Trying to make linkedlist in C

Question

I am trying to make a struct in C that is a linked list. I am not really sure what is going wrong though. My errors are:

linked.c:6:2: error: unknown type name         


        

Answer 1

The C compiler doesn't have a complete typedef of linkedList before you attempt to use it in your struct. You have a couple of options:

typedef struct linkedList
{
    int first;
    struct linkedList* rest;
} linkedList;

Or:

typedef struct linkedList linkedList;  // C allows this forward declaration

struct linkedList
{
    int first;
    linkedList* rest;
};

This is your starting point.

Additional problems include but are not limited to:

• Your makeList function refers to variable first but it doesn't appear to be defined anywhere.
• ll->rest = newL; assigned a type linkedList to a pointer to linkedList (linkedList *) you can't assign a value to a pointer-to-value. The compiler error message linked.c:43:13:... states this. It would need to be ll->rest = &newL;... HOWEVER...
• newL is LOCAL to the function addToList, so you can't assign it's address to a persistent list item since it will go out of scope when the code leaves that block.
• In addToList you are assigning pointer to integer to a variable that holds pointer to linkedList, e.g., second.rest = &c;.