path: root/gdb/stack.c

/* Print and select stack frames for GDB, the GNU debugger.
   Copyright 1986, 1987, 1989, 1991, 1992, 1993 Free Software Foundation, Inc.

This file is part of GDB.

This program 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 2 of the License, or
(at your option) any later version.

This program 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 this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include "defs.h"
#include "value.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "expression.h"
#include "language.h"
#include "frame.h"
#include "gdbcmd.h"
#include "gdbcore.h"
#include "target.h"
#include "breakpoint.h"
#include "demangle.h"
#include "inferior.h"

static void
return_command PARAMS ((char *, int));

static void
down_command PARAMS ((char *, int));

static void
down_silently_command PARAMS ((char *, int));

static void
up_command PARAMS ((char *, int));

static void
up_silently_command PARAMS ((char *, int));

static void
frame_command PARAMS ((char *, int));

static void
select_frame_command PARAMS ((char *, int));

static void
args_info PARAMS ((char *, int));

static void
print_frame_arg_vars PARAMS ((FRAME, GDB_FILE *));

static void
catch_info PARAMS ((char *, int));

static void
locals_info PARAMS ((char *, int));

static void
print_frame_label_vars PARAMS ((FRAME, int, GDB_FILE *));

static void
print_frame_local_vars PARAMS ((FRAME, GDB_FILE *));

static int
print_block_frame_labels PARAMS ((struct block *, int *, GDB_FILE *));

static int
print_block_frame_locals PARAMS ((struct block *, FRAME, GDB_FILE *));

static void
backtrace_command PARAMS ((char *, int));

static FRAME
parse_frame_specification PARAMS ((char *));

static void
frame_info PARAMS ((char *, int));


extern int addressprint;	/* Print addresses, or stay symbolic only? */
extern int info_verbose;	/* Verbosity of symbol reading msgs */
extern int lines_to_list;	/* # of lines "list" command shows by default */

/* The "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;


struct print_stack_frame_args {
  struct frame_info *fi;
  int level;
  int source;
  int args;
};

static int print_stack_frame_stub PARAMS ((char *));

/* Pass the args the way catch_errors wants them.  */
static int
print_stack_frame_stub (args)
     char *args;
{
  struct print_stack_frame_args *p = (struct print_stack_frame_args *)args;
  print_frame_info (p->fi, p->level, p->source, p->args);
  return 0;
}

/* 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.  */

void
print_stack_frame (frame, level, source)
     FRAME frame;
     int level;
     int source;
{
  struct print_stack_frame_args args;

  args.fi = get_frame_info (frame);
  args.level = level;
  args.source = source;
  args.args = 1;

  catch_errors (print_stack_frame_stub, (char *)&args, "", RETURN_MASK_ERROR);
}

struct print_args_args {
  struct symbol *func;
  struct frame_info *fi;
};

static int print_args_stub PARAMS ((char *));

/* Pass the args the way catch_errors wants them.  */
static int
print_args_stub (args)
     char *args;
{
  int numargs;
  struct print_args_args *p = (struct print_args_args *)args;
  FRAME_NUM_ARGS (numargs, (p->fi));
  print_frame_args (p->func, p->fi, numargs, gdb_stdout);
  return 0;
}

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;
  enum language funlang = language_unknown;
  char buf[MAX_REGISTER_RAW_SIZE];
  CORE_ADDR sp;

#if 0
  /* On the 68k, this spends too much time in m68k_find_saved_regs.  */

  /* Get the value of SP_REGNUM relative to the frame.  */
  get_saved_register (buf, (int *)NULL, (CORE_ADDR *)NULL,
		      FRAME_INFO_ID (fi), SP_REGNUM, (enum lval_type *)NULL);
  sp = extract_address (buf, REGISTER_RAW_SIZE (SP_REGNUM));

  /* This is not a perfect test, because if a function alloca's some
     memory, puts some code there, and then jumps into it, then the test
     will succeed even though there is no call dummy.  Probably best is
     to check for a bp_call_dummy breakpoint.  */
  if (PC_IN_CALL_DUMMY (fi->pc, sp, fi->frame))
#else
  if (frame_in_dummy (fi))
#endif
    {
      /* Do this regardless of SOURCE because we don't have any source
	 to list for this frame.  */
      if (level >= 0)
	printf_filtered ("#%-2d ", level);
      printf_filtered ("<function called from gdb>\n");
      return;
    }
  if (fi->signal_handler_caller)
    {
      /* Do this regardless of SOURCE because we don't have any source
	 to list for this frame.  */
      if (level >= 0)
	printf_filtered ("#%-2d ", level);
      printf_filtered ("<signal handler called>\n");
      return;
    }

  /* If fi is not the innermost frame, that normally means that fi->pc
     points to *after* the call instruction, and we want to get the line
     containing the call, never the next line.  But if the next frame is
     a signal_handler_caller or a dummy frame, then the next frame was
     not entered as the result of a call, and we want to get the line
     containing fi->pc.  */
  sal =
    find_pc_line (fi->pc,
		  fi->next != NULL
		  && !fi->next->signal_handler_caller
		  && !frame_in_dummy (fi->next));

  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).  This also occurs if the user uses asm() to create
	 a function but not stabs for it (in a file compiled -g).

	 So look in the minimal symbol tables 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 minimal symbols in the middle of a function; if this is
	 ever changed many parts of GDB will need to be changed (and we'll
	 create a find_pc_minimal_function or some such).  */

      struct minimal_symbol *msymbol = lookup_minimal_symbol_by_pc (fi->pc);
      if (msymbol != NULL
	  && (SYMBOL_VALUE_ADDRESS (msymbol) 
	      > 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 = SYMBOL_NAME (msymbol);
	  funlang = SYMBOL_LANGUAGE (msymbol);
	}
      else
	{
	  funname = SYMBOL_NAME (func);
	  funlang = SYMBOL_LANGUAGE (func);
	}
    }
  else
    {
      register struct minimal_symbol *msymbol = lookup_minimal_symbol_by_pc (fi->pc);
      if (msymbol != NULL)
	{
	  funname = SYMBOL_NAME (msymbol);
	  funlang = SYMBOL_LANGUAGE (msymbol);
	}
    }

  if (source >= 0 || !sal.symtab)
    {
      if (level >= 0)
	printf_filtered ("#%-2d ", level);
      if (addressprint)
	if (fi->pc != sal.pc || !sal.symtab)
	  {
	    print_address_numeric (fi->pc, gdb_stdout);
	    printf_filtered (" in ");
	  }
      fprintf_symbol_filtered (gdb_stdout, funname ? funname : "??", funlang,
			       DMGL_ANSI);
      wrap_here ("   ");
      fputs_filtered (" (", gdb_stdout);
      if (args)
	{
	  struct print_args_args args;
	  args.fi = fi;
	  args.func = func;
	  catch_errors (print_args_stub, (char *)&args, "", RETURN_MASK_ERROR);
	}
      printf_filtered (")");
      if (sal.symtab && sal.symtab->filename)
	{
          wrap_here ("   ");
	  printf_filtered (" at %s:%d", sal.symtab->filename, sal.line);
	}

#ifdef PC_LOAD_SEGMENT
     /* If we couldn't print out function name but if can figure out what
        load segment this pc value is from, at least print out some info
	about its load segment. */
      if (!funname) {
	wrap_here ("  ");
	printf_filtered (" from %s", PC_LOAD_SEGMENT (fi->pc));
      }
#endif
      printf_filtered ("\n");
    }

  if ((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,
				     fi->pc);
      if (!done)
	{
	  if (addressprint && mid_statement)
	    {
	      print_address_numeric (fi->pc, gdb_stdout);
	      printf_filtered ("\t");
	    }
	  print_source_lines (sal.symtab, sal.line, sal.line + 1, 0);
	}
      current_source_line = max (sal.line - lines_to_list/2, 1);
    }
  if (source != 0)
    set_default_breakpoint (1, fi->pc, sal.symtab, sal.line);

  gdb_flush (gdb_stdout);
}

/*
 * Read a frame specification in whatever the appropriate format is.
 * Call error() if the specification is in any way invalid (i.e.
 * this function never returns NULL).
 */
static FRAME
parse_frame_specification (frame_exp)
     char *frame_exp;
{
  int numargs = 0;
#define	MAXARGS	4
  CORE_ADDR args[MAXARGS];
  
  if (frame_exp)
    {
      char *addr_string, *p;
      struct cleanup *tmp_cleanup;

      while (*frame_exp == ' ') frame_exp++;

      while (*frame_exp)
	{
	  if (numargs > MAXARGS)
	    error ("Too many args in frame specification");
	  /* Parse an argument.  */
          for (p = frame_exp; *p && *p != ' '; p++)
	    ;
	  addr_string = savestring(frame_exp, p - frame_exp);

	  {
	    tmp_cleanup = make_cleanup (free, addr_string);
	    args[numargs++] = parse_and_eval_address (addr_string);
	    do_cleanups (tmp_cleanup);
	  }

	  /* Skip spaces, move to possible next arg.  */
	  while (*p == ' ') p++;
	  frame_exp = p;
	}
    }

  switch (numargs)
    {
    case 0:
      if (selected_frame == NULL)
	error ("No selected frame.");
      return selected_frame;
      /* NOTREACHED */
    case 1:
      {
	int level = args[0];
	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) != args[0];
	     fid = get_prev_frame (fid))
	  ;

	if (fid)
	  while ((tfid = get_prev_frame (fid)) &&
		 (FRAME_FP (tfid) == args[0]))
	    fid = tfid;
	  
	/* We couldn't identify the frame as an existing frame, but
	   perhaps we can create one with a single argument.
	   Fall through to default case; it's up to SETUP_ARBITRARY_FRAME
	   to complain if it doesn't like a single arg.  */
      }

     default:
#ifdef SETUP_ARBITRARY_FRAME
      return SETUP_ARBITRARY_FRAME (numargs, args);
#else
      /* Usual case.  Do it here rather than have everyone supply
	 a SETUP_ARBITRARY_FRAME that does this.  */
      if (numargs == 1)
	return create_new_frame (args[0], 0);
      error ("Too many args in frame specification");
#endif
      /* NOTREACHED */
    }
  /* NOTREACHED */
}

/* FRAME_ARGS_ADDRESS_CORRECT is just like FRAME_ARGS_ADDRESS except
   that if it is unsure about the answer, it returns 0
   instead of guessing (this happens on the VAX and i960, 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, from_tty)
     char *addr_exp;
     int from_tty;
{
  FRAME frame;
  struct frame_info *fi;
  struct frame_saved_regs fsr;
  struct symtab_and_line sal;
  struct symbol *func;
  struct symtab *s;
  FRAME calling_frame;
  int i, count;
  char *funname = 0;
  enum language funlang = language_unknown;

  if (!target_has_stack)
    error ("No stack.");

  frame = parse_frame_specification (addr_exp);
  if (!frame)
    error ("Invalid frame specified.");

  fi = get_frame_info (frame);
  sal = find_pc_line (fi->pc,
		      fi->next != NULL
		      && !fi->next->signal_handler_caller
		      && !frame_in_dummy (fi->next));
  func = get_frame_function (frame);
  s = find_pc_symtab(fi->pc);
  if (func)
    {
      funname = SYMBOL_NAME (func);
      funlang = SYMBOL_LANGUAGE (func);
    }
  else
    {
      register struct minimal_symbol *msymbol = lookup_minimal_symbol_by_pc (fi->pc);
      if (msymbol != NULL)
	{
	  funname = SYMBOL_NAME (msymbol);
	  funlang = SYMBOL_LANGUAGE (msymbol);
	}
    }
  calling_frame = get_prev_frame (frame);

  if (!addr_exp && selected_frame_level >= 0)
    {
      printf_filtered ("Stack level %d, frame at ", selected_frame_level);
      print_address_numeric (FRAME_FP(frame), gdb_stdout);
      printf_filtered (":\n");
    }
  else
    {
      printf_filtered ("Stack frame at ");
      print_address_numeric (FRAME_FP(frame), gdb_stdout);
      printf_filtered (":\n");
    }
  printf_filtered (" %s = ",
		   reg_names[PC_REGNUM]);
  print_address_numeric (fi->pc, gdb_stdout);

  wrap_here ("   ");
  if (funname)
    {
      printf_filtered (" in ");
      fprintf_symbol_filtered (gdb_stdout, funname, funlang,
			       DMGL_ANSI | DMGL_PARAMS);
    }
  wrap_here ("   ");
  if (sal.symtab)
    printf_filtered (" (%s:%d)", sal.symtab->filename, sal.line);
  puts_filtered ("; ");
  wrap_here ("    ");
  printf_filtered ("saved %s ", reg_names[PC_REGNUM]);
  print_address_numeric (FRAME_SAVED_PC (frame), gdb_stdout);
  printf_filtered ("\n");

  {
    int frameless = 0;
#ifdef FRAMELESS_FUNCTION_INVOCATION
    FRAMELESS_FUNCTION_INVOCATION (fi, frameless);
#endif
    if (frameless)
      printf_filtered (" (FRAMELESS),");
  }

  if (calling_frame)
    {
      printf_filtered (" called by frame at ");
      print_address_numeric (FRAME_FP (calling_frame), gdb_stdout);
    }
  if (fi->next && calling_frame)
    puts_filtered (",");
  wrap_here ("   ");
  if (fi->next)
    {
      printf_filtered (" caller of frame at ");
      print_address_numeric (fi->next->frame, gdb_stdout);
    }
  if (fi->next || calling_frame)
    puts_filtered ("\n");
  if (s)
    printf_filtered (" source language %s.\n", language_str (s->language));

#ifdef PRINT_EXTRA_FRAME_INFO
  PRINT_EXTRA_FRAME_INFO (fi);
#endif

  {
    /* Address of the argument list for this frame, or 0.  */
    CORE_ADDR arg_list = FRAME_ARGS_ADDRESS_CORRECT (fi);
    /* Number of args for this frame, or -1 if unknown.  */
    int numargs;

    if (arg_list == 0)
      printf_filtered (" Arglist at unknown address.\n");
    else
      {
	printf_filtered (" Arglist at ");
	print_address_numeric (arg_list, gdb_stdout);
	printf_filtered (",");

	FRAME_NUM_ARGS (numargs, fi);
	if (numargs < 0)
	  puts_filtered (" args: ");
	else if (numargs == 0)
	  puts_filtered (" no args.");
	else if (numargs == 1)
	  puts_filtered (" 1 arg: ");
	else
	  printf_filtered (" %d args: ", numargs);
	print_frame_args (func, fi, numargs, gdb_stdout);
	puts_filtered ("\n");
      }
  }
  {
    /* Address of the local variables for this frame, or 0.  */
    CORE_ADDR arg_list = FRAME_LOCALS_ADDRESS (fi);

    if (arg_list == 0)
      printf_filtered (" Locals at unknown address,");
    else
      {
	printf_filtered (" Locals at ");
	print_address_numeric (arg_list, gdb_stdout);
	printf_filtered (",");
      }
  }

#if defined (FRAME_FIND_SAVED_REGS)  
  get_frame_saved_regs (fi, &fsr);
  /* The sp is special; what's returned isn't the save address, but
     actually the value of the previous frame's sp.  */
  printf_filtered (" Previous frame's sp is ");
  print_address_numeric (fsr.regs[SP_REGNUM], gdb_stdout);
  printf_filtered ("\n");
  count = 0;
  for (i = 0; i < NUM_REGS; i++)
    if (fsr.regs[i] && i != SP_REGNUM)
      {
	if (count == 0)
	  puts_filtered (" Saved registers:\n ");
	else
	  puts_filtered (",");
	wrap_here (" ");
	printf_filtered (" %s at ", reg_names[i]);
	print_address_numeric (fsr.regs[i], gdb_stdout);
	count++;
      }
  if (count)
    puts_filtered ("\n");
#else  /* Have FRAME_FIND_SAVED_REGS.  */
  puts_filtered ("\n");
#endif /* Have FRAME_FIND_SAVED_REGS.  */
}

#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_unfiltered ("Backtrace limit: %d.\n", backtrace_limit);
}
#endif

/* Print briefly all stack frames or just the innermost COUNT frames.  */

static void
backtrace_command (count_exp, from_tty)
     char *count_exp;
     int from_tty;
{
  struct frame_info *fi;
  register int count;
  register FRAME frame;
  register int i;
  register FRAME trailing;
  register int trailing_level;

  if (!target_has_stack)
    error ("No stack.");

  /* 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--)
	    {
	      QUIT;
	      current = get_prev_frame (current);
	    }
	  
	  /* Will stop when CURRENT reaches the top of the stack.  TRAILING
	     will be COUNT below it.  */
	  while (current)
	    {
	      QUIT;
	      trailing = get_prev_frame (trailing);
	      current = get_prev_frame (current);
	      trailing_level++;
	    }
	  
	  count = -1;
	}
    }
  else
    count = -1;

  if (info_verbose)
    {
      struct partial_symtab *ps;
      
      /* Read in symbols for all of the frames.  Need to do this in
	 a separate pass so that "Reading in symbols for xxx" messages
	 don't screw up the appearance of the backtrace.  Also
	 if people have strong opinions against reading symbols for
	 backtrace this may have to be an option.  */
      i = count;
      for (frame = trailing;
	   frame != NULL && i--;
	   frame = get_prev_frame (frame))
	{
	  QUIT;
	  fi = get_frame_info (frame);
	  ps = find_pc_psymtab (fi->pc);
	  if (ps)
	    PSYMTAB_TO_SYMTAB (ps);	/* Force syms to come in */
	}
    }

  for (i = 0, frame = trailing;
       frame && count--;
       i++, frame = get_prev_frame (frame))
    {
      QUIT;
      fi = get_frame_info (frame);

      /* Don't use print_stack_frame; if an error() occurs it probably
	 means further attempts to backtrace would fail (on the other
	 hand, perhaps the code does or could be fixed to make sure
	 the frame->prev field gets set to NULL in that case).  */
      print_frame_info (fi, trailing_level + i, 0, 1);
    }

  /* If we've stopped before the end, mention that.  */
  if (frame && from_tty)
    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 GDB_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);
      switch (SYMBOL_CLASS (sym))
	{
	case LOC_LOCAL:
	case LOC_REGISTER:
	case LOC_STATIC:
	case LOC_BASEREG:
	  values_printed = 1;
	  fputs_filtered (SYMBOL_SOURCE_NAME (sym), stream);
	  fputs_filtered (" = ", stream);
	  print_variable_value (sym, frame, stream);
	  fprintf_filtered (stream, "\n");
	  break;

	default:
	  /* Ignore symbols which are not locals.  */
	  break;
	}
    }
  return values_printed;
}

/* Same, but print labels.  */

static int
print_block_frame_labels (b, have_default, stream)
     struct block *b;
     int *have_default;
     register GDB_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 (STREQ (SYMBOL_NAME (sym), "default"))
	{
	  if (*have_default)
	    continue;
	  *have_default = 1;
	}
      if (SYMBOL_CLASS (sym) == LOC_LABEL)
	{
	  struct symtab_and_line sal;
	  sal = find_pc_line (SYMBOL_VALUE_ADDRESS (sym), 0);
	  values_printed = 1;
	  fputs_filtered (SYMBOL_SOURCE_NAME (sym), stream);
	  if (addressprint)
	    {
	      fprintf_filtered (stream, " ");
	      print_address_numeric (SYMBOL_VALUE_ADDRESS (sym), stream);
	    }
	  fprintf_filtered (stream, " in file %s, line %d\n",
			    sal.symtab->filename, sal.line);
	}
    }
  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 void
print_frame_local_vars (frame, stream)
     register FRAME frame;
     register GDB_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");
      return;
    }
  
  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");
    }
}

/* Same, but print labels.  */

static void
print_frame_label_vars (frame, this_level_only, stream)
     register FRAME frame;
     int this_level_only;
     register GDB_FILE *stream;
{
  register struct blockvector *bl;
  register struct block *block = get_frame_block (frame);
  register int values_printed = 0;
  int index, have_default = 0;
  char *blocks_printed;
  struct frame_info *fi = get_frame_info (frame);
  CORE_ADDR pc = fi->pc;

  if (block == 0)
    {
      fprintf_filtered (stream, "No symbol table info available.\n");
      return;
    }

  bl = blockvector_for_pc (BLOCK_END (block) - 4, &index);
  blocks_printed = (char *) alloca (BLOCKVECTOR_NBLOCKS (bl) * sizeof (char));
  memset (blocks_printed, 0, BLOCKVECTOR_NBLOCKS (bl) * sizeof (char));

  while (block != 0)
    {
      CORE_ADDR end = BLOCK_END (block) - 4;
      int last_index;

      if (bl != blockvector_for_pc (end, &index))
	error ("blockvector blotch");
      if (BLOCKVECTOR_BLOCK (bl, index) != block)
	error ("blockvector botch");
      last_index = BLOCKVECTOR_NBLOCKS (bl);
      index += 1;

      /* Don't print out blocks that have gone by.  */
      while (index < last_index
	     && BLOCK_END (BLOCKVECTOR_BLOCK (bl, index)) < pc)
	index++;

      while (index < last_index
	     && BLOCK_END (BLOCKVECTOR_BLOCK (bl, index)) < end)
	{
	  if (blocks_printed[index] == 0)
	    {
	      if (print_block_frame_labels (BLOCKVECTOR_BLOCK (bl, index), &have_default, stream))
		values_printed = 1;
	      blocks_printed[index] = 1;
	    }
	  index++;
	}
      if (have_default)
	return;
      if (values_printed && this_level_only)
	return;

      /* 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 && !this_level_only)
    {
      fprintf_filtered (stream, "No catches.\n");
    }
}

/* ARGSUSED */
static void
locals_info (args, from_tty)
     char *args;
     int from_tty;
{
  if (!selected_frame)
    error ("No frame selected.");
  print_frame_local_vars (selected_frame, gdb_stdout);
}

static void
catch_info (ignore, from_tty)
     char *ignore;
     int from_tty;
{
  if (!selected_frame)
    error ("No frame selected.");
  print_frame_label_vars (selected_frame, 0, gdb_stdout);
}

static void
print_frame_arg_vars (frame, stream)
     register FRAME frame;
     register GDB_FILE *stream;
{
  struct symbol *func = get_frame_function (frame);
  register struct block *b;
  int nsyms;
  register int i;
  register struct symbol *sym, *sym2;
  register int values_printed = 0;

  if (func == 0)
    {
      fprintf_filtered (stream, "No symbol table info available.\n");
      return;
    }

  b = SYMBOL_BLOCK_VALUE (func);
  nsyms = BLOCK_NSYMS (b);

  for (i = 0; i < nsyms; i++)
    {
      sym = BLOCK_SYM (b, i);
      switch (SYMBOL_CLASS (sym))
	{
	case LOC_ARG:
	case LOC_LOCAL_ARG:
	case LOC_REF_ARG:
	case LOC_REGPARM:
	case LOC_REGPARM_ADDR:
	case LOC_BASEREG_ARG:
	  values_printed = 1;
	  fputs_filtered (SYMBOL_SOURCE_NAME (sym), stream);
	  fputs_filtered (" = ", stream);

	  /* We have to look up the symbol because arguments can have
	     two entries (one a parameter, one a local) and the one we
	     want is the local, which lookup_symbol will find for us.
	     This includes gcc1 (not gcc2) on the sparc when passing a
	     small structure and gcc2 when the argument type is float
	     and it is passed as a double and converted to float by
	     the prologue (in the latter case the type of the LOC_ARG
	     symbol is double and the type of the LOC_LOCAL symbol is
	     float).  There are also LOC_ARG/LOC_REGISTER pairs which
	     are not combined in symbol-reading.  */

	  sym2 = lookup_symbol (SYMBOL_NAME (sym),
			b, VAR_NAMESPACE, (int *)NULL, (struct symtab **)NULL);
	  print_variable_value (sym2, frame, stream);
	  fprintf_filtered (stream, "\n");
	  break;

	default:
	  /* Don't worry about things which aren't arguments.  */
	  break;
	}
    }

  if (!values_printed)
    {
      fprintf_filtered (stream, "No arguments.\n");
    }
}

static void
args_info (ignore, from_tty)
     char *ignore;
     int from_tty;
{
  if (!selected_frame)
    error ("No frame selected.");
  print_frame_arg_vars (selected_frame, gdb_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;
{
  register struct symtab *s;

  selected_frame = frame;
  selected_frame_level = level;

  /* Ensure that symbols for this frame are read in.  Also, determine the
     source language of this frame, and switch to it if desired.  */
  if (frame)
  {
    s = find_pc_symtab (get_frame_info (frame)->pc);
    if (s 
	&& s->language != current_language->la_language
	&& s->language != language_unknown
	&& language_mode == language_mode_auto) {
      set_language(s->language);
    }
  }
}

/* Store the selected frame and its level into *FRAMEP and *LEVELP.
   If there is no selected frame, *FRAMEP is set to NULL.  */

void
record_selected_frame (frameaddrp, levelp)
     FRAME_ADDR *frameaddrp;
     int *levelp;
{
  *frameaddrp = selected_frame ? FRAME_FP (selected_frame) : 0;
  *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 (!target_has_stack)
    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;

  /* 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 is just as simple.  */
  if (*level_offset_ptr < 0)
    {
      while (*level_offset_ptr < 0) {
	frame1 = get_next_frame (frame);
	if (!frame1)
	  break;
	frame = frame1;
	(*level_offset_ptr)++;
      }
    }
  return frame;
}

/* The "select_frame" command.  With no arg, NOP.
   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 select it.  See parse_frame_specification for more info on proper
   frame expressions. */

/* ARGSUSED */
static void
select_frame_command (level_exp, from_tty)
     char *level_exp;
     int from_tty;
{
  register FRAME frame, frame1;
  unsigned int level = 0;

  if (!target_has_stack)
    error ("No stack.");

  frame = parse_frame_specification (level_exp);

  /* Try to figure out what level this frame is.  But if there is
     no current stack, don't error out -- let the user set one.  */
  frame1 = 0;
  if (get_current_frame()) {
    for (frame1 = get_prev_frame (0);
	 frame1 && frame1 != frame;
	 frame1 = get_prev_frame (frame1))
      level++;
  }

  if (!frame1)
    level = 0;

  select_frame (frame, level);
}

/* The "frame" command.  With no arg, print selected frame briefly.
   With arg, behaves like select_frame and then prints the selected
   frame.  */

static void
frame_command (level_exp, from_tty)
     char *level_exp;
     int from_tty;
{
  select_frame_command (level_exp, from_tty);
  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.  */

/* ARGSUSED */
static void
up_silently_command (count_exp, from_tty)
     char *count_exp;
     int from_tty;
{
  register FRAME frame;
  int count = 1, count1;
  if (count_exp)
    count = parse_and_eval_address (count_exp);
  count1 = count;
  
  if (target_has_stack == 0 || selected_frame == 0)
    error ("No stack.");

  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);
}

static void
up_command (count_exp, from_tty)
     char *count_exp;
     int from_tty;
{
  up_silently_command (count_exp, from_tty);
  print_stack_frame (selected_frame, selected_frame_level, 1);
}

/* Select the frame down one or COUNT stack levels
   from the previously selected frame, and print it briefly.  */

/* ARGSUSED */
static void
down_silently_command (count_exp, from_tty)
     char *count_exp;
     int from_tty;
{
  register FRAME frame;
  int count = -1, count1;
  if (count_exp)
    count = - parse_and_eval_address (count_exp);
  count1 = count;
  
  if (target_has_stack == 0 || selected_frame == 0)
    error ("No stack.");

  frame = find_relative_frame (selected_frame, &count1);
  if (count1 != 0 && count_exp == 0)
    {

      /* We only do this if count_exp is not specified.  That way "down"
	 means to really go down (and let me know if that is
	 impossible), but "down 9999" can be used to mean go all the way
	 down without getting an error.  */

      error ("Bottom (i.e., innermost) frame selected; you cannot go down.");
    }

  select_frame (frame, selected_frame_level + count - count1);
}


static void
down_command (count_exp, from_tty)
     char *count_exp;
     int from_tty;
{
  down_silently_command (count_exp, from_tty);
  print_stack_frame (selected_frame, selected_frame_level, 1);
}

static void
return_command (retval_exp, from_tty)
     char *retval_exp;
     int from_tty;
{
  struct symbol *thisfun;
  FRAME_ADDR selected_frame_addr;
  CORE_ADDR selected_frame_pc;
  FRAME frame;
  value return_value = NULL;

  if (selected_frame == NULL)
    error ("No selected frame.");
  thisfun = get_frame_function (selected_frame);
  selected_frame_addr = FRAME_FP (selected_frame);
  selected_frame_pc = (get_frame_info (selected_frame))->pc;

  /* Compute the return value (if any -- possibly getting errors here).  */

  if (retval_exp)
    {
      return_value = parse_and_eval (retval_exp);

      /* Make sure we have fully evaluated it, since
	 it might live in the stack frame we're about to pop.  */
      if (VALUE_LAZY (return_value))
	value_fetch_lazy (return_value);
    }

  /* If interactive, require confirmation.  */

  if (from_tty)
    {
      if (thisfun != 0)
	{
	  if (!query ("Make %s return now? ", SYMBOL_SOURCE_NAME (thisfun)))
	    {
	      error ("Not confirmed.");
	      /* NOTREACHED */
	    }
	}
      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.  The pc comparison makes this work even if the
     selected frame shares its fp with another frame.  */

  while ( selected_frame_addr != FRAME_FP (frame = get_current_frame())
       || selected_frame_pc   != (get_frame_info (frame))->pc  )
    POP_FRAME;

  /* Then pop that frame.  */

  POP_FRAME;

  /* Compute the return value (if any) and store in the place
     for return values.  */

  if (retval_exp)
    set_return_value (return_value);

  /* If interactive, print the frame that is now current.  */

  if (from_tty)
    frame_command ("0", 1);
}

/* Gets the language of the current frame. */
enum language
get_frame_language()
{
   register struct symtab *s;
   FRAME fr;
   enum language flang;		/* The language of the current frame */
   
   fr = get_frame_info(selected_frame);
   if(fr)
   {
      s = find_pc_symtab(fr->pc);
      if(s)
	 flang = s->language;
      else
	 flang = language_unknown;
   }
   else
      flang = language_unknown;

   return flang;
}

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 ("up-silently", class_support, up_silently_command,
	   "Same as the `up' command, but does not print anything.\n\
This is useful in command scripts.");

  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_alias ("dow", "down", class_stack, 1);
  add_com ("down-silently", class_support, down_silently_command,
	   "Same as the `down' command, but does not print anything.\n\
This is useful in command scripts.");

  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 ("select-frame", class_stack, select_frame_command,
	   "Select a stack frame without printing anything.\n\
An argument specifies the frame to select.\n\
It can be a stack frame number or the address of the frame.\n");

  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.");
  add_info ("catch", catch_info,
	    "Exceptions that can be caught in the 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
}