rd, 2005

Re: The definiton of "Memory leaks"

A memory leak is simply allocating memory and failing to release it when you're done. Technically, the following illustrates a memory leak:

C++ Syntax (Toggle Plain Text)
#include <iostream>
 
using namespace std;
 
int main()
{
  int *p = new int;
 
  *p = 10;
 
  cout<< *p << endl;
}
#include <iostream>

using namespace std;

int main()
{
  int *p = new int;

  *p = 10;

  cout<< *p << endl;
}

In practice, the operating system will typically reclaim all memory allocated to a process when the process terminates, but that's not required by the language definition. However, long running programs can consume all fast memory and grind the program to a near halt, or crash the system if virtual memory is also exhausted. So any call to new must be paired with a call to delete:

C++ Syntax (Toggle Plain Text)
#include <iostream>
 
using namespace std;
 
int main()
{
  int *p = new int;
 
  *p = 10;
 
  cout<< *p << endl;
 
  delete p;
}
#include <iostream>

using namespace std;

int main()
{
  int *p = new int;

  *p = 10;

  cout<< *p << endl;

  delete p;
}

Narue

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Mar 28th, 2005

Re: The definiton of "Memory leaks"

Thank you for the answer.

tenoran

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Mar 28th, 2005

Re: The definiton of "Memory leaks"

the best bit is creating a loop of new arrays and watching the memory size increase

Acidburn

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Mar 28th, 2005

Re: The definiton of "Memory leaks"

Hello Acidburn,

If you are going to do that, be sure to save your work first! I have done some expirements with linux processes, and was able to crash a computer in 20 seconds or so.

Christian

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Mar 28th, 2005

Re: The definiton of "Memory leaks"

20 secs? may I have a look at the code? I'm running windows and it just fills up the memory very slowly ...took around 4 hrs! .. .

Acidburn

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