memory allocate free tracking

void *mmalloc(size_t size)
{
G_inUse += size;
return malloc(size);
}

void mfree(void *p)
{
size_t *sizePtr=((size_t *) p)-1;
G_inUse -= *sizePtr;
free(p);
}

Here if we request 10 bytes of memory, malloc will allocate 11 byte(for ex: address is 2000 means 1999 will have size of the alloceated memory)