extern structs in C Error: array type has incomplete element type

Question

I have two files, main.c and other.h. I declare a few global variables in main.c, and most of them are fine. I can say extern whatever in other.h and access those variables. However, I defined a struct like this (in main.c):

struct LSA {
     int myID;
     int seqNum;
     int neighborID[256];
     int costs[256];
 } local_LSA[256];

And when I try to access it in other.h like this

extern struct LSA local_LSA[256];

I get this error message

other.h:27:19: error: array type has incomplete element type ‘struct LSA’
extern struct LSA local_LSA[256];

I've been playing around with for a while, but... I appreciate any help anyone is able to provide!

Answer 1

The structure type needs to be defined before any instances of it can be created.

You need to move the struct definition into other.h before local_LSA is defined.