Updated for Tcl 7.5a2 and Tk 4.1a2

[binutils.git] / gdb / infrun.c

/* Target-struct-independent code to start (run) and stop an inferior process.
   Copyright 1986, 1987, 1988, 1989, 1991, 1992, 1993, 1994, 1995, 1996
   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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "gdb_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 "thread.h"
#include "annotate.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 ((enum target_signal));

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

/* Dynamic function trampolines are similar to solib trampolines in that they
   are between the caller and the callee.  The difference is that when you
   enter a dynamic trampoline, you can't determine the callee's address.  Some
   (usually complex) code needs to run in the dynamic trampoline to figure out
   the callee's address.  This macro is usually called twice.  First, when we
   enter the trampoline (looks like a normal function call at that point).  It
   should return the PC of a point within the trampoline where the callee's
   address is known.  Second, when we hit the breakpoint, this routine returns
   the callee's address.  At that point, things proceed as per a step resume
   breakpoint.  */

#ifndef DYNAMIC_TRAMPOLINE_NEXTPC
#define DYNAMIC_TRAMPOLINE_NEXTPC(pc) 0
#endif

/* For SVR4 shared libraries, each call goes through a small piece of
   trampoline code in the ".plt" section.  IN_SOLIB_CALL_TRAMPOLINE evaluates
   to nonzero if we are current stopped in one of these. */

#ifndef IN_SOLIB_CALL_TRAMPOLINE
#define IN_SOLIB_CALL_TRAMPOLINE(pc,name)       0
#endif

/* In some shared library schemes, the return path from a shared library
   call may need to go through a trampoline too.  */

#ifndef IN_SOLIB_RETURN_TRAMPOLINE
#define IN_SOLIB_RETURN_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 we want to give control to the user when we're notified
   of shared library events by the dynamic linker.  */
static int stop_on_solib_events;

#ifdef HP_OS_BUG
/* 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;
#endif

/* 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 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;
     enum target_signal sig;
{
  struct cleanup *old_cleanups = make_cleanup (resume_cleanups, 0);
  QUIT;

#ifdef CANNOT_STEP_BREAKPOINT
  /* Most targets can step a breakpoint instruction, thus executing it
     normally.  But if this one cannot, just continue and we will hit
     it anyway.  */
  if (step && breakpoints_inserted && breakpoint_here_p (read_pc ()))
    step = 0;
#endif

#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

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

  target_resume (-1, 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;
  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;
     enum target_signal 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 (breakpoint_here_p (read_pc ()))
        oneproc = 1;

#ifdef STEP_SKIPS_DELAY
      /* Check breakpoint_here_p first, because breakpoint_here_p is fast
         (it just checks internal GDB data structures) and STEP_SKIPS_DELAY
         is slow (it needs to read memory from the target).  */
      if (breakpoint_here_p (read_pc () + 4)
          && STEP_SKIPS_DELAY (read_pc ()))
        oneproc = 1;
#endif /* STEP_SKIPS_DELAY */
    }
  else
    write_pc (addr);

#ifdef PREPARE_TO_PROCEED
  /* In a multi-threaded task we may select another thread and then continue.
     
     In this case the thread that stopped at a breakpoint will immediately
     cause another stop, if it is not stepped over first. On the other hand,
     if (ADDR != -1) we only want to single step over the breakpoint if we did
     switch to another thread.

     If we are single stepping, don't do any of the above.
     (Note that in the current implementation single stepping another
     thread after a breakpoint and then continuing will cause the original
     breakpoint to be hit again, but you can always continue, so it's not
     a big deal.)  */

  if (! step && PREPARE_TO_PROCEED (1) && breakpoint_here_p (read_pc ()))
    oneproc = 1;
#endif /* PREPARE_TO_PROCEED */

#ifdef HP_OS_BUG
  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;
    }
#endif /* HP_OS_BUG */

  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;
    }

  if (siggnal != TARGET_SIGNAL_DEFAULT)
    stop_signal = siggnal;
  /* If this signal should not be seen by program,
     give it zero.  Used for debugging signals.  */
  else if (!signal_program[stop_signal])
    stop_signal = TARGET_SIGNAL_0;

  annotate_starting ();

  /* Make sure that output from GDB appears before output from the
     inferior.  */
  gdb_flush (gdb_stdout);

  /* 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_func_start;
static char *prev_func_name;

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

void
start_remote ()
{
  init_thread_list ();
  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_func_start = 0;
  prev_func_name = NULL;

#ifdef HP_OS_BUG
  trap_expected_after_continue = 0;
#endif
  breakpoints_inserted = 0;
  breakpoint_init_inferior ();

  /* Don't confuse first call to proceed(). */
  stop_signal = TARGET_SIGNAL_0;
}

static void
delete_breakpoint_current_contents (arg)
     PTR arg;
{
  struct breakpoint **breakpointp = (struct breakpoint **)arg;
  if (*breakpointp != NULL)
    delete_breakpoint (*breakpointp);
}
\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 ()
{
  struct cleanup *old_cleanups;
  struct target_waitstatus w;
  int another_trap;
  int random_signal;
  CORE_ADDR stop_func_start;
  CORE_ADDR stop_func_end;
  char *stop_func_name;
  CORE_ADDR prologue_pc = 0, tmp;
  struct symtab_and_line sal;
  int remove_breakpoints_on_following_step = 0;
  int current_line;
  struct symtab *current_symtab;
  int handling_longjmp = 0;     /* FIXME */
  struct breakpoint *step_resume_breakpoint = NULL;
  struct breakpoint *through_sigtramp_breakpoint = NULL;
  int pid;
  int update_step_sp = 0;

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

  /* Are we stepping?  */
#define CURRENTLY_STEPPING() \
  ((through_sigtramp_breakpoint == NULL \
    && !handling_longjmp \
    && ((step_range_end && step_resume_breakpoint == NULL) \
        || trap_expected)) \
   || bpstat_should_step ())

  while (1)
    {
      /* We have to invalidate the registers BEFORE calling target_wait because
         they can be loaded from the target while in target_wait.  This makes
         remote debugging a bit more efficient for those targets that provide
         critical registers as part of their normal status mechanism. */

      registers_changed ();

      if (target_wait_hook)
        pid = target_wait_hook (-1, &w);
      else
        pid = target_wait (-1, &w);

#ifdef HAVE_NONSTEPPABLE_WATCHPOINT
    have_waited:
#endif

      flush_cached_frames ();

      /* If it's a new process, add it to the thread database */

      if (pid != inferior_pid
          && !in_thread_list (pid))
        {
          fprintf_unfiltered (gdb_stderr, "[New %s]\n", target_pid_to_str (pid));
          add_thread (pid);

          /* We may want to consider not doing a resume here in order to give
             the user a chance to play with the new thread.  It might be good
             to make that a user-settable option.  */

          /* At this point, all threads are stopped (happens automatically in
             either the OS or the native code).  Therefore we need to continue
             all threads in order to make progress.  */

          target_resume (-1, 0, TARGET_SIGNAL_0);
          continue;
        }

      switch (w.kind)
        {
        case TARGET_WAITKIND_LOADED:
          /* Ignore it gracefully.  */
          if (breakpoints_inserted)
            {
              mark_breakpoints_out ();
              insert_breakpoints ();
            }
          resume (0, TARGET_SIGNAL_0);
          continue;

        case TARGET_WAITKIND_SPURIOUS:
          resume (0, TARGET_SIGNAL_0);
          continue;

        case TARGET_WAITKIND_EXITED:
          target_terminal_ours ();      /* Must do this before mourn anyway */
          annotate_exited (w.value.integer);
          if (w.value.integer)
            printf_filtered ("\nProgram exited with code 0%o.\n", 
                             (unsigned int)w.value.integer);
          else
            printf_filtered ("\nProgram exited normally.\n");

          /* Record the exit code in the convenience variable $_exitcode, so
             that the user can inspect this again later.  */
          set_internalvar (lookup_internalvar ("_exitcode"),
                           value_from_longest (builtin_type_int, 
                                               (LONGEST) w.value.integer));
          gdb_flush (gdb_stdout);
          target_mourn_inferior ();
#ifdef NO_SINGLE_STEP
          one_stepped = 0;
#endif
          stop_print_frame = 0;
          goto stop_stepping;

        case TARGET_WAITKIND_SIGNALLED:
          stop_print_frame = 0;
          stop_signal = w.value.sig;
          target_terminal_ours ();      /* Must do this before mourn anyway */
          annotate_signalled ();

          /* This looks pretty bogus to me.  Doesn't TARGET_WAITKIND_SIGNALLED
             mean it is already dead?  This has been here since GDB 2.8, so
             perhaps it means rms didn't understand unix waitstatuses?
             For the moment I'm just kludging around this in remote.c
             rather than trying to change it here --kingdon, 5 Dec 1994.  */
          target_kill ();               /* kill mourns as well */

          printf_filtered ("\nProgram terminated with signal ");
          annotate_signal_name ();
          printf_filtered ("%s", target_signal_to_name (stop_signal));
          annotate_signal_name_end ();
          printf_filtered (", ");
          annotate_signal_string ();
          printf_filtered ("%s", target_signal_to_string (stop_signal));
          annotate_signal_string_end ();
          printf_filtered (".\n");

          printf_filtered ("The program no longer exists.\n");
          gdb_flush (gdb_stdout);
#ifdef NO_SINGLE_STEP
          one_stepped = 0;
#endif
          goto stop_stepping;

        case TARGET_WAITKIND_STOPPED:
          /* This is the only case in which we keep going; the above cases
             end in a continue or goto.  */
          break;
        }

      stop_signal = w.value.sig;

      stop_pc = read_pc_pid (pid);

      /* See if a thread hit a thread-specific breakpoint that was meant for
         another thread.  If so, then step that thread past the breakpoint,
         and continue it.  */

      if (stop_signal == TARGET_SIGNAL_TRAP
          && breakpoints_inserted
          && breakpoint_here_p (stop_pc - DECR_PC_AFTER_BREAK))
        {
          random_signal = 0;
          if (!breakpoint_thread_match (stop_pc - DECR_PC_AFTER_BREAK, pid))
            {
              /* Saw a breakpoint, but it was hit by the wrong thread.  Just continue. */
              write_pc_pid (stop_pc - DECR_PC_AFTER_BREAK, pid);

              remove_breakpoints ();
              target_resume (pid, 1, TARGET_SIGNAL_0); /* Single step */
              /* FIXME: What if a signal arrives instead of the single-step
                 happening?  */

              if (target_wait_hook)
                target_wait_hook (pid, &w);
              else
                target_wait (pid, &w);
              insert_breakpoints ();

              /* We need to restart all the threads now.  */
              target_resume (-1, 0, TARGET_SIGNAL_0);
              continue;
            }
        }
      else
        random_signal = 1;

      /* See if something interesting happened to the non-current thread.  If
         so, then switch to that thread, and eventually give control back to
         the user.  */

      if (pid != inferior_pid)
        {
          int printed = 0;

          /* If it's a random signal for a non-current thread, notify user
             if he's expressed an interest.  */

          if (random_signal
              && signal_print[stop_signal])
            {
              printed = 1;
              target_terminal_ours_for_output ();
              printf_filtered ("\nProgram received signal %s, %s.\n",
                               target_signal_to_name (stop_signal),
                               target_signal_to_string (stop_signal));
              gdb_flush (gdb_stdout);
            }

          /* If it's not SIGTRAP and not a signal we want to stop for, then
             continue the thread. */

          if (stop_signal != TARGET_SIGNAL_TRAP
              && !signal_stop[stop_signal])
            {
              if (printed)
                target_terminal_inferior ();

              /* Clear the signal if it should not be passed.  */
              if (signal_program[stop_signal] == 0)
                stop_signal = TARGET_SIGNAL_0;

              target_resume (pid, 0, stop_signal);
              continue;
            }

          /* It's a SIGTRAP or a signal we're interested in.  Switch threads,
             and fall into the rest of wait_for_inferior().  */

          /* Save infrun state for the old thread.  */
          save_infrun_state (inferior_pid, prev_pc,
                             prev_func_start, prev_func_name,
                             trap_expected, step_resume_breakpoint,
                             through_sigtramp_breakpoint,
                             step_range_start, step_range_end,
                             step_frame_address, handling_longjmp,
                             another_trap);

          inferior_pid = pid;

          /* Load infrun state for the new thread.  */
          load_infrun_state (inferior_pid, &prev_pc,
                             &prev_func_start, &prev_func_name,
                             &trap_expected, &step_resume_breakpoint,
                             &through_sigtramp_breakpoint,
                             &step_range_start, &step_range_end,
                             &step_frame_address, &handling_longjmp,
                             &another_trap);
          printf_filtered ("[Switching to %s]\n", target_pid_to_str (pid));

          flush_cached_frames ();
        }

#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;
        }

#ifdef HAVE_STEPPABLE_WATCHPOINT
      /* It may not be necessary to disable the watchpoint to stop over
         it.  For example, the PA can (with some kernel cooperation) 
         single step over a watchpoint without disabling the watchpoint.  */
      if (STOPPED_BY_WATCHPOINT (w))
        {
          resume (1, 0);
          continue;
        }
#endif

#ifdef HAVE_NONSTEPPABLE_WATCHPOINT
      /* It is far more common to need to disable a watchpoint
         to step the inferior over it.  FIXME.  What else might
         a debug register or page protection watchpoint scheme need
         here?  */
      if (STOPPED_BY_WATCHPOINT (w))
        {
/* At this point, we are stopped at an instruction which has attempted to write
   to a piece of memory under control of a watchpoint.  The instruction hasn't
   actually executed yet.  If we were to evaluate the watchpoint expression
   now, we would get the old value, and therefore no change would seem to have
   occurred.

   In order to make watchpoints work `right', we really need to complete the
   memory write, and then evaluate the watchpoint expression.  The following
   code does that by removing the watchpoint (actually, all watchpoints and
   breakpoints), single-stepping the target, re-inserting watchpoints, and then
   falling through to let normal single-step processing handle proceed.  Since
   this includes evaluating watchpoints, things will come to a stop in the
   correct manner.  */

          write_pc (stop_pc - DECR_PC_AFTER_BREAK);

          remove_breakpoints ();
          target_resume (pid, 1, TARGET_SIGNAL_0); /* Single step */

          if (target_wait_hook)
            target_wait_hook (pid, &w);
          else
            target_wait (pid, &w);
          insert_breakpoints ();
          /* FIXME-maybe: is this cleaner than setting a flag?  Does it
             handle things like signals arriving and other things happening
             in combination correctly?  */
          goto have_waited;
        }
#endif

#ifdef HAVE_CONTINUABLE_WATCHPOINT
      /* It may be possible to simply continue after a watchpoint.  */
      STOPPED_BY_WATCHPOINT (w);
#endif

      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_end);
      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.  */
      
      /* 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 == TARGET_SIGNAL_TRAP
          || (breakpoints_inserted &&
              (stop_signal == TARGET_SIGNAL_ILL
               || stop_signal == TARGET_SIGNAL_EMT
            ))
          || stop_soon_quietly)
        {
          if (stop_signal == TARGET_SIGNAL_TRAP && 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 through_sigtramp_breakpoint
             will be set and we should check whether we've hit the
             step breakpoint.  */
          if (stop_signal == TARGET_SIGNAL_TRAP && trap_expected
              && through_sigtramp_breakpoint == NULL)
            bpstat_clear (&stop_bpstat);
          else
            {
              /* See if there is a breakpoint at the current PC.  */
              stop_bpstat = bpstat_stop_status
                (&stop_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.  */
                 (prev_pc != stop_pc - DECR_PC_AFTER_BREAK
                  && CURRENTLY_STEPPING ())
#else /* DECR_PC_AFTER_BREAK zero */
                 0
#endif /* DECR_PC_AFTER_BREAK zero */
                 );
              /* Following in case break condition called a
                 function.  */
              stop_print_frame = 1;
            }

          if (stop_signal == TARGET_SIGNAL_TRAP)
            random_signal
              = !(bpstat_explains_signal (stop_bpstat)
                  || trap_expected
#ifndef CALL_DUMMY_BREAKPOINT_OFFSET
                  || PC_IN_CALL_DUMMY (stop_pc, read_sp (),
                                       FRAME_FP (get_current_frame ()))
#endif /* No CALL_DUMMY_BREAKPOINT_OFFSET.  */
                  || (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.  */
#ifndef CALL_DUMMY_BREAKPOINT_OFFSET
                    || PC_IN_CALL_DUMMY (stop_pc, read_sp (),
                                         FRAME_FP (get_current_frame ()))
#endif /* No CALL_DUMMY_BREAKPOINT_OFFSET.  */
                    );
              if (!random_signal)
                stop_signal = TARGET_SIGNAL_TRAP;
            }
        }
      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 (signal_print[stop_signal])
            {
              printed = 1;
              target_terminal_ours_for_output ();
              annotate_signal ();
              printf_filtered ("\nProgram received signal ");
              annotate_signal_name ();
              printf_filtered ("%s", target_signal_to_name (stop_signal));
              annotate_signal_name_end ();
              printf_filtered (", ");
              annotate_signal_string ();
              printf_filtered ("%s", target_signal_to_string (stop_signal));
              annotate_signal_string_end ();
              printf_filtered (".\n");
              gdb_flush (gdb_stdout);
            }
          if (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 = TARGET_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);

        if (what.call_dummy)
          {
            stop_stack_dummy = 1;
#ifdef HP_OS_BUG
            trap_expected_after_continue = 1;
#endif
          }

        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;
              }
            /* Not sure whether we need to blow this away too, but probably
               it is like the step-resume breakpoint.  */
            if (through_sigtramp_breakpoint != NULL)
              {
                delete_breakpoint (through_sigtramp_breakpoint);
                through_sigtramp_breakpoint = NULL;
              }

#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
                && (FRAME_FP (get_current_frame ())
                    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 and
               through_sigtramp_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 and
               through_sigtramp_breakpoint via the cleanup chain, so
               no need to worry about it here.  */

            goto stop_stepping;

          case BPSTAT_WHAT_STEP_RESUME:
            delete_breakpoint (step_resume_breakpoint);
            step_resume_breakpoint = NULL;
            break;

          case BPSTAT_WHAT_THROUGH_SIGTRAMP:
            if (through_sigtramp_breakpoint)
              delete_breakpoint (through_sigtramp_breakpoint);
            through_sigtramp_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;
            break;

#ifdef SOLIB_ADD
          case BPSTAT_WHAT_CHECK_SHLIBS:
            {
              extern int auto_solib_add;

              /* Check for any newly added shared libraries if we're
                 supposed to be adding them automatically.  */
              if (auto_solib_add)
                SOLIB_ADD (NULL, 0, NULL);

              /* If requested, stop when the dynamic linker notifies
                 gdb of events.  This allows the user to get control
                 and place breakpoints in initializer routines for
                 dynamically loaded objects (among other things).  */
              if (stop_on_solib_events)
                {
                  stop_print_frame = 0;
                  goto stop_stepping;
                }
              else
                {
                  /* We want to step over this breakpoint, then keep going.  */
                  another_trap = 1;
                  remove_breakpoints_on_following_step = 1;
                  break;
                }
            }
#endif

          case BPSTAT_WHAT_LAST:
            /* Not a real code, but listed here to shut up gcc -Wall.  */

          case BPSTAT_WHAT_KEEP_CHECKING:
            break;
          }
      }

      /* 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.  */

#ifndef CALL_DUMMY_BREAKPOINT_OFFSET
      /* This is the old way of detecting the end of the stack dummy.
         An architecture which defines CALL_DUMMY_BREAKPOINT_OFFSET gets
         handled above.  As soon as we can test it on all of them, all
         architectures should define it.  */

      /* If this is the breakpoint at the end of a stack dummy,
         just stop silently, unless the user was doing an si/ni, in which
         case she'd better know what she's doing.  */

      if (PC_IN_CALL_DUMMY (stop_pc, read_sp (), FRAME_FP (get_current_frame ()))
          && !step_range_end)
        {
          stop_print_frame = 0;
          stop_stack_dummy = 1;
#ifdef HP_OS_BUG
          trap_expected_after_continue = 1;
#endif
          break;
        }
#endif /* No CALL_DUMMY_BREAKPOINT_OFFSET.  */

      if (step_resume_breakpoint)
        /* Having a step-resume breakpoint overrides anything
           else having to do with stepping commands until
           that breakpoint is reached.  */
        /* I'm not sure whether this needs to be check_sigtramp2 or
           whether it could/should be keep_going.  */
        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
#if 0
/* I haven't a clue what might trigger this clause, and it seems wrong anyway,
   so I've disabled it until someone complains.  -Stu 10/24/95 */

          /* 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
               && FRAME_FP (get_current_frame ())
               && (read_sp () INNER_THAN step_sp
                   || FRAME_FP (get_current_frame ()) != step_frame_address))
#endif
)
        {
          /* 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.  */

      /* We can't update step_sp every time through the loop, because
         reading the stack pointer would slow down stepping too much.
         But we can update it every time we leave the step range.  */
      update_step_sp = 1;

      /* Did we just take a signal?  */
      if (IN_SIGTRAMP (stop_pc, stop_func_name)
          && !IN_SIGTRAMP (prev_pc, prev_func_name))
        {
          /* We've just taken a signal; go until we are back to
             the point where we took it and one more.  */

          /* This code is needed at least in the following case:
             The user types "next" and then a signal arrives (before
             the "next" is done).  */

          /* Note that if we are stopped at a breakpoint, then we need
             the step_resume breakpoint to override any breakpoints at
             the same location, so that we will still step over the
             breakpoint even though the signal happened.  */

          {
            struct symtab_and_line sr_sal;

            sr_sal.pc = prev_pc;
            sr_sal.symtab = NULL;
            sr_sal.line = 0;
            /* We could probably be setting the frame to
               step_frame_address; I don't think anyone thought to try it.  */
            step_resume_breakpoint =
              set_momentary_breakpoint (sr_sal, NULL, 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 0
      /* I disabled this test because it was too complicated and slow.  The
         SKIP_PROLOGUE was especially slow, because it caused unnecessary
         prologue examination on various architectures.  The code in the #else
         clause has been tested on the Sparc, Mips, PA, and Power
         architectures, so it's pretty likely to be correct.  -Stu 10/24/95 */

      /* See if we left the step range due to a subroutine call that
         we should proceed to the end of.  */

      if (stop_func_start)
        {
          struct symtab *s;

          /* Do this after the IN_SIGTRAMP check; it might give
             an error.  */
          prologue_pc = stop_func_start;

          /* Don't skip the prologue if this is assembly source */
          s = find_pc_symtab (stop_pc);
          if (s && s->language != language_asm)
            SKIP_PROLOGUE (prologue_pc);
        }

      if ((/* Might be a non-recursive call.  If the symbols are missing
              enough that stop_func_start == prev_func_start even though
              they are really two functions, we will treat some calls as
              jumps.  */
           stop_func_start != prev_func_start

           /* Might be a recursive call if either we have a prologue
              or the call instruction itself saves the PC on the stack.  */
           || prologue_pc != stop_func_start
           || read_sp () != step_sp)
          && (/* PC is completely out of bounds of any known objfiles.  Treat
                 like a subroutine call. */
              ! stop_func_start

              /* If we do a call, we will be at the start of a function...  */
              || stop_pc == stop_func_start

              /* ...except on the Alpha with -O (and also Irix 5 and
                 perhaps others), in which we might call the address
                 after the load of gp.  Since prologues don't contain
                 calls, we can't return to within one, and we don't
                 jump back into them, so this check is OK.  */

              || stop_pc < prologue_pc

              /* ...and if it is a leaf function, the prologue might
                 consist of gp loading only, so the call transfers to
                 the first instruction after the prologue.  */
              || (stop_pc == prologue_pc

                  /* Distinguish this from the case where we jump back
                     to the first instruction after the prologue,
                     within a function.  */
                   && stop_func_start != prev_func_start)

              /* If we end up in certain places, it means we did a subroutine
                 call.  I'm not completely sure this is necessary now that we
                 have the above checks with stop_func_start (and now that
                 find_pc_partial_function is pickier).  */
              || IN_SOLIB_CALL_TRAMPOLINE (stop_pc, stop_func_name)

              /* If none of the above apply, it is a jump within a function,
                 or a return from a subroutine.  The other case is longjmp,
                 which can no longer happen here as long as the
                 handling_longjmp stuff is working.  */
              ))
#else
        /* This test is a much more streamlined, (but hopefully correct)
           replacement for the code above.  It's been tested on the Sparc,
           Mips, PA, and Power architectures with good results.  */

        if (stop_pc == stop_func_start /* Quick test */
            || in_prologue (stop_pc, stop_func_start)
            || IN_SOLIB_CALL_TRAMPOLINE (stop_pc, stop_func_name)
            || stop_func_start == 0)
#endif

        {
          /* 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;
          else
            {
              tmp = DYNAMIC_TRAMPOLINE_NEXTPC (stop_pc);
              if (tmp)
                {
                  struct symtab_and_line xxx;

                  xxx.pc = tmp;
                  xxx.symtab = NULL;
                  xxx.line = 0;
                  step_resume_breakpoint = 
                    set_momentary_breakpoint (xxx, NULL, bp_step_resume);
                  insert_breakpoints ();
                  goto keep_going;
                }
            }

          /* 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);
            step_resume_breakpoint->frame = step_frame_address;
            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.  */
          {
            struct symtab *s;

            s = find_pc_symtab (stop_pc);
            if (s && s->language != language_asm)
              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 (if it is still
             within the function).  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 && sal.end < stop_func_end)
            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, NULL, 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.  */

      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 we're in the return path from a shared library trampoline,
         we want to proceed through the trampoline when stepping.  */
      if (IN_SOLIB_RETURN_TRAMPOLINE(stop_pc, stop_func_name))
        {
          CORE_ADDR tmp;

          /* Determine where this trampoline returns.  */
          tmp = SKIP_TRAMPOLINE_CODE (stop_pc);

          /* Only proceed through if we know where it's going.  */
          if (tmp)
            {
              /* And put the step-breakpoint there and go until there. */
              struct symtab_and_line sr_sal;

              sr_sal.pc = tmp;
              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, NULL, bp_step_resume);
              if (breakpoints_inserted)
                insert_breakpoints ();

              /* Restart without fiddling with the step ranges or
                 other state.  */
              goto keep_going;
            }
        }
         
      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 || current_symtab != sal.symtab))
        {
          /* 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.)  */

      if (stop_func_end && sal.end >= stop_func_end)
        {
          /* If this is the last line of the function, don't keep stepping
             (it would probably step us out of the function).
             This is particularly necessary for a one-line function,
             in which after skipping the prologue we better stop even though
             we will be in mid-line.  */
          stop_step = 1;
          break;
        }
      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;
          /* We perhaps could set the frame if we kept track of what
             the frame corresponding to prev_pc was.  But we don't,
             so don't.  */
          through_sigtramp_breakpoint =
            set_momentary_breakpoint (sr_sal, NULL, bp_through_sigtramp);
          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;

      if (update_step_sp)
        step_sp = read_sp ();
      update_step_sp = 0;

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

      if (trap_expected && stop_signal != TARGET_SIGNAL_TRAP)
        {
          /* 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 (CURRENTLY_STEPPING (), 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
              && through_sigtramp_breakpoint == NULL
              && remove_breakpoints_on_following_step)
            {
              remove_breakpoints_on_following_step = 0;
              remove_breakpoints ();
              breakpoints_inserted = 0;
            }
          else if (!breakpoints_inserted &&
                   (through_sigtramp_breakpoint != NULL || !another_trap))
            {
              breakpoints_failed = insert_breakpoints ();
              if (breakpoints_failed)
                break;
              breakpoints_inserted = 1;
            }

          trap_expected = another_trap;

          if (stop_signal == TARGET_SIGNAL_TRAP)
            stop_signal = TARGET_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.  */
          /* FIXME: Shouldn't this be based on the valid bit of the SXIP?
             (this is only used on the 88k).  */

          if (!bpstat_explains_signal (stop_bpstat)
              && (stop_signal != TARGET_SIGNAL_CHLD) 
              && !stopped_by_random_signal)
            SHIFT_INST_REGS();
#endif /* SHIFT_INST_REGS */

          resume (CURRENTLY_STEPPING (), 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;
    }
  do_cleanups (old_cleanups);
}
\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())
    (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)
    goto done;

  target_terminal_ours ();

  if (stop_bpstat && stop_bpstat->breakpoint_at->type == bp_shlib_event)
    printf_filtered ("Stopped due to shared library event\n");

  /* 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)
    goto done;

  /* 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 == FRAME_FP (get_current_frame ())
                 && 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;
      /* Set stop_pc to what it was before we called the function.  Can't rely
         on restore_inferior_status because that only gets called if we don't
         stop in the called function.  */
      stop_pc = read_pc();
      select_frame (get_current_frame (), 0);
    }
 done:
  annotate_stopped ();
}

static int
hook_stop_stub (cmd)
     char *cmd;
{
  execute_user_command ((struct cmd_list_element *)cmd, 0);
  return (0);
}
\f
int signal_stop_state (signo)
     int signo;
{
  return signal_stop[signo];
}

int signal_print_state (signo)
     int signo;
{
  return signal_print[signo];
}

int signal_pass_state (signo)
     int signo;
{
  return signal_program[signo];
}

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

static void
sig_print_info (oursig)
     enum target_signal oursig;
{
  char *name = target_signal_to_name (oursig);
  printf_filtered ("%s", name);
  printf_filtered ("%*.*s ", 13 - strlen (name), 13 - strlen (name),
                   "                 ");
  printf_filtered ("%s\t", signal_stop[oursig] ? "Yes" : "No");
  printf_filtered ("%s\t", signal_print[oursig] ? "Yes" : "No");
  printf_filtered ("%s\t\t", signal_program[oursig] ? "Yes" : "No");
  printf_filtered ("%s\n", target_signal_to_string (oursig));
}

/* 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;
  enum target_signal oursig;
  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 = (int)TARGET_SIGNAL_LAST;
  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 oursigs, 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)
        {
          /* It is numeric.  The numeric signal refers to our own internal
             signal numbering from target.h, not to host/target signal number.
             This is a feature; users really should be using symbolic names
             anyway, and the common ones like SIGHUP, SIGINT, SIGALRM, etc.
             will work right anyway.  */

          sigfirst = siglast = (int) target_signal_from_command (atoi (*argv));
          if ((*argv)[digits] == '-')
            {
              siglast =
                (int) target_signal_from_command (atoi ((*argv) + digits + 1));
            }
          if (sigfirst > siglast)
            {
              /* Bet he didn't figure we'd think of this case... */
              signum = sigfirst;
              sigfirst = siglast;
              siglast = signum;
            }
        }
      else
        {
          oursig = target_signal_from_name (*argv);
          if (oursig != TARGET_SIGNAL_UNKNOWN)
            {
              sigfirst = siglast = (int)oursig;
            }
          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 ((enum target_signal)signum)
            {
              case TARGET_SIGNAL_TRAP:
              case TARGET_SIGNAL_INT:
                if (!allsigs && !sigs[signum])
                  {
                    if (query ("%s is used by the debugger.\n\
Are you sure you want to change it? ",
                               target_signal_to_name
                               ((enum target_signal)signum)))
                      {
                        sigs[signum] = 1;
                      }
                    else
                      {
                        printf_unfiltered ("Not confirmed, unchanged.\n");
                        gdb_flush (gdb_stdout);
                      }
                  }
                break;
              case TARGET_SIGNAL_0:
              case TARGET_SIGNAL_DEFAULT:
              case TARGET_SIGNAL_UNKNOWN:
                /* Make sure that "all" doesn't print these.  */
                break;
              default:
                sigs[signum] = 1;
                break;
            }
        }

      argv++;
    }

  target_notice_signals(inferior_pid);

  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.
   It is possible we should just be printing signals actually used
   by the current target (but for things to work right when switching
   targets, all signals should be in the signal tables).  */

static void
signals_info (signum_exp, from_tty)
     char *signum_exp;
     int from_tty;
{
  enum target_signal oursig;
  sig_print_header ();

  if (signum_exp)
    {
      /* First see if this is a symbol name.  */
      oursig = target_signal_from_name (signum_exp);
      if (oursig == TARGET_SIGNAL_UNKNOWN)
        {
          /* No, try numeric.  */
          oursig =
            target_signal_from_command (parse_and_eval_address (signum_exp));
        }
      sig_print_info (oursig);
      return;
    }

  printf_filtered ("\n");
  /* These ugly casts brought to you by the native VAX compiler.  */
  for (oursig = TARGET_SIGNAL_FIRST;
       (int)oursig < (int)TARGET_SIGNAL_LAST;
       oursig = (enum target_signal)((int)oursig + 1))
    {
      QUIT;

      if (oursig != TARGET_SIGNAL_UNKNOWN
          && oursig != TARGET_SIGNAL_DEFAULT
          && oursig != TARGET_SIGNAL_0)
        sig_print_info (oursig);
    }

  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->stop_signal = stop_signal;
  inf_status->stop_pc = stop_pc;
  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);

  read_register_bytes (0, inf_status->registers, REGISTER_BYTES);

  record_selected_frame (&(inf_status->selected_frame_address),
                         &(inf_status->selected_level));
  return;
}

struct restore_selected_frame_args {
  CORE_ADDR frame_address;
  int level;
};

static int restore_selected_frame PARAMS ((char *));

/* Restore the selected frame.  args is really a struct
   restore_selected_frame_args * (declared as char * for catch_errors)
   telling us what frame to restore.  Returns 1 for success, or 0 for
   failure.  An error message will have been printed on error.  */

static int
restore_selected_frame (args)
     char *args;
{
  struct restore_selected_frame_args *fr =
    (struct restore_selected_frame_args *) args;
  struct frame_info *frame;
  int level = fr->level;

  frame = find_relative_frame (get_current_frame (), &level);

  /* If inf_status->selected_frame_address is NULL, there was no
     previously selected frame.  */
  if (frame == NULL ||
      FRAME_FP (frame) != fr->frame_address ||
      level != 0)
    {
      warning ("Unable to restore previously selected frame.\n");
      return 0;
    }
  select_frame (frame, fr->level);
  return(1);
}

void
restore_inferior_status (inf_status)
     struct inferior_status *inf_status;
{
  stop_signal = inf_status->stop_signal;
  stop_pc = inf_status->stop_pc;
  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_execution)
    write_register_bytes (0, inf_status->registers, REGISTER_BYTES);

  /* The inferior can be gone if the user types "print exit(0)"
     (and perhaps other times).  */

  /* FIXME: If we are being called after stopping in a function which
     is called from gdb, we should not be trying to restore the
     selected frame; it just prints a spurious error message (The
     message is useful, however, in detecting bugs in gdb (like if gdb
     clobbers the stack)).  In fact, should we be restoring the
     inferior status at all in that case?  .  */

  if (target_has_stack && inf_status->restore_stack_info)
    {
      struct restore_selected_frame_args fr;
      fr.level = inf_status->selected_level;
      fr.frame_address = inf_status->selected_frame_address;
      /* The point of catch_errors is that if the stack is clobbered,
         walking the stack might encounter a garbage pointer and error()
         trying to dereference it.  */
      if (catch_errors (restore_selected_frame, &fr,
                        "Unable to restore previously selected frame:\n",
                        RETURN_MASK_ERROR) == 0)
        /* Error in restoring the selected frame.  Select the innermost
           frame.  */
        select_frame (get_current_frame (), 0);
    }
}

\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 as argument to print info on that signal only.");
  add_info_alias ("handle", "signals", 0);

  add_com ("handle", class_run, handle_command,
           concat ("Specify how to handle a signal.\n\
Args are signals and actions to apply to those signals.\n\
Symbolic signals (e.g. SIGSEGV) are recommended but numeric signals\n\
from 1-15 are allowed for compatibility with old versions of GDB.\n\
Numeric ranges may be specified with the form LOW-HIGH (e.g. 1-5).\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.", NULL));

  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 = (int)TARGET_SIGNAL_LAST;
  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[TARGET_SIGNAL_TRAP] = 0;
  signal_program[TARGET_SIGNAL_INT] = 0;

  /* Signals that are not errors should not normally enter the debugger.  */
  signal_stop[TARGET_SIGNAL_ALRM] = 0;
  signal_print[TARGET_SIGNAL_ALRM] = 0;
  signal_stop[TARGET_SIGNAL_VTALRM] = 0;
  signal_print[TARGET_SIGNAL_VTALRM] = 0;
  signal_stop[TARGET_SIGNAL_PROF] = 0;
  signal_print[TARGET_SIGNAL_PROF] = 0;
  signal_stop[TARGET_SIGNAL_CHLD] = 0;
  signal_print[TARGET_SIGNAL_CHLD] = 0;
  signal_stop[TARGET_SIGNAL_IO] = 0;
  signal_print[TARGET_SIGNAL_IO] = 0;
  signal_stop[TARGET_SIGNAL_POLL] = 0;
  signal_print[TARGET_SIGNAL_POLL] = 0;
  signal_stop[TARGET_SIGNAL_URG] = 0;
  signal_print[TARGET_SIGNAL_URG] = 0;

#ifdef SOLIB_ADD
  add_show_from_set
    (add_set_cmd ("stop-on-solib-events", class_support, var_zinteger,
                  (char *) &stop_on_solib_events,
                  "Set stopping for shared library events.\n\
If nonzero, gdb will give control to the user when the dynamic linker\n\
notifies gdb of shared library events.  The most common event of interest\n\
to the user would be loading/unloading of a new library.\n",
                  &setlist),
     &showlist);
#endif
}