@dgl @cks @lyda
In the majority of cases there actually is no separate inet_pton() manual page.
https://man.freebsd.org/cgi/man.cgi?query=inet_pton&sektion=3
https://man.netbsd.org/inet_pton.3
http://tribblix.org/man/man3c/inet_pton.html
https://man.omnios.org/man3c/inet.3c
http://uw714doc.xinuos.com/en/man/html.3N/inet.3N.html
Although most of those call out inet_pton(), SCO #UnixWare in fact documented the four human-readable IPv4 formats for inet_pton(), and did not even have an inet_aton().
In #NetBSD, the internal inet_pton4() function was indeed updated by Christos Zoulas from the old Paul Vixie code to support the four human-readable formats of inet_aton(), 22 years ago; although it's not clear where this additional IPv4 conversion functionality is actually used.
The old Paul Vixie code from 1996 is retained in GNU libc, #FreeBSD, & #OpenBSD; this being code from the BIND DNS client library.
It was superseded by a from-scratch reimplementation based around a str2inet_addr() function in #Solaris/ #Illumos/ #Tribblix/ #OmniOS. musl libc also has its own from-scratch version.
@ska