two or more data types in declaration of `lock_open'

#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

#define QUEUE_SIZE 10

struct flock lock, unlock;

struct data
{
char name [80];
}

라인 21==>

int lock_open( int fd, int index)
{
        unlock.l_start = index;
        unlock.l_type = F_WRLCK;
        unlock.l_len = 1;
        unlock.l_whence = SEEK_SET;
        return fcntl(fd, F_SETLKW, &lock);
}

아래 이런 에러가 계속 뜨네요. 이유가 뭘까요?
provider.c:21: two or more data types in declaration of `lock_open'