Expert: Narendra - 2/27/2006

Question
what happens if I do this (in C on unix)..

 /* program starts */
int *p;
p = (int *) calloc(100, sizeof(int));
 /* other lines of code where use 'p' */  
p = (int *) calloc(10, sizeof(int));
 /* in above line use calloc, instead of realloc */
 /* lines of code, and use 'p' */
free(p);
 /*program ends */

Want to know...?
1)how much memory will it free?
2)will there be any memory leak? If yes then how to check it?

Answer
Here you are allocating (100 * sizeof (int)) to p.
Again in the next line, you are overwriting it by allocating another (10 * sizeof(int)).
So, because of this, you have lost the address that you have got with the first allocation.

Becasue of this, if you try to free(p), it will free only the 10 locations that was allocated in the end.

Obviously there is a memory leak.
And there are some memory profilers available, which will very easily catch these type of leaks.
You can try memprof which is available for unix platforms.

Also, you can search in the google for any other better profilers.

Hope this helps.