Extern array of structs

Question

I have a global array of structure declared as

struct _links link[255][255][255];

in my main.c. This array of structures is also used in another file, action.c, and I tried to declare it in action.c as an extern, i.e.

extern struct _links link[255][255][255];

However, I got the error message "array type has incomplete element type". I don't understand what that means. How can I resolve this problem?

Thank you.

Do you include the file containing the definition of `_links` in the second file? — Some programmer dude, Jan 17 '12 at 11:12

score 5 · Accepted Answer · edited Jan 17 '12 at 12:42

5

Define your structure struct _links in a header file; include that in both my_main.c and action.c, compile them seperately and link them.

It works without header file for in-built data types. but for user defined data types, header file is needed.

edited Jan 17 '12 at 12:42

pmdj

answered Jan 17 '12 at 11:58

sekhy

Note that the main reason for this is that the compiler can't know the size and alignment of the array elements in action.c without a complete definition of `struct _links`. – pmdj Jan 17 '12 at 12:04

score 2 · Answer 2 · answered Jan 17 '12 at 11:14

2

You have to declare a type struct _links somewhere.

answered Jan 17 '12 at 11:14

ouah

score 1 · Answer 3 · edited May 23 '17 at 10:34

1

a good programming practice is to create a new file links.h which contains

extern struct _links link[255][255][255];

include this file on both main.c and action.c .

do not forget to define the variable only once.

for more informations about extern keyword,take a look at this post https://stackoverflow.com/a/1433387/1117720

edited May 23 '17 at 10:34

Community

answered Jan 17 '12 at 12:02

Amine Hajyoussef

3 Answers3