[bug #68420] [troff] assertion failures on impossible {normal, no-break} control character assignments

Dave <[email protected]> Mon, 8 Jun 2026 00:08:03 -0400 (EDT)

Newsgroups	gmane.comp.printing.groff.bugs
Message-ID	<[email protected]>

Follow-up Comment #12, bug #68420 (group groff):

[comment #7 comment #7:]
> CSTR #54 did not specify what happens when the control,
> no-break control, and escape characters are not all distinct.
...
> In _my opinion_, because the behavior is unspecified, no
> reliable prediction can be made.

This strikes me as somewhat a mischaracterization of CSTR #54.  To my
knowledge, it doesn't claim to be a specification.  One could argue that AT&T
troff itself is the specification; indeed, (1) many details about troff cannot
be answered by CSTR #54, and AT&T troff's behavior has been used to fill in
these gaps; and (2) when the behavior of AT&T troff differs from what CSTR #54
documents, it's the latter generally considered to be in error (unless the
"behavior is so anomalous that it must be considered a bug," as the groff
manual states at one point).

So the behavior in question is _undocumented_, but potentially still
_specified_, because AT&T troff did _something_ in this situation.

I don't know what that something is, so it too may fall in the
too-anomalous-to-clone bucket.  That is, the above are general observations,
not ironclad conclusions about this ticket.  I leave the exercise of applying
the general to the specific to Martin and/or the FreeBSD folk who authored the
unusual usage.


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