catch_with_backtrace/3 doesn't produce a backtrace message

[kamahen]

I modified packages/ltx2htm/latex2html.pl to output a backtrace on error, but didn't generate a backtrace when run as part of the build. When I ran the program by hand (using the -l option to avoid the automatic call to main/1), it trapped to the debugger and I could use the g command to get a backtrace. (The traceback shows catch_with_backtrace twice -- is this expected?)

@@ -81,6 +81,7 @@
 :- autoload(library(option),[option/2,select_option/3]).
 :- autoload(library(readutil),[read_file_to_codes/3]).
 :- autoload(library(statistics),[statistics/0]).
+:- use_module(library(prolog_stack)). % For catch_with_backtrace
 
 ltx2htm_version('0.98').                % for SWI-Prolog 5.6.18
 
@@ -3224,6 +3225,12 @@ cmd_layout(sloppy,     end,   1, 1).
 :- initialization(main, main).
 
 main(Argv) :-
+    catch_with_backtrace(main0(Argv),
+                         Error,
+                         (   print_message(error, Error),
+                             halt(1) )).
+
+main0(Argv) :-
     argv_options(Argv, Files, Options),
     set_debugging(Options),
     set_quiet(Options),

When I ran this by hand (reproducing what the build did), I got:

(cd /home/peter/src/swipl-devel/build.debug/packages/swipy && /home/peter/src/swipl-devel/build.debug/src/swipl -f none --no-packs /home/peter/src/swipl-devel/build.debug/home/library/ext/ltx2htm/latex2html.pl -- --quiet janus && /usr/bin/cmake -E remove /home/peter/src/swipl-devel/build.debug/home/doc/manindex.db)
ERROR: put_html_token/1: instantiation error
   Redo: (1,353) tex:write_html(nospace([])) ? 20g
  [1,353] tex:write_html(nospace([]))
  [1,352] tex:write_html([nospace([])])
  [1,351] tex:write_html([[nospace([])], nospace(')')])
  [1,349] tex:write_html([[nospace('('), [nospace([])], nospace(')')]])
  [1,347] tex:write_html([[py_dict_as, [nospace('('), [nospace([])], nospace(')')]], html('</b>')])
  [1,344] tex:write_html([lref(func, 'py_dict_as()', [py_dict_as, [nospace('('), [nospace(...)], nospace(...)]]), html('</code>'), html('</td>'), html('</tr>'), html('<tr>'), html('<td>'), lref(..., ..., ...)|...])
     [16] tex:run_latex2html('/home/peter/src/swipl-devel/build.debug/packages/swipy/janus.tex')
     [15] tex:latex2html(janus, [quiet(true)])
     [12] catch_with_backtrace('<garbage_collected>', '<garbage_collected>', '<garbage_collected>')
     [11] tex:main('<garbage_collected>')
      [9] catch_with_backtrace('<garbage_collected>', '<garbage_collected>', '<garbage_collected>')
      [8] prolog_main:main
      [5] run_init_goal('<garbage_collected>', @(tex:main, '/home/peter/src/swipl-devel/build.debug/home/library/ext/ltx2htm/latex2html.pl':3225))
   Redo: (1,353) tex:write_html(nospace([])) ? a
ERROR: Execution Aborted

When I ran this as part of the build, I got:

FAILED: packages/swipy/janus.html 
cd /home/peter/src/swipl-devel/build.debug/packages/swipy && /home/peter/src/swipl-devel/build.debug/src/swipl -f none --no-packs /home/peter/src/swipl-devel/build.debug/home/library/ext/ltx2htm/latex2html.pl -- --quiet janus && /usr/bin/cmake -E remove /home/peter/src/swipl-devel/build.debug/home/doc/manindex.db
ERROR: put_html_token/1: instantiation error
   Redo: (1,353) tex:write_html(nospace([])) ? EOF: exit (status 4)