Minor cleanup.

[deliverable/binutils-gdb.git] / gdb / infrun.c

/* Target-struct-independent code to start (run) and stop an inferior process.
   Copyright 1986, 1987, 1988, 1989, 1991, 1992 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
remove_step_breakpoint PARAMS ((void));

static void
insert_step_breakpoint PARAMS ((void));

static void
resume_cleanups PARAMS ((int));

static int
hook_stop_stub PARAMS ((char *));

/* Sigtramp is a routine that the kernel calls (which then calls the
   signal handler).  On most machines it is a library routine that
   is linked into the executable.

   This macro, given a program counter value and the name of the
   function in which that PC resides (which can be null if the
   name is not known), returns nonzero if the PC and name show
   that we are in sigtramp.

   On most machines just see if the name is sigtramp (and if we have
   no name, assume we are not in sigtramp).  */
#if !defined (IN_SIGTRAMP)
#define IN_SIGTRAMP(pc, name) \
  (name && !strcmp ("_sigtramp", name))
#endif

/* 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

#ifdef TDESC
#include "tdesc.h"
int safe_to_init_tdesc_context = 0;
extern dc_dcontext_t current_context;
#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 => address for special breakpoint for resuming stepping.  */

static CORE_ADDR step_resume_break_address;

/* Pointer to orig contents of the byte where the special breakpoint is.  */

static char step_resume_break_shadow[BREAKPOINT_MAX];

/* Nonzero means the special breakpoint is a duplicate
   so it has not itself been inserted.  */

static int step_resume_break_duplicate;

/* 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 */

\f
/* 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);
}

\f
/* 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;
  step_resume_break_address = 0;
  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_register (PC_REGNUM, addr);
#ifdef NPC_REGNUM
      write_register (NPC_REGNUM, addr + 4);
#ifdef NNPC_REGNUM
      write_register (NNPC_REGNUM, addr + 8);
#endif
#endif
    }

  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;

\f
/* 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(). */
}


\f
/* 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 ()
{
  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;
  int stop_step_resume_break;
  struct symtab_and_line sal;
  int remove_breakpoints_on_following_step = 0;
  int current_line;
  int handling_longjmp = 0;     /* FIXME */
  struct symtab *symtab;

  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))
        {
          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 %d, %s\n",
                           stop_signal, safe_strsignal (stop_signal));
#endif
          printf_filtered ("The inferior process 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_register (FP_REGNUM),
                                            read_pc ()));
      
      stop_frame_address = FRAME_FP (get_current_frame ());
      stop_sp = read_register (SP_REGNUM);
      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;
      stop_step_resume_break = 0;
      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_break_address
             will be set and we should check whether we've hit the
             step breakpoint.  */
          if (stop_signal == SIGTRAP && trap_expected
              && step_resume_break_address == 0)
            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_break_address
                  || handling_longjmp /* FIXME */)
#endif /* DECR_PC_AFTER_BREAK not zero */
                {
                  /* See if we stopped at the special breakpoint for
                     stepping over a subroutine call.  If both are zero,
                     this wasn't the reason for the stop.  */
                  if (step_resume_break_address
                      && stop_pc - DECR_PC_AFTER_BREAK
                         == step_resume_break_address)
                    {
                      stop_step_resume_break = 1;
                      if (DECR_PC_AFTER_BREAK)
                        {
                          stop_pc -= DECR_PC_AFTER_BREAK;
                          write_register (PC_REGNUM, stop_pc);
                          pc_changed = 0;
                        }
                    }
                  else
                    {
                      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
                  || stop_step_resume_break
                  || PC_IN_CALL_DUMMY (stop_pc, stop_sp, stop_frame_address)
                  || (step_range_end && !step_resume_break_address));
          else
            {
              random_signal
                = !(bpstat_explains_signal (stop_bpstat)
                    || stop_step_resume_break
                    /* 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])
            {
              printed = 1;
              target_terminal_ours_for_output ();
#ifdef PRINT_RANDOM_SIGNAL
              PRINT_RANDOM_SIGNAL (stop_signal);
#else
              printf_filtered ("\nProgram received signal %d, %s\n",
                               stop_signal, 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 ();

          /* Note that virtually all the code below does `if !random_signal'.
             Perhaps this code should end with a goto or continue.  At least
             one (now fixed) bug was caused by this -- a !random_signal was
             missing in one of the tests below.  */
        }

      /* Handle cases caused by hitting a breakpoint.  */

      if (!random_signal)
        if (bpstat_explains_signal (stop_bpstat))
          {
            CORE_ADDR jmp_buf_pc;

            switch (stop_bpstat->breakpoint_at->type) /* FIXME */
              {
                /* 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. */
              case bp_longjmp:
                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 */
                remove_step_breakpoint ();
                step_resume_break_address = 0;
                stop_step_resume_break = 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 bp_longjmp_resume:
                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 */
                break;

              default:
                fprintf(stderr, "Unknown breakpoint type %d\n",
                        stop_bpstat->breakpoint_at->type);
              case bp_watchpoint:
              case bp_breakpoint:
              case bp_until:
              case bp_finish:
                /* Does a breakpoint want us to stop?  */
                if (bpstat_stop (stop_bpstat))
                  {
                    stop_print_frame = bpstat_should_print (stop_bpstat);
                    goto stop_stepping;
                  }
                /* Otherwise, must remove breakpoints and single-step
                   to get us past the one we hit.  */
                else
                  {
                    remove_breakpoints ();
                    remove_step_breakpoint ();
                    breakpoints_inserted = 0;
                    another_trap = 1;
                  }
                break;
              }
          }
        else if (stop_step_resume_break)
          {
            /* But if we have hit the step-resumption breakpoint,
               remove it.  It has done its job getting us here.
               The sp test is to make sure that we don't get hung
               up in recursive calls in functions without frame
               pointers.  If the stack pointer isn't outside of
               where the breakpoint was set (within a routine to be
               stepped over), we're in the middle of a recursive
               call. Not true for reg window machines (sparc)
               because the must change frames to call things and
               the stack pointer doesn't have to change if it
               the bp was set in a routine without a frame (pc can
               be stored in some other window).
               
               The removal of the sp test is to allow calls to
               alloca.  Nasty things were happening.  Oh, well,
               gdb can only handle one level deep of lack of
               frame pointer. */

            /*
              Disable test for step_frame_address match so that we always stop even if the
              frames don't match.  Reason: if we hit the step_resume_breakpoint, there is
              no way to temporarily disable it so that we can step past it.  If we leave
              the breakpoint in, then we loop forever repeatedly hitting, but never
              getting past the breakpoint.  This change keeps nexting over recursive
              function calls from hanging gdb.
              */
#if 0
            if (* step_frame_address == 0
                || (step_frame_address == stop_frame_address))
#endif
              {
                remove_step_breakpoint ();
                step_resume_break_address = 0;

                /* 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 (!random_signal 
         && 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_break_address)
        /* Having a step-resume breakpoint overrides anything
           else having to do with stepping commands until
           that breakpoint is reached.  */
        ;
      /* If stepping through a line, keep going if still within it.  */
      else if (!random_signal
               && step_range_end
               && 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 stepped out of the stepping range.  See if that was due
         to a subroutine call that we should proceed to the end of.  */
      else if (!random_signal && step_range_end)
        {
          if (stop_func_start)
            {
              prologue_pc = stop_func_start;
              SKIP_PROLOGUE (prologue_pc);
            }

          /* 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.  */
              step_resume_break_address = prev_pc;
              step_resume_break_duplicate =
                breakpoint_here_p (step_resume_break_address);
              if (breakpoints_inserted)
                insert_step_breakpoint ();
              /* Make sure that the stepping range gets us past
                 that instruction.  */
              if (step_range_end == 1)
                step_range_end = (step_range_start = prev_pc) + 1;
              remove_breakpoints_on_following_step = 1;
              goto save_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.
                 (0)  If we are not stepping over any calls ("stepi"), we
                      just stop.
                 (1)  If we're doing a "next", we want to continue through
                      the call ("step over the call").
                 (2)  If we are in a function-call trampoline (a stub between
                      the calling routine and the real function), locate
                      the real function and change stop_func_start.
                 (3)  If we're doing a "step", and there are no debug symbols
                      at the target of the call, we want to continue through
                      it ("step over the call").
                 (4)  Otherwise, we want to stop soon, after the function
                      prologue ("step into the 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. */
                  stop_step = 1;
                  break;
                }

              if (step_over_calls > 0)
                goto step_over_function;

              tmp = SKIP_TRAMPOLINE_CODE (stop_pc);
              if (tmp != 0)
                stop_func_start = tmp;

              symtab = find_pc_symtab (stop_func_start);
              if (symtab && LINETABLE (symtab))
                goto step_into_function;

step_over_function:
              /* A subroutine call has happened.  */
              /* Set a special breakpoint after the return */
              step_resume_break_address =
                ADDR_BITS_REMOVE
                  (SAVED_PC_AFTER_CALL (get_current_frame ()));
              step_resume_break_duplicate
                = breakpoint_here_p (step_resume_break_address);
              if (breakpoints_inserted)
                insert_step_breakpoint ();
              goto save_pc;

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. */
                {
                  step_resume_break_address = stop_func_start;
                  
                  step_resume_break_duplicate
                    = breakpoint_here_p (step_resume_break_address);
                  if (breakpoints_inserted)
                    insert_step_breakpoint ();
                  /* 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_frame_address = 0;
                  /* And make sure stepping stops right away then.  */
                  step_range_end = step_range_start;
                }
              goto save_pc;
            }

          /* We've wandered out of the step range (but haven't done a
             subroutine call or return).  */

          sal = find_pc_line(stop_pc, 0);
          
          if (step_range_end == 1 ||    /* stepi or nexti */
              sal.line == 0 ||          /* ...or no line # info */
              (stop_pc == sal.pc        /* ...or we're at the start */
               && current_line != sal.line)) {  /* of a different line */
            /* Stop because we're done stepping.  */
            stop_step = 1;
            break;
          } else {
            /* We aren't done stepping, and we have line number info for $pc.
               Optimize by setting the step_range for 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 save_pc;
          }
          /* We never fall through here */
        }

      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.  */
          step_resume_break_address = prev_pc;
          /* Always 1, I think, but it's probably easier to have
             the step_resume_break as usual rather than trying to
             re-use the breakpoint which is already there.  */
          step_resume_break_duplicate =
            breakpoint_here_p (step_resume_break_address);
          if (breakpoints_inserted)
            insert_step_breakpoint ();
          remove_breakpoints_on_following_step = 1;
          another_trap = 1;
        }

/* My apologies to the gods of structured programming. */
/* Come to this label when you need to resume the inferior.  It's really much
   cleaner at this time to do a goto than to try and figure out what the
   if-else chain ought to look like!! */

    keep_going:

save_pc:
      /* 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_break_address)
                  || (trap_expected && !step_resume_break_address)
                  || 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_break_address &&
              remove_breakpoints_on_following_step)
            {
              remove_breakpoints_on_following_step = 0;
              remove_breakpoints ();
              breakpoints_inserted = 0;
            }
          else if (!breakpoints_inserted &&
                   (step_resume_break_address != 0 || !another_trap))
            {
              insert_step_breakpoint ();
              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_break_address
                   && !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;
    }
}
\f
/* 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)
    remove_step_breakpoint ();

  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");
    }

  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);
}

\f
static void
insert_step_breakpoint ()
{
  if (step_resume_break_address && !step_resume_break_duplicate)
    target_insert_breakpoint (step_resume_break_address,
                              step_resume_break_shadow);
}

static void
remove_step_breakpoint ()
{
  if (step_resume_break_address && !step_resume_break_duplicate)
    target_remove_breakpoint (step_resume_break_address,
                              step_resume_break_shadow);
}
\f
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");
}
\f
/* 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->step_resume_break_address = step_resume_break_address;
  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;
  step_resume_break_address = inf_status->step_resume_break_address;
  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);
    }
}

\f
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 inferior 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 */
}