The current POSIX.1-202x draft (1.1) was used as source material.
Corresponding NetBSD manpage for comparison: https://man.netbsd.org/tcgetwinsize.3
Corresponding Bugzilla entry: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=251868
If this patch is accepted, then please use "soumendraganguly AT gmail DOTCOM" for submitter email address in the commit.