/usr/share/man/man1/camlp4o.opt.1.gz is in camlp4 3.12.1-2ubuntu2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man1/camlp4.1.gz
/usr/share/man/man1/camlp4.1.gz