char pointer is struct array memory leak

Question

I'm having memory leaks in a larger program and I believe this is the cause of it.

#include <stdlib.h>
#include <Windows.h>

typedef struct _struct{
    char* name;
} str;

int main() {
    system("PAUSE");

    str* Character = (str*)malloc(sizeof(str) * 20000);

    for(int i = 0; i < 20000; i++){
        Character[i].name = (char*)malloc(20000);   // Assign memory.
    }

    for(int i = 0; i < 20000; i++){
        free(Character[i].name);            // Free memory.
    }

    free(Character);
    system("PAUSE");
}

Memory at first pause: ~500K.

Memory at second pause: ~1.7M.

Using VS2012 for testing. Any ideas?

Answer 1

How are you measuring the amount of memory occupied by the program? One thing off the top of my head is that you're looking at the size of the working set the OS is keeping track of. Since you've allocated and freed a lot of memory, the size of that set has increased. Some OSs will adjust the size of the working set after a while, some won't. What OS are we looking at here?

Answer 2

When you call malloc, memory is allocated on the heap. If there is insufficient space left on the heap, the program will ask the OS for more memory and another chunk is acquired. Memory acquired from the OS is usually not returned until the program finishes (although this is up to the OS).

Program size alone can not normally be used to check for memory leaks! Use Valgrind or a similar tool to check for memory that never gets freed.