void *my_malloc(size_t size)
{
    memblock_t result;
    if ((result = find_first_block(size)) == NULL)
        return (NULL);
    result->free = 0;
    result->size = size;
    return (result + sizeof(struct memblock_s));
}

memblock_t heap_memory = NULL;

void *find_first_block(size_t size)
{
    memblock_t tmp;

    if (heap_memory == NULL)
        init_heap_memory();
    tmp = heap_memory;
    while (tmp->next != NULL && (tmp->size < size || !tmp->free))
        tmp = tmp->next;
    if (tmp->next == NULL) {
        tmp->next = sbrk(0);
        if (sbrk(MEMBLOCK_SIZE + size) == (void*) -1)
            return (NULL);
        tmp->next->next = NULL;
        tmp->next->prev = tmp;
        brk(tmp->next + size + MEMBLOCK_SIZE);
    }
    return (tmp->next);
}



void init_heap_memory()
{
    if ((heap_memory = sbrk(MEMBLOCK_SIZE)) == (void*) -1)
        return;
    heap_memory->next = NULL;
    heap_memory->size = 0;
    heap_memory->prev = NULL;
    heap_memory->free = 0;
}

==32021== Invalid write of size 1
==32021==    at 0x4005E4: main (gdb-compliant-main.c:16)
==32021==  Address 0x4228422 is 902 bytes after the brk data segment limit 0x422809c