Add new function in pam_syslog.c - c

Question

My code uses Pam library for user authentication. When the there is a failure to login. I would need to print syslog message in a specific format, instead of the current syslog format in the function pam_vsyslog of libpam library.
I intend to write a new function that would write syslog in my required format.
Below are definitions : in file pam_ext.h
extern void PAM_FORMAT((printf, 3, 0)) PAM_NONNULL((3))
pam_kniwx_vsyslog (const pam_handle_t *pamh, int priority,
const char *fmt, va_list args);
extern void PAM_FORMAT((printf, 3, 4)) PAM_NONNULL((3))
pam_kniwx_syslog (const pam_handle_t *pamh, int priority, const char *fmt, ...);
Implementation: libpam/libpam/pam_syslog.c
pam_kniwx_vsyslog (const pam_handle_t *pamh, int priority,
const char *fmt, va_list args)
{
char *msgbuf2 = NULL;
int save_errno = errno;
errno = save_errno;
if (vasprintf (&msgbuf2, fmt, args) < 0)
{
syslog (LOG_AUTHPRIV|LOG_ERR, "vasprintf: %m");
_pam_drop (msgbuf1);
return;
}
errno = save_errno;
syslog (LOG_AUTHPRIV|priority, "%s", msgbuf2);
_pam_drop (msgbuf2);
}
void
pam_kniwx_syslog (const pam_handle_t *pamh, int priority,
const char *fmt, ...)
{
va_list args;
va_start (args, fmt);
pam_kniwx_vsyslog (pamh, priority, fmt, args);
va_end (args);
}
In case of authentication failure I would like to invoke pam_kniwx_syslog from libpam/modules/pam_unix/support.c function :
pam_kniwx_syslog(pamh, LOG_NOTICE,
"authentication failure; "
"logname=%s uid=%d euid=%d "
tty=%s ruser=%s rhost=%s "
"%s%s",
new->name, new->uid, new->euid,
tty ? (const char *)tty : "",
ruser ? (const char *)ruser : "",
rhost ? (const char *)rhost : "",
new->user && new->user[0] != '\0')
? " user=" : "",
new->user
);
With this change When I compile the code, I seem to run into undefined reference in spite having the definitions and the header file inclusion.
/usr/src/debug/libpam/1.3.0-r5/libpam-1.3.0/modules/pam_unix/../../../../../../../../libpam/modules/pam_unix/support.c:850: undefined reference to `pam_kniwx_syslog'
collect2: error: ld returned 1 exit status
Makefile:799: recipe for target 'pam_unix.la' failed
make[3]: *** [pam_unix.la] Error 1
make[3]: Leaving directory
Any help to resolve the issue is much appreciated.