Function free

test/libmm/memalloc.cpp:37–86

}

void free(void *block)
{
	header_t *header, *tmp;
	/* program break is the end of the process's data segment */
	void *programbreak;

	if (!block)
		return;
	pthread_mutex_lock(&global_malloc_lock);
	header = (header_t*)block - 1;
	/* sbrk(0) gives the current program break address */
	programbreak = sbrk(0);

	/*
	   Check if the block to be freed is the last one in the
	   linked list. If it is, then we could shrink the size of the
	   heap and release memory to OS. Else, we will keep the block
	   but mark it as free.
	 */
	if ((char*)block + header->s.size == programbreak) {
		if (head == tail) {
			head = tail = NULL;
		} else {
			tmp = head;
			while (tmp) {
				if(tmp->s.next == tail) {
					tmp->s.next = NULL;
					tail = tmp;
				}
				tmp = tmp->s.next;
			}
		}
		/*
		   sbrk() with a negative argument decrements the program break.
		   So memory is released by the program to OS.
		*/
		sbrk(0 - header->s.size - sizeof(header_t));
		/* Note: This lock does not really assure thread
		   safety, because sbrk() itself is not really
		   thread safe. Suppose there occurs a foregin sbrk(N)
		   after we find the program break and before we decrement
		   it, then we end up realeasing the memory obtained by
		   the foreign sbrk().
		*/
		pthread_mutex_unlock(&global_malloc_lock);
		return;
	}
	header->s.is_free = 1;
	pthread_mutex_unlock(&global_malloc_lock);
}

void *mymalloc(size_t size)
{