C Linked List valgrind Invalid Read of Size

Question

I have a problem with my Linked List and the valgrind output. Without further adieu here is my linked list:

typedef struct Map map;

struct Map
{
    void *addr         


        

Answer 1

One problem that I see is that in delete_map_node you free root (which might be map_list passed from find_and_free_address), but you don't actually change map_list which means that when delete_map_node returns the map_list variable points to unallocated memory. Accessing map_list afterwards leads to undefined behavior.

The simple solution to this is to assign the return value of delete_map_node to map_list:

map_list = delete_map_node(map_list, current->free_time);

Also, what happens when delete_map_node frees the node in the list that is current in the find_and_free_address function? Then current = current->next will also lead to undefined behavior.