release/1.1.5.1_cvsreleng/1

1 files changed, 960 insertions, 0 deletions

diff --git a/gnu/usr.bin/kgdb/stack.c b/gnu/usr.bin/kgdb/stack.c
new file mode 100644
index 000000000000..91218aae3656
--- /dev/null
+++ b/gnu/usr.bin/kgdb/stack.c
@@ -0,0 +1,960 @@
+/*-
+ * This code is derived from software copyrighted by the Free Software
+ * Foundation.
+ *
+ * Modified 1991 by Donn Seeley at UUNET Technologies, Inc.
+ * Modified 1990 by Van Jacobson at Lawrence Berkeley Laboratory.
+ */
+
+#ifndef lint
+static char sccsid[] = "@(#)stack.c	6.3 (Berkeley) 5/8/91";
+#endif /* not lint */
+
+/* Print and select stack frames for GDB, the GNU debugger.
+   Copyright (C) 1986, 1987, 1989 Free Software Foundation, Inc.
+
+This file is part of GDB.
+
+GDB 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 1, or (at your option)
+any later version.
+
+GDB 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 GDB; see the file COPYING.  If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+/* modified by rjc Thu Nov  1 16:46:57 1990, fixed return_command so that
+   it can return values, it still has problems when running on pmax,
+   cannot write register 65 */
+
+#include <stdio.h>
+
+#include "defs.h"
+#include "param.h"
+#include "symtab.h"
+#include "frame.h"
+#include "value.h"
+
+
+/* Thie "selected" stack frame is used by default for local and arg access.
+   May be zero, for no selected frame.  */
+
+FRAME selected_frame;
+
+/* Level of the selected frame:
+   0 for innermost, 1 for its caller, ...
+   or -1 for frame specified by address with no defined level.  */
+
+int selected_frame_level;
+
+/* Nonzero means print the full filename and linenumber
+   when a frame is printed, and do so in a format programs can parse.  */
+
+int frame_file_full_name = 0;
+
+static void select_calling_frame ();
+
+void print_frame_info ();
+
+/* Print a stack frame briefly.  FRAME should be the frame id
+   and LEVEL should be its level in the stack (or -1 for level not defined).
+   This prints the level, the function executing, the arguments,
+   and the file name and line number.
+   If the pc is not at the beginning of the source line,
+   the actual pc is printed at the beginning.
+
+   If SOURCE is 1, print the source line as well.
+   If SOURCE is -1, print ONLY the source line.  */
+
+static void
+print_stack_frame (frame, level, source)
+     FRAME frame;
+     int level;
+     int source;
+{
+  struct frame_info *fi;
+
+  fi = get_frame_info (frame);
+
+  print_frame_info (fi, level, source, 1);
+}
+
+/* Flag which will indicate when the frame has been changed
+   by and "up" or "down" command.  */
+static int frame_changed;
+
+void
+print_frame_info (fi, level, source, args)
+     struct frame_info *fi;
+     register int level;
+     int source;
+     int args;
+{
+  struct symtab_and_line sal;
+  struct symbol *func;
+  register char *funname = 0;
+  int numargs;
+  struct partial_symtab *pst;
+
+  /* Don't give very much information if we haven't readin the
+     symbol table yet.  */
+  pst = find_pc_psymtab (fi->pc);
+  if (pst && !pst->readin)
+    {
+      /* Abbreviated information.  */
+      char *fname;
+
+      if (!find_pc_partial_function (fi->pc, &fname, 0))
+	fname = "??";
+	
+      printf_filtered ("#%-2d ", level);
+      printf_filtered ("0x%x in ", fi->pc);
+
+      fputs_demangled(fname, stdout, -1);
+      fputs_filtered(" (...)\n", stdout);
+      
+      return;
+    }
+
+  sal = find_pc_line (fi->pc, fi->next_frame);
+  func = find_pc_function (fi->pc);
+  if (func)
+    {
+      /* In certain pathological cases, the symtabs give the wrong
+	 function (when we are in the first function in a file which
+	 is compiled without debugging symbols, the previous function
+	 is compiled with debugging symbols, and the "foo.o" symbol
+	 that is supposed to tell us where the file with debugging symbols
+	 ends has been truncated by ar because it is longer than 15
+	 characters).
+
+	 So look in the misc_function_vector as well, and if it comes
+	 up with a larger address for the function use that instead.
+	 I don't think this can ever cause any problems;
+	 there shouldn't be any
+	 misc_function_vector symbols in the middle of a function.  */
+      int misc_index = find_pc_misc_function (fi->pc);
+      if (misc_index >= 0
+	  && (misc_function_vector[misc_index].address
+	      > BLOCK_START (SYMBOL_BLOCK_VALUE (func))))
+	{
+	  /* In this case we have no way of knowing the source file
+	     and line number, so don't print them.  */
+	  sal.symtab = 0;
+	  /* We also don't know anything about the function besides
+	     its address and name.  */
+	  func = 0;
+	  funname = misc_function_vector[misc_index].name;
+	}
+      else
+	funname = SYMBOL_NAME (func);
+    }
+  else
+    {
+      register int misc_index = find_pc_misc_function (fi->pc);
+      if (misc_index >= 0)
+	funname = misc_function_vector[misc_index].name;
+    }
+
+  if (frame_changed || source >= 0 || !sal.symtab)
+    {
+      if (level >= 0)
+	printf_filtered ("#%-2d ", level);
+      else if (frame_changed)
+	printf ("#%-2d ", 0);
+      if (fi->pc != sal.pc || !sal.symtab)
+	printf_filtered ("0x%x in ", fi->pc);
+      fputs_demangled(funname ? funname : "??", stdout, -1);
+      printf_filtered(" (");
+      if (args)
+        {
+	  if (func)
+	    numargs = -1;
+	  else
+	    FRAME_NUM_ARGS (numargs, fi);
+
+	  print_frame_args (func, fi, numargs, stdout);
+	}
+      printf_filtered (")");
+      if (sal.symtab)
+	printf_filtered (" (%s line %d)", sal.symtab->filename, sal.line);
+      printf_filtered ("\n");
+    }
+
+  if ((frame_changed || source != 0) && sal.symtab)
+    {
+      int done = 0;
+      int mid_statement = source < 0 && fi->pc != sal.pc;
+      if (frame_file_full_name)
+	done = identify_source_line (sal.symtab, sal.line, mid_statement);
+      if (!done)
+	{
+	  if (mid_statement)
+	    printf_filtered ("0x%x\t", fi->pc);
+	  print_source_lines (sal.symtab, sal.line, sal.line + 1, 1);
+	}
+      current_source_line = max (sal.line - 5, 1);
+    }
+  frame_changed = 0;
+  if (source != 0)
+    set_default_breakpoint (1, fi->pc, sal.symtab, sal.line);
+
+  fflush (stdout);
+}
+
+/* Call here to print info on selected frame, after a trap.  */
+
+void
+print_sel_frame (just_source)
+     int just_source;
+{
+  print_stack_frame (selected_frame, -1, just_source ? -1 : 1);
+}
+
+/* Print info on the selected frame, including level number
+   but not source.  */
+
+void
+print_selected_frame ()
+{
+  print_stack_frame (selected_frame, selected_frame_level, 0);
+}
+
+void flush_cached_frames ();
+
+#ifdef FRAME_SPECIFICATION_DYADIC
+extern FRAME setup_arbitrary_frame ();
+#endif
+
+/*
+ * Read a frame specification in whatever the appropriate format is.
+ */
+static FRAME
+parse_frame_specification (frame_exp)
+     char *frame_exp;
+{
+  int numargs = 0;
+  int arg1, arg2;
+  
+  if (frame_exp)
+    {
+      char *addr_string, *p;
+      struct cleanup *tmp_cleanup;
+      struct frame_info *fci;
+
+      while (*frame_exp == ' ') frame_exp++;
+      for (p = frame_exp; *p && *p != ' '; p++)
+	;
+
+      if (*frame_exp)
+	{
+	  numargs = 1;
+	  addr_string = savestring(frame_exp, p - frame_exp);
+
+	  {
+	    tmp_cleanup = make_cleanup (free, addr_string);
+	    arg1 = parse_and_eval_address (addr_string);
+	    do_cleanups (tmp_cleanup);
+	  }
+
+	  while (*p == ' ') p++;
+	  
+	  if (*p)
+	    {
+	      numargs = 2;
+	      arg2 = parse_and_eval_address (p);
+	    }
+	}
+    }
+
+  switch (numargs)
+    {
+    case 0:
+      return selected_frame;
+      /* NOTREACHED */
+    case 1:
+      {
+	int level = arg1;
+	FRAME fid = find_relative_frame (get_current_frame (), &level);
+	FRAME tfid;
+
+	if (level == 0)
+	  /* find_relative_frame was successful */
+	  return fid;
+
+	/* If (s)he specifies the frame with an address, he deserves what
+	   (s)he gets.  Still, give the highest one that matches.  */
+
+	for (fid = get_current_frame ();
+	     fid && FRAME_FP (fid) != arg1;
+	     fid = get_prev_frame (fid))
+	  ;
+
+	if (fid)
+	  while ((tfid = get_prev_frame (fid)) &&
+		 (FRAME_FP (tfid) == arg1))
+	    fid = tfid;
+	  
+#ifdef FRAME_SPECIFICATION_DYADIC
+	if (!fid)
+	  error ("Incorrect number of args in frame specification");
+
+	return fid;
+#else
+	return create_new_frame (arg1, 0);
+#endif
+      }
+      /* NOTREACHED */
+    case 2:
+      /* Must be addresses */
+#ifndef FRAME_SPECIFICATION_DYADIC
+      error ("Incorrect number of args in frame specification");
+#else
+      return setup_arbitrary_frame (arg1, arg2);
+#endif
+      /* NOTREACHED */
+    }
+  fatal ("Internal: Error in parsing in parse_frame_specification");
+  /* NOTREACHED */
+}
+
+/* FRAME_ARGS_ADDRESS_CORRECT is just like FRAME_ARGS_ADDRESS except
+   that if it is unsure about the answer, it returns Frame_unknown
+   instead of guessing (this happens on the VAX, for example).
+
+   On most machines, we never have to guess about the args address,
+   so FRAME_ARGS_ADDRESS{,_CORRECT} are the same.  */
+#if !defined (FRAME_ARGS_ADDRESS_CORRECT)
+#define FRAME_ARGS_ADDRESS_CORRECT FRAME_ARGS_ADDRESS
+#endif
+
+/* Print verbosely the selected frame or the frame at address ADDR.
+   This means absolutely all information in the frame is printed.  */
+
+static void
+frame_info (addr_exp)
+     char *addr_exp;
+{
+  FRAME frame;
+  struct frame_info *fi;
+  struct frame_saved_regs fsr;
+  struct symtab_and_line sal;
+  struct symbol *func;
+  FRAME calling_frame;
+  int i, count;
+  char *funname = 0;
+
+  if (!(have_inferior_p () || have_core_file_p ()))
+    error ("No inferior or core file.");
+
+  frame = parse_frame_specification (addr_exp);
+  if (!frame)
+    error ("Invalid frame specified.");
+
+  fi = get_frame_info (frame);
+  get_frame_saved_regs (fi, &fsr);
+  sal = find_pc_line (fi->pc, fi->next_frame);
+  func = get_frame_function (frame);
+  if (func)
+    funname = SYMBOL_NAME (func);
+  else
+    {
+      register int misc_index = find_pc_misc_function (fi->pc);
+      if (misc_index >= 0)
+	funname = misc_function_vector[misc_index].name;
+    }
+  calling_frame = get_prev_frame (frame);
+
+  if (!addr_exp && selected_frame_level >= 0)
+    printf ("Stack level %d, frame at 0x%x:\n pc = 0x%x",
+	    selected_frame_level, FRAME_FP(frame), fi->pc);
+  else
+    printf ("Stack frame at 0x%x:\n pc = 0x%x",
+	    FRAME_FP(frame), fi->pc);
+
+  if (funname)
+    printf (" in %s", funname);
+  if (sal.symtab)
+    printf (" (%s line %d)", sal.symtab->filename, sal.line);
+  printf ("; saved pc 0x%x\n", FRAME_SAVED_PC (frame));
+  if (calling_frame)
+    printf (" called by frame at 0x%x", FRAME_FP (calling_frame));
+  if (fi->next_frame && calling_frame)
+    printf (",");
+  if (fi->next_frame)
+    printf (" caller of frame at 0x%x", fi->next_frame);
+  if (fi->next_frame || calling_frame)
+    printf ("\n");
+
+  {
+    /* Address of the argument list for this frame, or Frame_unknown.  */
+    CORE_ADDR arg_list = FRAME_ARGS_ADDRESS_CORRECT (fi);
+    /* Number of args for this frame, or -1 if unknown.  */
+    int numargs;
+
+    if (arg_list != Frame_unknown)
+      {
+	printf (" Arglist at 0x%x,", arg_list);
+
+	FRAME_NUM_ARGS (numargs, fi);
+	if (numargs < 0)
+	  printf (" args: ");
+	else if (numargs == 0)
+	  printf (" no args.");
+	else if (numargs == 1)
+	  printf (" 1 arg: ");
+	else
+	  printf (" %d args: ", numargs);
+	print_frame_args (func, fi, numargs, stdout);
+	printf ("\n");
+      }
+  }
+  
+  /* The sp is special; what's returned isn't the save address, but
+     actually the value of the previous frame's sp.  */
+  printf (" Previous frame's sp is 0x%x\n", fsr.regs[SP_REGNUM]);
+  count = 0;
+  for (i = 0; i < NUM_REGS; i++)
+    if (fsr.regs[i] && i != SP_REGNUM)
+      {
+	if (count % 4 != 0)
+	  printf (", ");
+	else
+	  {
+	    if (count == 0)
+	      printf (" Saved registers:");
+	    printf ("\n  ");
+	  }
+	printf ("%s at 0x%x", reg_names[i], fsr.regs[i]);
+	count++;
+      }
+  if (count)
+    printf ("\n");
+}
+
+#if 0
+/* Set a limit on the number of frames printed by default in a
+   backtrace.  */
+
+static int backtrace_limit;
+
+static void
+set_backtrace_limit_command (count_exp, from_tty)
+     char *count_exp;
+     int from_tty;
+{
+  int count = parse_and_eval_address (count_exp);
+
+  if (count < 0)
+    error ("Negative argument not meaningful as backtrace limit.");
+
+  backtrace_limit = count;
+}
+
+static void
+backtrace_limit_info (arg, from_tty)
+     char *arg;
+     int from_tty;
+{
+  if (arg)
+    error ("\"Info backtrace-limit\" takes no arguments.");
+
+  printf ("Backtrace limit: %d.\n", backtrace_limit);
+}
+#endif
+
+/* Print briefly all stack frames or just the innermost COUNT frames.  */
+
+static void
+backtrace_command (count_exp)
+     char *count_exp;
+{
+  struct frame_info *fi;
+  register int count;
+  register FRAME frame;
+  register int i;
+  register FRAME trailing;
+  register int trailing_level;
+
+  /* The following code must do two things.  First, it must
+     set the variable TRAILING to the frame from which we should start
+     printing.  Second, it must set the variable count to the number
+     of frames which we should print, or -1 if all of them.  */
+  trailing = get_current_frame ();
+  trailing_level = 0;
+  if (count_exp)
+    {
+      count = parse_and_eval_address (count_exp);
+      if (count < 0)
+	{
+	  FRAME current;
+
+	  count = -count;
+
+	  current = trailing;
+	  while (current && count--)
+	    current = get_prev_frame (current);
+	  
+	  /* Will stop when CURRENT reaches the top of the stack.  TRAILING
+	     will be COUNT below it.  */
+	  while (current)
+	    {
+	      trailing = get_prev_frame (trailing);
+	      current = get_prev_frame (current);
+	      trailing_level++;
+	    }
+	  
+	  count = -1;
+	}
+    }
+  else
+    count = -1;
+
+  for (i = 0, frame = trailing;
+       frame && count--;
+       i++, frame = get_prev_frame (frame))
+    {
+      QUIT;
+      fi = get_frame_info (frame);
+      print_frame_info (fi, trailing_level + i, 0, 1);
+    }
+
+  /* If we've stopped before the end, mention that.  */
+  if (frame)
+    printf_filtered ("(More stack frames follow...)\n");
+}
+
+/* Print the local variables of a block B active in FRAME.
+   Return 1 if any variables were printed; 0 otherwise.  */
+
+static int
+print_block_frame_locals (b, frame, stream)
+     struct block *b;
+     register FRAME frame;
+     register FILE *stream;
+{
+  int nsyms;
+  register int i;
+  register struct symbol *sym;
+  register int values_printed = 0;
+
+  nsyms = BLOCK_NSYMS (b);
+
+  for (i = 0; i < nsyms; i++)
+    {
+      sym = BLOCK_SYM (b, i);
+      if (SYMBOL_CLASS (sym) == LOC_LOCAL
+	  || SYMBOL_CLASS (sym) == LOC_REGISTER
+	  || SYMBOL_CLASS (sym) == LOC_STATIC)
+	{
+	  values_printed = 1;
+	  fputs_filtered (SYMBOL_NAME (sym), stream);
+	  fputs_filtered (" = ", stream);
+	  print_variable_value (sym, frame, stream);
+	  fprintf_filtered (stream, "\n");
+	  fflush (stream);
+	}
+    }
+  return values_printed;
+}
+
+/* Print on STREAM all the local variables in frame FRAME,
+   including all the blocks active in that frame
+   at its current pc.
+
+   Returns 1 if the job was done,
+   or 0 if nothing was printed because we have no info
+   on the function running in FRAME.  */
+
+static int
+print_frame_local_vars (frame, stream)
+     register FRAME frame;
+     register FILE *stream;
+{
+  register struct block *block = get_frame_block (frame);
+  register int values_printed = 0;
+
+  if (block == 0)
+    {
+      fprintf_filtered (stream, "No symbol table info available.\n");
+      fflush (stream);
+      return 0;
+    }
+  
+  while (block != 0)
+    {
+      if (print_block_frame_locals (block, frame, stream))
+	values_printed = 1;
+      /* After handling the function's top-level block, stop.
+	 Don't continue to its superblock, the block of
+	 per-file symbols.  */
+      if (BLOCK_FUNCTION (block))
+	break;
+      block = BLOCK_SUPERBLOCK (block);
+    }
+
+  if (!values_printed)
+    {
+      fprintf_filtered (stream, "No locals.\n");
+      fflush (stream);
+    }
+  
+  return 1;
+}
+
+static void
+locals_info ()
+{
+  if (!have_inferior_p () && !have_core_file_p ())
+    error ("No inferior or core file.");
+
+  print_frame_local_vars (selected_frame, stdout);
+}
+
+static int
+print_frame_arg_vars (frame, stream)
+     register FRAME frame;
+     register FILE *stream;
+{
+  struct symbol *func = get_frame_function (frame);
+  register struct block *b;
+  int nsyms;
+  register int i;
+  register struct symbol *sym;
+  register int values_printed = 0;
+
+  if (func == 0)
+    {
+      fprintf_filtered (stream, "No symbol table info available.\n");
+      fflush (stream);
+      return 0;
+    }
+
+  b = SYMBOL_BLOCK_VALUE (func);
+  nsyms = BLOCK_NSYMS (b);
+
+  for (i = 0; i < nsyms; i++)
+    {
+      sym = BLOCK_SYM (b, i);
+      if (SYMBOL_CLASS (sym) == LOC_ARG
+	  || SYMBOL_CLASS (sym) == LOC_REF_ARG
+	  || SYMBOL_CLASS (sym) == LOC_REGPARM)
+	{
+	  values_printed = 1;
+	  fputs_filtered (SYMBOL_NAME (sym), stream);
+	  fputs_filtered (" = ", stream);
+	  print_variable_value (sym, frame, stream);
+	  fprintf_filtered (stream, "\n");
+	  fflush (stream);
+	}
+    }
+
+  if (!values_printed)
+    {
+      fprintf_filtered (stream, "No arguments.\n");
+      fflush (stream);
+    }
+
+  return 1;
+}
+
+static void
+args_info ()
+{
+  if (!have_inferior_p () && !have_core_file_p ())
+    error ("No inferior or core file.");
+  print_frame_arg_vars (selected_frame, stdout);
+}
+
+/* Select frame FRAME, and note that its stack level is LEVEL.
+   LEVEL may be -1 if an actual level number is not known.  */
+
+void
+select_frame (frame, level)
+     FRAME frame;
+     int level;
+{
+  selected_frame = frame;
+  selected_frame_level = level;
+  /* Ensure that symbols for this frame are readin.  */
+  if (frame)
+    find_pc_symtab (get_frame_info (frame)->pc);
+}
+
+/* Store the selected frame and its level into *FRAMEP and *LEVELP.  */
+
+void
+record_selected_frame (frameaddrp, levelp)
+     FRAME_ADDR *frameaddrp;
+     int *levelp;
+{
+  *frameaddrp = FRAME_FP (selected_frame);
+  *levelp = selected_frame_level;
+}
+
+/* Return the symbol-block in which the selected frame is executing.
+   Can return zero under various legitimate circumstances.  */
+
+struct block *
+get_selected_block ()
+{
+  if (!have_inferior_p () && !have_core_file_p ())
+    return 0;
+
+  if (!selected_frame)
+    return get_current_block ();
+  return get_frame_block (selected_frame);
+}
+
+/* Find a frame a certain number of levels away from FRAME.
+   LEVEL_OFFSET_PTR points to an int containing the number of levels.
+   Positive means go to earlier frames (up); negative, the reverse.
+   The int that contains the number of levels is counted toward
+   zero as the frames for those levels are found.
+   If the top or bottom frame is reached, that frame is returned,
+   but the final value of *LEVEL_OFFSET_PTR is nonzero and indicates
+   how much farther the original request asked to go.  */
+
+FRAME
+find_relative_frame (frame, level_offset_ptr)
+     register FRAME frame;
+     register int* level_offset_ptr;
+{
+  register FRAME prev;
+  register FRAME frame1, frame2;
+
+  /* Going up is simple: just do get_prev_frame enough times
+     or until initial frame is reached.  */
+  while (*level_offset_ptr > 0)
+    {
+      prev = get_prev_frame (frame);
+      if (prev == 0)
+	break;
+      (*level_offset_ptr)--;
+      frame = prev;
+    }
+  /* Going down could be done by iterating get_frame_info to
+     find the next frame, but that would be quadratic
+     since get_frame_info must scan all the way from the current frame.
+     The following algorithm is linear.  */
+  if (*level_offset_ptr < 0)
+    {
+      /* First put frame1 at innermost frame
+	 and frame2 N levels up from there.  */
+      frame1 = get_current_frame ();
+      frame2 = frame1;
+      while (*level_offset_ptr < 0 && frame2 != frame)
+	{
+	  frame2 = get_prev_frame (frame2);
+	  (*level_offset_ptr) ++;
+	}
+      /* Then slide frame1 and frame2 up in synchrony
+	 and when frame2 reaches our starting point
+	 frame1 must be N levels down from there.  */
+      while (frame2 != frame)
+	{
+	  frame1 = get_prev_frame (frame1);
+	  frame2 = get_prev_frame (frame2);
+	}
+      return frame1;
+    }
+  return frame;
+}
+
+/* The "frame" command.  With no arg, print selected frame briefly.
+   With arg LEVEL_EXP, select the frame at level LEVEL if it is a
+   valid level.  Otherwise, treat level_exp as an address expression
+   and print it.  See parse_frame_specification for more info on proper
+   frame expressions. */
+
+static void
+frame_command (level_exp, from_tty)
+     char *level_exp;
+     int from_tty;
+{
+  register FRAME frame, frame1;
+  unsigned int level = 0;
+
+  if (!have_inferior_p () && ! have_core_file_p ())
+    error ("No inferior or core file.");
+
+  frame = parse_frame_specification (level_exp);
+
+  for (frame1 = get_prev_frame (0);
+       frame1 && frame1 != frame;
+       frame1 = get_prev_frame (frame1))
+    level++;
+
+  if (!frame1)
+    level = 0;
+
+  frame_changed = level;
+  select_frame (frame, level);
+
+  if (!from_tty)
+    return;
+
+  print_stack_frame (selected_frame, selected_frame_level, 1);
+}
+
+/* Select the frame up one or COUNT stack levels
+   from the previously selected frame, and print it briefly.  */
+
+static void
+up_command (count_exp)
+     char *count_exp;
+{
+  register FRAME frame;
+  int count = 1, count1;
+  if (count_exp)
+    count = parse_and_eval_address (count_exp);
+  count1 = count;
+  
+  if (!have_inferior_p () && !have_core_file_p ())
+    error ("No inferior or core file.");
+
+  frame = find_relative_frame (selected_frame, &count1);
+  if (count1 != 0 && count_exp == 0)
+    error ("Initial frame selected; you cannot go up.");
+  select_frame (frame, selected_frame_level + count - count1);
+
+  print_stack_frame (selected_frame, selected_frame_level, 1);
+  frame_changed++;
+}
+
+/* Select the frame down one or COUNT stack levels
+   from the previously selected frame, and print it briefly.  */
+
+static void
+down_command (count_exp)
+     char *count_exp;
+{
+  register FRAME frame;
+  int count = -1, count1;
+  if (count_exp)
+    count = - parse_and_eval_address (count_exp);
+  count1 = count;
+  
+  frame = find_relative_frame (selected_frame, &count1);
+  if (count1 != 0 && count_exp == 0)
+    error ("Bottom (i.e., innermost) frame selected; you cannot go down.");
+  select_frame (frame, selected_frame_level + count - count1);
+
+  print_stack_frame (selected_frame, selected_frame_level, 1);
+  frame_changed--;
+}
+
+static void
+return_command (retval_exp, from_tty)
+     char *retval_exp;
+     int from_tty;
+{
+    value return_value;
+  struct symbol *thisfun = get_frame_function (selected_frame);
+  FRAME_ADDR selected_frame_addr = FRAME_FP (selected_frame);
+
+  /* If interactive, require confirmation.  */
+
+  if (from_tty)
+    {
+      if (thisfun != 0)
+	{
+	  if (!query ("Make %s return now? ", SYMBOL_NAME (thisfun)))
+	    error ("Not confirmed.");
+	}
+      else
+	if (!query ("Make selected stack frame return now? "))
+	  error ("Not confirmed.");
+    }
+
+  /* Do the real work.  Pop until the specified frame is current.  We
+     use this method because the selected_frame is not valid after
+     a POP_FRAME.  Note that this will not work if the selected frame
+     shares it's fp with another frame.  */
+
+  while (selected_frame_addr != FRAME_FP (get_current_frame()))
+    POP_FRAME;
+
+  /* get the return value while still in this frame */
+  if (retval_exp) 
+      return_value = parse_and_eval (retval_exp);
+
+  /* Then pop that frame.  */
+  POP_FRAME;
+
+  /* Store the return value if there was one */
+
+  if (retval_exp)
+    set_return_value (return_value);
+
+  /* If interactive, print the frame that is now current.  */
+
+  if (from_tty)
+    frame_command ("0", 1);
+}
+
+extern struct cmd_list_element *setlist;
+
+void
+_initialize_stack ()
+{
+#if 0  
+  backtrace_limit = 30;
+#endif
+
+  add_com ("return", class_stack, return_command,
+	   "Make selected stack frame return to its caller.\n\
+Control remains in the debugger, but when you continue\n\
+execution will resume in the frame above the one now selected.\n\
+If an argument is given, it is an expression for the value to return.");
+
+  add_com ("up", class_stack, up_command,
+	   "Select and print stack frame that called this one.\n\
+An argument says how many frames up to go.");
+
+  add_com ("down", class_stack, down_command,
+	   "Select and print stack frame called by this one.\n\
+An argument says how many frames down to go.");
+  add_com_alias ("do", "down", class_stack, 1);
+
+  add_com ("frame", class_stack, frame_command,
+	   "Select and print a stack frame.\n\
+With no argument, print the selected stack frame.  (See also \"info frame\").\n\
+An argument specifies the frame to select.\n\
+It can be a stack frame number or the address of the frame.\n\
+With argument, nothing is printed if input is coming from\n\
+a command file or a user-defined command.");
+
+  add_com_alias ("f", "frame", class_stack, 1);
+
+  add_com ("backtrace", class_stack, backtrace_command,
+	   "Print backtrace of all stack frames, or innermost COUNT frames.\n\
+With a negative argument, print outermost -COUNT frames.");
+  add_com_alias ("bt", "backtrace", class_stack, 0);
+  add_com_alias ("where", "backtrace", class_alias, 0);
+  add_info ("stack", backtrace_command,
+	    "Backtrace of the stack, or innermost COUNT frames.");
+  add_info_alias ("s", "stack", 1);
+  add_info ("frame", frame_info,
+	    "All about selected stack frame, or frame at ADDR.");
+  add_info_alias ("f", "frame", 1);
+  add_info ("locals", locals_info,
+	    "Local variables of current stack frame.");
+  add_info ("args", args_info,
+	    "Argument variables of current stack frame.");
+
+#if 0
+  add_cmd ("backtrace-limit", class_stack, set_backtrace_limit_command, 
+	   "Specify maximum number of frames for \"backtrace\" to print by default.",
+	   &setlist);
+  add_info ("backtrace-limit", backtrace_limit_info,
+	    "The maximum number of frames for \"backtrace\" to print by default.");
+#endif
+}
+