binutils-gdb/gdb/infrun.c

/* Target-struct-independent code to start (run) and stop an inferior process.
   Copyright 1986, 1987, 1988, 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.  */

/* Notes on the algorithm used in wait_for_inferior to determine if we
   just did a subroutine call when stepping.  We have the following
   information at that point:

                  Current and previous (just before this step) pc.
		  Current and previous sp.
		  Current and previous start of current function.

   If the starts of the functions don't match, then

   	a) We did a subroutine call.

   In this case, the pc will be at the beginning of a function.

	b) We did a subroutine return.

   Otherwise.

	c) We did a longjmp.

   If we did a longjump, we were doing "nexti", since a next would
   have attempted to skip over the assembly language routine in which
   the longjmp is coded and would have simply been the equivalent of a
   continue.  I consider this ok behaivior.  We'd like one of two
   things to happen if we are doing a nexti through the longjmp()
   routine: 1) It behaves as a stepi, or 2) It acts like a continue as
   above.  Given that this is a special case, and that anybody who
   thinks that the concept of sub calls is meaningful in the context
   of a longjmp, I'll take either one.  Let's see what happens.  

   Acts like a subroutine return.  I can handle that with no problem
   at all.

   -->So: If the current and previous beginnings of the current
   function don't match, *and* the pc is at the start of a function,
   we've done a subroutine call.  If the pc is not at the start of a
   function, we *didn't* do a subroutine call.  

   -->If the beginnings of the current and previous function do match,
   either: 

   	a) We just did a recursive call.

	   In this case, we would be at the very beginning of a
	   function and 1) it will have a prologue (don't jump to
	   before prologue, or 2) (we assume here that it doesn't have
	   a prologue) there will have been a change in the stack
	   pointer over the last instruction.  (Ie. it's got to put
	   the saved pc somewhere.  The stack is the usual place.  In
	   a recursive call a register is only an option if there's a
	   prologue to do something with it.  This is even true on
	   register window machines; the prologue sets up the new
	   window.  It might not be true on a register window machine
	   where the call instruction moved the register window
	   itself.  Hmmm.  One would hope that the stack pointer would
	   also change.  If it doesn't, somebody send me a note, and
	   I'll work out a more general theory.
	   bug-gdb@prep.ai.mit.edu).  This is true (albeit slipperly
	   so) on all machines I'm aware of:

	      m68k:	Call changes stack pointer.  Regular jumps don't.

	      sparc:	Recursive calls must have frames and therefor,
	                prologues.

	      vax:	All calls have frames and hence change the
	                stack pointer.

	b) We did a return from a recursive call.  I don't see that we
	   have either the ability or the need to distinguish this
	   from an ordinary jump.  The stack frame will be printed
	   when and if the frame pointer changes; if we are in a
	   function without a frame pointer, it's the users own
	   lookout.

	c) We did a jump within a function.  We assume that this is
	   true if we didn't do a recursive call.

	d) We are in no-man's land ("I see no symbols here").  We
	   don't worry about this; it will make calls look like simple
	   jumps (and the stack frames will be printed when the frame
	   pointer moves), which is a reasonably non-violent response.
*/

#include "defs.h"
#include <string.h>
#include <ctype.h>
#include "symtab.h"
#include "frame.h"
#include "inferior.h"
#include "breakpoint.h"
#include "wait.h"
#include "gdbcore.h"
#include "gdbcmd.h"
#include "target.h"

#include <signal.h>

/* unistd.h is needed to #define X_OK */
#ifdef USG
#include <unistd.h>
#else
#include <sys/file.h>
#endif

/* Prototypes for local functions */

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

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

static void
sig_print_info PARAMS ((int));

static void
sig_print_header PARAMS ((void));

static void
resume_cleanups PARAMS ((int));

static int
hook_stop_stub PARAMS ((char *));

/* GET_LONGJMP_TARGET returns the PC at which longjmp() will resume the
   program.  It needs to examine the jmp_buf argument and extract the PC
   from it.  The return value is non-zero on success, zero otherwise. */
#ifndef GET_LONGJMP_TARGET
#define GET_LONGJMP_TARGET(PC_ADDR) 0
#endif


/* Some machines have trampoline code that sits between function callers
   and the actual functions themselves.  If this machine doesn't have
   such things, disable their processing.  */
#ifndef SKIP_TRAMPOLINE_CODE
#define	SKIP_TRAMPOLINE_CODE(pc)	0
#endif

/* For SVR4 shared libraries, each call goes through a small piece of
   trampoline code in the ".init" section.  IN_SOLIB_TRAMPOLINE evaluates
   to nonzero if we are current stopped in one of these. */
#ifndef IN_SOLIB_TRAMPOLINE
#define IN_SOLIB_TRAMPOLINE(pc,name)	0
#endif

/* On some systems, the PC may be left pointing at an instruction that  won't
   actually be executed.  This is usually indicated by a bit in the PSW.  If
   we find ourselves in such a state, then we step the target beyond the
   nullified instruction before returning control to the user so as to avoid
   confusion. */

#ifndef INSTRUCTION_NULLIFIED
#define INSTRUCTION_NULLIFIED 0
#endif

/* Tables of how to react to signals; the user sets them.  */

static unsigned char *signal_stop;
static unsigned char *signal_print;
static unsigned char *signal_program;

#define SET_SIGS(nsigs,sigs,flags) \
  do { \
    int signum = (nsigs); \
    while (signum-- > 0) \
      if ((sigs)[signum]) \
	(flags)[signum] = 1; \
  } while (0)

#define UNSET_SIGS(nsigs,sigs,flags) \
  do { \
    int signum = (nsigs); \
    while (signum-- > 0) \
      if ((sigs)[signum]) \
	(flags)[signum] = 0; \
  } while (0)


/* Command list pointer for the "stop" placeholder.  */

static struct cmd_list_element *stop_command;

/* Nonzero if breakpoints are now inserted in the inferior.  */

static int breakpoints_inserted;

/* Function inferior was in as of last step command.  */

static struct symbol *step_start_function;

/* Nonzero if we are expecting a trace trap and should proceed from it.  */

static int trap_expected;

/* Nonzero if the next time we try to continue the inferior, it will
   step one instruction and generate a spurious trace trap.
   This is used to compensate for a bug in HP-UX.  */

static int trap_expected_after_continue;

/* Nonzero means expecting a trace trap
   and should stop the inferior and return silently when it happens.  */

int stop_after_trap;

/* Nonzero means expecting a trap and caller will handle it themselves.
   It is used after attach, due to attaching to a process;
   when running in the shell before the child program has been exec'd;
   and when running some kinds of remote stuff (FIXME?).  */

int stop_soon_quietly;

/* Nonzero if pc has been changed by the debugger
   since the inferior stopped.  */

int pc_changed;

/* Nonzero if proceed is being used for a "finish" command or a similar
   situation when stop_registers should be saved.  */

int proceed_to_finish;

/* Save register contents here when about to pop a stack dummy frame,
   if-and-only-if proceed_to_finish is set.
   Thus this contains the return value from the called function (assuming
   values are returned in a register).  */

char stop_registers[REGISTER_BYTES];

/* Nonzero if program stopped due to error trying to insert breakpoints.  */

static int breakpoints_failed;

/* Nonzero after stop if current stack frame should be printed.  */

static int stop_print_frame;

#ifdef NO_SINGLE_STEP
extern int one_stepped;		/* From machine dependent code */
extern void single_step ();	/* Same. */
#endif /* NO_SINGLE_STEP */


/* Things to clean up if we QUIT out of resume ().  */
/* ARGSUSED */
static void
resume_cleanups (arg)
     int arg;
{
  normal_stop ();
}

/* Resume the inferior, but allow a QUIT.  This is useful if the user
   wants to interrupt some lengthy single-stepping operation
   (for child processes, the SIGINT goes to the inferior, and so
   we get a SIGINT random_signal, but for remote debugging and perhaps
   other targets, that's not true).

   STEP nonzero if we should step (zero to continue instead).
   SIG is the signal to give the inferior (zero for none).  */
void
resume (step, sig)
     int step;
     int sig;
{
  struct cleanup *old_cleanups = make_cleanup (resume_cleanups, 0);
  QUIT;

#ifdef NO_SINGLE_STEP
  if (step) {
    single_step(sig);	/* Do it the hard way, w/temp breakpoints */
    step = 0;		/* ...and don't ask hardware to do it.  */
  }
#endif

  /* Handle any optimized stores to the inferior NOW...  */
#ifdef DO_DEFERRED_STORES
  DO_DEFERRED_STORES;
#endif

  target_resume (step, sig);
  discard_cleanups (old_cleanups);
}


/* Clear out all variables saying what to do when inferior is continued.
   First do this, then set the ones you want, then call `proceed'.  */

void
clear_proceed_status ()
{
  trap_expected = 0;
  step_range_start = 0;
  step_range_end = 0;
  step_frame_address = 0;
  step_over_calls = -1;
  stop_after_trap = 0;
  stop_soon_quietly = 0;
  proceed_to_finish = 0;
  breakpoint_proceeded = 1;	/* We're about to proceed... */

  /* Discard any remaining commands or status from previous stop.  */
  bpstat_clear (&stop_bpstat);
}

/* Basic routine for continuing the program in various fashions.

   ADDR is the address to resume at, or -1 for resume where stopped.
   SIGGNAL is the signal to give it, or 0 for none,
     or -1 for act according to how it stopped.
   STEP is nonzero if should trap after one instruction.
     -1 means return after that and print nothing.
     You should probably set various step_... variables
     before calling here, if you are stepping.

   You should call clear_proceed_status before calling proceed.  */

void
proceed (addr, siggnal, step)
     CORE_ADDR addr;
     int siggnal;
     int step;
{
  int oneproc = 0;

  if (step > 0)
    step_start_function = find_pc_function (read_pc ());
  if (step < 0)
    stop_after_trap = 1;

  if (addr == (CORE_ADDR)-1)
    {
      /* If there is a breakpoint at the address we will resume at,
	 step one instruction before inserting breakpoints
	 so that we do not stop right away.  */

      if (!pc_changed && breakpoint_here_p (read_pc ()))
	oneproc = 1;
    }
  else
    write_pc (addr);

  if (trap_expected_after_continue)
    {
      /* If (step == 0), a trap will be automatically generated after
	 the first instruction is executed.  Force step one
	 instruction to clear this condition.  This should not occur
	 if step is nonzero, but it is harmless in that case.  */
      oneproc = 1;
      trap_expected_after_continue = 0;
    }

  if (oneproc)
    /* We will get a trace trap after one instruction.
       Continue it automatically and insert breakpoints then.  */
    trap_expected = 1;
  else
    {
      int temp = insert_breakpoints ();
      if (temp)
	{
	  print_sys_errmsg ("ptrace", temp);
	  error ("Cannot insert breakpoints.\n\
The same program may be running in another process.");
	}
      breakpoints_inserted = 1;
    }

  /* Install inferior's terminal modes.  */
  target_terminal_inferior ();

  if (siggnal >= 0)
    stop_signal = siggnal;
  /* If this signal should not be seen by program,
     give it zero.  Used for debugging signals.  */
  else if (stop_signal < NSIG && !signal_program[stop_signal])
    stop_signal= 0;

  /* Resume inferior.  */
  resume (oneproc || step || bpstat_should_step (), stop_signal);

  /* Wait for it to stop (if not standalone)
     and in any case decode why it stopped, and act accordingly.  */

  wait_for_inferior ();
  normal_stop ();
}

/* Record the pc and sp of the program the last time it stopped.
   These are just used internally by wait_for_inferior, but need
   to be preserved over calls to it and cleared when the inferior
   is started.  */
static CORE_ADDR prev_pc;
static CORE_ADDR prev_sp;
static CORE_ADDR prev_func_start;
static char *prev_func_name;


/* Start remote-debugging of a machine over a serial link.  */

void
start_remote ()
{
  init_wait_for_inferior ();
  clear_proceed_status ();
  stop_soon_quietly = 1;
  trap_expected = 0;
  wait_for_inferior ();
  normal_stop ();
}

/* Initialize static vars when a new inferior begins.  */

void
init_wait_for_inferior ()
{
  /* These are meaningless until the first time through wait_for_inferior.  */
  prev_pc = 0;
  prev_sp = 0;
  prev_func_start = 0;
  prev_func_name = NULL;

  trap_expected_after_continue = 0;
  breakpoints_inserted = 0;
  mark_breakpoints_out ();
  stop_signal = 0;		/* Don't confuse first call to proceed(). */
}

static void
delete_breakpoint_current_contents (arg)
     PTR arg;
{
  struct breakpoint **breakpointp = (struct breakpoint **)arg;
  if (*breakpointp != NULL)
    delete_breakpoint (*breakpointp);
}

/* Wait for control to return from inferior to debugger.
   If inferior gets a signal, we may decide to start it up again
   instead of returning.  That is why there is a loop in this function.
   When this function actually returns it means the inferior
   should be left stopped and GDB should read more commands.  */

void
wait_for_inferior ()
{
  struct cleanup *old_cleanups;
  WAITTYPE w;
  int another_trap;
  int random_signal;
  CORE_ADDR stop_sp;
  CORE_ADDR stop_func_start;
  char *stop_func_name;
  CORE_ADDR prologue_pc, tmp;
  struct symtab_and_line sal;
  int remove_breakpoints_on_following_step = 0;
  int current_line;
  int handling_longjmp = 0;	/* FIXME */
  struct symtab *symtab;
  struct breakpoint *step_resume_breakpoint = NULL;

  old_cleanups = make_cleanup (delete_breakpoint_current_contents,
			       &step_resume_breakpoint);
  sal = find_pc_line(prev_pc, 0);
  current_line = sal.line;

  while (1)
    {
      /* Clean up saved state that will become invalid.  */
      pc_changed = 0;
      flush_cached_frames ();
      registers_changed ();

      target_wait (&w);

#ifdef SIGTRAP_STOP_AFTER_LOAD

      /* Somebody called load(2), and it gave us a "trap signal after load".
         Ignore it gracefully. */

      SIGTRAP_STOP_AFTER_LOAD (w);
#endif

      /* See if the process still exists; clean up if it doesn't.  */
      if (WIFEXITED (w))
	{
	  target_terminal_ours ();	/* Must do this before mourn anyway */
	  if (WEXITSTATUS (w))
	    printf_filtered ("\nProgram exited with code 0%o.\n", 
		     (unsigned int)WEXITSTATUS (w));
	  else
	    if (!batch_mode())
	      printf_filtered ("\nProgram exited normally.\n");
	  fflush (stdout);
	  target_mourn_inferior ();
#ifdef NO_SINGLE_STEP
	  one_stepped = 0;
#endif
	  stop_print_frame = 0;
	  break;
	}
      else if (!WIFSTOPPED (w))
	{
	  char *signame;
	  
	  stop_print_frame = 0;
	  stop_signal = WTERMSIG (w);
	  target_terminal_ours ();	/* Must do this before mourn anyway */
	  target_kill ();		/* kill mourns as well */
#ifdef PRINT_RANDOM_SIGNAL
	  printf_filtered ("\nProgram terminated: ");
	  PRINT_RANDOM_SIGNAL (stop_signal);
#else
	  printf_filtered ("\nProgram terminated with signal ");
	  signame = strsigno (stop_signal);
	  if (signame == NULL)
	    printf_filtered ("%d", stop_signal);
	  else
	    /* Do we need to print the number in addition to the name?  */
	    printf_filtered ("%s (%d)", signame, stop_signal);
	  printf_filtered (", %s\n", safe_strsignal (stop_signal));
#endif
	  printf_filtered ("The program no longer exists.\n");
	  fflush (stdout);
#ifdef NO_SINGLE_STEP
	  one_stepped = 0;
#endif
	  break;
	}
      
#ifdef NO_SINGLE_STEP
      if (one_stepped)
	single_step (0);	/* This actually cleans up the ss */
#endif /* NO_SINGLE_STEP */
      
/* If PC is pointing at a nullified instruction, then step beyond it so that
   the user won't be confused when GDB appears to be ready to execute it. */

      if (INSTRUCTION_NULLIFIED)
	{
	  resume (1, 0);
	  continue;
	}

      stop_pc = read_pc ();
      set_current_frame ( create_new_frame (read_fp (),
					    read_pc ()));

      stop_frame_address = FRAME_FP (get_current_frame ());
      stop_sp = read_sp ();
      stop_func_start = 0;
      stop_func_name = 0;
      /* Don't care about return value; stop_func_start and stop_func_name
	 will both be 0 if it doesn't work.  */
      find_pc_partial_function (stop_pc, &stop_func_name, &stop_func_start);
      stop_func_start += FUNCTION_START_OFFSET;
      another_trap = 0;
      bpstat_clear (&stop_bpstat);
      stop_step = 0;
      stop_stack_dummy = 0;
      stop_print_frame = 1;
      random_signal = 0;
      stopped_by_random_signal = 0;
      breakpoints_failed = 0;
      
      /* Look at the cause of the stop, and decide what to do.
	 The alternatives are:
	 1) break; to really stop and return to the debugger,
	 2) drop through to start up again
	 (set another_trap to 1 to single step once)
	 3) set random_signal to 1, and the decision between 1 and 2
	 will be made according to the signal handling tables.  */
      
      stop_signal = WSTOPSIG (w);
      
      /* First, distinguish signals caused by the debugger from signals
	 that have to do with the program's own actions.
	 Note that breakpoint insns may cause SIGTRAP or SIGILL
	 or SIGEMT, depending on the operating system version.
	 Here we detect when a SIGILL or SIGEMT is really a breakpoint
	 and change it to SIGTRAP.  */
      
      if (stop_signal == SIGTRAP
	  || (breakpoints_inserted &&
	      (stop_signal == SIGILL
#ifdef SIGEMT
	       || stop_signal == SIGEMT
#endif
            ))
	  || stop_soon_quietly)
	{
	  if (stop_signal == SIGTRAP && stop_after_trap)
	    {
	      stop_print_frame = 0;
	      break;
	    }
	  if (stop_soon_quietly)
	    break;

	  /* Don't even think about breakpoints
	     if just proceeded over a breakpoint.

	     However, if we are trying to proceed over a breakpoint
	     and end up in sigtramp, then step_resume_breakpoint
	     will be set and we should check whether we've hit the
	     step breakpoint.  */
	  if (stop_signal == SIGTRAP && trap_expected
	      && step_resume_breakpoint == NULL)
	    bpstat_clear (&stop_bpstat);
	  else
	    {
	      /* See if there is a breakpoint at the current PC.  */
#if DECR_PC_AFTER_BREAK
	      /* Notice the case of stepping through a jump
		 that lands just after a breakpoint.
		 Don't confuse that with hitting the breakpoint.
		 What we check for is that 1) stepping is going on
		 and 2) the pc before the last insn does not match
		 the address of the breakpoint before the current pc.  */
	      if (prev_pc == stop_pc - DECR_PC_AFTER_BREAK
		  || !step_range_end
		  || step_resume_breakpoint != NULL
		  || handling_longjmp /* FIXME */)
#endif /* DECR_PC_AFTER_BREAK not zero */
		{
		  stop_bpstat =
		    bpstat_stop_status (&stop_pc, stop_frame_address);
		  /* Following in case break condition called a
		     function.  */
		  stop_print_frame = 1;
		}
	    }

	  if (stop_signal == SIGTRAP)
	    random_signal
	      = !(bpstat_explains_signal (stop_bpstat)
		  || trap_expected
		  || PC_IN_CALL_DUMMY (stop_pc, stop_sp, stop_frame_address)
		  || (step_range_end && step_resume_breakpoint == NULL));
	  else
	    {
	      random_signal
		= !(bpstat_explains_signal (stop_bpstat)
		    /* End of a stack dummy.  Some systems (e.g. Sony
		       news) give another signal besides SIGTRAP,
		       so check here as well as above.  */
		    || PC_IN_CALL_DUMMY (stop_pc, stop_sp, stop_frame_address)
		    );
	      if (!random_signal)
		stop_signal = SIGTRAP;
	    }
	}
      else
	random_signal = 1;

      /* For the program's own signals, act according to
	 the signal handling tables.  */

      if (random_signal)
	{
	  /* Signal not for debugging purposes.  */
	  int printed = 0;
	  
	  stopped_by_random_signal = 1;
	  
	  if (stop_signal >= NSIG
	      || signal_print[stop_signal])
	    {
	      char *signame;
	      printed = 1;
	      target_terminal_ours_for_output ();
#ifdef PRINT_RANDOM_SIGNAL
	      PRINT_RANDOM_SIGNAL (stop_signal);
#else
	      printf_filtered ("\nProgram received signal ");
	      signame = strsigno (stop_signal);
	      if (signame == NULL)
		printf_filtered ("%d", stop_signal);
	      else
		/* Do we need to print the number as well as the name?  */
		printf_filtered ("%s (%d)", signame, stop_signal);
	      printf_filtered (", %s\n", safe_strsignal (stop_signal));
#endif /* PRINT_RANDOM_SIGNAL */
	      fflush (stdout);
	    }
	  if (stop_signal >= NSIG
	      || signal_stop[stop_signal])
	    break;
	  /* If not going to stop, give terminal back
	     if we took it away.  */
	  else if (printed)
	    target_terminal_inferior ();

	  /* Clear the signal if it should not be passed.  */
	  if (signal_program[stop_signal] == 0)
	    stop_signal = 0;

	  /* I'm not sure whether this needs to be check_sigtramp2 or
	     whether it could/should be keep_going.  */
	  goto check_sigtramp2;
	}

      /* Handle cases caused by hitting a breakpoint.  */
      {
	CORE_ADDR jmp_buf_pc;
	struct bpstat_what what;

	what = bpstat_what (stop_bpstat);

	switch (what.main_action)
	  {
	  case BPSTAT_WHAT_SET_LONGJMP_RESUME:
	    /* If we hit the breakpoint at longjmp, disable it for the
	       duration of this command.  Then, install a temporary
	       breakpoint at the target of the jmp_buf. */
	    disable_longjmp_breakpoint();
	    remove_breakpoints ();
	    breakpoints_inserted = 0;
	    if (!GET_LONGJMP_TARGET(&jmp_buf_pc)) goto keep_going;

	    /* Need to blow away step-resume breakpoint, as it
	       interferes with us */
	    if (step_resume_breakpoint != NULL)
	      {
		delete_breakpoint (step_resume_breakpoint);
		step_resume_breakpoint = NULL;
		what.step_resume = 0;
	      }

#if 0
	    /* FIXME - Need to implement nested temporary breakpoints */
	    if (step_over_calls > 0)
	      set_longjmp_resume_breakpoint(jmp_buf_pc,
					    get_current_frame());
	    else
#endif				/* 0 */
	      set_longjmp_resume_breakpoint(jmp_buf_pc, NULL);
	    handling_longjmp = 1; /* FIXME */
	    goto keep_going;

	  case BPSTAT_WHAT_CLEAR_LONGJMP_RESUME:
	  case BPSTAT_WHAT_CLEAR_LONGJMP_RESUME_SINGLE:
	    remove_breakpoints ();
	    breakpoints_inserted = 0;
#if 0
	    /* FIXME - Need to implement nested temporary breakpoints */
	    if (step_over_calls
		&& (stop_frame_address
		    INNER_THAN step_frame_address))
	      {
		another_trap = 1;
		goto keep_going;
	      }
#endif				/* 0 */
	    disable_longjmp_breakpoint();
	    handling_longjmp = 0; /* FIXME */
	    if (what.main_action == BPSTAT_WHAT_CLEAR_LONGJMP_RESUME)
	      break;
	    /* else fallthrough */

	  case BPSTAT_WHAT_SINGLE:
	    if (breakpoints_inserted)
	      remove_breakpoints ();
	    breakpoints_inserted = 0;
	    another_trap = 1;
	    /* Still need to check other stuff, at least the case
	       where we are stepping and step out of the right range.  */
	    break;

	  case BPSTAT_WHAT_STOP_NOISY:
	    stop_print_frame = 1;
	    /* We are about to nuke the step_resume_breakpoint via the
	       cleanup chain, so no need to worry about it here.  */
	    goto stop_stepping;

	  case BPSTAT_WHAT_STOP_SILENT:
	    stop_print_frame = 0;
	    /* We are about to nuke the step_resume_breakpoint via the
	       cleanup chain, so no need to worry about it here.  */
	    goto stop_stepping;

	  case BPSTAT_WHAT_KEEP_CHECKING:
	    break;
	  }

	if (what.step_resume)
	  {
	    delete_breakpoint (step_resume_breakpoint);
	    step_resume_breakpoint = NULL;

	    /* If were waiting for a trap, hitting the step_resume_break
	       doesn't count as getting it.  */
	    if (trap_expected)
	      another_trap = 1;
	  }
      }

      /* We come here if we hit a breakpoint but should not
	 stop for it.  Possibly we also were stepping
	 and should stop for that.  So fall through and
	 test for stepping.  But, if not stepping,
	 do not stop.  */

      /* If this is the breakpoint at the end of a stack dummy,
	 just stop silently.  */
      if (PC_IN_CALL_DUMMY (stop_pc, stop_sp, stop_frame_address))
	  {
	    stop_print_frame = 0;
	    stop_stack_dummy = 1;
#ifdef HP_OS_BUG
	    trap_expected_after_continue = 1;
#endif
	    break;
	  }
      
      if (step_resume_breakpoint)
	/* Having a step-resume breakpoint overrides anything
	   else having to do with stepping commands until
	   that breakpoint is reached.  */
	/* I suspect this could/should be keep_going, because if the
	   check_sigtramp2 check succeeds, then it will put in another
	   step_resume_breakpoint, and we aren't (yet) prepared to nest
	   them.  */
	goto check_sigtramp2;

      if (step_range_end == 0)
	/* Likewise if we aren't even stepping.  */
	/* I'm not sure whether this needs to be check_sigtramp2 or
	   whether it could/should be keep_going.  */
	goto check_sigtramp2;

      /* If stepping through a line, keep going if still within it.  */
      if (stop_pc >= step_range_start
	  && stop_pc < step_range_end
	  /* The step range might include the start of the
	     function, so if we are at the start of the
	     step range and either the stack or frame pointers
	     just changed, we've stepped outside */
	  && !(stop_pc == step_range_start
	       && stop_frame_address
	       && (stop_sp INNER_THAN prev_sp
		   || stop_frame_address != step_frame_address)))
	{
	  /* We might be doing a BPSTAT_WHAT_SINGLE and getting a signal.
	     So definately need to check for sigtramp here.  */
	  goto check_sigtramp2;
	}

      /* We stepped out of the stepping range.  See if that was due
	 to a subroutine call that we should proceed to the end of.  */

      /* Did we just take a signal?  */
      if (IN_SIGTRAMP (stop_pc, stop_func_name)
	  && !IN_SIGTRAMP (prev_pc, prev_func_name))
	{
	  /* This code is needed at least in the following case:
	     The user types "next" and then a signal arrives (before
	     the "next" is done).  */
	  /* We've just taken a signal; go until we are back to
	     the point where we took it and one more.  */
	  {
	    struct symtab_and_line sr_sal;

	    sr_sal.pc = prev_pc;
	    sr_sal.symtab = NULL;
	    sr_sal.line = 0;
	    step_resume_breakpoint =
	      set_momentary_breakpoint (sr_sal, get_current_frame (),
					bp_step_resume);
	    if (breakpoints_inserted)
	      insert_breakpoints ();
	  }

	  /* If this is stepi or nexti, make sure that the stepping range
	     gets us past that instruction.  */
	  if (step_range_end == 1)
	    /* FIXME: Does this run afoul of the code below which, if
	       we step into the middle of a line, resets the stepping
	       range?  */
	    step_range_end = (step_range_start = prev_pc) + 1;

	  remove_breakpoints_on_following_step = 1;
	  goto keep_going;
	}

      if (stop_func_start)
	{
	  /* Do this after the IN_SIGTRAMP check; it might give
	     an error.  */
	  prologue_pc = stop_func_start;
	  SKIP_PROLOGUE (prologue_pc);
	}

      /* ==> See comments at top of file on this algorithm.  <==*/

      if ((stop_pc == stop_func_start
	   || IN_SOLIB_TRAMPOLINE (stop_pc, stop_func_name))
	  && (stop_func_start != prev_func_start
	      || prologue_pc != stop_func_start
	      || stop_sp != prev_sp))
	{
	  /* It's a subroutine call.  */

	  if (step_over_calls == 0)
	    {
	      /* I presume that step_over_calls is only 0 when we're
		 supposed to be stepping at the assembly language level
		 ("stepi").  Just stop.  */
	      stop_step = 1;
	      break;
	    }

	  if (step_over_calls > 0)
	    /* We're doing a "next".  */
	    goto step_over_function;

	  /* If we are in a function call trampoline (a stub between
	     the calling routine and the real function), locate the real
	     function.  That's what tells us (a) whether we want to step
	     into it at all, and (b) what prologue we want to run to
	     the end of, if we do step into it.  */
	  tmp = SKIP_TRAMPOLINE_CODE (stop_pc);
	  if (tmp != 0)
	    stop_func_start = tmp;

	  /* If we have line number information for the function we
	     are thinking of stepping into, step into it.

	     If there are several symtabs at that PC (e.g. with include
	     files), just want to know whether *any* of them have line
	     numbers.  find_pc_line handles this.  */
	  {
	    struct symtab_and_line tmp_sal;

	    tmp_sal = find_pc_line (stop_func_start, 0);
	    if (tmp_sal.line != 0)
	      goto step_into_function;
	  }

step_over_function:
	  /* A subroutine call has happened.  */
	  {
	    /* Set a special breakpoint after the return */
	    struct symtab_and_line sr_sal;
	    sr_sal.pc = 
	      ADDR_BITS_REMOVE
		(SAVED_PC_AFTER_CALL (get_current_frame ()));
	    sr_sal.symtab = NULL;
	    sr_sal.line = 0;
	    step_resume_breakpoint =
	      set_momentary_breakpoint (sr_sal, get_current_frame (),
					bp_step_resume);
	    if (breakpoints_inserted)
	      insert_breakpoints ();
	  }
	  goto keep_going;

step_into_function:
	  /* Subroutine call with source code we should not step over.
	     Do step to the first line of code in it.  */
	  SKIP_PROLOGUE (stop_func_start);
	  sal = find_pc_line (stop_func_start, 0);
	  /* Use the step_resume_break to step until
	     the end of the prologue, even if that involves jumps
	     (as it seems to on the vax under 4.2).  */
	  /* If the prologue ends in the middle of a source line,
	     continue to the end of that source line.
	     Otherwise, just go to end of prologue.  */
#ifdef PROLOGUE_FIRSTLINE_OVERLAP
	  /* no, don't either.  It skips any code that's
	     legitimately on the first line.  */
#else
	  if (sal.end && sal.pc != stop_func_start)
	    stop_func_start = sal.end;
#endif

	  if (stop_func_start == stop_pc)
	    {
	      /* We are already there: stop now.  */
	      stop_step = 1;
	      break;
	    }
	  else
	    /* Put the step-breakpoint there and go until there. */
	    {
	      struct symtab_and_line sr_sal;

	      sr_sal.pc = stop_func_start;
	      sr_sal.symtab = NULL;
	      sr_sal.line = 0;
	      /* Do not specify what the fp should be when we stop
		 since on some machines the prologue
		 is where the new fp value is established.  */
	      step_resume_breakpoint =
		set_momentary_breakpoint (sr_sal, (CORE_ADDR)0,
					  bp_step_resume);
	      if (breakpoints_inserted)
		insert_breakpoints ();

	      /* And make sure stepping stops right away then.  */
	      step_range_end = step_range_start;
	    }
	  goto keep_going;
	}

      /* We've wandered out of the step range (but haven't done a
	 subroutine call or return).  (Is that true?  I think we get
	 here if we did a return and maybe a longjmp).  */

      sal = find_pc_line(stop_pc, 0);

      if (step_range_end == 1)
	{
	  /* It is stepi or nexti.  We always want to stop stepping after
	     one instruction.  */
	  stop_step = 1;
	  break;
	}

      if (sal.line == 0)
	{
	  /* We have no line number information.  That means to stop
	     stepping (does this always happen right after one instruction,
	     when we do "s" in a function with no line numbers,
	     or can this happen as a result of a return or longjmp?).  */
	  stop_step = 1;
	  break;
	}

      if (stop_pc == sal.pc && current_line != sal.line)
	{
	  /* We are at the start of a different line.  So stop.  Note that
	     we don't stop if we step into the middle of a different line.
	     That is said to make things like for (;;) statements work
	     better.  */
	  stop_step = 1;
	  break;
	}

      /* We aren't done stepping.

	 Optimize by setting the stepping range to the line.
	 (We might not be in the original line, but if we entered a
	 new line in mid-statement, we continue stepping.  This makes 
	 things like for(;;) statements work better.)  */
      step_range_start = sal.pc;
      step_range_end = sal.end;
      goto keep_going;

    check_sigtramp2:
      if (trap_expected
	  && IN_SIGTRAMP (stop_pc, stop_func_name)
	  && !IN_SIGTRAMP (prev_pc, prev_func_name))
	{
	  /* What has happened here is that we have just stepped the inferior
	     with a signal (because it is a signal which shouldn't make
	     us stop), thus stepping into sigtramp.

	     So we need to set a step_resume_break_address breakpoint
	     and continue until we hit it, and then step.  FIXME: This should
	     be more enduring than a step_resume breakpoint; we should know
	     that we will later need to keep going rather than re-hitting
	     the breakpoint here (see testsuite/gdb.t06/signals.exp where
	     it says "exceedingly difficult").  */
	  struct symtab_and_line sr_sal;

	  sr_sal.pc = prev_pc;
	  sr_sal.symtab = NULL;
	  sr_sal.line = 0;
	  step_resume_breakpoint =
	    set_momentary_breakpoint (sr_sal, get_current_frame (),
				      bp_step_resume);
	  if (breakpoints_inserted)
	    insert_breakpoints ();

	  remove_breakpoints_on_following_step = 1;
	  another_trap = 1;
	}

    keep_going:
      /* Come to this label when you need to resume the inferior.
	 It's really much cleaner to do a goto than a maze of if-else
	 conditions.  */

      /* Save the pc before execution, to compare with pc after stop.  */
      prev_pc = read_pc ();	/* Might have been DECR_AFTER_BREAK */
      prev_func_start = stop_func_start; /* Ok, since if DECR_PC_AFTER
					  BREAK is defined, the
					  original pc would not have
					  been at the start of a
					  function. */
      prev_func_name = stop_func_name;
      prev_sp = stop_sp;

      /* If we did not do break;, it means we should keep
	 running the inferior and not return to debugger.  */

      if (trap_expected && stop_signal != SIGTRAP)
	{
	  /* We took a signal (which we are supposed to pass through to
	     the inferior, else we'd have done a break above) and we
	     haven't yet gotten our trap.  Simply continue.  */
	  resume ((step_range_end && step_resume_breakpoint == NULL)
		  || (trap_expected && step_resume_breakpoint == NULL)
		  || bpstat_should_step (),
		  stop_signal);
	}
      else
	{
	  /* Either the trap was not expected, but we are continuing
	     anyway (the user asked that this signal be passed to the
	     child)
	       -- or --
	     The signal was SIGTRAP, e.g. it was our signal, but we
	     decided we should resume from it.

	     We're going to run this baby now!

	     Insert breakpoints now, unless we are trying
	     to one-proceed past a breakpoint.  */
	  /* If we've just finished a special step resume and we don't
	     want to hit a breakpoint, pull em out.  */
	  if (step_resume_breakpoint == NULL &&
	      remove_breakpoints_on_following_step)
	    {
	      remove_breakpoints_on_following_step = 0;
	      remove_breakpoints ();
	      breakpoints_inserted = 0;
	    }
	  else if (!breakpoints_inserted &&
		   (step_resume_breakpoint != NULL || !another_trap))
	    {
	      breakpoints_failed = insert_breakpoints ();
	      if (breakpoints_failed)
		break;
	      breakpoints_inserted = 1;
	    }

	  trap_expected = another_trap;

	  if (stop_signal == SIGTRAP)
	    stop_signal = 0;

#ifdef SHIFT_INST_REGS
	  /* I'm not sure when this following segment applies.  I do know, now,
	     that we shouldn't rewrite the regs when we were stopped by a
	     random signal from the inferior process.  */

          if (!bpstat_explains_signal (stop_bpstat)
	      && (stop_signal != SIGCLD) 
              && !stopped_by_random_signal)
            {
            CORE_ADDR pc_contents = read_register (PC_REGNUM);
            CORE_ADDR npc_contents = read_register (NPC_REGNUM);
            if (pc_contents != npc_contents)
              {
              write_register (NNPC_REGNUM, npc_contents);
              write_register (NPC_REGNUM, pc_contents);
	      }
            }
#endif /* SHIFT_INST_REGS */

	  resume ((step_resume_breakpoint == NULL
		   && !handling_longjmp
		   && (step_range_end
		       || trap_expected))
		  || bpstat_should_step (),
		  stop_signal);
	}
    }

 stop_stepping:
  if (target_has_execution)
    {
      /* Assuming the inferior still exists, set these up for next
	 time, just like we did above if we didn't break out of the
	 loop.  */
      prev_pc = read_pc ();
      prev_func_start = stop_func_start;
      prev_func_name = stop_func_name;
      prev_sp = stop_sp;
    }
  do_cleanups (old_cleanups);
}

/* Here to return control to GDB when the inferior stops for real.
   Print appropriate messages, remove breakpoints, give terminal our modes.

   STOP_PRINT_FRAME nonzero means print the executing frame
   (pc, function, args, file, line number and line text).
   BREAKPOINTS_FAILED nonzero means stop was due to error
   attempting to insert breakpoints.  */

void
normal_stop ()
{
  /* Make sure that the current_frame's pc is correct.  This
     is a correction for setting up the frame info before doing
     DECR_PC_AFTER_BREAK */
  if (target_has_execution)
    (get_current_frame ())->pc = read_pc ();
  
  if (breakpoints_failed)
    {
      target_terminal_ours_for_output ();
      print_sys_errmsg ("ptrace", breakpoints_failed);
      printf_filtered ("Stopped; cannot insert breakpoints.\n\
The same program may be running in another process.\n");
    }

  if (target_has_execution && breakpoints_inserted)
    if (remove_breakpoints ())
      {
	target_terminal_ours_for_output ();
	printf_filtered ("Cannot remove breakpoints because program is no longer writable.\n\
It might be running in another process.\n\
Further execution is probably impossible.\n");
      }

  breakpoints_inserted = 0;

  /* Delete the breakpoint we stopped at, if it wants to be deleted.
     Delete any breakpoint that is to be deleted at the next stop.  */

  breakpoint_auto_delete (stop_bpstat);

  /* If an auto-display called a function and that got a signal,
     delete that auto-display to avoid an infinite recursion.  */

  if (stopped_by_random_signal)
    disable_current_display ();

  if (step_multi && stop_step)
    return;

  target_terminal_ours ();

  /* Look up the hook_stop and run it if it exists.  */

  if (stop_command->hook)
    {
      catch_errors (hook_stop_stub, (char *)stop_command->hook,
		    "Error while running hook_stop:\n", RETURN_MASK_ALL);
    }

  if (!target_has_stack)
    return;

  /* Select innermost stack frame except on return from a stack dummy routine,
     or if the program has exited.  Print it without a level number if
     we have changed functions or hit a breakpoint.  Print source line
     if we have one.  */
  if (!stop_stack_dummy)
    {
      select_frame (get_current_frame (), 0);

      if (stop_print_frame)
	{
	  int source_only;

	  source_only = bpstat_print (stop_bpstat);
	  source_only = source_only ||
	        (   stop_step
		 && step_frame_address == stop_frame_address
		 && step_start_function == find_pc_function (stop_pc));

          print_stack_frame (selected_frame, -1, source_only? -1: 1);

	  /* Display the auto-display expressions.  */
	  do_displays ();
	}
    }

  /* Save the function value return registers, if we care.
     We might be about to restore their previous contents.  */
  if (proceed_to_finish)
    read_register_bytes (0, stop_registers, REGISTER_BYTES);

  if (stop_stack_dummy)
    {
      /* Pop the empty frame that contains the stack dummy.
         POP_FRAME ends with a setting of the current frame, so we
	 can use that next. */
      POP_FRAME;
      select_frame (get_current_frame (), 0);
    }
}

static int
hook_stop_stub (cmd)
     char *cmd;
{
  execute_user_command ((struct cmd_list_element *)cmd, 0);
  return (0);
}

int signal_stop_state (signo)
     int signo;
{
  return ((signo >= 0 && signo < NSIG) ? signal_stop[signo] : 0);
}

int signal_print_state (signo)
     int signo;
{
  return ((signo >= 0 && signo < NSIG) ? signal_print[signo] : 0);
}

int signal_pass_state (signo)
     int signo;
{
  return ((signo >= 0 && signo < NSIG) ? signal_program[signo] : 0);
}

static void
sig_print_header ()
{
  printf_filtered ("Signal\t\tStop\tPrint\tPass to program\tDescription\n");
}

static void
sig_print_info (number)
     int number;
{
  char *name;

  if ((name = strsigno (number)) == NULL)
    printf_filtered ("%d\t\t", number);
  else
    printf_filtered ("%s (%d)\t", name, number);
  printf_filtered ("%s\t", signal_stop[number] ? "Yes" : "No");
  printf_filtered ("%s\t", signal_print[number] ? "Yes" : "No");
  printf_filtered ("%s\t\t", signal_program[number] ? "Yes" : "No");
  printf_filtered ("%s\n", safe_strsignal (number));
}

/* Specify how various signals in the inferior should be handled.  */

static void
handle_command (args, from_tty)
     char *args;
     int from_tty;
{
  char **argv;
  int digits, wordlen;
  int sigfirst, signum, siglast;
  int allsigs;
  int nsigs;
  unsigned char *sigs;
  struct cleanup *old_chain;

  if (args == NULL)
    {
      error_no_arg ("signal to handle");
    }

  /* Allocate and zero an array of flags for which signals to handle. */

  nsigs = signo_max () + 1;
  sigs = (unsigned char *) alloca (nsigs);
  memset (sigs, 0, nsigs);

  /* Break the command line up into args. */

  argv = buildargv (args);
  if (argv == NULL)
    {
      nomem (0);
    }
  old_chain = make_cleanup (freeargv, (char *) argv);

  /* Walk through the args, looking for signal numbers, signal names, and
     actions.  Signal numbers and signal names may be interspersed with
     actions, with the actions being performed for all signals cumulatively
     specified.  Signal ranges can be specified as <LOW>-<HIGH>. */

  while (*argv != NULL)
    {
      wordlen = strlen (*argv);
      for (digits = 0; isdigit ((*argv)[digits]); digits++) {;}
      allsigs = 0;
      sigfirst = siglast = -1;

      if (wordlen >= 1 && !strncmp (*argv, "all", wordlen))
	{
	  /* Apply action to all signals except those used by the
	     debugger.  Silently skip those. */
	  allsigs = 1;
	  sigfirst = 0;
	  siglast = nsigs - 1;
	}
      else if (wordlen >= 1 && !strncmp (*argv, "stop", wordlen))
	{
	  SET_SIGS (nsigs, sigs, signal_stop);
	  SET_SIGS (nsigs, sigs, signal_print);
	}
      else if (wordlen >= 1 && !strncmp (*argv, "ignore", wordlen))
	{
	  UNSET_SIGS (nsigs, sigs, signal_program);
	}
      else if (wordlen >= 2 && !strncmp (*argv, "print", wordlen))
	{
	  SET_SIGS (nsigs, sigs, signal_print);
	}
      else if (wordlen >= 2 && !strncmp (*argv, "pass", wordlen))
	{
	  SET_SIGS (nsigs, sigs, signal_program);
	}
      else if (wordlen >= 3 && !strncmp (*argv, "nostop", wordlen))
	{
	  UNSET_SIGS (nsigs, sigs, signal_stop);
	}
      else if (wordlen >= 3 && !strncmp (*argv, "noignore", wordlen))
	{
	  SET_SIGS (nsigs, sigs, signal_program);
	}
      else if (wordlen >= 4 && !strncmp (*argv, "noprint", wordlen))
	{
	  UNSET_SIGS (nsigs, sigs, signal_print);
	  UNSET_SIGS (nsigs, sigs, signal_stop);
	}
      else if (wordlen >= 4 && !strncmp (*argv, "nopass", wordlen))
	{
	  UNSET_SIGS (nsigs, sigs, signal_program);
	}
      else if (digits > 0)
	{
	  sigfirst = siglast = atoi (*argv);
	  if ((*argv)[digits] == '-')
	    {
	      siglast = atoi ((*argv) + digits + 1);
	    }
	  if (sigfirst > siglast)
	    {
	      /* Bet he didn't figure we'd think of this case... */
	      signum = sigfirst;
	      sigfirst = siglast;
	      siglast = signum;
	    }
	  if (sigfirst < 0 || sigfirst >= nsigs)
	    {
	      error ("Signal %d not in range 0-%d", sigfirst, nsigs - 1);
	    }
	  if (siglast < 0 || siglast >= nsigs)
	    {
	      error ("Signal %d not in range 0-%d", siglast, nsigs - 1);
	    }
	}
      else if ((signum = strtosigno (*argv)) != 0)
	{
	  sigfirst = siglast = signum;
	}
      else
	{
	  /* Not a number and not a recognized flag word => complain.  */
	  error ("Unrecognized or ambiguous flag word: \"%s\".", *argv);
	}

      /* If any signal numbers or symbol names were found, set flags for
	 which signals to apply actions to. */

      for (signum = sigfirst; signum >= 0 && signum <= siglast; signum++)
	{
	  switch (signum)
	    {
	      case SIGTRAP:
	      case SIGINT:
	        if (!allsigs && !sigs[signum])
		  {
		    if (query ("%s is used by the debugger.\nAre you sure you want to change it? ", strsigno (signum)))
		      {
			sigs[signum] = 1;
		      }
		    else
		      {
			printf ("Not confirmed, unchanged.\n");
			fflush (stdout);
		      }
		  }
		break;
	      default:
		sigs[signum] = 1;
		break;
	    }
	}

      argv++;
    }

  target_notice_signals();

  if (from_tty)
    {
      /* Show the results.  */
      sig_print_header ();
      for (signum = 0; signum < nsigs; signum++)
	{
	  if (sigs[signum])
	    {
	      sig_print_info (signum);
	    }
	}
    }

  do_cleanups (old_chain);
}

/* Print current contents of the tables set by the handle command.  */

static void
signals_info (signum_exp, from_tty)
     char *signum_exp;
     int from_tty;
{
  register int i;
  sig_print_header ();

  if (signum_exp)
    {
      /* First see if this is a symbol name.  */
      i = strtosigno (signum_exp);
      if (i == 0)
	{
	  /* Nope, maybe it's an address which evaluates to a signal
	     number.  */
	  i = parse_and_eval_address (signum_exp);
	  if (i >= NSIG || i < 0)
	    error ("Signal number out of bounds.");
	}
      sig_print_info (i);
      return;
    }

  printf_filtered ("\n");
  for (i = 0; i < NSIG; i++)
    {
      QUIT;

      sig_print_info (i);
    }

  printf_filtered ("\nUse the \"handle\" command to change these tables.\n");
}

/* Save all of the information associated with the inferior<==>gdb
   connection.  INF_STATUS is a pointer to a "struct inferior_status"
   (defined in inferior.h).  */

void
save_inferior_status (inf_status, restore_stack_info)
     struct inferior_status *inf_status;
     int restore_stack_info;
{
  inf_status->pc_changed = pc_changed;
  inf_status->stop_signal = stop_signal;
  inf_status->stop_pc = stop_pc;
  inf_status->stop_frame_address = stop_frame_address;
  inf_status->stop_step = stop_step;
  inf_status->stop_stack_dummy = stop_stack_dummy;
  inf_status->stopped_by_random_signal = stopped_by_random_signal;
  inf_status->trap_expected = trap_expected;
  inf_status->step_range_start = step_range_start;
  inf_status->step_range_end = step_range_end;
  inf_status->step_frame_address = step_frame_address;
  inf_status->step_over_calls = step_over_calls;
  inf_status->stop_after_trap = stop_after_trap;
  inf_status->stop_soon_quietly = stop_soon_quietly;
  /* Save original bpstat chain here; replace it with copy of chain. 
     If caller's caller is walking the chain, they'll be happier if we
     hand them back the original chain when restore_i_s is called.  */
  inf_status->stop_bpstat = stop_bpstat;
  stop_bpstat = bpstat_copy (stop_bpstat);
  inf_status->breakpoint_proceeded = breakpoint_proceeded;
  inf_status->restore_stack_info = restore_stack_info;
  inf_status->proceed_to_finish = proceed_to_finish;
  
  memcpy (inf_status->stop_registers, stop_registers, REGISTER_BYTES);
  
  record_selected_frame (&(inf_status->selected_frame_address),
			 &(inf_status->selected_level));
  return;
}

void
restore_inferior_status (inf_status)
     struct inferior_status *inf_status;
{
  FRAME fid;
  int level = inf_status->selected_level;

  pc_changed = inf_status->pc_changed;
  stop_signal = inf_status->stop_signal;
  stop_pc = inf_status->stop_pc;
  stop_frame_address = inf_status->stop_frame_address;
  stop_step = inf_status->stop_step;
  stop_stack_dummy = inf_status->stop_stack_dummy;
  stopped_by_random_signal = inf_status->stopped_by_random_signal;
  trap_expected = inf_status->trap_expected;
  step_range_start = inf_status->step_range_start;
  step_range_end = inf_status->step_range_end;
  step_frame_address = inf_status->step_frame_address;
  step_over_calls = inf_status->step_over_calls;
  stop_after_trap = inf_status->stop_after_trap;
  stop_soon_quietly = inf_status->stop_soon_quietly;
  bpstat_clear (&stop_bpstat);
  stop_bpstat = inf_status->stop_bpstat;
  breakpoint_proceeded = inf_status->breakpoint_proceeded;
  proceed_to_finish = inf_status->proceed_to_finish;

  memcpy (stop_registers, inf_status->stop_registers, REGISTER_BYTES);

  /* The inferior can be gone if the user types "print exit(0)"
     (and perhaps other times).  */
  if (target_has_stack && inf_status->restore_stack_info)
    {
      fid = find_relative_frame (get_current_frame (),
				 &level);

      /* If inf_status->selected_frame_address is NULL, there was no
	 previously selected frame.  */
      if (fid == 0 ||
	  FRAME_FP (fid) != inf_status->selected_frame_address ||
	  level != 0)
	{
#if 1
	  /* I'm not sure this error message is a good idea.  I have
	     only seen it occur after "Can't continue previously
	     requested operation" (we get called from do_cleanups), in
	     which case it just adds insult to injury (one confusing
	     error message after another.  Besides which, does the
	     user really care if we can't restore the previously
	     selected frame?  */
	  fprintf (stderr, "Unable to restore previously selected frame.\n");
#endif
	  select_frame (get_current_frame (), 0);
	  return;
	}
      
      select_frame (fid, inf_status->selected_level);
    }
}


void
_initialize_infrun ()
{
  register int i;
  register int numsigs;

  add_info ("signals", signals_info,
	    "What debugger does when program gets various signals.\n\
Specify a signal number as argument to print info on that signal only.");
  add_info_alias ("handle", "signals", 0);

  add_com ("handle", class_run, handle_command,
	   "Specify how to handle a signal.\n\
Args are signal numbers and actions to apply to those signals.\n\
Signal numbers may be numeric (ex. 11) or symbolic (ex. SIGSEGV).\n\
Numeric ranges may be specified with the form LOW-HIGH (ex. 14-21).\n\
The special arg \"all\" is recognized to mean all signals except those\n\
used by the debugger, typically SIGTRAP and SIGINT.\n\
Recognized actions include \"stop\", \"nostop\", \"print\", \"noprint\",\n\
\"pass\", \"nopass\", \"ignore\", or \"noignore\".\n\
Stop means reenter debugger if this signal happens (implies print).\n\
Print means print a message if this signal happens.\n\
Pass means let program see this signal; otherwise program doesn't know.\n\
Ignore is a synonym for nopass and noignore is a synonym for pass.\n\
Pass and Stop may be combined.");

  stop_command = add_cmd ("stop", class_obscure, not_just_help_class_command,
	   "There is no `stop' command, but you can set a hook on `stop'.\n\
This allows you to set a list of commands to be run each time execution\n\
of the program stops.", &cmdlist);

  numsigs = signo_max () + 1;
  signal_stop    = (unsigned char *)    
		   xmalloc (sizeof (signal_stop[0]) * numsigs);
  signal_print   = (unsigned char *)
		   xmalloc (sizeof (signal_print[0]) * numsigs);
  signal_program = (unsigned char *)
		   xmalloc (sizeof (signal_program[0]) * numsigs);
  for (i = 0; i < numsigs; i++)
    {
      signal_stop[i] = 1;
      signal_print[i] = 1;
      signal_program[i] = 1;
    }

  /* Signals caused by debugger's own actions
     should not be given to the program afterwards.  */
  signal_program[SIGTRAP] = 0;
  signal_program[SIGINT] = 0;

  /* Signals that are not errors should not normally enter the debugger.  */
#ifdef SIGALRM
  signal_stop[SIGALRM] = 0;
  signal_print[SIGALRM] = 0;
#endif /* SIGALRM */
#ifdef SIGVTALRM
  signal_stop[SIGVTALRM] = 0;
  signal_print[SIGVTALRM] = 0;
#endif /* SIGVTALRM */
#ifdef SIGPROF
  signal_stop[SIGPROF] = 0;
  signal_print[SIGPROF] = 0;
#endif /* SIGPROF */
#ifdef SIGCHLD
  signal_stop[SIGCHLD] = 0;
  signal_print[SIGCHLD] = 0;
#endif /* SIGCHLD */
#ifdef SIGCLD
  signal_stop[SIGCLD] = 0;
  signal_print[SIGCLD] = 0;
#endif /* SIGCLD */
#ifdef SIGIO
  signal_stop[SIGIO] = 0;
  signal_print[SIGIO] = 0;
#endif /* SIGIO */
#ifdef SIGURG
  signal_stop[SIGURG] = 0;
  signal_print[SIGURG] = 0;
#endif /* SIGURG */
}