lists.h
#include "structs.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct list{
   Instr head;
   struct list *tail;
} *ILIST;

ILIST mkList(Instr, ILIST);```

lists.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>

ILIST mkList(Instr n, ILIST l1) {
  ILIST l = malloc(sizeof(struct list));
  l->head = n;
  l->tail = l1;
  return l;
}


structs.h


#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef enum  {START, QUIT, ATRIB, ADD, SUB, MUL, PRINT, READ, IF, GOTO, LABEL} OpKind;
typedef enum {INT_CONST, STRING, EMPTY} ElemKind;

typedef struct{
  ElemKind kind;
  union
  {
    int val;
    char* name;
  }content;
} Elem;


structs.c


#include "structs.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>


I get erros like this

In file included from lists.h:1:0,
                 from main.c:3:
structs.h:5:16: error: redeclaration of enumerator ‘START’
 typedef enum  {START, QUIT, ATRIB, ADD, SUB, MUL, PRINT, READ, IF, GOTO, LABEL} OpKind;
                ^~~~~

In file included from main.c:1:0:
structs.h:5:16: note: previous definition of ‘START’ was here
 typedef enum  {START, QUIT, ATRIB, ADD, SUB, MUL, PRINT, READ, IF, GOTO, LABEL} OpKind;
                ^~~~~