QNX4 User Authentication (Newbie)

I’m a QNX Newbie who is trying to port an secure ftpd to qnx. The daemon
need to validate the userid and make sure the password matches the shadow
file. Everything works except for user authentication, getspnam is in
shadow.h but won’t link and I can’t find it in /usr/lib with a grep. Am I
doing something wrong? Are there any code examples availble in contributed
software or the documentation that shows user authentication on QNX 4.25?