What is memory leak?

Question

From so many days I was thinking what should be treated as memory leak and what should not be. Checked few links and wiki also but could not get satisfactory answer so that to ask here?

What you guys say about it i.e. what is considered as a memory leak in a program?

Answer 1

As per theoretical definition, if a process allocates a memory chunk and does not release after using it. This event is known as "Memory Leak".
Now come to practical definition of it. Every software has some requirement parameters like processor, memory, primary storage and secondary storage etc. While running if software takes memory more then what it suppose to take then it is known as memory leak and that situation may lead segmentation fault/system crash.

It is better to use tools like valgrind, purify etc to detect possible memory leaks and fix it before making any software release.

Answer 2

Just a high level info in simple words.
Whenever our application needs memory, it requests the Operating System because OS is the resource manager who takes care of sharing the valuable resources like CPU time & RAM among all the processes in a fair manner.

So when an application requests the OS for memory, the OS TAGS that memory location signifying that no other process is supposed to use this memory. And when we free this memory, the OS UNTAGS it so that it can be used by other processes. Now guess what happens if we forget to free this memory after our job is done??

This memory is left useless & wasted. Now since this memory is TAGGED, the OS cannot allocate this to any other process. This is called memory leak where the memory is only reserved but not used.

So to avoid this, the best practice is to run your code with valgrind / purify as suggested by Harshita.

Hope this helps!!