src/debug.cc

/*

Copyright (C) 2007, 2008, 2009 John Swensen
Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006 Ben Sapp

This file is part of Octave.

Octave is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 3 of the License, or (at your
option) any later version.

Octave is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with Octave; see the file COPYING.  If not, see
<http://www.gnu.org/licenses/>.

*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <deque>
#include <fstream>
#include <iostream>
#include <set>
#include <string>

#include "file-stat.h"

#include "defun.h"
#include "error.h"
#include "help.h"
#include "input.h"
#include "pager.h"
#include "oct-obj.h"
#include "utils.h"
#include "parse.h"
#include "symtab.h"
#include "gripes.h"
#include "ov.h"
#include "ov-usr-fcn.h"
#include "ov-fcn.h"
#include "ov-struct.h"
#include "pt-pr-code.h"
#include "pt-bp.h"
#include "pt-eval.h"
#include "pt-stmt.h"
#include "toplev.h"
#include "unwind-prot.h"
#include "variables.h"

#include "debug.h"

// Initialize the singleton object
bp_table *bp_table::instance = 0;

static std::string
snarf_file (const std::string& fname)
{
  std::string retval;

  file_stat fs (fname);

  if (fs)
    {
      size_t sz = fs.size ();

      std::ifstream file (fname.c_str (), std::ios::in|std::ios::binary);

      if (file)
	{
	  std::string buf (sz+1, 0);

	  file.read (&buf[0], sz+1);

	  if (file.eof ())
	    {
	      // Expected to read the entire file.

	      retval = buf;
	    }
	  else
	    error ("error reading file %s", fname.c_str ());
	}
    }

  return retval;
}

static std::deque<size_t>
get_line_offsets (const std::string& buf)
{
  // This could maybe be smarter.  Is deque the right thing to use
  // here?

  std::deque<size_t> offsets;

  offsets.push_back (0);

  size_t len = buf.length ();

  for (size_t i = 0; i < len; i++)
    {
      char c = buf[i];

      if (c == '\r' && ++i < len)
	{
	  c = buf[i];

	  if (c == '\n')
	    offsets.push_back (i+1);
	  else
	    offsets.push_back (i);
	}
      else if (c == '\n')
	offsets.push_back (i+1);
    }

  offsets.push_back (len);

  return offsets;
}

std::string
get_file_line (const std::string& fname, size_t line)
{
  std::string retval;

  static std::string last_fname;

  static std::string buf;

  static std::deque<size_t> offsets;

  if (fname != last_fname)
    {
      buf = snarf_file (fname);

      offsets = get_line_offsets (buf);
    }

  if (line > 0)
    line--;

  if (line < offsets.size () - 1)
    {
      size_t bol = offsets[line];
      size_t eol = offsets[line+1];

      while (eol > 0 && (buf[eol-1] == '\n' || buf[eol-1] == '\r'))
	eol--;

      retval = buf.substr (bol, eol - bol);
    }

  return retval;
}

// Return a pointer to the user-defined function FNAME.  If FNAME is
// empty, search backward for the first user-defined function in the
// current call stack.

static octave_user_code *
get_user_code (const std::string& fname = std::string ())
{
  octave_user_code *dbg_fcn = 0;

  if (fname.empty ())
    dbg_fcn = octave_call_stack::caller_user_code ();
  else
    {
      octave_value fcn = symbol_table::find_function (fname);

      if (fcn.is_defined () && fcn.is_user_code ())
	dbg_fcn = fcn.user_code_value ();
    }

  return dbg_fcn;
}

static void
parse_dbfunction_params (const char *who, const octave_value_list& args, 
			 std::string& symbol_name, bp_table::intmap& lines)
{
  int nargin = args.length ();
  int idx = 0;
  int list_idx = 0;
  symbol_name = std::string ();
  lines = bp_table::intmap ();

  if (args.length () == 0)
    return;

  // If we are already in a debugging function.
  if (octave_call_stack::caller_user_code ())
    {
      idx = 0;
      symbol_name = get_user_code ()->name ();
    }
  else if (args(0).is_map ())
    {
      // Problem because parse_dbfunction_params() can only pass out a
      // single function
    }
  else if (args(0).is_string())
    {
      symbol_name = args(0).string_value ();
      if (error_state)
	return;
      idx = 1;
    }
  else
    error ("%s: invalid parameter specified", who);

  for (int i = idx; i < nargin; i++ )
    {
      if (args(i).is_string ())
	{
	  int line = atoi (args(i).string_value().c_str ());
	  if (error_state)
	    break;
	  lines[list_idx++] = line;
	}
      else if (args(i).is_map ())
	octave_stdout << who << ": accepting a struct" << std::endl;
      else
	{
	  const NDArray arg = args(i).array_value ();
	  
	  if (error_state)
	    break;
	  
	  for (octave_idx_type j = 0; j < arg.nelem (); j++)
	    {
	      int line = static_cast<int> (arg.elem (j));
	      if (error_state)
		break;
	      lines[list_idx++] = line;
	    }
	  
	  if (error_state)
	    break;
	}
    } 
}

bp_table::intmap
bp_table::do_add_breakpoint (const std::string& fname, 
			     const bp_table::intmap& line)
{
  intmap retval;

  octave_idx_type len = line.size ();

  octave_user_code *dbg_fcn = get_user_code (fname);

  if (dbg_fcn)
    {
      tree_statement_list *cmds = dbg_fcn->body ();

      if (cmds)
	{
	  for (int i = 0; i < len; i++)
	    {
	      const_intmap_iterator p = line.find (i);

	      if (p != line.end ())
		{
		  int lineno = p->second;

		  retval[i] = cmds->set_breakpoint (lineno);

		  if (retval[i] != 0)
		    {
		      bp_set.insert (fname);
		    }
		}
	    }
	}
    }
  else
    error ("add_breakpoint: unable to find the function requested\n");

  tree_evaluator::debug_mode = bp_table::have_breakpoints () || Vdebugging;

  return retval;
}


int 
bp_table::do_remove_breakpoint (const std::string& fname, 
				const bp_table::intmap& line)
{
  int retval = 0;

  octave_idx_type len = line.size ();

  if (len == 0)
    {
      intmap results = remove_all_breakpoints_in_file (fname);
      retval = results.size ();
    }
  else
    {
      octave_user_code *dbg_fcn = get_user_code (fname);

      if (dbg_fcn)
	{
	  tree_statement_list *cmds = dbg_fcn->body ();

	  if (cmds)
	    {
	      octave_value_list results = cmds->list_breakpoints ();

	      if (results.length () > 0)
		{
		  for (int i = 0; i < len; i++)
		    {
		      const_intmap_iterator p = line.find (i);

		      if (p != line.end ())
			cmds->delete_breakpoint (p->second);
		    }

		  results = cmds->list_breakpoints ();

		  bp_set_iterator it = bp_set.find (fname);
		  if (results.length () == 0 && it != bp_set.end ())
		    bp_set.erase (it);

		}

	      retval = results.length ();
	    }
	}
      else
	error ("remove_breakpoint: unable to find the function requested\n");
    }

  tree_evaluator::debug_mode = bp_table::have_breakpoints () || Vdebugging;

  return retval;
}


bp_table::intmap
bp_table::do_remove_all_breakpoints_in_file (const std::string& fname, 
					     bool silent)
{
  intmap retval;

  octave_user_code *dbg_fcn = get_user_code (fname);
  
  if (dbg_fcn)
    {
      tree_statement_list *cmds = dbg_fcn->body ();

      if (cmds)
	{
	  octave_value_list bkpts = cmds->list_breakpoints ();

	  for (int i = 0; i < bkpts.length (); i++)
	    {
	      int lineno = static_cast<int> (bkpts(i).int_value ());
	      cmds->delete_breakpoint (lineno);
	      retval[i] = lineno;
	    }

	  bp_set_iterator it = bp_set.find (fname);
	  if (it != bp_set.end ())
	    bp_set.erase (it);

	}
    }
  else if (! silent)
    error ("remove_all_breakpoint_in_file: "
	   "unable to find the function requested\n");

  tree_evaluator::debug_mode = bp_table::have_breakpoints () || Vdebugging;

  return retval;
}

void 
bp_table::do_remove_all_breakpoints (void)
{
  for (const_bp_set_iterator it = bp_set.begin (); it != bp_set.end (); it++)
    remove_all_breakpoints_in_file (*it);


  tree_evaluator::debug_mode = bp_table::have_breakpoints () || Vdebugging;
}

std::string 
do_find_bkpt_list (octave_value_list slist, 
		   std::string match)
{
  std::string retval;

  for (int i = 0; i < slist.length (); i++)
    {
      if (slist (i).string_value () == match)
	{
	  retval = slist(i).string_value ();
	  break;
	}
    }

  return retval;
}


bp_table::fname_line_map
bp_table::do_get_breakpoint_list (const octave_value_list& fname_list)
{
  fname_line_map retval;

  for (bp_set_iterator it = bp_set.begin (); it != bp_set.end (); it++)
    {
      if (fname_list.length () == 0
	  || do_find_bkpt_list (fname_list, *it) != "")
	{
	  octave_user_code *f = get_user_code (*it);

	  if (f)
	    {
	      tree_statement_list *cmds = f->body ();

	      if (cmds)
		{
		  octave_value_list bkpts = cmds->list_breakpoints ();
		  octave_idx_type len = bkpts.length (); 

		  if (len > 0)
		    {
		      bp_table::intmap bkpts_vec;
		      
		      for (int i = 0; i < len; i++)
			bkpts_vec[i] = bkpts (i).double_value ();
		      
		      std::string symbol_name = f->name ();

		      retval[symbol_name] = bkpts_vec;
		    }
		}
	    }
	}
    }

  return retval;
}

static octave_value
intmap_to_ov (const bp_table::intmap& line) 
{
  int idx = 0;

  NDArray retval (dim_vector (1, line.size ()));

  for (size_t i = 0; i < line.size (); i++)
    {
      bp_table::const_intmap_iterator p = line.find (i);

      if (p != line.end ())
	{
	  int lineno = p->second;
	  retval(idx++) = lineno;
	}
    }

  retval.resize (dim_vector (1, idx));

  return retval;
}

DEFUN (dbstop, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Loadable Function} {@var{rline} =} dbstop (@var{func}, @var{line}, @dots{})\n\
Set a breakpoint in a function\n\
@table @code\n\
@item func\n\
String representing the function name.  When already in debug\n\
mode this should be left out and only the line should be given.\n\
@item line\n\
Line number you would like the breakpoint to be set on.  Multiple\n\
lines might be given as separate arguments or as a vector.\n\
@end table\n\
\n\
The rline returned is the real line that the breakpoint was set at.\n\
@seealso{dbclear, dbstatus, dbstep}\n\
@end deftypefn")
{
  bp_table::intmap retval;
  std::string symbol_name;
  bp_table::intmap lines;

  parse_dbfunction_params ("dbstop", args, symbol_name, lines);

  if (lines.size () == 0)
    lines[0] = 1;

  if (! error_state)
    retval = bp_table::add_breakpoint (symbol_name, lines);

  return intmap_to_ov (retval);
}

DEFUN (dbclear, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Loadable Function} {} dbclear (@var{func}, @var{line}, @dots{})\n\
Delete a breakpoint in a function\n\
@table @code\n\
@item func\n\
String representing the function name.  When already in debug\n\
mode this should be left out and only the line should be given.\n\
@item line\n\
Line number where you would like to remove the breakpoint.  Multiple\n\
lines might be given as separate arguments or as a vector.\n\
@end table\n\
No checking is done to make sure that the line you requested is really\n\
a breakpoint.  If you get the wrong line nothing will happen.\n\
@seealso{dbstop, dbstatus, dbwhere}\n\
@end deftypefn")
{
  octave_value retval;
  std::string symbol_name = "";
  bp_table::intmap lines;

  parse_dbfunction_params ("dbclear", args, symbol_name, lines);
      
  if (! error_state)
    bp_table::remove_breakpoint (symbol_name, lines);

  return retval;
}

DEFUN (dbstatus, args, nargout,
  "-*- texinfo -*-\n\
@deftypefn {Loadable Function} {lst =} dbstatus (@var{func})\n\
Return a vector containing the lines on which a function has \n\
breakpoints set.\n\
@table @code\n\
@item func\n\
String representing the function name.  When already in debug\n\
mode this should be left out.\n\
@end table\n\
@seealso{dbclear, dbwhere}\n\
@end deftypefn")
{
  Octave_map retval;
  int nargin = args.length ();
  octave_value_list fcn_list;
  bp_table::fname_line_map bp_list;
  std::string symbol_name;

  if (nargin != 0 && nargin != 1)
    {
      error ("dbstatus: only zero or one arguements accepted\n");
      return octave_value ();
    }

  if (nargin == 1)
    {
      if (args(0).is_string ())
	{
	  symbol_name = args(0).string_value ();
	  fcn_list(0) = symbol_name;
	  bp_list = bp_table::get_breakpoint_list (fcn_list);
	}
      else
	gripe_wrong_type_arg ("dbstatus", args(0));
    }
  else
    {
       octave_user_code *dbg_fcn = get_user_code ();
       if (dbg_fcn)
	 {
	   symbol_name = dbg_fcn->name ();
	   fcn_list(0) = symbol_name;
	 }

       bp_list = bp_table::get_breakpoint_list (fcn_list);
    }

  if (nargout == 0)
    {
      // Print out the breakpoint information.

      for (bp_table::fname_line_map_iterator it = bp_list.begin ();
	   it != bp_list.end (); it++)
	{	  
	  octave_stdout << "Breakpoint in " << it->first << " at line(s) ";

	  bp_table::intmap m = it->second;

	  size_t nel = m.size ();

	  for (size_t j = 0; j < nel; j++)
	    octave_stdout << m[j] << ((j < nel - 1) ? ", " : ".");

	  if (nel > 0)
	    octave_stdout << std::endl;
	}
      return octave_value ();
    }
  else
    {
      // Fill in an array for return.

      int i = 0;
      Cell names (dim_vector (bp_list.size (), 1));
      Cell file (dim_vector (bp_list.size (), 1));
      Cell line (dim_vector (bp_list.size (), 1));

      for (bp_table::const_fname_line_map_iterator it = bp_list.begin ();
	   it != bp_list.end (); it++)
	{
	  names(i) = it->first;
	  line(i) = intmap_to_ov (it->second);
	  file(i) = do_which (it->first);
	  i++;
	}

      retval.assign ("name", names);
      retval.assign ("file", file);
      retval.assign ("line", line);

      return octave_value (retval);
    }
}

DEFUN (dbwhere, , ,
  "-*- texinfo -*-\n\
@deftypefn {Loadable Function} {} dbwhere ()\n\
Show where we are in the code\n\
@seealso{dbclear, dbstatus, dbstop}\n\
@end deftypefn")
{
  octave_value retval;

  octave_user_code *dbg_fcn = get_user_code ();

  if (dbg_fcn)
    {
      bool have_file = true;

      std::string name = dbg_fcn->fcn_file_name ();

      if (name.empty ())
	{
	  have_file = false;

	  name = dbg_fcn->name ();
	}

      octave_stdout << name << ":";

      unwind_protect frame;

      frame.add_fcn (octave_call_stack::restore_frame, 
                     octave_call_stack::current_frame ());

      // Skip the frame assigned to the dbwhere function.
      octave_call_stack::goto_frame_relative (0);

      int l = octave_call_stack::current_line ();

      if (l > 0)
	{
	  octave_stdout << " line " << l;

	  int c = octave_call_stack::current_column ();

	  if (c > 0)
	    octave_stdout << ", column " << c;

	  octave_stdout << std::endl;

	  if (have_file)
	    {
	      std::string line = get_file_line (name, l);

	      if (! line.empty ())
		octave_stdout << l << ": " << line << std::endl;
	    }
	}
      else
	octave_stdout << " (unknown line)\n";
    }
  else
    error ("dbwhere: must be inside of a user function to use dbwhere\n");

  return retval;
}

// Copied and modified from the do_type command in help.cc
// Maybe we could share some code?
void
do_dbtype (std::ostream& os, const std::string& name, int start, int end)
{
  std::string ff = fcn_file_in_path (name);

  if (! ff.empty ())
    {
      std::ifstream fs (ff.c_str (), std::ios::in);

      if (fs)
	{
	  char ch;
	  int line = 1;
	
	  if (line >= start && line <= end)
	    os << line << "\t";
 	
	  while (fs.get (ch))
	    {
	      if (line >= start && line <= end)
		{
		  os << ch;
		}

	      if (ch == '\n')
		{
		  line++;
		  if (line >= start && line <= end)
		    os << line << "\t";
		}
	    }
	}
      else
	os << "dbtype: unable to open `" << ff << "' for reading!\n";
    }
  else
    os << "dbtype: unknown function " << name << "\n";

  os.flush ();
}

DEFUN (dbtype, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Loadable Function} {} dbtype ()\n\
List script file with line numbers.\n\
@seealso{dbclear, dbstatus, dbstop}\n\
@end deftypefn")
{
  octave_value retval;
  octave_user_code *dbg_fcn;

  int nargin = args.length ();
  string_vector argv = args.make_argv ("dbtype");

  if (! error_state)
    {
      switch (nargin)
	{
	case 0: // dbtype
	  dbg_fcn = get_user_code ();

	  if (dbg_fcn)
	    do_dbtype (octave_stdout, dbg_fcn->name (), 0, INT_MAX);
	  else
	    error ("dbtype: must be in a user function to give no arguments to dbtype\n");
	  break;

	case 1: // (dbtype func) || (dbtype start:end)
	  dbg_fcn = get_user_code (argv[1]);

	  if (dbg_fcn)
	    do_dbtype (octave_stdout, dbg_fcn->name (), 0, INT_MAX);
	  else
	    {
	      dbg_fcn = get_user_code ();

	      if (dbg_fcn)
		{
		  std::string arg = argv[1];

		  size_t ind = arg.find (':');

		  if (ind != std::string::npos)
		    {
		      std::string start_str = arg.substr (0, ind);
		      std::string end_str = arg.substr (ind + 1);

		      int start = atoi (start_str.c_str ());
		      int end = atoi (end_str.c_str ());
		
		      if (std::min (start, end) <= 0)
 			error ("dbtype: start and end lines must be >= 1\n");

		      if (start <= end)
			do_dbtype (octave_stdout, dbg_fcn->name (), start, end);
		      else
			error ("dbtype: start line must be less than end line\n");
		    }
		  else
		    error ("dbtype: line specification must be `start:end'");
		}
	    }
	  break;

	case 2: // (dbtype func start:end) , (dbtype func start)
	  dbg_fcn = get_user_code (argv[1]);

	  if (dbg_fcn)
	    {
	      std::string arg = argv[2];
	      int start = 0;
	      int end = 0;
	      size_t ind = arg.find (':');

	      if (ind != std::string::npos)
		{
		  std::string start_str = arg.substr (0, ind);
		  std::string end_str = arg.substr (ind + 1);

		  start = atoi (start_str.c_str ());
		  end = atoi (end_str.c_str ());
		  
		}
	      else
		{
		  start = atoi (arg.c_str ());
		  end = start;
		}

	      if (std::min (start, end) <= 0)
		error ("dbtype: start and end lines must be >= 1\n");
	      
	      if (start <= end)
		do_dbtype (octave_stdout, dbg_fcn->name (), start, end);
	      else
		error ("dbtype: start line must be less than end line\n");
	    }
	  break;

	default:
	  error ("dbtype: expecting zero, one, or two arguments\n");
	}
    }

  return retval;
}

DEFUN (dbstack, args, nargout,
  "-*- texinfo -*-\n\
@deftypefn {Loadable Function} {[@var{stack}, @var{idx}]} dbstack (@var{n})\n\
Print or return current stack information.  With optional argument\n\
@var{n}, omit the @var{n} innermost stack frames.\n\
@seealso{dbclear, dbstatus, dbstop}\n\
@end deftypefn")
{
  octave_value_list retval;

  unwind_protect frame;

  octave_idx_type curr_frame = -1;

  size_t nskip = 0;

  if (args.length () == 1)
    {
      int n = 0;

      octave_value arg = args(0);

      if (arg.is_string ())
	{
	  std::string s_arg = arg.string_value ();

	  n = atoi (s_arg.c_str ());
	}
      else
	n = args(0).int_value ();

      if (n > 0)
	nskip = n;
      else
	error ("dbstack: expecting N to be a nonnegative integer");
    }

  if (! error_state)
    {
      Octave_map stk = octave_call_stack::backtrace (nskip, curr_frame);

      if (nargout == 0)
	{
	  octave_idx_type nframes_to_display = stk.numel ();

	  if (nframes_to_display > 0)
	    {
	      octave_stdout << "Stopped in:\n\n";

	      Cell names = stk.contents ("name");
	      Cell lines = stk.contents ("line");
	      Cell columns = stk.contents ("column");

	      for (octave_idx_type i = 0; i < nframes_to_display; i++)
		{
		  octave_value name = names(i);
		  octave_value line = lines(i);
		  octave_value column = columns(i);

		  octave_stdout << (i == curr_frame ? "--> " : "    ")
				<< name.string_value ()
				<< " at line " << line.int_value ()
				<< " column " << column.int_value ()
				<< std::endl;
		}
	    }
	}
      else
	{
	  retval(1) = curr_frame < 0 ? 1 : curr_frame + 1;
	  retval(0) = stk;
	}
    }

  return retval;
}

static void
do_dbupdown (const octave_value_list& args, const std::string& who)
{
  int n = 1;

  if (args.length () == 1)
    {
      octave_value arg = args(0);

      if (arg.is_string ())
	{
	  std::string s_arg = arg.string_value ();

	  n = atoi (s_arg.c_str ());
	}
      else
	n = args(0).int_value ();
    }

  if (! error_state)
    {
      if (who == "dbup")
	n = -n;

      if (! octave_call_stack::goto_frame_relative (n, true))
	error ("%s: invalid stack frame", who.c_str ());
    }
}

DEFUN (dbup, args, ,
  "-*- texinfo -*-\n\
@deftypefn  {Loadable Function} {} dbup\n\
@deftypefnx {Loadable Function} {} dbup (@var{n})\n\
In debugging mode, move up the execution stack @var{n} frames.\n\
If @var{n} is omitted, move up one frame.\n\
@seealso{dbstack}\n\
@end deftypefn")
{
  octave_value retval;

  do_dbupdown (args, "dbup");

  return retval;
}

DEFUN (dbdown, args, ,
  "-*- texinfo -*-\n\
@deftypefn  {Loadable Function} {} dbdown\n\
@deftypefnx {Loadable Function} {} dbdown (@var{n})\n\
In debugging mode, move down the execution stack @var{n} frames.\n\
If @var{n} is omitted, move down one frame.\n\
@seealso{dbstack}\n\
@end deftypefn")
{
  octave_value retval;

  do_dbupdown (args, "dbdown");

  return retval;
}

DEFUN (dbstep, args, ,
  "-*- texinfo -*-\n\
@deftypefn  {Command} {} dbstep\n\
@deftypefnx {Command} {} dbstep @var{n}\n\
@deftypefnx {Command} {} dbstep in\n\
@deftypefnx {Command} {} dbstep out\n\
In debugging mode, execute the next @var{n} lines of code.\n\
If @var{n} is omitted , execute the next single line of code.\n\
If the next line of code is itself\n\
defined in terms of an m-file remain in the existing function.\n\
\n\
Using @code{dbstep in} will cause execution of the next line to step into\n\
any m-files defined on the next line.  Using @code{dbstep out} will cause\n\
execution to continue until the current function returns.\n\
@seealso{dbcont, dbquit}\n\
@end deftypefn")
{
  if (Vdebugging)
    {
      int nargin = args.length ();
      
      if (nargin > 1)
	print_usage ();
      else if (nargin == 1)
	{
	  if (args(0).is_string ())
	    {
	      std::string arg = args(0).string_value ();

	      if (! error_state)
		{
		  if (arg == "in")
		    {
		      Vdebugging = false;

		      tree_evaluator::dbstep_flag = -1;
		    }
		  else if (arg == "out")
		    {
		      Vdebugging = false;

		      tree_evaluator::dbstep_flag = -2;
		    }
		  else
		    {
		      int n = atoi (arg.c_str ());

		      if (n > 0)
			{
			  Vdebugging = false;

			  tree_evaluator::dbstep_flag = n;
			}
		      else
			error ("dbstep: invalid argument");
		    }
		}
	    }
	  else
	    error ("dbstep: expecting character string as argument");
	}
      else
	{
	  Vdebugging = false;

	  tree_evaluator::dbstep_flag = 1;
	}
    }
  else
    error ("dbstep: can only be called in debug mode");

  return octave_value_list ();
}

DEFALIAS (dbnext, dbstep);

DEFUN (dbcont, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Command} {} dbcont\n\
In debugging mode, quit debugging mode and continue execution.\n\
@seealso{dbstep, dbquit}\n\
@end deftypefn")
{
  if (Vdebugging)
    {
      if (args.length () == 0)
	{
	  Vdebugging = false;

          tree_evaluator::reset_debug_state ();
	}
      else
	print_usage ();
    }
  else
    error ("dbcont: can only be called in debug mode");

  return octave_value_list ();
}

DEFUN (dbquit, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Command} {} dbquit\n\
In debugging mode, quit debugging mode and return to the top level.\n\
@seealso{dbstep, dbcont}\n\
@end deftypefn")
{
  if (Vdebugging)
    {
      if (args.length () == 0)
	{
	  Vdebugging = false;

          tree_evaluator::reset_debug_state ();

	  octave_throw_interrupt_exception ();
	}
      else
	print_usage ();
    }
  else
    error ("dbquit: can only be called in debug mode");

  return octave_value_list ();
}

DEFUN (isdebugmode, args, ,
  "-*- texinfo -*-\n\
@deftypefn {Loadable Function} {} isdebugmode ()\n\
Return true if debug mode is on, otherwise false.\n\
@seealso{dbstack, dbclear, dbstop, dbstatus}\n\
@end deftypefn")
{
  octave_value retval;

  if (args.length () == 0)
    retval = Vdebugging;
  else
    print_usage ();

  return retval;
}