[bug #65322] [troff] chopping box diversions can crash the formatter

[G. Branden Robinson]

Update of bug #65322 (group groff):

                  Status:               Confirmed => Unreproducible         
             Assigned to:                gbranden => None                   
                 Summary: [troff] certain diversion stunts can crash the
formatter => [troff] chopping box diversions can crash the formatter

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Follow-up Comment #5:

I found out today that the reproducer no longer works to provoke this bug.

Deri changed _gropdf_ to stop provoking the bug as one of the "various
problems" resolved by a commit of his in April.

This ticket has nothing to do with bug #65585 because this one long predates
commit cd9fde325f (4 March 2024).  This bug reproduces all the way back to
_groff_ 1.22.3, well before my influence brought the codebase to ruin.  ;-) 
As noted in comment #0, the crash was due to an assertion failure put in by
James Clark decades ago.

Still, Deri's commit didn't change any C++ code.  So presumably it remains
possible to crash the formatter with appropriately crafted input.  Both the
code that Deri removed in this commit and the code at issue below (in comment
#0, "pdfmomclean") involve doing surgery on diversions (box diversions only?)
with the `chop` request.

So we need a new reproducer.


2387949ffc11b753dd91480dcb85be6c22819790 is the first fixed commit
commit 2387949ffc11b753dd91480dcb85be6c22819790
Author: Deri James <deri@chuzzlewit.myzen.co.uk>
Date:   Fri Apr 12 17:10:49 2024 +0100

    Correct linear search introduced in commit cd9fde325f
    
    * tmac/pdf.tmac: Various problems have been rectified, speed
    improvements to the linear search, Keith protection against
    illegal characters being used in string identifiers.
    
    * contrib/mom/om.tmac: Switch to using Branden's linear search
    so that we don't have to maintain two different methods.
    
    Fixes <https://savannah.gnu.org/bugs/?65585>

 ChangeLog           | 31 ++++++++++++++++++++++
 contrib/mom/om.tmac |  5 ++--
 tmac/pdf.tmac       | 76
+++++++++++++++++++++++------------------------------
 3 files changed, 67 insertions(+), 45 deletions(-)




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