eclipse - C: Implicit declaration of function ‘vsyslog’ -

i trying implement sys logger pam module. code follows:

#define __use_bsd #include <syslog.h> #include <stdarg.h>  #include <string.h>  static void _log(int level, const char *format, ...) {     va_list args;     va_start(args, format);     openlog("my_app", log_cons|log_pid|log_perror, log_auth);     vsyslog(level, format, args);     va_end(args);     closelog(); }  pam_extern int pam_sm_authenticate( pam_handle_t *pamh,     int flags,int argc, const char **argv ) {      /* something... */      _log(log_info, "username check");     if (strcmp(username, "jdoe") != 0) {         _log(log_err, "auth error");         return pam_ignore;     }      /* else... *  } 

but, when compile, eclipse cdt returns me warning:

../src/mypam.c:33:5: warning: implicit declaration of function ‘vsyslog’ [-wimplicit-function-declaration] 

how fix it? note using centos 7 dev machine.

fixed, defining both __use_bsd , _bsd_source follows:

#define __use_bsd #define _bsd_source #include <syslog.h> #include <stdarg.h>  // ...