C: implicit declaration of function ‘getpwnam_r’ - c

Question

While retrieving the broken-out fields of the record in the password database (e.g., the local password file /etc/passwd, NIS, and LDAP) that matches a provided username name, I am using the getpwnam_r (http://linux.die.net/man/3/getpwnam_r) function.
#define __USE_BSD
#define _BSD_SOURCE
#include <pwd.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
int
main(int argc, char *argv[])
{
struct passwd pwd;
struct passwd *result;
char *buf;
size_t bufsize;
int s;
if (argc != 2) {
fprintf(stderr, "Usage: %s username\n", argv[0]);
exit(EXIT_FAILURE);
}
bufsize = sysconf(_SC_GETPW_R_SIZE_MAX);
if (bufsize == -1) /* Value was indeterminate */
bufsize = 16384; /* Should be more than enough */
buf = malloc(bufsize);
if (buf == NULL) {
perror("malloc");
exit(EXIT_FAILURE);
}
s = getpwnam_r(argv[1], &pwd, buf, bufsize, &result);
if (result == NULL) {
if (s == 0)
printf("Not found\n");
else {
errno = s;
perror("getpwnam_r");
}
exit(EXIT_FAILURE);
}
printf("Name: %s; UID: %ld\n", pwd.pw_gecos, (long) pwd.pw_uid);
exit(EXIT_SUCCESS);
}
The code works fine, but Eclipse shows me a warning as follows:
warning: implicit declaration of function ‘getpwnam_r’ [-Wimplicit-function-declaration]
How could I fix it?
Note that I'm currently using Ubuntu 14.04 LTS.

Answer 1

To use this function you need two includes :
#include <sys/types.h>
#include <pwd.h>
Add them and it should not complain anymore.
You can see that by running man getpwnam_r.
You also need to define either __USE_MISC or __USE_SVID since it a POSIX only function.