[bug #68340] [troff] ASAN runtime error when formatting groff_mdoc(7) in troff mode: ../src/roff/troff/input.cpp:4006:22

"G. Branden Robinson" <[email protected]> Mon, 25 May 2026 01:44:46 -0400 (EDT)

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

Update of bug #68340 (group groff):

                  Status:             In Progress => Fixed
             Open/Closed:                    Open => Closed

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Follow-up Comment #2:


commit fb2432fe60225d6c34e43b630e67cbc1c24e61d5
Author: G. Branden Robinson <[email protected]>
Date:   Sun May 17 14:32:33 2026 -0500

    [troff]: Remove heap-overreading optimization.
    
    * src/roff/troff/input.cpp (char_list::get): De-optimize read access at
      the end of a `char_list`, because the pointer arithmetic used can
      access heap storage beyond the end of the underlying `char_block` used
      to house the list.
    
    Fixes <https://savannah.gnu.org/bugs/?68340>.  Resolves ASAN runtime
    error when formatting the groff_mdoc(7) man page in troff mode.  Thanks
    to Bjarni Ingi Gislason for the report.
    
    Performance analysis
    ====================
    
    This change slows groff pipline operation by about 5% across the corpus
    of documents produced in its own build.  If someone would like to craft
    a new, more memory-safe optimization to recover the performance, please
    contact the groff at gnu dot org mailing list and share your proposal.
    
    (A better long-term fix might be to migrate `char_list` to an ISO C++98
    STL templated container type; these are often performance-tuned already
    by the compiler vendor.)
    
    $ cat measure.bash
    shopt -s extglob
    
    make -C build -j >/dev/null 2>&1
    
    for n in $(seq 20)
    do
            rm -f build/doc/!(groff).pdf build/doc/*.ps \
                    build/doc/!(groff).html \
                    build/contrib/hdtbl/examples/*.ps \
                    build/contrib/mom/examples/*.pdf \
                    contrib/sboxes/msboxes.pdf \
                    doc/groff-man-pages.utf8.txt
            t=$({ time -p make -C build >/dev/null 2>&1; } 2>/dev/stdout)
            echo "$t" | awk '/real/ { print $2; }'
    done
    
    Before
    ------
    
    $ bash ./measure.bash | tee | datamash range 1 mean 1 sstdev 1
    0.86    31.9025 0.24063239052218
    
    After
    -----
    
    $ bash ./measure.bash | tee | datamash range 1 mean 1 sstdev 1
    6.91    33.545  1.8817363202498




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