[bug #61402] [man] handles degenerate input poorly

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?61402>

                 Summary: [man] handles degenerate input poorly
                 Project: GNU troff
            Submitted by: gbranden
            Submitted on: Sat 30 Oct 2021 02:19:45 AM UTC
                Category: Macro - man
                Severity: 3 - Normal
              Item Group: Warning/Suspicious behaviour
                  Status: In Progress
                 Privacy: Public
             Assigned to: gbranden
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None

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Details:

This is a regression from groff 1.22.4.


troff: backtrace: '.../groff/build/../tmac/an.tmac':475: macro 'an-footer'
troff: backtrace: '.../groff/build/../tmac/an.tmac':110: trap-called macro
'an-end'
troff: warning: register 'PS' not defined
troff: backtrace: '.../groff/build/../tmac/an.tmac':476: macro 'an-footer'
troff: backtrace: '.../groff/build/../tmac/an.tmac':110: trap-called macro
'an-end'
troff: warning: register 'VS' not defined
troff: backtrace: '.../groff/build/../tmac/an.tmac':479: macro 'an-footer'
troff: backtrace: '.../groff/build/../tmac/an.tmac':110: trap-called macro
'an-end'
troff: warning: macro 'an-pageref' not defined
troff: backtrace: '.../groff/build/../tmac/an.tmac':396: macro
'an-prepare-inner-footer'
troff: backtrace: '.../groff/build/../tmac/an.tmac':489: macro 'an-footer'
troff: backtrace: '.../groff/build/../tmac/an.tmac':110: trap-called macro
'an-end'
troff: warning: macro 'an-extra1' not defined
troff: backtrace: '.../groff/build/../tmac/an.tmac':399: macro
'an-prepare-inner-footer'
troff: backtrace: '.../groff/build/../tmac/an.tmac':489: macro 'an-footer'
troff: backtrace: '.../groff/build/../tmac/an.tmac':110: trap-called macro
'an-end'
troff: warning: start and end index of substring out of range
troff: backtrace: '.../groff/build/../tmac/an.tmac':401: macro
'an-prepare-inner-footer'
troff: backtrace: '.../groff/build/../tmac/an.tmac':489: macro 'an-footer'
troff: backtrace: '.../groff/build/../tmac/an.tmac':110: trap-called macro
'an-end'
troff: warning: macro 'an-extra2' not defined


Feeding our man(7) package blank lines as input should not result in this riot
of noise.  The problem is that our traps assume that TH has been called, which
is true for _useful_ man(7) documents.  Given n blank lines of input, groff
1.22.4 quietly produces a blank page as output, and so should groff 1.23.0.

Both versions of groff handle _null_ input silently.




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