[bug #65930] [me] Large values of register "tv" cause fatal error

[Dave]

URL:
  <https://savannah.gnu.org/bugs/?65930>

                 Summary: [me] Large values of register "tv" cause fatal error
                   Group: GNU roff
               Submitter: barx
               Submitted: Sat 29 Jun 2024 03:48:35 PM CDT
                Category: Macro package me
                Severity: 3 - Normal
              Item Group: Incorrect 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: Sat 29 Jun 2024 03:48:35 PM CDT By: Dave <barx>
This bug is in at least 1.22.4 and 1.23.  The below example uses the register
name "$v" rather than its more modern alias "tv", so that the example works
the same in current and pre-1.23 code (which had not yet defined "tv").

$ cat stack-limit.me
.mso e.tmac
.br
.nr $v 421
$ groff stack-limit.me | wc
troff: fatal error: input stack limit exceeded (probable infinite loop)
    238     780    4673

Observations:
* The bug only happens with the .br request present.
* Values 420 and lower do not trigger the bug.  Values 421 and higher do.
        * This applies to output on the ps device.  On the ascii device, 421 
does not
trigger the bug, but 440 does.
* If any text is appended to the input file (either with or without a -me
paragraphing macro), that text _is_ present in the output, despite the error
above it being "fatal."

Yes, 421 is higher than most real-world values for the $v/tv register, so I
don't have a problem with this exceeding a supported limit.  But exceeding
that limit shouldn't provoke an ostensibly fatal error.  And "stack limit
exceeded" is a peculiar error for this to trigger.







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