[bug #64104] [troff] you can set the control and no-break control characters to the same thing

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?64104>

                 Summary: [troff] you can set the control and no-break control
characters to the same thing
                   Group: GNU roff
               Submitter: gbranden
               Submitted: Mon 24 Apr 2023 10:08:22 AM UTC
                Category: Core
                Severity: 3 - Normal
              Item Group: Warning/Suspicious behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Mon 24 Apr 2023 10:08:22 AM UTC By: G. Branden Robinson <gbranden>
You can set the control and no-break control characters to the same thing.

If you try:

DWB and Heirloom treat `c2` as always winning; groff treats `cc` as always
winning.


.c2 @
@cc @
foo
@br
bar
@pl \n(nlu



.cc @
@c2 @
foo
@br
bar
@pl \n(nlu


For both of the above inputs, groff produces


foo
bar


while DWB and Heirloom Doctools troff produce


foo bar


This should not be allowed.  Attempts should be diagnosed and ignored.  You
can swap 'em or whatever, if you want, but they should never be the same.

Also, doing this breaks the interpretation of the `pl` request on both DWB and
Heirloom.  No idea why.  Bugs dating back to the dawn of man, I reckon.







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