Debugging embeded scheme

* Debugging embeded scheme
@ 2004-04-03  4:31 Linas Vepstas
  2004-04-03  5:08 ` Viktor Pavlenko
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Linas Vepstas @ 2004-04-03  4:31 UTC (permalink / raw)
  Cc: linas

Hi,

I'm having a miserable time figuring out how to debug embeded
scheme/guile.  I just can't figure out how to get meaningful
debugging info.  Let me explain what the problem is:

Application is GnoTime (gttr.sourceforge.net)

The pseudocode is roughly:

    scm_c_define_gsubr(...) /* 20 or 30 of these */
    scm_c_primitive_load ("/wherever/gtt.scm");
    while () {
       gh_eval_str_with_catch (str, my_catch_handler);
    }

where I use the following:

static SCM
my_catch_handler (void *data, SCM tag, SCM throw_args)
{
   printf ("Error: GnoTime caught error during scheme parse\n");
   if (SCM_SYMBOLP(tag))
   {
      char * str  = SCM_SYMBOL_CHARS (tag);
      printf ("\tScheme error was: %s\n", str);
   }
   scm_backtrace();
   return SCM_EOL;
}

As long as things were simple, I could "guess" where the bug was;
but its now gotten out of control.  The above setup gives me output
that is unhelpful to the extreme:  gtt.scm is several hundred lines
long, and the embeded stuff in gh_eval_str_with_catch() is dozens
of lines longer.  And all I get is:

   Error: GnoTime caught error during scheme parse
           Scheme error was: unbound-variable
   No backtrace available.
   Error: GnoTime caught error during scheme parse
           Scheme error was: misc-error
   No backtrace available.
   Error: GnoTime caught error during scheme parse
           Scheme error was: wrong-type-arg
   No backtrace available.

Adding things like
   (trace (my-fun))   is what produced the first unbound-variable.
Although clearly my-fun is  defined and works fine...

After googling, I tried adding things like
(debug-enable 'debug 'backtrace) and all I got
for my efforts was a flat out crash:

   ERROR: In procedure debug-options-interface:
   ERROR: Unknown mode flag: debug

   Program exited with code 02.

I am trying to decipher the gh_stack_trace type functions right now,
but I thought I'd ask on the mailing list ... It sure would be nice
if the guile documentation actually described how to use this stuff.

I'm also looking at scm_display_backtrace() but I can't figure out 
how to use 'ports' (since my app does no i/o; there's no stdin/stdout,
since its a graphical app. ).  I'm also staring at 
scm_internal_stack_catch() but with a name like that, can't figure out 
if its legal for apps to use it or not.

--linas.

-- 
pub  1024D/01045933 2001-02-01 Linas Vepstas (Labas!) <linas@linas.org>
PGP Key fingerprint = 8305 2521 6000 0B5E 8984  3F54 64A9 9A82 0104 5933

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