[bug #61798] [grohtml] "invalid argument 'H' to output suppression escape sequence"

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?61798>

                 Summary: [grohtml] "invalid argument 'H' to output
suppression escape sequence"
                 Project: GNU troff
            Submitted by: gbranden
            Submitted on: Tue 11 Jan 2022 09:40:59 PM UTC
                Category: Preprocessor html
                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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Details:

This issue is spawned off of comment #1 from bug #61748.

Bjarni reported:


  I do not get any trouble processing the minimal example.

  I do get errors when processing "doc/grnexmpl.me":

  The pipe is

soelim grnexmpl.me | grn -Thtml | eqn -Tps:html | pre-grohtml troff -b \
  -ww -me -Thtml | post-grohtml

  The strings "10", and "g9" come from "eqn" (eqn grnexmpl.me).

  The "output suppression escape sequence" is "\O" and valid arguments
are the numbers 0-4 and string "5...".

  An exaple of the error messages is:

troff: backtrace: './grnexmpl.me':44: string '10'
troff: backtrace: file './grnexmpl.me':43
troff:./grnexmpl.me:43: error: invalid argument 'H' to output suppression
escape sequence
troff: backtrace: './grnexmpl.me':44: string '10'
troff: backtrace: file './grnexmpl.me':43
troff:./grnexmpl.me:43: error: invalid argument 'H' to output suppression
escape sequence
troff: backtrace: './grnexmpl.me':44: string '10'
troff: backtrace: file './grnexmpl.me':43

  All messages are in the attachment.


I've seen this too, occasionally, but had no reproducer.  Bjarni followed up.


Correction to comment #1
  String '10' comes from "grnexmpl.g", string 'g9' from "grn".
####
  Using programs from the repository.

  This produces no '\O' output:

soelim grnexmpl.me | grn -Thtml | eqn -Thtml |& less

  This produces '\O' output:

soelim grnexmpl.me | grn -Thtml | eqn -Tps:html |& less

  For example:

.i "spreading ratio" .
.nr 0C \n(.C
.cp 0
.ds 10
.eo
.as 10 "This reset phase is controlled by clocks
.ec
.as1 10 \O[HTML-IMAGE-INLINE-BEGIN]
.nr 0sfont \n[.f]
.ft
.nr 0spfont \n[.f]

  Using groff 1.22.4 (Debian/testing), that is with a prefix "/usr/bin"
to each command and in the directory /usr/share/doc/groff-base/examples,
shows the same results.


I have an inkling that the issue is with `pre-grohtml`, but I'm not certain. 
Assigning it to that category tentatively.




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