If I run grog on an installed man page, for example

   grog -Tps /usr/share/man/man8/disklabel.8

it produces the output

   groff -mdoc.old -Tps /usr/share/man/man8/disklabel.8

This implies that there should be a troff macro file

     /usr/share/tmac/tmac.doc.old

There is no such file installed, so this command fails as a means of
identifying what troff options to use.

Am I doing something wrong here, or is this a bug?  Should there be a
tmac.doc.old file?  Should grog be changed?

Thanks for your help.

Cheers,
Brook