Initialization discards qualifiers from pointer target type
It's this part:
LIST *start = head;The parameter for the function is a pointer to a constant, const LIST *head; this means you cannot change what it is pointing to. However, the pointer above is to non-const; you could dereference it and change it.
It needs to be const as well:
const LIST *start = head;The same applies to your return type.
All the compiler is saying is: "Hey, you said to the caller 'I won't change anything', but you're opening up opportunities for that."
In following function, would get the warning that you encountered with.
void test(const char *str) { char *s = str;}There are 3 choices:
Remove the const modifier of param:
void test(char *str) { char *s = str;}Declare the target variable also as const:
void test(const char *str) { const char *s = str;}Use a type convert:
void test(const char *str) { char *s = (char *)str;}