PR python/17372 - Python hangs when displaying help()

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

/* Target-struct-independent code to start (run) and stop an inferior
   process.

   Copyright (C) 1986-2014 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 3 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, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "infrun.h"
#include <ctype.h>
#include "symtab.h"
#include "frame.h"
#include "inferior.h"
#include "breakpoint.h"
#include "gdb_wait.h"
#include "gdbcore.h"
#include "gdbcmd.h"
#include "cli/cli-script.h"
#include "target.h"
#include "gdbthread.h"
#include "annotate.h"
#include "symfile.h"
#include "top.h"
#include <signal.h>
#include "inf-loop.h"
#include "regcache.h"
#include "value.h"
#include "observer.h"
#include "language.h"
#include "solib.h"
#include "main.h"
#include "dictionary.h"
#include "block.h"
#include "mi/mi-common.h"
#include "event-top.h"
#include "record.h"
#include "record-full.h"
#include "inline-frame.h"
#include "jit.h"
#include "tracepoint.h"
#include "continuations.h"
#include "interps.h"
#include "skip.h"
#include "probe.h"
#include "objfiles.h"
#include "completer.h"
#include "target-descriptions.h"
#include "target-dcache.h"
#include "terminal.h"

/* Prototypes for local functions */

static void signals_info (char *, int);

static void handle_command (char *, int);

static void sig_print_info (enum gdb_signal);

static void sig_print_header (void);

static void resume_cleanups (void *);

static int hook_stop_stub (void *);

static int restore_selected_frame (void *);

static int follow_fork (void);

static int follow_fork_inferior (int follow_child, int detach_fork);

static void follow_inferior_reset_breakpoints (void);

static void set_schedlock_func (char *args, int from_tty,
                                struct cmd_list_element *c);

static int currently_stepping (struct thread_info *tp);

static void xdb_handle_command (char *args, int from_tty);

void _initialize_infrun (void);

void nullify_last_target_wait_ptid (void);

static void insert_hp_step_resume_breakpoint_at_frame (struct frame_info *);

static void insert_step_resume_breakpoint_at_caller (struct frame_info *);

static void insert_longjmp_resume_breakpoint (struct gdbarch *, CORE_ADDR);

/* When set, stop the 'step' command if we enter a function which has
   no line number information.  The normal behavior is that we step
   over such function.  */
int step_stop_if_no_debug = 0;
static void
show_step_stop_if_no_debug (struct ui_file *file, int from_tty,
                            struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Mode of the step operation is %s.\n"), value);
}

/* In asynchronous mode, but simulating synchronous execution.  */

int sync_execution = 0;

/* proceed and normal_stop use this to notify the user when the
   inferior stopped in a different thread than it had been running
   in.  */

static ptid_t previous_inferior_ptid;

/* If set (default for legacy reasons), when following a fork, GDB
   will detach from one of the fork branches, child or parent.
   Exactly which branch is detached depends on 'set follow-fork-mode'
   setting.  */

static int detach_fork = 1;

int debug_displaced = 0;
static void
show_debug_displaced (struct ui_file *file, int from_tty,
                      struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Displace stepping debugging is %s.\n"), value);
}

unsigned int debug_infrun = 0;
static void
show_debug_infrun (struct ui_file *file, int from_tty,
                   struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Inferior debugging is %s.\n"), value);
}


/* Support for disabling address space randomization.  */

int disable_randomization = 1;

static void
show_disable_randomization (struct ui_file *file, int from_tty,
                            struct cmd_list_element *c, const char *value)
{
  if (target_supports_disable_randomization ())
    fprintf_filtered (file,
                      _("Disabling randomization of debuggee's "
                        "virtual address space is %s.\n"),
                      value);
  else
    fputs_filtered (_("Disabling randomization of debuggee's "
                      "virtual address space is unsupported on\n"
                      "this platform.\n"), file);
}

static void
set_disable_randomization (char *args, int from_tty,
                           struct cmd_list_element *c)
{
  if (!target_supports_disable_randomization ())
    error (_("Disabling randomization of debuggee's "
             "virtual address space is unsupported on\n"
             "this platform."));
}

/* User interface for non-stop mode.  */

int non_stop = 0;
static int non_stop_1 = 0;

static void
set_non_stop (char *args, int from_tty,
              struct cmd_list_element *c)
{
  if (target_has_execution)
    {
      non_stop_1 = non_stop;
      error (_("Cannot change this setting while the inferior is running."));
    }

  non_stop = non_stop_1;
}

static void
show_non_stop (struct ui_file *file, int from_tty,
               struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file,
                    _("Controlling the inferior in non-stop mode is %s.\n"),
                    value);
}

/* "Observer mode" is somewhat like a more extreme version of
   non-stop, in which all GDB operations that might affect the
   target's execution have been disabled.  */

int observer_mode = 0;
static int observer_mode_1 = 0;

static void
set_observer_mode (char *args, int from_tty,
                   struct cmd_list_element *c)
{
  if (target_has_execution)
    {
      observer_mode_1 = observer_mode;
      error (_("Cannot change this setting while the inferior is running."));
    }

  observer_mode = observer_mode_1;

  may_write_registers = !observer_mode;
  may_write_memory = !observer_mode;
  may_insert_breakpoints = !observer_mode;
  may_insert_tracepoints = !observer_mode;
  /* We can insert fast tracepoints in or out of observer mode,
     but enable them if we're going into this mode.  */
  if (observer_mode)
    may_insert_fast_tracepoints = 1;
  may_stop = !observer_mode;
  update_target_permissions ();

  /* Going *into* observer mode we must force non-stop, then
     going out we leave it that way.  */
  if (observer_mode)
    {
      pagination_enabled = 0;
      non_stop = non_stop_1 = 1;
    }

  if (from_tty)
    printf_filtered (_("Observer mode is now %s.\n"),
                     (observer_mode ? "on" : "off"));
}

static void
show_observer_mode (struct ui_file *file, int from_tty,
                    struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Observer mode is %s.\n"), value);
}

/* This updates the value of observer mode based on changes in
   permissions.  Note that we are deliberately ignoring the values of
   may-write-registers and may-write-memory, since the user may have
   reason to enable these during a session, for instance to turn on a
   debugging-related global.  */

void
update_observer_mode (void)
{
  int newval;

  newval = (!may_insert_breakpoints
            && !may_insert_tracepoints
            && may_insert_fast_tracepoints
            && !may_stop
            && non_stop);

  /* Let the user know if things change.  */
  if (newval != observer_mode)
    printf_filtered (_("Observer mode is now %s.\n"),
                     (newval ? "on" : "off"));

  observer_mode = observer_mode_1 = newval;
}

/* 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;

/* Table of signals that are registered with "catch signal".  A
   non-zero entry indicates that the signal is caught by some "catch
   signal" command.  This has size GDB_SIGNAL_LAST, to accommodate all
   signals.  */
static unsigned char *signal_catch;

/* Table of signals that the target may silently handle.
   This is automatically determined from the flags above,
   and simply cached here.  */
static unsigned char *signal_pass;

#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)

/* Update the target's copy of SIGNAL_PROGRAM.  The sole purpose of
   this function is to avoid exporting `signal_program'.  */

void
update_signals_program_target (void)
{
  target_program_signals ((int) GDB_SIGNAL_LAST, signal_program);
}

/* Value to pass to target_resume() to cause all threads to resume.  */

#define RESUME_ALL minus_one_ptid

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

static struct cmd_list_element *stop_command;

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

static struct symbol *step_start_function;

/* Nonzero if we want to give control to the user when we're notified
   of shared library events by the dynamic linker.  */
int stop_on_solib_events;

/* Enable or disable optional shared library event breakpoints
   as appropriate when the above flag is changed.  */

static void
set_stop_on_solib_events (char *args, int from_tty, struct cmd_list_element *c)
{
  update_solib_breakpoints ();
}

static void
show_stop_on_solib_events (struct ui_file *file, int from_tty,
                           struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Stopping for shared library events is %s.\n"),
                    value);
}

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

int stop_after_trap;

/* Save register contents here when executing a "finish" command or are
   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).  */

struct regcache *stop_registers;

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

static int stop_print_frame;

/* This is a cached copy of the pid/waitstatus of the last event
   returned by target_wait()/deprecated_target_wait_hook().  This
   information is returned by get_last_target_status().  */
static ptid_t target_last_wait_ptid;
static struct target_waitstatus target_last_waitstatus;

static void context_switch (ptid_t ptid);

void init_thread_stepping_state (struct thread_info *tss);

static const char follow_fork_mode_child[] = "child";
static const char follow_fork_mode_parent[] = "parent";

static const char *const follow_fork_mode_kind_names[] = {
  follow_fork_mode_child,
  follow_fork_mode_parent,
  NULL
};

static const char *follow_fork_mode_string = follow_fork_mode_parent;
static void
show_follow_fork_mode_string (struct ui_file *file, int from_tty,
                              struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file,
                    _("Debugger response to a program "
                      "call of fork or vfork is \"%s\".\n"),
                    value);
}
\f

/* Handle changes to the inferior list based on the type of fork,
   which process is being followed, and whether the other process
   should be detached.  On entry inferior_ptid must be the ptid of
   the fork parent.  At return inferior_ptid is the ptid of the
   followed inferior.  */

static int
follow_fork_inferior (int follow_child, int detach_fork)
{
  int has_vforked;
  int parent_pid, child_pid;

  has_vforked = (inferior_thread ()->pending_follow.kind
                 == TARGET_WAITKIND_VFORKED);
  parent_pid = ptid_get_lwp (inferior_ptid);
  if (parent_pid == 0)
    parent_pid = ptid_get_pid (inferior_ptid);
  child_pid
    = ptid_get_pid (inferior_thread ()->pending_follow.value.related_pid);

  if (has_vforked
      && !non_stop /* Non-stop always resumes both branches.  */
      && (!target_is_async_p () || sync_execution)
      && !(follow_child || detach_fork || sched_multi))
    {
      /* The parent stays blocked inside the vfork syscall until the
         child execs or exits.  If we don't let the child run, then
         the parent stays blocked.  If we're telling the parent to run
         in the foreground, the user will not be able to ctrl-c to get
         back the terminal, effectively hanging the debug session.  */
      fprintf_filtered (gdb_stderr, _("\
Can not resume the parent process over vfork in the foreground while\n\
holding the child stopped.  Try \"set detach-on-fork\" or \
\"set schedule-multiple\".\n"));
      /* FIXME output string > 80 columns.  */
      return 1;
    }

  if (!follow_child)
    {
      /* Detach new forked process?  */
      if (detach_fork)
        {
          struct cleanup *old_chain;

          /* Before detaching from the child, remove all breakpoints
             from it.  If we forked, then this has already been taken
             care of by infrun.c.  If we vforked however, any
             breakpoint inserted in the parent is visible in the
             child, even those added while stopped in a vfork
             catchpoint.  This will remove the breakpoints from the
             parent also, but they'll be reinserted below.  */
          if (has_vforked)
            {
              /* Keep breakpoints list in sync.  */
              remove_breakpoints_pid (ptid_get_pid (inferior_ptid));
            }

          if (info_verbose || debug_infrun)
            {
              target_terminal_ours_for_output ();
              fprintf_filtered (gdb_stdlog,
                                _("Detaching after %s from "
                                  "child process %d.\n"),
                                has_vforked ? "vfork" : "fork",
                                child_pid);
            }
        }
      else
        {
          struct inferior *parent_inf, *child_inf;
          struct cleanup *old_chain;

          /* Add process to GDB's tables.  */
          child_inf = add_inferior (child_pid);

          parent_inf = current_inferior ();
          child_inf->attach_flag = parent_inf->attach_flag;
          copy_terminal_info (child_inf, parent_inf);
          child_inf->gdbarch = parent_inf->gdbarch;
          copy_inferior_target_desc_info (child_inf, parent_inf);

          old_chain = save_inferior_ptid ();
          save_current_program_space ();

          inferior_ptid = ptid_build (child_pid, child_pid, 0);
          add_thread (inferior_ptid);
          child_inf->symfile_flags = SYMFILE_NO_READ;

          /* If this is a vfork child, then the address-space is
             shared with the parent.  */
          if (has_vforked)
            {
              child_inf->pspace = parent_inf->pspace;
              child_inf->aspace = parent_inf->aspace;

              /* The parent will be frozen until the child is done
                 with the shared region.  Keep track of the
                 parent.  */
              child_inf->vfork_parent = parent_inf;
              child_inf->pending_detach = 0;
              parent_inf->vfork_child = child_inf;
              parent_inf->pending_detach = 0;
            }
          else
            {
              child_inf->aspace = new_address_space ();
              child_inf->pspace = add_program_space (child_inf->aspace);
              child_inf->removable = 1;
              set_current_program_space (child_inf->pspace);
              clone_program_space (child_inf->pspace, parent_inf->pspace);

              /* Let the shared library layer (e.g., solib-svr4) learn
                 about this new process, relocate the cloned exec, pull
                 in shared libraries, and install the solib event
                 breakpoint.  If a "cloned-VM" event was propagated
                 better throughout the core, this wouldn't be
                 required.  */
              solib_create_inferior_hook (0);
            }

          do_cleanups (old_chain);
        }

      if (has_vforked)
        {
          struct inferior *parent_inf;

          parent_inf = current_inferior ();

          /* If we detached from the child, then we have to be careful
             to not insert breakpoints in the parent until the child
             is done with the shared memory region.  However, if we're
             staying attached to the child, then we can and should
             insert breakpoints, so that we can debug it.  A
             subsequent child exec or exit is enough to know when does
             the child stops using the parent's address space.  */
          parent_inf->waiting_for_vfork_done = detach_fork;
          parent_inf->pspace->breakpoints_not_allowed = detach_fork;
        }
    }
  else
    {
      /* Follow the child.  */
      struct inferior *parent_inf, *child_inf;
      struct program_space *parent_pspace;

      if (info_verbose || debug_infrun)
        {
          target_terminal_ours_for_output ();
          fprintf_filtered (gdb_stdlog,
                            _("Attaching after process %d "
                              "%s to child process %d.\n"),
                            parent_pid,
                            has_vforked ? "vfork" : "fork",
                            child_pid);
        }

      /* Add the new inferior first, so that the target_detach below
         doesn't unpush the target.  */

      child_inf = add_inferior (child_pid);

      parent_inf = current_inferior ();
      child_inf->attach_flag = parent_inf->attach_flag;
      copy_terminal_info (child_inf, parent_inf);
      child_inf->gdbarch = parent_inf->gdbarch;
      copy_inferior_target_desc_info (child_inf, parent_inf);

      parent_pspace = parent_inf->pspace;

      /* If we're vforking, we want to hold on to the parent until the
         child exits or execs.  At child exec or exit time we can
         remove the old breakpoints from the parent and detach or
         resume debugging it.  Otherwise, detach the parent now; we'll
         want to reuse it's program/address spaces, but we can't set
         them to the child before removing breakpoints from the
         parent, otherwise, the breakpoints module could decide to
         remove breakpoints from the wrong process (since they'd be
         assigned to the same address space).  */

      if (has_vforked)
        {
          gdb_assert (child_inf->vfork_parent == NULL);
          gdb_assert (parent_inf->vfork_child == NULL);
          child_inf->vfork_parent = parent_inf;
          child_inf->pending_detach = 0;
          parent_inf->vfork_child = child_inf;
          parent_inf->pending_detach = detach_fork;
          parent_inf->waiting_for_vfork_done = 0;
        }
      else if (detach_fork)
        {
          if (info_verbose || debug_infrun)
            {
              target_terminal_ours_for_output ();
              fprintf_filtered (gdb_stdlog,
                                _("Detaching after fork from "
                                  "child process %d.\n"),
                                child_pid);
            }

          target_detach (NULL, 0);
        }

      /* Note that the detach above makes PARENT_INF dangling.  */

      /* Add the child thread to the appropriate lists, and switch to
         this new thread, before cloning the program space, and
         informing the solib layer about this new process.  */

      inferior_ptid = ptid_build (child_pid, child_pid, 0);
      add_thread (inferior_ptid);

      /* If this is a vfork child, then the address-space is shared
         with the parent.  If we detached from the parent, then we can
         reuse the parent's program/address spaces.  */
      if (has_vforked || detach_fork)
        {
          child_inf->pspace = parent_pspace;
          child_inf->aspace = child_inf->pspace->aspace;
        }
      else
        {
          child_inf->aspace = new_address_space ();
          child_inf->pspace = add_program_space (child_inf->aspace);
          child_inf->removable = 1;
          child_inf->symfile_flags = SYMFILE_NO_READ;
          set_current_program_space (child_inf->pspace);
          clone_program_space (child_inf->pspace, parent_pspace);

          /* Let the shared library layer (e.g., solib-svr4) learn
             about this new process, relocate the cloned exec, pull in
             shared libraries, and install the solib event breakpoint.
             If a "cloned-VM" event was propagated better throughout
             the core, this wouldn't be required.  */
          solib_create_inferior_hook (0);
        }
    }

  return target_follow_fork (follow_child, detach_fork);
}

/* Tell the target to follow the fork we're stopped at.  Returns true
   if the inferior should be resumed; false, if the target for some
   reason decided it's best not to resume.  */

static int
follow_fork (void)
{
  int follow_child = (follow_fork_mode_string == follow_fork_mode_child);
  int should_resume = 1;
  struct thread_info *tp;

  /* Copy user stepping state to the new inferior thread.  FIXME: the
     followed fork child thread should have a copy of most of the
     parent thread structure's run control related fields, not just these.
     Initialized to avoid "may be used uninitialized" warnings from gcc.  */
  struct breakpoint *step_resume_breakpoint = NULL;
  struct breakpoint *exception_resume_breakpoint = NULL;
  CORE_ADDR step_range_start = 0;
  CORE_ADDR step_range_end = 0;
  struct frame_id step_frame_id = { 0 };
  struct interp *command_interp = NULL;

  if (!non_stop)
    {
      ptid_t wait_ptid;
      struct target_waitstatus wait_status;

      /* Get the last target status returned by target_wait().  */
      get_last_target_status (&wait_ptid, &wait_status);

      /* If not stopped at a fork event, then there's nothing else to
         do.  */
      if (wait_status.kind != TARGET_WAITKIND_FORKED
          && wait_status.kind != TARGET_WAITKIND_VFORKED)
        return 1;

      /* Check if we switched over from WAIT_PTID, since the event was
         reported.  */
      if (!ptid_equal (wait_ptid, minus_one_ptid)
          && !ptid_equal (inferior_ptid, wait_ptid))
        {
          /* We did.  Switch back to WAIT_PTID thread, to tell the
             target to follow it (in either direction).  We'll
             afterwards refuse to resume, and inform the user what
             happened.  */
          switch_to_thread (wait_ptid);
          should_resume = 0;
        }
    }

  tp = inferior_thread ();

  /* If there were any forks/vforks that were caught and are now to be
     followed, then do so now.  */
  switch (tp->pending_follow.kind)
    {
    case TARGET_WAITKIND_FORKED:
    case TARGET_WAITKIND_VFORKED:
      {
        ptid_t parent, child;

        /* If the user did a next/step, etc, over a fork call,
           preserve the stepping state in the fork child.  */
        if (follow_child && should_resume)
          {
            step_resume_breakpoint = clone_momentary_breakpoint
                                         (tp->control.step_resume_breakpoint);
            step_range_start = tp->control.step_range_start;
            step_range_end = tp->control.step_range_end;
            step_frame_id = tp->control.step_frame_id;
            exception_resume_breakpoint
              = clone_momentary_breakpoint (tp->control.exception_resume_breakpoint);
            command_interp = tp->control.command_interp;

            /* For now, delete the parent's sr breakpoint, otherwise,
               parent/child sr breakpoints are considered duplicates,
               and the child version will not be installed.  Remove
               this when the breakpoints module becomes aware of
               inferiors and address spaces.  */
            delete_step_resume_breakpoint (tp);
            tp->control.step_range_start = 0;
            tp->control.step_range_end = 0;
            tp->control.step_frame_id = null_frame_id;
            delete_exception_resume_breakpoint (tp);
            tp->control.command_interp = NULL;
          }

        parent = inferior_ptid;
        child = tp->pending_follow.value.related_pid;

        /* Set up inferior(s) as specified by the caller, and tell the
           target to do whatever is necessary to follow either parent
           or child.  */
        if (follow_fork_inferior (follow_child, detach_fork))
          {
            /* Target refused to follow, or there's some other reason
               we shouldn't resume.  */
            should_resume = 0;
          }
        else
          {
            /* This pending follow fork event is now handled, one way
               or another.  The previous selected thread may be gone
               from the lists by now, but if it is still around, need
               to clear the pending follow request.  */
            tp = find_thread_ptid (parent);
            if (tp)
              tp->pending_follow.kind = TARGET_WAITKIND_SPURIOUS;

            /* This makes sure we don't try to apply the "Switched
               over from WAIT_PID" logic above.  */
            nullify_last_target_wait_ptid ();

            /* If we followed the child, switch to it...  */
            if (follow_child)
              {
                switch_to_thread (child);

                /* ... and preserve the stepping state, in case the
                   user was stepping over the fork call.  */
                if (should_resume)
                  {
                    tp = inferior_thread ();
                    tp->control.step_resume_breakpoint
                      = step_resume_breakpoint;
                    tp->control.step_range_start = step_range_start;
                    tp->control.step_range_end = step_range_end;
                    tp->control.step_frame_id = step_frame_id;
                    tp->control.exception_resume_breakpoint
                      = exception_resume_breakpoint;
                    tp->control.command_interp = command_interp;
                  }
                else
                  {
                    /* If we get here, it was because we're trying to
                       resume from a fork catchpoint, but, the user
                       has switched threads away from the thread that
                       forked.  In that case, the resume command
                       issued is most likely not applicable to the
                       child, so just warn, and refuse to resume.  */
                    warning (_("Not resuming: switched threads "
                               "before following fork child.\n"));
                  }

                /* Reset breakpoints in the child as appropriate.  */
                follow_inferior_reset_breakpoints ();
              }
            else
              switch_to_thread (parent);
          }
      }
      break;
    case TARGET_WAITKIND_SPURIOUS:
      /* Nothing to follow.  */
      break;
    default:
      internal_error (__FILE__, __LINE__,
                      "Unexpected pending_follow.kind %d\n",
                      tp->pending_follow.kind);
      break;
    }

  return should_resume;
}

static void
follow_inferior_reset_breakpoints (void)
{
  struct thread_info *tp = inferior_thread ();

  /* Was there a step_resume breakpoint?  (There was if the user
     did a "next" at the fork() call.)  If so, explicitly reset its
     thread number.  Cloned step_resume breakpoints are disabled on
     creation, so enable it here now that it is associated with the
     correct thread.

     step_resumes are a form of bp that are made to be per-thread.
     Since we created the step_resume bp when the parent process
     was being debugged, and now are switching to the child process,
     from the breakpoint package's viewpoint, that's a switch of
     "threads".  We must update the bp's notion of which thread
     it is for, or it'll be ignored when it triggers.  */

  if (tp->control.step_resume_breakpoint)
    {
      breakpoint_re_set_thread (tp->control.step_resume_breakpoint);
      tp->control.step_resume_breakpoint->loc->enabled = 1;
    }

  /* Treat exception_resume breakpoints like step_resume breakpoints.  */
  if (tp->control.exception_resume_breakpoint)
    {
      breakpoint_re_set_thread (tp->control.exception_resume_breakpoint);
      tp->control.exception_resume_breakpoint->loc->enabled = 1;
    }

  /* Reinsert all breakpoints in the child.  The user may have set
     breakpoints after catching the fork, in which case those
     were never set in the child, but only in the parent.  This makes
     sure the inserted breakpoints match the breakpoint list.  */

  breakpoint_re_set ();
  insert_breakpoints ();
}

/* The child has exited or execed: resume threads of the parent the
   user wanted to be executing.  */

static int
proceed_after_vfork_done (struct thread_info *thread,
                          void *arg)
{
  int pid = * (int *) arg;

  if (ptid_get_pid (thread->ptid) == pid
      && is_running (thread->ptid)
      && !is_executing (thread->ptid)
      && !thread->stop_requested
      && thread->suspend.stop_signal == GDB_SIGNAL_0)
    {
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: resuming vfork parent thread %s\n",
                            target_pid_to_str (thread->ptid));

      switch_to_thread (thread->ptid);
      clear_proceed_status (0);
      proceed ((CORE_ADDR) -1, GDB_SIGNAL_DEFAULT, 0);
    }

  return 0;
}

/* Called whenever we notice an exec or exit event, to handle
   detaching or resuming a vfork parent.  */

static void
handle_vfork_child_exec_or_exit (int exec)
{
  struct inferior *inf = current_inferior ();

  if (inf->vfork_parent)
    {
      int resume_parent = -1;

      /* This exec or exit marks the end of the shared memory region
         between the parent and the child.  If the user wanted to
         detach from the parent, now is the time.  */

      if (inf->vfork_parent->pending_detach)
        {
          struct thread_info *tp;
          struct cleanup *old_chain;
          struct program_space *pspace;
          struct address_space *aspace;

          /* follow-fork child, detach-on-fork on.  */

          inf->vfork_parent->pending_detach = 0;

          if (!exec)
            {
              /* If we're handling a child exit, then inferior_ptid
                 points at the inferior's pid, not to a thread.  */
              old_chain = save_inferior_ptid ();
              save_current_program_space ();
              save_current_inferior ();
            }
          else
            old_chain = save_current_space_and_thread ();

          /* We're letting loose of the parent.  */
          tp = any_live_thread_of_process (inf->vfork_parent->pid);
          switch_to_thread (tp->ptid);

          /* We're about to detach from the parent, which implicitly
             removes breakpoints from its address space.  There's a
             catch here: we want to reuse the spaces for the child,
             but, parent/child are still sharing the pspace at this
             point, although the exec in reality makes the kernel give
             the child a fresh set of new pages.  The problem here is
             that the breakpoints module being unaware of this, would
             likely chose the child process to write to the parent
             address space.  Swapping the child temporarily away from
             the spaces has the desired effect.  Yes, this is "sort
             of" a hack.  */

          pspace = inf->pspace;
          aspace = inf->aspace;
          inf->aspace = NULL;
          inf->pspace = NULL;

          if (debug_infrun || info_verbose)
            {
              target_terminal_ours_for_output ();

              if (exec)
                {
                  fprintf_filtered (gdb_stdlog,
                                    _("Detaching vfork parent process "
                                      "%d after child exec.\n"),
                                    inf->vfork_parent->pid);
                }
              else
                {
                  fprintf_filtered (gdb_stdlog,
                                    _("Detaching vfork parent process "
                                      "%d after child exit.\n"),
                                    inf->vfork_parent->pid);
                }
            }

          target_detach (NULL, 0);

          /* Put it back.  */
          inf->pspace = pspace;
          inf->aspace = aspace;

          do_cleanups (old_chain);
        }
      else if (exec)
        {
          /* We're staying attached to the parent, so, really give the
             child a new address space.  */
          inf->pspace = add_program_space (maybe_new_address_space ());
          inf->aspace = inf->pspace->aspace;
          inf->removable = 1;
          set_current_program_space (inf->pspace);

          resume_parent = inf->vfork_parent->pid;

          /* Break the bonds.  */
          inf->vfork_parent->vfork_child = NULL;
        }
      else
        {
          struct cleanup *old_chain;
          struct program_space *pspace;

          /* If this is a vfork child exiting, then the pspace and
             aspaces were shared with the parent.  Since we're
             reporting the process exit, we'll be mourning all that is
             found in the address space, and switching to null_ptid,
             preparing to start a new inferior.  But, since we don't
             want to clobber the parent's address/program spaces, we
             go ahead and create a new one for this exiting
             inferior.  */

          /* Switch to null_ptid, so that clone_program_space doesn't want
             to read the selected frame of a dead process.  */
          old_chain = save_inferior_ptid ();
          inferior_ptid = null_ptid;

          /* This inferior is dead, so avoid giving the breakpoints
             module the option to write through to it (cloning a
             program space resets breakpoints).  */
          inf->aspace = NULL;
          inf->pspace = NULL;
          pspace = add_program_space (maybe_new_address_space ());
          set_current_program_space (pspace);
          inf->removable = 1;
          inf->symfile_flags = SYMFILE_NO_READ;
          clone_program_space (pspace, inf->vfork_parent->pspace);
          inf->pspace = pspace;
          inf->aspace = pspace->aspace;

          /* Put back inferior_ptid.  We'll continue mourning this
             inferior.  */
          do_cleanups (old_chain);

          resume_parent = inf->vfork_parent->pid;
          /* Break the bonds.  */
          inf->vfork_parent->vfork_child = NULL;
        }

      inf->vfork_parent = NULL;

      gdb_assert (current_program_space == inf->pspace);

      if (non_stop && resume_parent != -1)
        {
          /* If the user wanted the parent to be running, let it go
             free now.  */
          struct cleanup *old_chain = make_cleanup_restore_current_thread ();

          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: resuming vfork parent process %d\n",
                                resume_parent);

          iterate_over_threads (proceed_after_vfork_done, &resume_parent);

          do_cleanups (old_chain);
        }
    }
}

/* Enum strings for "set|show follow-exec-mode".  */

static const char follow_exec_mode_new[] = "new";
static const char follow_exec_mode_same[] = "same";
static const char *const follow_exec_mode_names[] =
{
  follow_exec_mode_new,
  follow_exec_mode_same,
  NULL,
};

static const char *follow_exec_mode_string = follow_exec_mode_same;
static void
show_follow_exec_mode_string (struct ui_file *file, int from_tty,
                              struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Follow exec mode is \"%s\".\n"),  value);
}

/* EXECD_PATHNAME is assumed to be non-NULL.  */

static void
follow_exec (ptid_t pid, char *execd_pathname)
{
  struct thread_info *th = inferior_thread ();
  struct inferior *inf = current_inferior ();

  /* This is an exec event that we actually wish to pay attention to.
     Refresh our symbol table to the newly exec'd program, remove any
     momentary bp's, etc.

     If there are breakpoints, they aren't really inserted now,
     since the exec() transformed our inferior into a fresh set
     of instructions.

     We want to preserve symbolic breakpoints on the list, since
     we have hopes that they can be reset after the new a.out's
     symbol table is read.

     However, any "raw" breakpoints must be removed from the list
     (e.g., the solib bp's), since their address is probably invalid
     now.

     And, we DON'T want to call delete_breakpoints() here, since
     that may write the bp's "shadow contents" (the instruction
     value that was overwritten witha TRAP instruction).  Since
     we now have a new a.out, those shadow contents aren't valid.  */

  mark_breakpoints_out ();

  update_breakpoints_after_exec ();

  /* If there was one, it's gone now.  We cannot truly step-to-next
     statement through an exec().  */
  th->control.step_resume_breakpoint = NULL;
  th->control.exception_resume_breakpoint = NULL;
  th->control.single_step_breakpoints = NULL;
  th->control.step_range_start = 0;
  th->control.step_range_end = 0;

  /* The target reports the exec event to the main thread, even if
     some other thread does the exec, and even if the main thread was
     already stopped --- if debugging in non-stop mode, it's possible
     the user had the main thread held stopped in the previous image
     --- release it now.  This is the same behavior as step-over-exec
     with scheduler-locking on in all-stop mode.  */
  th->stop_requested = 0;

  /* What is this a.out's name?  */
  printf_unfiltered (_("%s is executing new program: %s\n"),
                     target_pid_to_str (inferior_ptid),
                     execd_pathname);

  /* We've followed the inferior through an exec.  Therefore, the
     inferior has essentially been killed & reborn.  */

  gdb_flush (gdb_stdout);

  breakpoint_init_inferior (inf_execd);

  if (gdb_sysroot && *gdb_sysroot)
    {
      char *name = alloca (strlen (gdb_sysroot)
                            + strlen (execd_pathname)
                            + 1);

      strcpy (name, gdb_sysroot);
      strcat (name, execd_pathname);
      execd_pathname = name;
    }

  /* Reset the shared library package.  This ensures that we get a
     shlib event when the child reaches "_start", at which point the
     dld will have had a chance to initialize the child.  */
  /* Also, loading a symbol file below may trigger symbol lookups, and
     we don't want those to be satisfied by the libraries of the
     previous incarnation of this process.  */
  no_shared_libraries (NULL, 0);

  if (follow_exec_mode_string == follow_exec_mode_new)
    {
      struct program_space *pspace;

      /* The user wants to keep the old inferior and program spaces
         around.  Create a new fresh one, and switch to it.  */

      inf = add_inferior (current_inferior ()->pid);
      pspace = add_program_space (maybe_new_address_space ());
      inf->pspace = pspace;
      inf->aspace = pspace->aspace;

      exit_inferior_num_silent (current_inferior ()->num);

      set_current_inferior (inf);
      set_current_program_space (pspace);
    }
  else
    {
      /* The old description may no longer be fit for the new image.
         E.g, a 64-bit process exec'ed a 32-bit process.  Clear the
         old description; we'll read a new one below.  No need to do
         this on "follow-exec-mode new", as the old inferior stays
         around (its description is later cleared/refetched on
         restart).  */
      target_clear_description ();
    }

  gdb_assert (current_program_space == inf->pspace);

  /* That a.out is now the one to use.  */
  exec_file_attach (execd_pathname, 0);

  /* SYMFILE_DEFER_BP_RESET is used as the proper displacement for PIE
     (Position Independent Executable) main symbol file will get applied by
     solib_create_inferior_hook below.  breakpoint_re_set would fail to insert
     the breakpoints with the zero displacement.  */

  symbol_file_add (execd_pathname,
                   (inf->symfile_flags
                    | SYMFILE_MAINLINE | SYMFILE_DEFER_BP_RESET),
                   NULL, 0);

  if ((inf->symfile_flags & SYMFILE_NO_READ) == 0)
    set_initial_language ();

  /* If the target can specify a description, read it.  Must do this
     after flipping to the new executable (because the target supplied
     description must be compatible with the executable's
     architecture, and the old executable may e.g., be 32-bit, while
     the new one 64-bit), and before anything involving memory or
     registers.  */
  target_find_description ();

  solib_create_inferior_hook (0);

  jit_inferior_created_hook ();

  breakpoint_re_set ();

  /* Reinsert all breakpoints.  (Those which were symbolic have
     been reset to the proper address in the new a.out, thanks
     to symbol_file_command...).  */
  insert_breakpoints ();

  /* The next resume of this inferior should bring it to the shlib
     startup breakpoints.  (If the user had also set bp's on
     "main" from the old (parent) process, then they'll auto-
     matically get reset there in the new process.).  */
}

/* Info about an instruction that is being stepped over.  */

struct step_over_info
{
  /* If we're stepping past a breakpoint, this is the address space
     and address of the instruction the breakpoint is set at.  We'll
     skip inserting all breakpoints here.  Valid iff ASPACE is
     non-NULL.  */
  struct address_space *aspace;
  CORE_ADDR address;

  /* The instruction being stepped over triggers a nonsteppable
     watchpoint.  If true, we'll skip inserting watchpoints.  */
  int nonsteppable_watchpoint_p;
};

/* The step-over info of the location that is being stepped over.

   Note that with async/breakpoint always-inserted mode, a user might
   set a new breakpoint/watchpoint/etc. exactly while a breakpoint is
   being stepped over.  As setting a new breakpoint inserts all
   breakpoints, we need to make sure the breakpoint being stepped over
   isn't inserted then.  We do that by only clearing the step-over
   info when the step-over is actually finished (or aborted).

   Presently GDB can only step over one breakpoint at any given time.
   Given threads that can't run code in the same address space as the
   breakpoint's can't really miss the breakpoint, GDB could be taught
   to step-over at most one breakpoint per address space (so this info
   could move to the address space object if/when GDB is extended).
   The set of breakpoints being stepped over will normally be much
   smaller than the set of all breakpoints, so a flag in the
   breakpoint location structure would be wasteful.  A separate list
   also saves complexity and run-time, as otherwise we'd have to go
   through all breakpoint locations clearing their flag whenever we
   start a new sequence.  Similar considerations weigh against storing
   this info in the thread object.  Plus, not all step overs actually
   have breakpoint locations -- e.g., stepping past a single-step
   breakpoint, or stepping to complete a non-continuable
   watchpoint.  */
static struct step_over_info step_over_info;

/* Record the address of the breakpoint/instruction we're currently
   stepping over.  */

static void
set_step_over_info (struct address_space *aspace, CORE_ADDR address,
                    int nonsteppable_watchpoint_p)
{
  step_over_info.aspace = aspace;
  step_over_info.address = address;
  step_over_info.nonsteppable_watchpoint_p = nonsteppable_watchpoint_p;
}

/* Called when we're not longer stepping over a breakpoint / an
   instruction, so all breakpoints are free to be (re)inserted.  */

static void
clear_step_over_info (void)
{
  step_over_info.aspace = NULL;
  step_over_info.address = 0;
  step_over_info.nonsteppable_watchpoint_p = 0;
}

/* See infrun.h.  */

int
stepping_past_instruction_at (struct address_space *aspace,
                              CORE_ADDR address)
{
  return (step_over_info.aspace != NULL
          && breakpoint_address_match (aspace, address,
                                       step_over_info.aspace,
                                       step_over_info.address));
}

/* See infrun.h.  */

int
stepping_past_nonsteppable_watchpoint (void)
{
  return step_over_info.nonsteppable_watchpoint_p;
}

/* Returns true if step-over info is valid.  */

static int
step_over_info_valid_p (void)
{
  return (step_over_info.aspace != NULL
          || stepping_past_nonsteppable_watchpoint ());
}

\f
/* Displaced stepping.  */

/* In non-stop debugging mode, we must take special care to manage
   breakpoints properly; in particular, the traditional strategy for
   stepping a thread past a breakpoint it has hit is unsuitable.
   'Displaced stepping' is a tactic for stepping one thread past a
   breakpoint it has hit while ensuring that other threads running
   concurrently will hit the breakpoint as they should.

   The traditional way to step a thread T off a breakpoint in a
   multi-threaded program in all-stop mode is as follows:

   a0) Initially, all threads are stopped, and breakpoints are not
       inserted.
   a1) We single-step T, leaving breakpoints uninserted.
   a2) We insert breakpoints, and resume all threads.

   In non-stop debugging, however, this strategy is unsuitable: we
   don't want to have to stop all threads in the system in order to
   continue or step T past a breakpoint.  Instead, we use displaced
   stepping:

   n0) Initially, T is stopped, other threads are running, and
       breakpoints are inserted.
   n1) We copy the instruction "under" the breakpoint to a separate
       location, outside the main code stream, making any adjustments
       to the instruction, register, and memory state as directed by
       T's architecture.
   n2) We single-step T over the instruction at its new location.
   n3) We adjust the resulting register and memory state as directed
       by T's architecture.  This includes resetting T's PC to point
       back into the main instruction stream.
   n4) We resume T.

   This approach depends on the following gdbarch methods:

   - gdbarch_max_insn_length and gdbarch_displaced_step_location
     indicate where to copy the instruction, and how much space must
     be reserved there.  We use these in step n1.

   - gdbarch_displaced_step_copy_insn copies a instruction to a new
     address, and makes any necessary adjustments to the instruction,
     register contents, and memory.  We use this in step n1.

   - gdbarch_displaced_step_fixup adjusts registers and memory after
     we have successfuly single-stepped the instruction, to yield the
     same effect the instruction would have had if we had executed it
     at its original address.  We use this in step n3.

   - gdbarch_displaced_step_free_closure provides cleanup.

   The gdbarch_displaced_step_copy_insn and
   gdbarch_displaced_step_fixup functions must be written so that
   copying an instruction with gdbarch_displaced_step_copy_insn,
   single-stepping across the copied instruction, and then applying
   gdbarch_displaced_insn_fixup should have the same effects on the
   thread's memory and registers as stepping the instruction in place
   would have.  Exactly which responsibilities fall to the copy and
   which fall to the fixup is up to the author of those functions.

   See the comments in gdbarch.sh for details.

   Note that displaced stepping and software single-step cannot
   currently be used in combination, although with some care I think
   they could be made to.  Software single-step works by placing
   breakpoints on all possible subsequent instructions; if the
   displaced instruction is a PC-relative jump, those breakpoints
   could fall in very strange places --- on pages that aren't
   executable, or at addresses that are not proper instruction
   boundaries.  (We do generally let other threads run while we wait
   to hit the software single-step breakpoint, and they might
   encounter such a corrupted instruction.)  One way to work around
   this would be to have gdbarch_displaced_step_copy_insn fully
   simulate the effect of PC-relative instructions (and return NULL)
   on architectures that use software single-stepping.

   In non-stop mode, we can have independent and simultaneous step
   requests, so more than one thread may need to simultaneously step
   over a breakpoint.  The current implementation assumes there is
   only one scratch space per process.  In this case, we have to
   serialize access to the scratch space.  If thread A wants to step
   over a breakpoint, but we are currently waiting for some other
   thread to complete a displaced step, we leave thread A stopped and
   place it in the displaced_step_request_queue.  Whenever a displaced
   step finishes, we pick the next thread in the queue and start a new
   displaced step operation on it.  See displaced_step_prepare and
   displaced_step_fixup for details.  */

struct displaced_step_request
{
  ptid_t ptid;
  struct displaced_step_request *next;
};

/* Per-inferior displaced stepping state.  */
struct displaced_step_inferior_state
{
  /* Pointer to next in linked list.  */
  struct displaced_step_inferior_state *next;

  /* The process this displaced step state refers to.  */
  int pid;

  /* A queue of pending displaced stepping requests.  One entry per
     thread that needs to do a displaced step.  */
  struct displaced_step_request *step_request_queue;

  /* If this is not null_ptid, this is the thread carrying out a
     displaced single-step in process PID.  This thread's state will
     require fixing up once it has completed its step.  */
  ptid_t step_ptid;

  /* The architecture the thread had when we stepped it.  */
  struct gdbarch *step_gdbarch;

  /* The closure provided gdbarch_displaced_step_copy_insn, to be used
     for post-step cleanup.  */
  struct displaced_step_closure *step_closure;

  /* The address of the original instruction, and the copy we
     made.  */
  CORE_ADDR step_original, step_copy;

  /* Saved contents of copy area.  */
  gdb_byte *step_saved_copy;
};

/* The list of states of processes involved in displaced stepping
   presently.  */
static struct displaced_step_inferior_state *displaced_step_inferior_states;

/* Get the displaced stepping state of process PID.  */

static struct displaced_step_inferior_state *
get_displaced_stepping_state (int pid)
{
  struct displaced_step_inferior_state *state;

  for (state = displaced_step_inferior_states;
       state != NULL;
       state = state->next)
    if (state->pid == pid)
      return state;

  return NULL;
}

/* Add a new displaced stepping state for process PID to the displaced
   stepping state list, or return a pointer to an already existing
   entry, if it already exists.  Never returns NULL.  */

static struct displaced_step_inferior_state *
add_displaced_stepping_state (int pid)
{
  struct displaced_step_inferior_state *state;

  for (state = displaced_step_inferior_states;
       state != NULL;
       state = state->next)
    if (state->pid == pid)
      return state;

  state = xcalloc (1, sizeof (*state));
  state->pid = pid;
  state->next = displaced_step_inferior_states;
  displaced_step_inferior_states = state;

  return state;
}

/* If inferior is in displaced stepping, and ADDR equals to starting address
   of copy area, return corresponding displaced_step_closure.  Otherwise,
   return NULL.  */

struct displaced_step_closure*
get_displaced_step_closure_by_addr (CORE_ADDR addr)
{
  struct displaced_step_inferior_state *displaced
    = get_displaced_stepping_state (ptid_get_pid (inferior_ptid));

  /* If checking the mode of displaced instruction in copy area.  */
  if (displaced && !ptid_equal (displaced->step_ptid, null_ptid)
     && (displaced->step_copy == addr))
    return displaced->step_closure;

  return NULL;
}

/* Remove the displaced stepping state of process PID.  */

static void
remove_displaced_stepping_state (int pid)
{
  struct displaced_step_inferior_state *it, **prev_next_p;

  gdb_assert (pid != 0);

  it = displaced_step_inferior_states;
  prev_next_p = &displaced_step_inferior_states;
  while (it)
    {
      if (it->pid == pid)
        {
          *prev_next_p = it->next;
          xfree (it);
          return;
        }

      prev_next_p = &it->next;
      it = *prev_next_p;
    }
}

static void
infrun_inferior_exit (struct inferior *inf)
{
  remove_displaced_stepping_state (inf->pid);
}

/* If ON, and the architecture supports it, GDB will use displaced
   stepping to step over breakpoints.  If OFF, or if the architecture
   doesn't support it, GDB will instead use the traditional
   hold-and-step approach.  If AUTO (which is the default), GDB will
   decide which technique to use to step over breakpoints depending on
   which of all-stop or non-stop mode is active --- displaced stepping
   in non-stop mode; hold-and-step in all-stop mode.  */

static enum auto_boolean can_use_displaced_stepping = AUTO_BOOLEAN_AUTO;

static void
show_can_use_displaced_stepping (struct ui_file *file, int from_tty,
                                 struct cmd_list_element *c,
                                 const char *value)
{
  if (can_use_displaced_stepping == AUTO_BOOLEAN_AUTO)
    fprintf_filtered (file,
                      _("Debugger's willingness to use displaced stepping "
                        "to step over breakpoints is %s (currently %s).\n"),
                      value, non_stop ? "on" : "off");
  else
    fprintf_filtered (file,
                      _("Debugger's willingness to use displaced stepping "
                        "to step over breakpoints is %s.\n"), value);
}

/* Return non-zero if displaced stepping can/should be used to step
   over breakpoints.  */

static int
use_displaced_stepping (struct gdbarch *gdbarch)
{
  return (((can_use_displaced_stepping == AUTO_BOOLEAN_AUTO && non_stop)
           || can_use_displaced_stepping == AUTO_BOOLEAN_TRUE)
          && gdbarch_displaced_step_copy_insn_p (gdbarch)
          && find_record_target () == NULL);
}

/* Clean out any stray displaced stepping state.  */
static void
displaced_step_clear (struct displaced_step_inferior_state *displaced)
{
  /* Indicate that there is no cleanup pending.  */
  displaced->step_ptid = null_ptid;

  if (displaced->step_closure)
    {
      gdbarch_displaced_step_free_closure (displaced->step_gdbarch,
                                           displaced->step_closure);
      displaced->step_closure = NULL;
    }
}

static void
displaced_step_clear_cleanup (void *arg)
{
  struct displaced_step_inferior_state *state = arg;

  displaced_step_clear (state);
}

/* Dump LEN bytes at BUF in hex to FILE, followed by a newline.  */
void
displaced_step_dump_bytes (struct ui_file *file,
                           const gdb_byte *buf,
                           size_t len)
{
  int i;

  for (i = 0; i < len; i++)
    fprintf_unfiltered (file, "%02x ", buf[i]);
  fputs_unfiltered ("\n", file);
}

/* Prepare to single-step, using displaced stepping.

   Note that we cannot use displaced stepping when we have a signal to
   deliver.  If we have a signal to deliver and an instruction to step
   over, then after the step, there will be no indication from the
   target whether the thread entered a signal handler or ignored the
   signal and stepped over the instruction successfully --- both cases
   result in a simple SIGTRAP.  In the first case we mustn't do a
   fixup, and in the second case we must --- but we can't tell which.
   Comments in the code for 'random signals' in handle_inferior_event
   explain how we handle this case instead.

   Returns 1 if preparing was successful -- this thread is going to be
   stepped now; or 0 if displaced stepping this thread got queued.  */
static int
displaced_step_prepare (ptid_t ptid)
{
  struct cleanup *old_cleanups, *ignore_cleanups;
  struct thread_info *tp = find_thread_ptid (ptid);
  struct regcache *regcache = get_thread_regcache (ptid);
  struct gdbarch *gdbarch = get_regcache_arch (regcache);
  CORE_ADDR original, copy;
  ULONGEST len;
  struct displaced_step_closure *closure;
  struct displaced_step_inferior_state *displaced;
  int status;

  /* We should never reach this function if the architecture does not
     support displaced stepping.  */
  gdb_assert (gdbarch_displaced_step_copy_insn_p (gdbarch));

  /* Disable range stepping while executing in the scratch pad.  We
     want a single-step even if executing the displaced instruction in
     the scratch buffer lands within the stepping range (e.g., a
     jump/branch).  */
  tp->control.may_range_step = 0;

  /* We have to displaced step one thread at a time, as we only have
     access to a single scratch space per inferior.  */

  displaced = add_displaced_stepping_state (ptid_get_pid (ptid));

  if (!ptid_equal (displaced->step_ptid, null_ptid))
    {
      /* Already waiting for a displaced step to finish.  Defer this
         request and place in queue.  */
      struct displaced_step_request *req, *new_req;

      if (debug_displaced)
        fprintf_unfiltered (gdb_stdlog,
                            "displaced: defering step of %s\n",
                            target_pid_to_str (ptid));

      new_req = xmalloc (sizeof (*new_req));
      new_req->ptid = ptid;
      new_req->next = NULL;

      if (displaced->step_request_queue)
        {
          for (req = displaced->step_request_queue;
               req && req->next;
               req = req->next)
            ;
          req->next = new_req;
        }
      else
        displaced->step_request_queue = new_req;

      return 0;
    }
  else
    {
      if (debug_displaced)
        fprintf_unfiltered (gdb_stdlog,
                            "displaced: stepping %s now\n",
                            target_pid_to_str (ptid));
    }

  displaced_step_clear (displaced);

  old_cleanups = save_inferior_ptid ();
  inferior_ptid = ptid;

  original = regcache_read_pc (regcache);

  copy = gdbarch_displaced_step_location (gdbarch);
  len = gdbarch_max_insn_length (gdbarch);

  /* Save the original contents of the copy area.  */
  displaced->step_saved_copy = xmalloc (len);
  ignore_cleanups = make_cleanup (free_current_contents,
                                  &displaced->step_saved_copy);
  status = target_read_memory (copy, displaced->step_saved_copy, len);
  if (status != 0)
    throw_error (MEMORY_ERROR,
                 _("Error accessing memory address %s (%s) for "
                   "displaced-stepping scratch space."),
                 paddress (gdbarch, copy), safe_strerror (status));
  if (debug_displaced)
    {
      fprintf_unfiltered (gdb_stdlog, "displaced: saved %s: ",
                          paddress (gdbarch, copy));
      displaced_step_dump_bytes (gdb_stdlog,
                                 displaced->step_saved_copy,
                                 len);
    };

  closure = gdbarch_displaced_step_copy_insn (gdbarch,
                                              original, copy, regcache);

  /* We don't support the fully-simulated case at present.  */
  gdb_assert (closure);

  /* Save the information we need to fix things up if the step
     succeeds.  */
  displaced->step_ptid = ptid;
  displaced->step_gdbarch = gdbarch;
  displaced->step_closure = closure;
  displaced->step_original = original;
  displaced->step_copy = copy;

  make_cleanup (displaced_step_clear_cleanup, displaced);

  /* Resume execution at the copy.  */
  regcache_write_pc (regcache, copy);

  discard_cleanups (ignore_cleanups);

  do_cleanups (old_cleanups);

  if (debug_displaced)
    fprintf_unfiltered (gdb_stdlog, "displaced: displaced pc to %s\n",
                        paddress (gdbarch, copy));

  return 1;
}

static void
write_memory_ptid (ptid_t ptid, CORE_ADDR memaddr,
                   const gdb_byte *myaddr, int len)
{
  struct cleanup *ptid_cleanup = save_inferior_ptid ();

  inferior_ptid = ptid;
  write_memory (memaddr, myaddr, len);
  do_cleanups (ptid_cleanup);
}

/* Restore the contents of the copy area for thread PTID.  */

static void
displaced_step_restore (struct displaced_step_inferior_state *displaced,
                        ptid_t ptid)
{
  ULONGEST len = gdbarch_max_insn_length (displaced->step_gdbarch);

  write_memory_ptid (ptid, displaced->step_copy,
                     displaced->step_saved_copy, len);
  if (debug_displaced)
    fprintf_unfiltered (gdb_stdlog, "displaced: restored %s %s\n",
                        target_pid_to_str (ptid),
                        paddress (displaced->step_gdbarch,
                                  displaced->step_copy));
}

static void
displaced_step_fixup (ptid_t event_ptid, enum gdb_signal signal)
{
  struct cleanup *old_cleanups;
  struct displaced_step_inferior_state *displaced
    = get_displaced_stepping_state (ptid_get_pid (event_ptid));

  /* Was any thread of this process doing a displaced step?  */
  if (displaced == NULL)
    return;

  /* Was this event for the pid we displaced?  */
  if (ptid_equal (displaced->step_ptid, null_ptid)
      || ! ptid_equal (displaced->step_ptid, event_ptid))
    return;

  old_cleanups = make_cleanup (displaced_step_clear_cleanup, displaced);

  displaced_step_restore (displaced, displaced->step_ptid);

  /* Did the instruction complete successfully?  */
  if (signal == GDB_SIGNAL_TRAP)
    {
      /* Fix up the resulting state.  */
      gdbarch_displaced_step_fixup (displaced->step_gdbarch,
                                    displaced->step_closure,
                                    displaced->step_original,
                                    displaced->step_copy,
                                    get_thread_regcache (displaced->step_ptid));
    }
  else
    {
      /* Since the instruction didn't complete, all we can do is
         relocate the PC.  */
      struct regcache *regcache = get_thread_regcache (event_ptid);
      CORE_ADDR pc = regcache_read_pc (regcache);

      pc = displaced->step_original + (pc - displaced->step_copy);
      regcache_write_pc (regcache, pc);
    }

  do_cleanups (old_cleanups);

  displaced->step_ptid = null_ptid;

  /* Are there any pending displaced stepping requests?  If so, run
     one now.  Leave the state object around, since we're likely to
     need it again soon.  */
  while (displaced->step_request_queue)
    {
      struct displaced_step_request *head;
      ptid_t ptid;
      struct regcache *regcache;
      struct gdbarch *gdbarch;
      CORE_ADDR actual_pc;
      struct address_space *aspace;

      head = displaced->step_request_queue;
      ptid = head->ptid;
      displaced->step_request_queue = head->next;
      xfree (head);

      context_switch (ptid);

      regcache = get_thread_regcache (ptid);
      actual_pc = regcache_read_pc (regcache);
      aspace = get_regcache_aspace (regcache);

      if (breakpoint_here_p (aspace, actual_pc))
        {
          if (debug_displaced)
            fprintf_unfiltered (gdb_stdlog,
                                "displaced: stepping queued %s now\n",
                                target_pid_to_str (ptid));

          displaced_step_prepare (ptid);

          gdbarch = get_regcache_arch (regcache);

          if (debug_displaced)
            {
              CORE_ADDR actual_pc = regcache_read_pc (regcache);
              gdb_byte buf[4];

              fprintf_unfiltered (gdb_stdlog, "displaced: run %s: ",
                                  paddress (gdbarch, actual_pc));
              read_memory (actual_pc, buf, sizeof (buf));
              displaced_step_dump_bytes (gdb_stdlog, buf, sizeof (buf));
            }

          if (gdbarch_displaced_step_hw_singlestep (gdbarch,
                                                    displaced->step_closure))
            target_resume (ptid, 1, GDB_SIGNAL_0);
          else
            target_resume (ptid, 0, GDB_SIGNAL_0);

          /* Done, we're stepping a thread.  */
          break;
        }
      else
        {
          int step;
          struct thread_info *tp = inferior_thread ();

          /* The breakpoint we were sitting under has since been
             removed.  */
          tp->control.trap_expected = 0;

          /* Go back to what we were trying to do.  */
          step = currently_stepping (tp);

          if (debug_displaced)
            fprintf_unfiltered (gdb_stdlog,
                                "displaced: breakpoint is gone: %s, step(%d)\n",
                                target_pid_to_str (tp->ptid), step);

          target_resume (ptid, step, GDB_SIGNAL_0);
          tp->suspend.stop_signal = GDB_SIGNAL_0;

          /* This request was discarded.  See if there's any other
             thread waiting for its turn.  */
        }
    }
}

/* Update global variables holding ptids to hold NEW_PTID if they were
   holding OLD_PTID.  */
static void
infrun_thread_ptid_changed (ptid_t old_ptid, ptid_t new_ptid)
{
  struct displaced_step_request *it;
  struct displaced_step_inferior_state *displaced;

  if (ptid_equal (inferior_ptid, old_ptid))
    inferior_ptid = new_ptid;

  for (displaced = displaced_step_inferior_states;
       displaced;
       displaced = displaced->next)
    {
      if (ptid_equal (displaced->step_ptid, old_ptid))
        displaced->step_ptid = new_ptid;

      for (it = displaced->step_request_queue; it; it = it->next)
        if (ptid_equal (it->ptid, old_ptid))
          it->ptid = new_ptid;
    }
}

\f
/* Resuming.  */

/* Things to clean up if we QUIT out of resume ().  */
static void
resume_cleanups (void *ignore)
{
  if (!ptid_equal (inferior_ptid, null_ptid))
    delete_single_step_breakpoints (inferior_thread ());

  normal_stop ();
}

static const char schedlock_off[] = "off";
static const char schedlock_on[] = "on";
static const char schedlock_step[] = "step";
static const char *const scheduler_enums[] = {
  schedlock_off,
  schedlock_on,
  schedlock_step,
  NULL
};
static const char *scheduler_mode = schedlock_off;
static void
show_scheduler_mode (struct ui_file *file, int from_tty,
                     struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file,
                    _("Mode for locking scheduler "
                      "during execution is \"%s\".\n"),
                    value);
}

static void
set_schedlock_func (char *args, int from_tty, struct cmd_list_element *c)
{
  if (!target_can_lock_scheduler)
    {
      scheduler_mode = schedlock_off;
      error (_("Target '%s' cannot support this command."), target_shortname);
    }
}

/* True if execution commands resume all threads of all processes by
   default; otherwise, resume only threads of the current inferior
   process.  */
int sched_multi = 0;

/* Try to setup for software single stepping over the specified location.
   Return 1 if target_resume() should use hardware single step.

   GDBARCH the current gdbarch.
   PC the location to step over.  */

static int
maybe_software_singlestep (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  int hw_step = 1;

  if (execution_direction == EXEC_FORWARD
      && gdbarch_software_single_step_p (gdbarch)
      && gdbarch_software_single_step (gdbarch, get_current_frame ()))
    {
      hw_step = 0;
    }
  return hw_step;
}

ptid_t
user_visible_resume_ptid (int step)
{
  /* By default, resume all threads of all processes.  */
  ptid_t resume_ptid = RESUME_ALL;

  /* Maybe resume only all threads of the current process.  */
  if (!sched_multi && target_supports_multi_process ())
    {
      resume_ptid = pid_to_ptid (ptid_get_pid (inferior_ptid));
    }

  /* Maybe resume a single thread after all.  */
  if (non_stop)
    {
      /* With non-stop mode on, threads are always handled
         individually.  */
      resume_ptid = inferior_ptid;
    }
  else if ((scheduler_mode == schedlock_on)
           || (scheduler_mode == schedlock_step && step))
    {
      /* User-settable 'scheduler' mode requires solo thread resume.  */
      resume_ptid = inferior_ptid;
    }

  /* We may actually resume fewer threads at first, e.g., if a thread
     is stopped at a breakpoint that needs stepping-off, but that
     should not be visible to the user/frontend, and neither should
     the frontend/user be allowed to proceed any of the threads that
     happen to be stopped for internal run control handling, if a
     previous command wanted them resumed.  */
  return resume_ptid;
}

/* 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 (int step, enum gdb_signal sig)
{
  struct cleanup *old_cleanups = make_cleanup (resume_cleanups, 0);
  struct regcache *regcache = get_current_regcache ();
  struct gdbarch *gdbarch = get_regcache_arch (regcache);
  struct thread_info *tp = inferior_thread ();
  CORE_ADDR pc = regcache_read_pc (regcache);
  struct address_space *aspace = get_regcache_aspace (regcache);
  ptid_t resume_ptid;
  /* From here on, this represents the caller's step vs continue
     request, while STEP represents what we'll actually request the
     target to do.  STEP can decay from a step to a continue, if e.g.,
     we need to implement single-stepping with breakpoints (software
     single-step).  When deciding whether "set scheduler-locking step"
     applies, it's the callers intention that counts.  */
  const int entry_step = step;

  QUIT;

  if (current_inferior ()->waiting_for_vfork_done)
    {
      /* Don't try to single-step a vfork parent that is waiting for
         the child to get out of the shared memory region (by exec'ing
         or exiting).  This is particularly important on software
         single-step archs, as the child process would trip on the
         software single step breakpoint inserted for the parent
         process.  Since the parent will not actually execute any
         instruction until the child is out of the shared region (such
         are vfork's semantics), it is safe to simply continue it.
         Eventually, we'll see a TARGET_WAITKIND_VFORK_DONE event for
         the parent, and tell it to `keep_going', which automatically
         re-sets it stepping.  */
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: resume : clear step\n");
      step = 0;
    }

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: resume (step=%d, signal=%s), "
                        "trap_expected=%d, current thread [%s] at %s\n",
                        step, gdb_signal_to_symbol_string (sig),
                        tp->control.trap_expected,
                        target_pid_to_str (inferior_ptid),
                        paddress (gdbarch, pc));

  /* Normally, by the time we reach `resume', the breakpoints are either
     removed or inserted, as appropriate.  The exception is if we're sitting
     at a permanent breakpoint; we need to step over it, but permanent
     breakpoints can't be removed.  So we have to test for it here.  */
  if (breakpoint_here_p (aspace, pc) == permanent_breakpoint_here)
    {
      if (gdbarch_skip_permanent_breakpoint_p (gdbarch))
        gdbarch_skip_permanent_breakpoint (gdbarch, regcache);
      else
        error (_("\
The program is stopped at a permanent breakpoint, but GDB does not know\n\
how to step past a permanent breakpoint on this architecture.  Try using\n\
a command like `return' or `jump' to continue execution."));
    }

  /* If we have a breakpoint to step over, make sure to do a single
     step only.  Same if we have software watchpoints.  */
  if (tp->control.trap_expected || bpstat_should_step ())
    tp->control.may_range_step = 0;

  /* If enabled, step over breakpoints by executing a copy of the
     instruction at a different address.

     We can't use displaced stepping when we have a signal to deliver;
     the comments for displaced_step_prepare explain why.  The
     comments in the handle_inferior event for dealing with 'random
     signals' explain what we do instead.

     We can't use displaced stepping when we are waiting for vfork_done
     event, displaced stepping breaks the vfork child similarly as single
     step software breakpoint.  */
  if (use_displaced_stepping (gdbarch)
      && tp->control.trap_expected
      && sig == GDB_SIGNAL_0
      && !current_inferior ()->waiting_for_vfork_done)
    {
      struct displaced_step_inferior_state *displaced;

      if (!displaced_step_prepare (inferior_ptid))
        {
          /* Got placed in displaced stepping queue.  Will be resumed
             later when all the currently queued displaced stepping
             requests finish.  The thread is not executing at this
             point, and the call to set_executing will be made later.
             But we need to call set_running here, since from the
             user/frontend's point of view, threads were set running.
             Unless we're calling an inferior function, as in that
             case we pretend the inferior doesn't run at all.  */
          if (!tp->control.in_infcall)
            set_running (user_visible_resume_ptid (entry_step), 1);
          discard_cleanups (old_cleanups);
          return;
        }

      /* Update pc to reflect the new address from which we will execute
         instructions due to displaced stepping.  */
      pc = regcache_read_pc (get_thread_regcache (inferior_ptid));

      displaced = get_displaced_stepping_state (ptid_get_pid (inferior_ptid));
      step = gdbarch_displaced_step_hw_singlestep (gdbarch,
                                                   displaced->step_closure);
    }

  /* Do we need to do it the hard way, w/temp breakpoints?  */
  else if (step)
    step = maybe_software_singlestep (gdbarch, pc);

  /* Currently, our software single-step implementation leads to different
     results than hardware single-stepping in one situation: when stepping
     into delivering a signal which has an associated signal handler,
     hardware single-step will stop at the first instruction of the handler,
     while software single-step will simply skip execution of the handler.

     For now, this difference in behavior is accepted since there is no
     easy way to actually implement single-stepping into a signal handler
     without kernel support.

     However, there is one scenario where this difference leads to follow-on
     problems: if we're stepping off a breakpoint by removing all breakpoints
     and then single-stepping.  In this case, the software single-step
     behavior means that even if there is a *breakpoint* in the signal
     handler, GDB still would not stop.

     Fortunately, we can at least fix this particular issue.  We detect
     here the case where we are about to deliver a signal while software
     single-stepping with breakpoints removed.  In this situation, we
     revert the decisions to remove all breakpoints and insert single-
     step breakpoints, and instead we install a step-resume breakpoint
     at the current address, deliver the signal without stepping, and
     once we arrive back at the step-resume breakpoint, actually step
     over the breakpoint we originally wanted to step over.  */
  if (thread_has_single_step_breakpoints_set (tp)
      && sig != GDB_SIGNAL_0
      && step_over_info_valid_p ())
    {
      /* If we have nested signals or a pending signal is delivered
         immediately after a handler returns, might might already have
         a step-resume breakpoint set on the earlier handler.  We cannot
         set another step-resume breakpoint; just continue on until the
         original breakpoint is hit.  */
      if (tp->control.step_resume_breakpoint == NULL)
        {
          insert_hp_step_resume_breakpoint_at_frame (get_current_frame ());
          tp->step_after_step_resume_breakpoint = 1;
        }

      delete_single_step_breakpoints (tp);

      clear_step_over_info ();
      tp->control.trap_expected = 0;

      insert_breakpoints ();
    }

  /* If STEP is set, it's a request to use hardware stepping
     facilities.  But in that case, we should never
     use singlestep breakpoint.  */
  gdb_assert (!(thread_has_single_step_breakpoints_set (tp) && step));

  /* Decide the set of threads to ask the target to resume.  Start
     by assuming everything will be resumed, than narrow the set
     by applying increasingly restricting conditions.  */
  resume_ptid = user_visible_resume_ptid (entry_step);

  /* Even if RESUME_PTID is a wildcard, and we end up resuming less
     (e.g., we might need to step over a breakpoint), from the
     user/frontend's point of view, all threads in RESUME_PTID are now
     running.  Unless we're calling an inferior function, as in that
     case pretend we inferior doesn't run at all.  */
  if (!tp->control.in_infcall)
    set_running (resume_ptid, 1);

  /* Maybe resume a single thread after all.  */
  if ((step || thread_has_single_step_breakpoints_set (tp))
      && tp->control.trap_expected)
    {
      /* We're allowing a thread to run past a breakpoint it has
         hit, by single-stepping the thread with the breakpoint
         removed.  In which case, we need to single-step only this
         thread, and keep others stopped, as they can miss this
         breakpoint if allowed to run.  */
      resume_ptid = inferior_ptid;
    }

  if (execution_direction != EXEC_REVERSE
      && step && breakpoint_inserted_here_p (aspace, pc))
    {
      /* The only case we currently need to step a breakpoint
         instruction is when we have a signal to deliver.  See
         handle_signal_stop where we handle random signals that could
         take out us out of the stepping range.  Normally, in that
         case we end up continuing (instead of stepping) over the
         signal handler with a breakpoint at PC, but there are cases
         where we should _always_ single-step, even if we have a
         step-resume breakpoint, like when a software watchpoint is
         set.  Assuming single-stepping and delivering a signal at the
         same time would takes us to the signal handler, then we could
         have removed the breakpoint at PC to step over it.  However,
         some hardware step targets (like e.g., Mac OS) can't step
         into signal handlers, and for those, we need to leave the
         breakpoint at PC inserted, as otherwise if the handler
         recurses and executes PC again, it'll miss the breakpoint.
         So we leave the breakpoint inserted anyway, but we need to
         record that we tried to step a breakpoint instruction, so
         that adjust_pc_after_break doesn't end up confused.  */
      gdb_assert (sig != GDB_SIGNAL_0);

      tp->stepped_breakpoint = 1;

      /* 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 (gdbarch_cannot_step_breakpoint (gdbarch))
        step = 0;
    }

  if (debug_displaced
      && use_displaced_stepping (gdbarch)
      && tp->control.trap_expected)
    {
      struct regcache *resume_regcache = get_thread_regcache (resume_ptid);
      struct gdbarch *resume_gdbarch = get_regcache_arch (resume_regcache);
      CORE_ADDR actual_pc = regcache_read_pc (resume_regcache);
      gdb_byte buf[4];

      fprintf_unfiltered (gdb_stdlog, "displaced: run %s: ",
                          paddress (resume_gdbarch, actual_pc));
      read_memory (actual_pc, buf, sizeof (buf));
      displaced_step_dump_bytes (gdb_stdlog, buf, sizeof (buf));
    }

  if (tp->control.may_range_step)
    {
      /* If we're resuming a thread with the PC out of the step
         range, then we're doing some nested/finer run control
         operation, like stepping the thread out of the dynamic
         linker or the displaced stepping scratch pad.  We
         shouldn't have allowed a range step then.  */
      gdb_assert (pc_in_thread_step_range (pc, tp));
    }

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

  /* Avoid confusing the next resume, if the next stop/resume
     happens to apply to another thread.  */
  tp->suspend.stop_signal = GDB_SIGNAL_0;

  /* Advise target which signals may be handled silently.  If we have
     removed breakpoints because we are stepping over one (in any
     thread), we need to receive all signals to avoid accidentally
     skipping a breakpoint during execution of a signal handler.  */
  if (step_over_info_valid_p ())
    target_pass_signals (0, NULL);
  else
    target_pass_signals ((int) GDB_SIGNAL_LAST, signal_pass);

  target_resume (resume_ptid, step, sig);

  discard_cleanups (old_cleanups);
}
\f
/* Proceeding.  */

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

static void
clear_proceed_status_thread (struct thread_info *tp)
{
  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: clear_proceed_status_thread (%s)\n",
                        target_pid_to_str (tp->ptid));

  /* If this signal should not be seen by program, give it zero.
     Used for debugging signals.  */
  if (!signal_pass_state (tp->suspend.stop_signal))
    tp->suspend.stop_signal = GDB_SIGNAL_0;

  tp->control.trap_expected = 0;
  tp->control.step_range_start = 0;
  tp->control.step_range_end = 0;
  tp->control.may_range_step = 0;
  tp->control.step_frame_id = null_frame_id;
  tp->control.step_stack_frame_id = null_frame_id;
  tp->control.step_over_calls = STEP_OVER_UNDEBUGGABLE;
  tp->stop_requested = 0;

  tp->control.stop_step = 0;

  tp->control.proceed_to_finish = 0;

  tp->control.command_interp = NULL;

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

void
clear_proceed_status (int step)
{
  if (!non_stop)
    {
      struct thread_info *tp;
      ptid_t resume_ptid;

      resume_ptid = user_visible_resume_ptid (step);

      /* In all-stop mode, delete the per-thread status of all threads
         we're about to resume, implicitly and explicitly.  */
      ALL_NON_EXITED_THREADS (tp)
        {
          if (!ptid_match (tp->ptid, resume_ptid))
            continue;
          clear_proceed_status_thread (tp);
        }
    }

  if (!ptid_equal (inferior_ptid, null_ptid))
    {
      struct inferior *inferior;

      if (non_stop)
        {
          /* If in non-stop mode, only delete the per-thread status of
             the current thread.  */
          clear_proceed_status_thread (inferior_thread ());
        }

      inferior = current_inferior ();
      inferior->control.stop_soon = NO_STOP_QUIETLY;
    }

  stop_after_trap = 0;

  clear_step_over_info ();

  observer_notify_about_to_proceed ();

  if (stop_registers)
    {
      regcache_xfree (stop_registers);
      stop_registers = NULL;
    }
}

/* Returns true if TP is still stopped at a breakpoint that needs
   stepping-over in order to make progress.  If the breakpoint is gone
   meanwhile, we can skip the whole step-over dance.  */

static int
thread_still_needs_step_over (struct thread_info *tp)
{
  if (tp->stepping_over_breakpoint)
    {
      struct regcache *regcache = get_thread_regcache (tp->ptid);

      if (breakpoint_here_p (get_regcache_aspace (regcache),
                             regcache_read_pc (regcache)))
        return 1;

      tp->stepping_over_breakpoint = 0;
    }

  return 0;
}

/* Returns true if scheduler locking applies.  STEP indicates whether
   we're about to do a step/next-like command to a thread.  */

static int
schedlock_applies (int step)
{
  return (scheduler_mode == schedlock_on
          || (scheduler_mode == schedlock_step
              && step));
}

/* Look a thread other than EXCEPT that has previously reported a
   breakpoint event, and thus needs a step-over in order to make
   progress.  Returns NULL is none is found.  STEP indicates whether
   we're about to step the current thread, in order to decide whether
   "set scheduler-locking step" applies.  */

static struct thread_info *
find_thread_needs_step_over (int step, struct thread_info *except)
{
  struct thread_info *tp, *current;

  /* With non-stop mode on, threads are always handled individually.  */
  gdb_assert (! non_stop);

  current = inferior_thread ();

  /* If scheduler locking applies, we can avoid iterating over all
     threads.  */
  if (schedlock_applies (step))
    {
      if (except != current
          && thread_still_needs_step_over (current))
        return current;

      return NULL;
    }

  ALL_NON_EXITED_THREADS (tp)
    {
      /* Ignore the EXCEPT thread.  */
      if (tp == except)
        continue;
      /* Ignore threads of processes we're not resuming.  */
      if (!sched_multi
          && ptid_get_pid (tp->ptid) != ptid_get_pid (inferior_ptid))
        continue;

      if (thread_still_needs_step_over (tp))
        return tp;
    }

  return NULL;
}

/* 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 (CORE_ADDR addr, enum gdb_signal siggnal, int step)
{
  struct regcache *regcache;
  struct gdbarch *gdbarch;
  struct thread_info *tp;
  CORE_ADDR pc;
  struct address_space *aspace;

  /* If we're stopped at a fork/vfork, follow the branch set by the
     "set follow-fork-mode" command; otherwise, we'll just proceed
     resuming the current thread.  */
  if (!follow_fork ())
    {
      /* The target for some reason decided not to resume.  */
      normal_stop ();
      if (target_can_async_p ())
        inferior_event_handler (INF_EXEC_COMPLETE, NULL);
      return;
    }

  /* We'll update this if & when we switch to a new thread.  */
  previous_inferior_ptid = inferior_ptid;

  regcache = get_current_regcache ();
  gdbarch = get_regcache_arch (regcache);
  aspace = get_regcache_aspace (regcache);
  pc = regcache_read_pc (regcache);
  tp = inferior_thread ();

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

  /* Fill in with reasonable starting values.  */
  init_thread_stepping_state (tp);

  if (addr == (CORE_ADDR) -1)
    {
      if (pc == stop_pc && breakpoint_here_p (aspace, pc)
          && execution_direction != EXEC_REVERSE)
        /* 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 (and report a second hit at this
           breakpoint).

           Note, we don't do this in reverse, because we won't
           actually be executing the breakpoint insn anyway.
           We'll be (un-)executing the previous instruction.  */
        tp->stepping_over_breakpoint = 1;
      else if (gdbarch_single_step_through_delay_p (gdbarch)
               && gdbarch_single_step_through_delay (gdbarch,
                                                     get_current_frame ()))
        /* We stepped onto an instruction that needs to be stepped
           again before re-inserting the breakpoint, do so.  */
        tp->stepping_over_breakpoint = 1;
    }
  else
    {
      regcache_write_pc (regcache, addr);
    }

  if (siggnal != GDB_SIGNAL_DEFAULT)
    tp->suspend.stop_signal = siggnal;

  /* Record the interpreter that issued the execution command that
     caused this thread to resume.  If the top level interpreter is
     MI/async, and the execution command was a CLI command
     (next/step/etc.), we'll want to print stop event output to the MI
     console channel (the stepped-to line, etc.), as if the user
     entered the execution command on a real GDB console.  */
  inferior_thread ()->control.command_interp = command_interp ();

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: proceed (addr=%s, signal=%s, step=%d)\n",
                        paddress (gdbarch, addr),
                        gdb_signal_to_symbol_string (siggnal), step);

  if (non_stop)
    /* In non-stop, each thread is handled individually.  The context
       must already be set to the right thread here.  */
    ;
  else
    {
      struct thread_info *step_over;

      /* In a multi-threaded task we may select another thread and
         then continue or step.

         But if the old thread was stopped at a breakpoint, it will
         immediately cause another breakpoint stop without any
         execution (i.e. it will report a breakpoint hit incorrectly).
         So we must step over it first.

         Look for a thread other than the current (TP) that reported a
         breakpoint hit and hasn't been resumed yet since.  */
      step_over = find_thread_needs_step_over (step, tp);
      if (step_over != NULL)
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: need to step-over [%s] first\n",
                                target_pid_to_str (step_over->ptid));

          /* Store the prev_pc for the stepping thread too, needed by
             switch_back_to_stepping thread.  */
          tp->prev_pc = regcache_read_pc (get_current_regcache ());
          switch_to_thread (step_over->ptid);
          tp = step_over;
        }
    }

  /* If we need to step over a breakpoint, and we're not using
     displaced stepping to do so, insert all breakpoints (watchpoints,
     etc.) but the one we're stepping over, step one instruction, and
     then re-insert the breakpoint when that step is finished.  */
  if (tp->stepping_over_breakpoint && !use_displaced_stepping (gdbarch))
    {
      struct regcache *regcache = get_current_regcache ();

      set_step_over_info (get_regcache_aspace (regcache),
                          regcache_read_pc (regcache), 0);
    }
  else
    clear_step_over_info ();

  insert_breakpoints ();

  tp->control.trap_expected = tp->stepping_over_breakpoint;

  annotate_starting ();

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

  /* Refresh prev_pc value just prior to resuming.  This used to be
     done in stop_waiting, however, setting prev_pc there did not handle
     scenarios such as inferior function calls or returning from
     a function via the return command.  In those cases, the prev_pc
     value was not set properly for subsequent commands.  The prev_pc value 
     is used to initialize the starting line number in the ecs.  With an 
     invalid value, the gdb next command ends up stopping at the position
     represented by the next line table entry past our start position.
     On platforms that generate one line table entry per line, this
     is not a problem.  However, on the ia64, the compiler generates
     extraneous line table entries that do not increase the line number.
     When we issue the gdb next command on the ia64 after an inferior call
     or a return command, we often end up a few instructions forward, still 
     within the original line we started.

     An attempt was made to refresh the prev_pc at the same time the
     execution_control_state is initialized (for instance, just before
     waiting for an inferior event).  But this approach did not work
     because of platforms that use ptrace, where the pc register cannot
     be read unless the inferior is stopped.  At that point, we are not
     guaranteed the inferior is stopped and so the regcache_read_pc() call
     can fail.  Setting the prev_pc value here ensures the value is updated
     correctly when the inferior is stopped.  */
  tp->prev_pc = regcache_read_pc (get_current_regcache ());

  /* Resume inferior.  */
  resume (tp->control.trap_expected || step || bpstat_should_step (),
          tp->suspend.stop_signal);

  /* Wait for it to stop (if not standalone)
     and in any case decode why it stopped, and act accordingly.  */
  /* Do this only if we are not using the event loop, or if the target
     does not support asynchronous execution.  */
  if (!target_can_async_p ())
    {
      wait_for_inferior ();
      normal_stop ();
    }
}
\f

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

void
start_remote (int from_tty)
{
  struct inferior *inferior;

  inferior = current_inferior ();
  inferior->control.stop_soon = STOP_QUIETLY_REMOTE;

  /* Always go on waiting for the target, regardless of the mode.  */
  /* FIXME: cagney/1999-09-23: At present it isn't possible to
     indicate to wait_for_inferior that a target should timeout if
     nothing is returned (instead of just blocking).  Because of this,
     targets expecting an immediate response need to, internally, set
     things up so that the target_wait() is forced to eventually
     timeout.  */
  /* FIXME: cagney/1999-09-24: It isn't possible for target_open() to
     differentiate to its caller what the state of the target is after
     the initial open has been performed.  Here we're assuming that
     the target has stopped.  It should be possible to eventually have
     target_open() return to the caller an indication that the target
     is currently running and GDB state should be set to the same as
     for an async run.  */
  wait_for_inferior ();

  /* Now that the inferior has stopped, do any bookkeeping like
     loading shared libraries.  We want to do this before normal_stop,
     so that the displayed frame is up to date.  */
  post_create_inferior (&current_target, from_tty);

  normal_stop ();
}

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

void
init_wait_for_inferior (void)
{
  /* These are meaningless until the first time through wait_for_inferior.  */

  breakpoint_init_inferior (inf_starting);

  clear_proceed_status (0);

  target_last_wait_ptid = minus_one_ptid;

  previous_inferior_ptid = inferior_ptid;

  /* Discard any skipped inlined frames.  */
  clear_inline_frame_state (minus_one_ptid);
}

\f
/* This enum encodes possible reasons for doing a target_wait, so that
   wfi can call target_wait in one place.  (Ultimately the call will be
   moved out of the infinite loop entirely.) */

enum infwait_states
{
  infwait_normal_state,
  infwait_step_watch_state,
  infwait_nonstep_watch_state
};

/* Current inferior wait state.  */
static enum infwait_states infwait_state;

/* Data to be passed around while handling an event.  This data is
   discarded between events.  */
struct execution_control_state
{
  ptid_t ptid;
  /* The thread that got the event, if this was a thread event; NULL
     otherwise.  */
  struct thread_info *event_thread;

  struct target_waitstatus ws;
  int stop_func_filled_in;
  CORE_ADDR stop_func_start;
  CORE_ADDR stop_func_end;
  const char *stop_func_name;
  int wait_some_more;

  /* True if the event thread hit the single-step breakpoint of
     another thread.  Thus the event doesn't cause a stop, the thread
     needs to be single-stepped past the single-step breakpoint before
     we can switch back to the original stepping thread.  */
  int hit_singlestep_breakpoint;
};

static void handle_inferior_event (struct execution_control_state *ecs);

static void handle_step_into_function (struct gdbarch *gdbarch,
                                       struct execution_control_state *ecs);
static void handle_step_into_function_backward (struct gdbarch *gdbarch,
                                                struct execution_control_state *ecs);
static void handle_signal_stop (struct execution_control_state *ecs);
static void check_exception_resume (struct execution_control_state *,
                                    struct frame_info *);

static void end_stepping_range (struct execution_control_state *ecs);
static void stop_waiting (struct execution_control_state *ecs);
static void prepare_to_wait (struct execution_control_state *ecs);
static void keep_going (struct execution_control_state *ecs);
static void process_event_stop_test (struct execution_control_state *ecs);
static int switch_back_to_stepped_thread (struct execution_control_state *ecs);

/* Callback for iterate over threads.  If the thread is stopped, but
   the user/frontend doesn't know about that yet, go through
   normal_stop, as if the thread had just stopped now.  ARG points at
   a ptid.  If PTID is MINUS_ONE_PTID, applies to all threads.  If
   ptid_is_pid(PTID) is true, applies to all threads of the process
   pointed at by PTID.  Otherwise, apply only to the thread pointed by
   PTID.  */

static int
infrun_thread_stop_requested_callback (struct thread_info *info, void *arg)
{
  ptid_t ptid = * (ptid_t *) arg;

  if ((ptid_equal (info->ptid, ptid)
       || ptid_equal (minus_one_ptid, ptid)
       || (ptid_is_pid (ptid)
           && ptid_get_pid (ptid) == ptid_get_pid (info->ptid)))
      && is_running (info->ptid)
      && !is_executing (info->ptid))
    {
      struct cleanup *old_chain;
      struct execution_control_state ecss;
      struct execution_control_state *ecs = &ecss;

      memset (ecs, 0, sizeof (*ecs));

      old_chain = make_cleanup_restore_current_thread ();

      overlay_cache_invalid = 1;
      /* Flush target cache before starting to handle each event.
         Target was running and cache could be stale.  This is just a
         heuristic.  Running threads may modify target memory, but we
         don't get any event.  */
      target_dcache_invalidate ();

      /* Go through handle_inferior_event/normal_stop, so we always
         have consistent output as if the stop event had been
         reported.  */
      ecs->ptid = info->ptid;
      ecs->event_thread = find_thread_ptid (info->ptid);
      ecs->ws.kind = TARGET_WAITKIND_STOPPED;
      ecs->ws.value.sig = GDB_SIGNAL_0;

      handle_inferior_event (ecs);

      if (!ecs->wait_some_more)
        {
          struct thread_info *tp;

          normal_stop ();

          /* Finish off the continuations.  */
          tp = inferior_thread ();
          do_all_intermediate_continuations_thread (tp, 1);
          do_all_continuations_thread (tp, 1);
        }

      do_cleanups (old_chain);
    }

  return 0;
}

/* This function is attached as a "thread_stop_requested" observer.
   Cleanup local state that assumed the PTID was to be resumed, and
   report the stop to the frontend.  */

static void
infrun_thread_stop_requested (ptid_t ptid)
{
  struct displaced_step_inferior_state *displaced;

  /* PTID was requested to stop.  Remove it from the displaced
     stepping queue, so we don't try to resume it automatically.  */

  for (displaced = displaced_step_inferior_states;
       displaced;
       displaced = displaced->next)
    {
      struct displaced_step_request *it, **prev_next_p;

      it = displaced->step_request_queue;
      prev_next_p = &displaced->step_request_queue;
      while (it)
        {
          if (ptid_match (it->ptid, ptid))
            {
              *prev_next_p = it->next;
              it->next = NULL;
              xfree (it);
            }
          else
            {
              prev_next_p = &it->next;
            }

          it = *prev_next_p;
        }
    }

  iterate_over_threads (infrun_thread_stop_requested_callback, &ptid);
}

static void
infrun_thread_thread_exit (struct thread_info *tp, int silent)
{
  if (ptid_equal (target_last_wait_ptid, tp->ptid))
    nullify_last_target_wait_ptid ();
}

/* Delete the step resume, single-step and longjmp/exception resume
   breakpoints of TP.  */

static void
delete_thread_infrun_breakpoints (struct thread_info *tp)
{
  delete_step_resume_breakpoint (tp);
  delete_exception_resume_breakpoint (tp);
  delete_single_step_breakpoints (tp);
}

/* If the target still has execution, call FUNC for each thread that
   just stopped.  In all-stop, that's all the non-exited threads; in
   non-stop, that's the current thread, only.  */

typedef void (*for_each_just_stopped_thread_callback_func)
  (struct thread_info *tp);

static void
for_each_just_stopped_thread (for_each_just_stopped_thread_callback_func func)
{
  if (!target_has_execution || ptid_equal (inferior_ptid, null_ptid))
    return;

  if (non_stop)
    {
      /* If in non-stop mode, only the current thread stopped.  */
      func (inferior_thread ());
    }
  else
    {
      struct thread_info *tp;

      /* In all-stop mode, all threads have stopped.  */
      ALL_NON_EXITED_THREADS (tp)
        {
          func (tp);
        }
    }
}

/* Delete the step resume and longjmp/exception resume breakpoints of
   the threads that just stopped.  */

static void
delete_just_stopped_threads_infrun_breakpoints (void)
{
  for_each_just_stopped_thread (delete_thread_infrun_breakpoints);
}

/* Delete the single-step breakpoints of the threads that just
   stopped.  */

static void
delete_just_stopped_threads_single_step_breakpoints (void)
{
  for_each_just_stopped_thread (delete_single_step_breakpoints);
}

/* A cleanup wrapper.  */

static void
delete_just_stopped_threads_infrun_breakpoints_cleanup (void *arg)
{
  delete_just_stopped_threads_infrun_breakpoints ();
}

/* Pretty print the results of target_wait, for debugging purposes.  */

static void
print_target_wait_results (ptid_t waiton_ptid, ptid_t result_ptid,
                           const struct target_waitstatus *ws)
{
  char *status_string = target_waitstatus_to_string (ws);
  struct ui_file *tmp_stream = mem_fileopen ();
  char *text;

  /* The text is split over several lines because it was getting too long.
     Call fprintf_unfiltered (gdb_stdlog) once so that the text is still
     output as a unit; we want only one timestamp printed if debug_timestamp
     is set.  */

  fprintf_unfiltered (tmp_stream,
                      "infrun: target_wait (%d", ptid_get_pid (waiton_ptid));
  if (ptid_get_pid (waiton_ptid) != -1)
    fprintf_unfiltered (tmp_stream,
                        " [%s]", target_pid_to_str (waiton_ptid));
  fprintf_unfiltered (tmp_stream, ", status) =\n");
  fprintf_unfiltered (tmp_stream,
                      "infrun:   %d [%s],\n",
                      ptid_get_pid (result_ptid),
                      target_pid_to_str (result_ptid));
  fprintf_unfiltered (tmp_stream,
                      "infrun:   %s\n",
                      status_string);

  text = ui_file_xstrdup (tmp_stream, NULL);

  /* This uses %s in part to handle %'s in the text, but also to avoid
     a gcc error: the format attribute requires a string literal.  */
  fprintf_unfiltered (gdb_stdlog, "%s", text);

  xfree (status_string);
  xfree (text);
  ui_file_delete (tmp_stream);
}

/* Prepare and stabilize the inferior for detaching it.  E.g.,
   detaching while a thread is displaced stepping is a recipe for
   crashing it, as nothing would readjust the PC out of the scratch
   pad.  */

void
prepare_for_detach (void)
{
  struct inferior *inf = current_inferior ();
  ptid_t pid_ptid = pid_to_ptid (inf->pid);
  struct cleanup *old_chain_1;
  struct displaced_step_inferior_state *displaced;

  displaced = get_displaced_stepping_state (inf->pid);

  /* Is any thread of this process displaced stepping?  If not,
     there's nothing else to do.  */
  if (displaced == NULL || ptid_equal (displaced->step_ptid, null_ptid))
    return;

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "displaced-stepping in-process while detaching");

  old_chain_1 = make_cleanup_restore_integer (&inf->detaching);
  inf->detaching = 1;

  while (!ptid_equal (displaced->step_ptid, null_ptid))
    {
      struct cleanup *old_chain_2;
      struct execution_control_state ecss;
      struct execution_control_state *ecs;

      ecs = &ecss;
      memset (ecs, 0, sizeof (*ecs));

      overlay_cache_invalid = 1;
      /* Flush target cache before starting to handle each event.
         Target was running and cache could be stale.  This is just a
         heuristic.  Running threads may modify target memory, but we
         don't get any event.  */
      target_dcache_invalidate ();

      if (deprecated_target_wait_hook)
        ecs->ptid = deprecated_target_wait_hook (pid_ptid, &ecs->ws, 0);
      else
        ecs->ptid = target_wait (pid_ptid, &ecs->ws, 0);

      if (debug_infrun)
        print_target_wait_results (pid_ptid, ecs->ptid, &ecs->ws);

      /* If an error happens while handling the event, propagate GDB's
         knowledge of the executing state to the frontend/user running
         state.  */
      old_chain_2 = make_cleanup (finish_thread_state_cleanup,
                                  &minus_one_ptid);

      /* Now figure out what to do with the result of the result.  */
      handle_inferior_event (ecs);

      /* No error, don't finish the state yet.  */
      discard_cleanups (old_chain_2);

      /* Breakpoints and watchpoints are not installed on the target
         at this point, and signals are passed directly to the
         inferior, so this must mean the process is gone.  */
      if (!ecs->wait_some_more)
        {
          discard_cleanups (old_chain_1);
          error (_("Program exited while detaching"));
        }
    }

  discard_cleanups (old_chain_1);
}

/* 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 (void)
{
  struct cleanup *old_cleanups;

  if (debug_infrun)
    fprintf_unfiltered
      (gdb_stdlog, "infrun: wait_for_inferior ()\n");

  old_cleanups
    = make_cleanup (delete_just_stopped_threads_infrun_breakpoints_cleanup,
                    NULL);

  while (1)
    {
      struct execution_control_state ecss;
      struct execution_control_state *ecs = &ecss;
      struct cleanup *old_chain;
      ptid_t waiton_ptid = minus_one_ptid;

      memset (ecs, 0, sizeof (*ecs));

      overlay_cache_invalid = 1;

      /* Flush target cache before starting to handle each event.
         Target was running and cache could be stale.  This is just a
         heuristic.  Running threads may modify target memory, but we
         don't get any event.  */
      target_dcache_invalidate ();

      if (deprecated_target_wait_hook)
        ecs->ptid = deprecated_target_wait_hook (waiton_ptid, &ecs->ws, 0);
      else
        ecs->ptid = target_wait (waiton_ptid, &ecs->ws, 0);

      if (debug_infrun)
        print_target_wait_results (waiton_ptid, ecs->ptid, &ecs->ws);

      /* If an error happens while handling the event, propagate GDB's
         knowledge of the executing state to the frontend/user running
         state.  */
      old_chain = make_cleanup (finish_thread_state_cleanup, &minus_one_ptid);

      /* Now figure out what to do with the result of the result.  */
      handle_inferior_event (ecs);

      /* No error, don't finish the state yet.  */
      discard_cleanups (old_chain);

      if (!ecs->wait_some_more)
        break;
    }

  do_cleanups (old_cleanups);
}

/* Cleanup that reinstalls the readline callback handler, if the
   target is running in the background.  If while handling the target
   event something triggered a secondary prompt, like e.g., a
   pagination prompt, we'll have removed the callback handler (see
   gdb_readline_wrapper_line).  Need to do this as we go back to the
   event loop, ready to process further input.  Note this has no
   effect if the handler hasn't actually been removed, because calling
   rl_callback_handler_install resets the line buffer, thus losing
   input.  */

static void
reinstall_readline_callback_handler_cleanup (void *arg)
{
  if (async_command_editing_p && !sync_execution)
    gdb_rl_callback_handler_reinstall ();
}

/* Asynchronous version of wait_for_inferior.  It is called by the
   event loop whenever a change of state is detected on the file
   descriptor corresponding to the target.  It can be called more than
   once to complete a single execution command.  In such cases we need
   to keep the state in a global variable ECSS.  If it is the last time
   that this function is called for a single execution command, then
   report to the user that the inferior has stopped, and do the
   necessary cleanups.  */

void
fetch_inferior_event (void *client_data)
{
  struct execution_control_state ecss;
  struct execution_control_state *ecs = &ecss;
  struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
  struct cleanup *ts_old_chain;
  int was_sync = sync_execution;
  int cmd_done = 0;
  ptid_t waiton_ptid = minus_one_ptid;

  memset (ecs, 0, sizeof (*ecs));

  /* End up with readline processing input, if necessary.  */
  make_cleanup (reinstall_readline_callback_handler_cleanup, NULL);

  /* We're handling a live event, so make sure we're doing live
     debugging.  If we're looking at traceframes while the target is
     running, we're going to need to get back to that mode after
     handling the event.  */
  if (non_stop)
    {
      make_cleanup_restore_current_traceframe ();
      set_current_traceframe (-1);
    }

  if (non_stop)
    /* In non-stop mode, the user/frontend should not notice a thread
       switch due to internal events.  Make sure we reverse to the
       user selected thread and frame after handling the event and
       running any breakpoint commands.  */
    make_cleanup_restore_current_thread ();

  overlay_cache_invalid = 1;
  /* Flush target cache before starting to handle each event.  Target
     was running and cache could be stale.  This is just a heuristic.
     Running threads may modify target memory, but we don't get any
     event.  */
  target_dcache_invalidate ();

  make_cleanup_restore_integer (&execution_direction);
  execution_direction = target_execution_direction ();

  if (deprecated_target_wait_hook)
    ecs->ptid =
      deprecated_target_wait_hook (waiton_ptid, &ecs->ws, TARGET_WNOHANG);
  else
    ecs->ptid = target_wait (waiton_ptid, &ecs->ws, TARGET_WNOHANG);

  if (debug_infrun)
    print_target_wait_results (waiton_ptid, ecs->ptid, &ecs->ws);

  /* If an error happens while handling the event, propagate GDB's
     knowledge of the executing state to the frontend/user running
     state.  */
  if (!non_stop)
    ts_old_chain = make_cleanup (finish_thread_state_cleanup, &minus_one_ptid);
  else
    ts_old_chain = make_cleanup (finish_thread_state_cleanup, &ecs->ptid);

  /* Get executed before make_cleanup_restore_current_thread above to apply
     still for the thread which has thrown the exception.  */
  make_bpstat_clear_actions_cleanup ();

  make_cleanup (delete_just_stopped_threads_infrun_breakpoints_cleanup, NULL);

  /* Now figure out what to do with the result of the result.  */
  handle_inferior_event (ecs);

  if (!ecs->wait_some_more)
    {
      struct inferior *inf = find_inferior_pid (ptid_get_pid (ecs->ptid));

      delete_just_stopped_threads_infrun_breakpoints ();

      /* We may not find an inferior if this was a process exit.  */
      if (inf == NULL || inf->control.stop_soon == NO_STOP_QUIETLY)
        normal_stop ();

      if (target_has_execution
          && ecs->ws.kind != TARGET_WAITKIND_NO_RESUMED
          && ecs->ws.kind != TARGET_WAITKIND_EXITED
          && ecs->ws.kind != TARGET_WAITKIND_SIGNALLED
          && ecs->event_thread->step_multi
          && ecs->event_thread->control.stop_step)
        inferior_event_handler (INF_EXEC_CONTINUE, NULL);
      else
        {
          inferior_event_handler (INF_EXEC_COMPLETE, NULL);
          cmd_done = 1;
        }
    }

  /* No error, don't finish the thread states yet.  */
  discard_cleanups (ts_old_chain);

  /* Revert thread and frame.  */
  do_cleanups (old_chain);

  /* If the inferior was in sync execution mode, and now isn't,
     restore the prompt (a synchronous execution command has finished,
     and we're ready for input).  */
  if (interpreter_async && was_sync && !sync_execution)
    observer_notify_sync_execution_done ();

  if (cmd_done
      && !was_sync
      && exec_done_display_p
      && (ptid_equal (inferior_ptid, null_ptid)
          || !is_running (inferior_ptid)))
    printf_unfiltered (_("completed.\n"));
}

/* Record the frame and location we're currently stepping through.  */
void
set_step_info (struct frame_info *frame, struct symtab_and_line sal)
{
  struct thread_info *tp = inferior_thread ();

  tp->control.step_frame_id = get_frame_id (frame);
  tp->control.step_stack_frame_id = get_stack_frame_id (frame);

  tp->current_symtab = sal.symtab;
  tp->current_line = sal.line;
}

/* Clear context switchable stepping state.  */

void
init_thread_stepping_state (struct thread_info *tss)
{
  tss->stepped_breakpoint = 0;
  tss->stepping_over_breakpoint = 0;
  tss->stepping_over_watchpoint = 0;
  tss->step_after_step_resume_breakpoint = 0;
}

/* Set the cached copy of the last ptid/waitstatus.  */

static void
set_last_target_status (ptid_t ptid, struct target_waitstatus status)
{
  target_last_wait_ptid = ptid;
  target_last_waitstatus = status;
}

/* Return the cached copy of the last pid/waitstatus returned by
   target_wait()/deprecated_target_wait_hook().  The data is actually
   cached by handle_inferior_event(), which gets called immediately
   after target_wait()/deprecated_target_wait_hook().  */

void
get_last_target_status (ptid_t *ptidp, struct target_waitstatus *status)
{
  *ptidp = target_last_wait_ptid;
  *status = target_last_waitstatus;
}

void
nullify_last_target_wait_ptid (void)
{
  target_last_wait_ptid = minus_one_ptid;
}

/* Switch thread contexts.  */

static void
context_switch (ptid_t ptid)
{
  if (debug_infrun && !ptid_equal (ptid, inferior_ptid))
    {
      fprintf_unfiltered (gdb_stdlog, "infrun: Switching context from %s ",
                          target_pid_to_str (inferior_ptid));
      fprintf_unfiltered (gdb_stdlog, "to %s\n",
                          target_pid_to_str (ptid));
    }

  switch_to_thread (ptid);
}

static void
adjust_pc_after_break (struct execution_control_state *ecs)
{
  struct regcache *regcache;
  struct gdbarch *gdbarch;
  struct address_space *aspace;
  CORE_ADDR breakpoint_pc, decr_pc;

  /* If we've hit a breakpoint, we'll normally be stopped with SIGTRAP.  If
     we aren't, just return.

     We assume that waitkinds other than TARGET_WAITKIND_STOPPED are not
     affected by gdbarch_decr_pc_after_break.  Other waitkinds which are
     implemented by software breakpoints should be handled through the normal
     breakpoint layer.

     NOTE drow/2004-01-31: On some targets, breakpoints may generate
     different signals (SIGILL or SIGEMT for instance), but it is less
     clear where the PC is pointing afterwards.  It may not match
     gdbarch_decr_pc_after_break.  I don't know any specific target that
     generates these signals at breakpoints (the code has been in GDB since at
     least 1992) so I can not guess how to handle them here.

     In earlier versions of GDB, a target with 
     gdbarch_have_nonsteppable_watchpoint would have the PC after hitting a
     watchpoint affected by gdbarch_decr_pc_after_break.  I haven't found any
     target with both of these set in GDB history, and it seems unlikely to be
     correct, so gdbarch_have_nonsteppable_watchpoint is not checked here.  */

  if (ecs->ws.kind != TARGET_WAITKIND_STOPPED)
    return;

  if (ecs->ws.value.sig != GDB_SIGNAL_TRAP)
    return;

  /* In reverse execution, when a breakpoint is hit, the instruction
     under it has already been de-executed.  The reported PC always
     points at the breakpoint address, so adjusting it further would
     be wrong.  E.g., consider this case on a decr_pc_after_break == 1
     architecture:

       B1         0x08000000 :   INSN1
       B2         0x08000001 :   INSN2
                  0x08000002 :   INSN3
            PC -> 0x08000003 :   INSN4

     Say you're stopped at 0x08000003 as above.  Reverse continuing
     from that point should hit B2 as below.  Reading the PC when the
     SIGTRAP is reported should read 0x08000001 and INSN2 should have
     been de-executed already.

       B1         0x08000000 :   INSN1
       B2   PC -> 0x08000001 :   INSN2
                  0x08000002 :   INSN3
                  0x08000003 :   INSN4

     We can't apply the same logic as for forward execution, because
     we would wrongly adjust the PC to 0x08000000, since there's a
     breakpoint at PC - 1.  We'd then report a hit on B1, although
     INSN1 hadn't been de-executed yet.  Doing nothing is the correct
     behaviour.  */
  if (execution_direction == EXEC_REVERSE)
    return;

  /* If this target does not decrement the PC after breakpoints, then
     we have nothing to do.  */
  regcache = get_thread_regcache (ecs->ptid);
  gdbarch = get_regcache_arch (regcache);

  decr_pc = target_decr_pc_after_break (gdbarch);
  if (decr_pc == 0)
    return;

  aspace = get_regcache_aspace (regcache);

  /* Find the location where (if we've hit a breakpoint) the
     breakpoint would be.  */
  breakpoint_pc = regcache_read_pc (regcache) - decr_pc;

  /* Check whether there actually is a software breakpoint inserted at
     that location.

     If in non-stop mode, a race condition is possible where we've
     removed a breakpoint, but stop events for that breakpoint were
     already queued and arrive later.  To suppress those spurious
     SIGTRAPs, we keep a list of such breakpoint locations for a bit,
     and retire them after a number of stop events are reported.  */
  if (software_breakpoint_inserted_here_p (aspace, breakpoint_pc)
      || (non_stop && moribund_breakpoint_here_p (aspace, breakpoint_pc)))
    {
      struct cleanup *old_cleanups = make_cleanup (null_cleanup, NULL);

      if (record_full_is_used ())
        record_full_gdb_operation_disable_set ();

      /* When using hardware single-step, a SIGTRAP is reported for both
         a completed single-step and a software breakpoint.  Need to
         differentiate between the two, as the latter needs adjusting
         but the former does not.

         The SIGTRAP can be due to a completed hardware single-step only if 
          - we didn't insert software single-step breakpoints
          - the thread to be examined is still the current thread
          - this thread is currently being stepped

         If any of these events did not occur, we must have stopped due
         to hitting a software breakpoint, and have to back up to the
         breakpoint address.

         As a special case, we could have hardware single-stepped a
         software breakpoint.  In this case (prev_pc == breakpoint_pc),
         we also need to back up to the breakpoint address.  */

      if (thread_has_single_step_breakpoints_set (ecs->event_thread)
          || !ptid_equal (ecs->ptid, inferior_ptid)
          || !currently_stepping (ecs->event_thread)
          || (ecs->event_thread->stepped_breakpoint
              && ecs->event_thread->prev_pc == breakpoint_pc))
        regcache_write_pc (regcache, breakpoint_pc);

      do_cleanups (old_cleanups);
    }
}

static int
stepped_in_from (struct frame_info *frame, struct frame_id step_frame_id)
{
  for (frame = get_prev_frame (frame);
       frame != NULL;
       frame = get_prev_frame (frame))
    {
      if (frame_id_eq (get_frame_id (frame), step_frame_id))
        return 1;
      if (get_frame_type (frame) != INLINE_FRAME)
        break;
    }

  return 0;
}

/* Auxiliary function that handles syscall entry/return events.
   It returns 1 if the inferior should keep going (and GDB
   should ignore the event), or 0 if the event deserves to be
   processed.  */

static int
handle_syscall_event (struct execution_control_state *ecs)
{
  struct regcache *regcache;
  int syscall_number;

  if (!ptid_equal (ecs->ptid, inferior_ptid))
    context_switch (ecs->ptid);

  regcache = get_thread_regcache (ecs->ptid);
  syscall_number = ecs->ws.value.syscall_number;
  stop_pc = regcache_read_pc (regcache);

  if (catch_syscall_enabled () > 0
      && catching_syscall_number (syscall_number) > 0)
    {
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: syscall number = '%d'\n",
                            syscall_number);

      ecs->event_thread->control.stop_bpstat
        = bpstat_stop_status (get_regcache_aspace (regcache),
                              stop_pc, ecs->ptid, &ecs->ws);

      if (bpstat_causes_stop (ecs->event_thread->control.stop_bpstat))
        {
          /* Catchpoint hit.  */
          return 0;
        }
    }

  /* If no catchpoint triggered for this, then keep going.  */
  keep_going (ecs);
  return 1;
}

/* Lazily fill in the execution_control_state's stop_func_* fields.  */

static void
fill_in_stop_func (struct gdbarch *gdbarch,
                   struct execution_control_state *ecs)
{
  if (!ecs->stop_func_filled_in)
    {
      /* 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, &ecs->stop_func_name,
                                &ecs->stop_func_start, &ecs->stop_func_end);
      ecs->stop_func_start
        += gdbarch_deprecated_function_start_offset (gdbarch);

      if (gdbarch_skip_entrypoint_p (gdbarch))
        ecs->stop_func_start = gdbarch_skip_entrypoint (gdbarch,
                                                        ecs->stop_func_start);

      ecs->stop_func_filled_in = 1;
    }
}


/* Return the STOP_SOON field of the inferior pointed at by PTID.  */

static enum stop_kind
get_inferior_stop_soon (ptid_t ptid)
{
  struct inferior *inf = find_inferior_pid (ptid_get_pid (ptid));

  gdb_assert (inf != NULL);
  return inf->control.stop_soon;
}

/* Given an execution control state that has been freshly filled in by
   an event from the inferior, figure out what it means and take
   appropriate action.

   The alternatives are:

   1) stop_waiting and return; to really stop and return to the
   debugger.

   2) keep_going and return; to wait for the next event (set
   ecs->event_thread->stepping_over_breakpoint to 1 to single step
   once).  */

static void
handle_inferior_event (struct execution_control_state *ecs)
{
  enum stop_kind stop_soon;

  if (ecs->ws.kind == TARGET_WAITKIND_IGNORE)
    {
      /* We had an event in the inferior, but we are not interested in
         handling it at this level.  The lower layers have already
         done what needs to be done, if anything.

         One of the possible circumstances for this is when the
         inferior produces output for the console.  The inferior has
         not stopped, and we are ignoring the event.  Another possible
         circumstance is any event which the lower level knows will be
         reported multiple times without an intervening resume.  */
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_IGNORE\n");
      prepare_to_wait (ecs);
      return;
    }

  if (ecs->ws.kind == TARGET_WAITKIND_NO_RESUMED
      && target_can_async_p () && !sync_execution)
    {
      /* There were no unwaited-for children left in the target, but,
         we're not synchronously waiting for events either.  Just
         ignore.  Otherwise, if we were running a synchronous
         execution command, we need to cancel it and give the user
         back the terminal.  */
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: TARGET_WAITKIND_NO_RESUMED (ignoring)\n");
      prepare_to_wait (ecs);
      return;
    }

  /* Cache the last pid/waitstatus.  */
  set_last_target_status (ecs->ptid, ecs->ws);

  /* Always clear state belonging to the previous time we stopped.  */
  stop_stack_dummy = STOP_NONE;

  if (ecs->ws.kind == TARGET_WAITKIND_NO_RESUMED)
    {
      /* No unwaited-for children left.  IOW, all resumed children
         have exited.  */
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_NO_RESUMED\n");

      stop_print_frame = 0;
      stop_waiting (ecs);
      return;
    }

  if (ecs->ws.kind != TARGET_WAITKIND_EXITED
      && ecs->ws.kind != TARGET_WAITKIND_SIGNALLED)
    {
      ecs->event_thread = find_thread_ptid (ecs->ptid);
      /* If it's a new thread, add it to the thread database.  */
      if (ecs->event_thread == NULL)
        ecs->event_thread = add_thread (ecs->ptid);

      /* Disable range stepping.  If the next step request could use a
         range, this will be end up re-enabled then.  */
      ecs->event_thread->control.may_range_step = 0;
    }

  /* Dependent on valid ECS->EVENT_THREAD.  */
  adjust_pc_after_break (ecs);

  /* Dependent on the current PC value modified by adjust_pc_after_break.  */
  reinit_frame_cache ();

  breakpoint_retire_moribund ();

  /* 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.  We do
     something similar for SIGSEGV, since a SIGSEGV will be generated
     when we're trying to execute a breakpoint instruction on a
     non-executable stack.  This happens for call dummy breakpoints
     for architectures like SPARC that place call dummies on the
     stack.  */
  if (ecs->ws.kind == TARGET_WAITKIND_STOPPED
      && (ecs->ws.value.sig == GDB_SIGNAL_ILL
          || ecs->ws.value.sig == GDB_SIGNAL_SEGV
          || ecs->ws.value.sig == GDB_SIGNAL_EMT))
    {
      struct regcache *regcache = get_thread_regcache (ecs->ptid);

      if (breakpoint_inserted_here_p (get_regcache_aspace (regcache),
                                      regcache_read_pc (regcache)))
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: Treating signal as SIGTRAP\n");
          ecs->ws.value.sig = GDB_SIGNAL_TRAP;
        }
    }

  /* Mark the non-executing threads accordingly.  In all-stop, all
     threads of all processes are stopped when we get any event
     reported.  In non-stop mode, only the event thread stops.  If
     we're handling a process exit in non-stop mode, there's nothing
     to do, as threads of the dead process are gone, and threads of
     any other process were left running.  */
  if (!non_stop)
    set_executing (minus_one_ptid, 0);
  else if (ecs->ws.kind != TARGET_WAITKIND_SIGNALLED
           && ecs->ws.kind != TARGET_WAITKIND_EXITED)
    set_executing (ecs->ptid, 0);

  switch (ecs->ws.kind)
    {
    case TARGET_WAITKIND_LOADED:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_LOADED\n");
      if (!ptid_equal (ecs->ptid, inferior_ptid))
        context_switch (ecs->ptid);
      /* Ignore gracefully during startup of the inferior, as it might
         be the shell which has just loaded some objects, otherwise
         add the symbols for the newly loaded objects.  Also ignore at
         the beginning of an attach or remote session; we will query
         the full list of libraries once the connection is
         established.  */

      stop_soon = get_inferior_stop_soon (ecs->ptid);
      if (stop_soon == NO_STOP_QUIETLY)
        {
          struct regcache *regcache;

          regcache = get_thread_regcache (ecs->ptid);

          handle_solib_event ();

          ecs->event_thread->control.stop_bpstat
            = bpstat_stop_status (get_regcache_aspace (regcache),
                                  stop_pc, ecs->ptid, &ecs->ws);

          if (bpstat_causes_stop (ecs->event_thread->control.stop_bpstat))
            {
              /* A catchpoint triggered.  */
              process_event_stop_test (ecs);
              return;
            }

          /* 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).  */
          ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;
          if (stop_on_solib_events)
            {
              /* Make sure we print "Stopped due to solib-event" in
                 normal_stop.  */
              stop_print_frame = 1;

              stop_waiting (ecs);
              return;
            }
        }

      /* If we are skipping through a shell, or through shared library
         loading that we aren't interested in, resume the program.  If
         we're running the program normally, also resume.  */
      if (stop_soon == STOP_QUIETLY || stop_soon == NO_STOP_QUIETLY)
        {
          /* Loading of shared libraries might have changed breakpoint
             addresses.  Make sure new breakpoints are inserted.  */
          if (stop_soon == NO_STOP_QUIETLY)
            insert_breakpoints ();
          resume (0, GDB_SIGNAL_0);
          prepare_to_wait (ecs);
          return;
        }

      /* But stop if we're attaching or setting up a remote
         connection.  */
      if (stop_soon == STOP_QUIETLY_NO_SIGSTOP
          || stop_soon == STOP_QUIETLY_REMOTE)
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog, "infrun: quietly stopped\n");
          stop_waiting (ecs);
          return;
        }

      internal_error (__FILE__, __LINE__,
                      _("unhandled stop_soon: %d"), (int) stop_soon);

    case TARGET_WAITKIND_SPURIOUS:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_SPURIOUS\n");
      if (!ptid_equal (ecs->ptid, inferior_ptid))
        context_switch (ecs->ptid);
      resume (0, GDB_SIGNAL_0);
      prepare_to_wait (ecs);
      return;

    case TARGET_WAITKIND_EXITED:
    case TARGET_WAITKIND_SIGNALLED:
      if (debug_infrun)
        {
          if (ecs->ws.kind == TARGET_WAITKIND_EXITED)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: TARGET_WAITKIND_EXITED\n");
          else
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: TARGET_WAITKIND_SIGNALLED\n");
        }

      inferior_ptid = ecs->ptid;
      set_current_inferior (find_inferior_pid (ptid_get_pid (ecs->ptid)));
      set_current_program_space (current_inferior ()->pspace);
      handle_vfork_child_exec_or_exit (0);
      target_terminal_ours ();  /* Must do this before mourn anyway.  */

      /* Clearing any previous state of convenience variables.  */
      clear_exit_convenience_vars ();

      if (ecs->ws.kind == TARGET_WAITKIND_EXITED)
        {
          /* Record the exit code in the convenience variable $_exitcode, so
             that the user can inspect this again later.  */
          set_internalvar_integer (lookup_internalvar ("_exitcode"),
                                   (LONGEST) ecs->ws.value.integer);

          /* Also record this in the inferior itself.  */
          current_inferior ()->has_exit_code = 1;
          current_inferior ()->exit_code = (LONGEST) ecs->ws.value.integer;

          /* Support the --return-child-result option.  */
          return_child_result_value = ecs->ws.value.integer;

          observer_notify_exited (ecs->ws.value.integer);
        }
      else
        {
          struct regcache *regcache = get_thread_regcache (ecs->ptid);
          struct gdbarch *gdbarch = get_regcache_arch (regcache);

          if (gdbarch_gdb_signal_to_target_p (gdbarch))
            {
              /* Set the value of the internal variable $_exitsignal,
                 which holds the signal uncaught by the inferior.  */
              set_internalvar_integer (lookup_internalvar ("_exitsignal"),
                                       gdbarch_gdb_signal_to_target (gdbarch,
                                                          ecs->ws.value.sig));
            }
          else
            {
              /* We don't have access to the target's method used for
                 converting between signal numbers (GDB's internal
                 representation <-> target's representation).
                 Therefore, we cannot do a good job at displaying this
                 information to the user.  It's better to just warn
                 her about it (if infrun debugging is enabled), and
                 give up.  */
              if (debug_infrun)
                fprintf_filtered (gdb_stdlog, _("\
Cannot fill $_exitsignal with the correct signal number.\n"));
            }

          observer_notify_signal_exited (ecs->ws.value.sig);
        }

      gdb_flush (gdb_stdout);
      target_mourn_inferior ();
      stop_print_frame = 0;
      stop_waiting (ecs);
      return;

      /* The following are the only cases in which we keep going;
         the above cases end in a continue or goto.  */
    case TARGET_WAITKIND_FORKED:
    case TARGET_WAITKIND_VFORKED:
      if (debug_infrun)
        {
          if (ecs->ws.kind == TARGET_WAITKIND_FORKED)
            fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_FORKED\n");
          else
            fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_VFORKED\n");
        }

      /* Check whether the inferior is displaced stepping.  */
      {
        struct regcache *regcache = get_thread_regcache (ecs->ptid);
        struct gdbarch *gdbarch = get_regcache_arch (regcache);
        struct displaced_step_inferior_state *displaced
          = get_displaced_stepping_state (ptid_get_pid (ecs->ptid));

        /* If checking displaced stepping is supported, and thread
           ecs->ptid is displaced stepping.  */
        if (displaced && ptid_equal (displaced->step_ptid, ecs->ptid))
          {
            struct inferior *parent_inf
              = find_inferior_pid (ptid_get_pid (ecs->ptid));
            struct regcache *child_regcache;
            CORE_ADDR parent_pc;

            /* GDB has got TARGET_WAITKIND_FORKED or TARGET_WAITKIND_VFORKED,
               indicating that the displaced stepping of syscall instruction
               has been done.  Perform cleanup for parent process here.  Note
               that this operation also cleans up the child process for vfork,
               because their pages are shared.  */
            displaced_step_fixup (ecs->ptid, GDB_SIGNAL_TRAP);

            if (ecs->ws.kind == TARGET_WAITKIND_FORKED)
              {
                /* Restore scratch pad for child process.  */
                displaced_step_restore (displaced, ecs->ws.value.related_pid);
              }

            /* Since the vfork/fork syscall instruction was executed in the scratchpad,
               the child's PC is also within the scratchpad.  Set the child's PC
               to the parent's PC value, which has already been fixed up.
               FIXME: we use the parent's aspace here, although we're touching
               the child, because the child hasn't been added to the inferior
               list yet at this point.  */

            child_regcache
              = get_thread_arch_aspace_regcache (ecs->ws.value.related_pid,
                                                 gdbarch,
                                                 parent_inf->aspace);
            /* Read PC value of parent process.  */
            parent_pc = regcache_read_pc (regcache);

            if (debug_displaced)
              fprintf_unfiltered (gdb_stdlog,
                                  "displaced: write child pc from %s to %s\n",
                                  paddress (gdbarch,
                                            regcache_read_pc (child_regcache)),
                                  paddress (gdbarch, parent_pc));

            regcache_write_pc (child_regcache, parent_pc);
          }
      }

      if (!ptid_equal (ecs->ptid, inferior_ptid))
        context_switch (ecs->ptid);

      /* Immediately detach breakpoints from the child before there's
         any chance of letting the user delete breakpoints from the
         breakpoint lists.  If we don't do this early, it's easy to
         leave left over traps in the child, vis: "break foo; catch
         fork; c; <fork>; del; c; <child calls foo>".  We only follow
         the fork on the last `continue', and by that time the
         breakpoint at "foo" is long gone from the breakpoint table.
         If we vforked, then we don't need to unpatch here, since both
         parent and child are sharing the same memory pages; we'll
         need to unpatch at follow/detach time instead to be certain
         that new breakpoints added between catchpoint hit time and
         vfork follow are detached.  */
      if (ecs->ws.kind != TARGET_WAITKIND_VFORKED)
        {
          /* This won't actually modify the breakpoint list, but will
             physically remove the breakpoints from the child.  */
          detach_breakpoints (ecs->ws.value.related_pid);
        }

      delete_just_stopped_threads_single_step_breakpoints ();

      /* In case the event is caught by a catchpoint, remember that
         the event is to be followed at the next resume of the thread,
         and not immediately.  */
      ecs->event_thread->pending_follow = ecs->ws;

      stop_pc = regcache_read_pc (get_thread_regcache (ecs->ptid));

      ecs->event_thread->control.stop_bpstat
        = bpstat_stop_status (get_regcache_aspace (get_current_regcache ()),
                              stop_pc, ecs->ptid, &ecs->ws);

      /* If no catchpoint triggered for this, then keep going.  Note
         that we're interested in knowing the bpstat actually causes a
         stop, not just if it may explain the signal.  Software
         watchpoints, for example, always appear in the bpstat.  */
      if (!bpstat_causes_stop (ecs->event_thread->control.stop_bpstat))
        {
          ptid_t parent;
          ptid_t child;
          int should_resume;
          int follow_child
            = (follow_fork_mode_string == follow_fork_mode_child);

          ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;

          should_resume = follow_fork ();

          parent = ecs->ptid;
          child = ecs->ws.value.related_pid;

          /* In non-stop mode, also resume the other branch.  */
          if (non_stop && !detach_fork)
            {
              if (follow_child)
                switch_to_thread (parent);
              else
                switch_to_thread (child);

              ecs->event_thread = inferior_thread ();
              ecs->ptid = inferior_ptid;
              keep_going (ecs);
            }

          if (follow_child)
            switch_to_thread (child);
          else
            switch_to_thread (parent);

          ecs->event_thread = inferior_thread ();
          ecs->ptid = inferior_ptid;

          if (should_resume)
            keep_going (ecs);
          else
            stop_waiting (ecs);
          return;
        }
      process_event_stop_test (ecs);
      return;

    case TARGET_WAITKIND_VFORK_DONE:
      /* Done with the shared memory region.  Re-insert breakpoints in
         the parent, and keep going.  */

      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: TARGET_WAITKIND_VFORK_DONE\n");

      if (!ptid_equal (ecs->ptid, inferior_ptid))
        context_switch (ecs->ptid);

      current_inferior ()->waiting_for_vfork_done = 0;
      current_inferior ()->pspace->breakpoints_not_allowed = 0;
      /* This also takes care of reinserting breakpoints in the
         previously locked inferior.  */
      keep_going (ecs);
      return;

    case TARGET_WAITKIND_EXECD:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_EXECD\n");

      if (!ptid_equal (ecs->ptid, inferior_ptid))
        context_switch (ecs->ptid);

      stop_pc = regcache_read_pc (get_thread_regcache (ecs->ptid));

      /* Do whatever is necessary to the parent branch of the vfork.  */
      handle_vfork_child_exec_or_exit (1);

      /* This causes the eventpoints and symbol table to be reset.
         Must do this now, before trying to determine whether to
         stop.  */
      follow_exec (inferior_ptid, ecs->ws.value.execd_pathname);

      ecs->event_thread->control.stop_bpstat
        = bpstat_stop_status (get_regcache_aspace (get_current_regcache ()),
                              stop_pc, ecs->ptid, &ecs->ws);

      /* Note that this may be referenced from inside
         bpstat_stop_status above, through inferior_has_execd.  */
      xfree (ecs->ws.value.execd_pathname);
      ecs->ws.value.execd_pathname = NULL;

      /* If no catchpoint triggered for this, then keep going.  */
      if (!bpstat_causes_stop (ecs->event_thread->control.stop_bpstat))
        {
          ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;
          keep_going (ecs);
          return;
        }
      process_event_stop_test (ecs);
      return;

      /* Be careful not to try to gather much state about a thread
         that's in a syscall.  It's frequently a losing proposition.  */
    case TARGET_WAITKIND_SYSCALL_ENTRY:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: TARGET_WAITKIND_SYSCALL_ENTRY\n");
      /* Getting the current syscall number.  */
      if (handle_syscall_event (ecs) == 0)
        process_event_stop_test (ecs);
      return;

      /* Before examining the threads further, step this thread to
         get it entirely out of the syscall.  (We get notice of the
         event when the thread is just on the verge of exiting a
         syscall.  Stepping one instruction seems to get it back
         into user code.)  */
    case TARGET_WAITKIND_SYSCALL_RETURN:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: TARGET_WAITKIND_SYSCALL_RETURN\n");
      if (handle_syscall_event (ecs) == 0)
        process_event_stop_test (ecs);
      return;

    case TARGET_WAITKIND_STOPPED:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_STOPPED\n");
      ecs->event_thread->suspend.stop_signal = ecs->ws.value.sig;
      handle_signal_stop (ecs);
      return;

    case TARGET_WAITKIND_NO_HISTORY:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_NO_HISTORY\n");
      /* Reverse execution: target ran out of history info.  */

      delete_just_stopped_threads_single_step_breakpoints ();
      stop_pc = regcache_read_pc (get_thread_regcache (ecs->ptid));
      observer_notify_no_history ();
      stop_waiting (ecs);
      return;
    }
}

/* Come here when the program has stopped with a signal.  */

static void
handle_signal_stop (struct execution_control_state *ecs)
{
  struct frame_info *frame;
  struct gdbarch *gdbarch;
  int stopped_by_watchpoint;
  enum stop_kind stop_soon;
  int random_signal;

  gdb_assert (ecs->ws.kind == TARGET_WAITKIND_STOPPED);

  /* Do we need to clean up the state of a thread that has
     completed a displaced single-step?  (Doing so usually affects
     the PC, so do it here, before we set stop_pc.)  */
  displaced_step_fixup (ecs->ptid,
                        ecs->event_thread->suspend.stop_signal);

  /* If we either finished a single-step or hit a breakpoint, but
     the user wanted this thread to be stopped, pretend we got a
     SIG0 (generic unsignaled stop).  */
  if (ecs->event_thread->stop_requested
      && ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP)
    ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;

  stop_pc = regcache_read_pc (get_thread_regcache (ecs->ptid));

  if (debug_infrun)
    {
      struct regcache *regcache = get_thread_regcache (ecs->ptid);
      struct gdbarch *gdbarch = get_regcache_arch (regcache);
      struct cleanup *old_chain = save_inferior_ptid ();

      inferior_ptid = ecs->ptid;

      fprintf_unfiltered (gdb_stdlog, "infrun: stop_pc = %s\n",
                          paddress (gdbarch, stop_pc));
      if (target_stopped_by_watchpoint ())
        {
          CORE_ADDR addr;

          fprintf_unfiltered (gdb_stdlog, "infrun: stopped by watchpoint\n");

          if (target_stopped_data_address (&current_target, &addr))
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: stopped data address = %s\n",
                                paddress (gdbarch, addr));
          else
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: (no data address available)\n");
        }

      do_cleanups (old_chain);
    }

  /* This is originated from start_remote(), start_inferior() and
     shared libraries hook functions.  */
  stop_soon = get_inferior_stop_soon (ecs->ptid);
  if (stop_soon == STOP_QUIETLY || stop_soon == STOP_QUIETLY_REMOTE)
    {
      if (!ptid_equal (ecs->ptid, inferior_ptid))
        context_switch (ecs->ptid);
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: quietly stopped\n");
      stop_print_frame = 1;
      stop_waiting (ecs);
      return;
    }

  if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP
      && stop_after_trap)
    {
      if (!ptid_equal (ecs->ptid, inferior_ptid))
        context_switch (ecs->ptid);
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: stopped\n");
      stop_print_frame = 0;
      stop_waiting (ecs);
      return;
    }

  /* This originates from attach_command().  We need to overwrite
     the stop_signal here, because some kernels don't ignore a
     SIGSTOP in a subsequent ptrace(PTRACE_CONT,SIGSTOP) call.
     See more comments in inferior.h.  On the other hand, if we
     get a non-SIGSTOP, report it to the user - assume the backend
     will handle the SIGSTOP if it should show up later.

     Also consider that the attach is complete when we see a
     SIGTRAP.  Some systems (e.g. Windows), and stubs supporting
     target extended-remote report it instead of a SIGSTOP
     (e.g. gdbserver).  We already rely on SIGTRAP being our
     signal, so this is no exception.

     Also consider that the attach is complete when we see a
     GDB_SIGNAL_0.  In non-stop mode, GDB will explicitly tell
     the target to stop all threads of the inferior, in case the
     low level attach operation doesn't stop them implicitly.  If
     they weren't stopped implicitly, then the stub will report a
     GDB_SIGNAL_0, meaning: stopped for no particular reason
     other than GDB's request.  */
  if (stop_soon == STOP_QUIETLY_NO_SIGSTOP
      && (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_STOP
          || ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP
          || ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_0))
    {
      stop_print_frame = 1;
      stop_waiting (ecs);
      ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;
      return;
    }

  /* See if something interesting happened to the non-current thread.  If
     so, then switch to that thread.  */
  if (!ptid_equal (ecs->ptid, inferior_ptid))
    {
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: context switch\n");

      context_switch (ecs->ptid);

      if (deprecated_context_hook)
        deprecated_context_hook (pid_to_thread_id (ecs->ptid));
    }

  /* At this point, get hold of the now-current thread's frame.  */
  frame = get_current_frame ();
  gdbarch = get_frame_arch (frame);

  /* Pull the single step breakpoints out of the target.  */
  if (gdbarch_software_single_step_p (gdbarch))
    {
      if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP)
        {
          struct regcache *regcache;
          struct address_space *aspace;
          CORE_ADDR pc;

          regcache = get_thread_regcache (ecs->ptid);
          aspace = get_regcache_aspace (regcache);
          pc = regcache_read_pc (regcache);

          /* However, before doing so, if this single-step breakpoint was
             actually for another thread, set this thread up for moving
             past it.  */
          if (!thread_has_single_step_breakpoint_here (ecs->event_thread,
                                                       aspace, pc))
            {
              if (single_step_breakpoint_inserted_here_p (aspace, pc))
                {
                  if (debug_infrun)
                    {
                      fprintf_unfiltered (gdb_stdlog,
                                          "infrun: [%s] hit another thread's "
                                          "single-step breakpoint\n",
                                          target_pid_to_str (ecs->ptid));
                    }
                  ecs->hit_singlestep_breakpoint = 1;
                }
            }
          else
            {
              if (debug_infrun)
                {
                  fprintf_unfiltered (gdb_stdlog,
                                      "infrun: [%s] hit its "
                                      "single-step breakpoint\n",
                                      target_pid_to_str (ecs->ptid));
                }
            }
        }

      delete_just_stopped_threads_single_step_breakpoints ();
    }

  if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP
      && ecs->event_thread->control.trap_expected
      && ecs->event_thread->stepping_over_watchpoint)
    stopped_by_watchpoint = 0;
  else
    stopped_by_watchpoint = watchpoints_triggered (&ecs->ws);

  /* If necessary, step over this watchpoint.  We'll be back to display
     it in a moment.  */
  if (stopped_by_watchpoint
      && (target_have_steppable_watchpoint
          || gdbarch_have_nonsteppable_watchpoint (gdbarch)))
    {
      /* 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.  We do this by single-stepping the
         target.

         It may not be necessary to disable the watchpoint to step over
         it.  For example, the PA can (with some kernel cooperation)
         single step over a watchpoint without disabling the watchpoint.

         It is far more common to need to disable a watchpoint to step
         the inferior over it.  If we have non-steppable watchpoints,
         we must disable the current watchpoint; it's simplest to
         disable all watchpoints.

         Any breakpoint at PC must also be stepped over -- if there's
         one, it will have already triggered before the watchpoint
         triggered, and we either already reported it to the user, or
         it didn't cause a stop and we called keep_going.  In either
         case, if there was a breakpoint at PC, we must be trying to
         step past it.  */
      ecs->event_thread->stepping_over_watchpoint = 1;
      keep_going (ecs);
      return;
    }

  ecs->event_thread->stepped_breakpoint = 0;
  ecs->event_thread->stepping_over_breakpoint = 0;
  ecs->event_thread->stepping_over_watchpoint = 0;
  bpstat_clear (&ecs->event_thread->control.stop_bpstat);
  ecs->event_thread->control.stop_step = 0;
  stop_print_frame = 1;
  stopped_by_random_signal = 0;

  /* Hide inlined functions starting here, unless we just performed stepi or
     nexti.  After stepi and nexti, always show the innermost frame (not any
     inline function call sites).  */
  if (ecs->event_thread->control.step_range_end != 1)
    {
      struct address_space *aspace = 
        get_regcache_aspace (get_thread_regcache (ecs->ptid));

      /* skip_inline_frames is expensive, so we avoid it if we can
         determine that the address is one where functions cannot have
         been inlined.  This improves performance with inferiors that
         load a lot of shared libraries, because the solib event
         breakpoint is defined as the address of a function (i.e. not
         inline).  Note that we have to check the previous PC as well
         as the current one to catch cases when we have just
         single-stepped off a breakpoint prior to reinstating it.
         Note that we're assuming that the code we single-step to is
         not inline, but that's not definitive: there's nothing
         preventing the event breakpoint function from containing
         inlined code, and the single-step ending up there.  If the
         user had set a breakpoint on that inlined code, the missing
         skip_inline_frames call would break things.  Fortunately
         that's an extremely unlikely scenario.  */
      if (!pc_at_non_inline_function (aspace, stop_pc, &ecs->ws)
          && !(ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP
               && ecs->event_thread->control.trap_expected
               && pc_at_non_inline_function (aspace,
                                             ecs->event_thread->prev_pc,
                                             &ecs->ws)))
        {
          skip_inline_frames (ecs->ptid);

          /* Re-fetch current thread's frame in case that invalidated
             the frame cache.  */
          frame = get_current_frame ();
          gdbarch = get_frame_arch (frame);
        }
    }

  if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP
      && ecs->event_thread->control.trap_expected
      && gdbarch_single_step_through_delay_p (gdbarch)
      && currently_stepping (ecs->event_thread))
    {
      /* We're trying to step off a breakpoint.  Turns out that we're
         also on an instruction that needs to be stepped multiple
         times before it's been fully executing.  E.g., architectures
         with a delay slot.  It needs to be stepped twice, once for
         the instruction and once for the delay slot.  */
      int step_through_delay
        = gdbarch_single_step_through_delay (gdbarch, frame);

      if (debug_infrun && step_through_delay)
        fprintf_unfiltered (gdb_stdlog, "infrun: step through delay\n");
      if (ecs->event_thread->control.step_range_end == 0
          && step_through_delay)
        {
          /* The user issued a continue when stopped at a breakpoint.
             Set up for another trap and get out of here.  */
         ecs->event_thread->stepping_over_breakpoint = 1;
         keep_going (ecs);
         return;
        }
      else if (step_through_delay)
        {
          /* The user issued a step when stopped at a breakpoint.
             Maybe we should stop, maybe we should not - the delay
             slot *might* correspond to a line of source.  In any
             case, don't decide that here, just set 
             ecs->stepping_over_breakpoint, making sure we 
             single-step again before breakpoints are re-inserted.  */
          ecs->event_thread->stepping_over_breakpoint = 1;
        }
    }

  /* See if there is a breakpoint/watchpoint/catchpoint/etc. that
     handles this event.  */
  ecs->event_thread->control.stop_bpstat
    = bpstat_stop_status (get_regcache_aspace (get_current_regcache ()),
                          stop_pc, ecs->ptid, &ecs->ws);

  /* Following in case break condition called a
     function.  */
  stop_print_frame = 1;

  /* This is where we handle "moribund" watchpoints.  Unlike
     software breakpoints traps, hardware watchpoint traps are
     always distinguishable from random traps.  If no high-level
     watchpoint is associated with the reported stop data address
     anymore, then the bpstat does not explain the signal ---
     simply make sure to ignore it if `stopped_by_watchpoint' is
     set.  */

  if (debug_infrun
      && ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP
      && !bpstat_explains_signal (ecs->event_thread->control.stop_bpstat,
                                  GDB_SIGNAL_TRAP)
      && stopped_by_watchpoint)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: no user watchpoint explains "
                        "watchpoint SIGTRAP, ignoring\n");

  /* NOTE: cagney/2003-03-29: These checks for a random signal
     at one stage in the past included checks for an inferior
     function call's call dummy's return breakpoint.  The original
     comment, that went with the test, read:

     ``End of a stack dummy.  Some systems (e.g. Sony news) give
     another signal besides SIGTRAP, so check here as well as
     above.''

     If someone ever tries to get call dummys on a
     non-executable stack to work (where the target would stop
     with something like a SIGSEGV), then those tests might need
     to be re-instated.  Given, however, that the tests were only
     enabled when momentary breakpoints were not being used, I
     suspect that it won't be the case.

     NOTE: kettenis/2004-02-05: Indeed such checks don't seem to
     be necessary for call dummies on a non-executable stack on
     SPARC.  */

  /* See if the breakpoints module can explain the signal.  */
  random_signal
    = !bpstat_explains_signal (ecs->event_thread->control.stop_bpstat,
                               ecs->event_thread->suspend.stop_signal);

  /* If not, perhaps stepping/nexting can.  */
  if (random_signal)
    random_signal = !(ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP
                      && currently_stepping (ecs->event_thread));

  /* Perhaps the thread hit a single-step breakpoint of _another_
     thread.  Single-step breakpoints are transparent to the
     breakpoints module.  */
  if (random_signal)
    random_signal = !ecs->hit_singlestep_breakpoint;

  /* No?  Perhaps we got a moribund watchpoint.  */
  if (random_signal)
    random_signal = !stopped_by_watchpoint;

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

  if (random_signal)
    {
      /* Signal not for debugging purposes.  */
      struct inferior *inf = find_inferior_pid (ptid_get_pid (ecs->ptid));
      enum gdb_signal stop_signal = ecs->event_thread->suspend.stop_signal;

      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog, "infrun: random signal (%s)\n",
                             gdb_signal_to_symbol_string (stop_signal));

      stopped_by_random_signal = 1;

      /* Always stop on signals if we're either just gaining control
         of the program, or the user explicitly requested this thread
         to remain stopped.  */
      if (stop_soon != NO_STOP_QUIETLY
          || ecs->event_thread->stop_requested
          || (!inf->detaching
              && signal_stop_state (ecs->event_thread->suspend.stop_signal)))
        {
          stop_waiting (ecs);
          return;
        }

      /* Notify observers the signal has "handle print" set.  Note we
         returned early above if stopping; normal_stop handles the
         printing in that case.  */
      if (signal_print[ecs->event_thread->suspend.stop_signal])
        {
          /* The signal table tells us to print about this signal.  */
          target_terminal_ours_for_output ();
          observer_notify_signal_received (ecs->event_thread->suspend.stop_signal);
          target_terminal_inferior ();
        }

      /* Clear the signal if it should not be passed.  */
      if (signal_program[ecs->event_thread->suspend.stop_signal] == 0)
        ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;

      if (ecs->event_thread->prev_pc == stop_pc
          && ecs->event_thread->control.trap_expected
          && ecs->event_thread->control.step_resume_breakpoint == NULL)
        {
          /* We were just starting a new sequence, attempting to
             single-step off of a breakpoint and expecting a SIGTRAP.
             Instead this signal arrives.  This signal will take us out
             of the stepping range so GDB needs to remember to, when
             the signal handler returns, resume stepping off that
             breakpoint.  */
          /* To simplify things, "continue" is forced to use the same
             code paths as single-step - set a breakpoint at the
             signal return address and then, once hit, step off that
             breakpoint.  */
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: signal arrived while stepping over "
                                "breakpoint\n");

          insert_hp_step_resume_breakpoint_at_frame (frame);
          ecs->event_thread->step_after_step_resume_breakpoint = 1;
          /* Reset trap_expected to ensure breakpoints are re-inserted.  */
          ecs->event_thread->control.trap_expected = 0;

          /* If we were nexting/stepping some other thread, switch to
             it, so that we don't continue it, losing control.  */
          if (!switch_back_to_stepped_thread (ecs))
            keep_going (ecs);
          return;
        }

      if (ecs->event_thread->suspend.stop_signal != GDB_SIGNAL_0
          && (pc_in_thread_step_range (stop_pc, ecs->event_thread)
              || ecs->event_thread->control.step_range_end == 1)
          && frame_id_eq (get_stack_frame_id (frame),
                          ecs->event_thread->control.step_stack_frame_id)
          && ecs->event_thread->control.step_resume_breakpoint == NULL)
        {
          /* The inferior is about to take a signal that will take it
             out of the single step range.  Set a breakpoint at the
             current PC (which is presumably where the signal handler
             will eventually return) and then allow the inferior to
             run free.

             Note that this is only needed for a signal delivered
             while in the single-step range.  Nested signals aren't a
             problem as they eventually all return.  */
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: signal may take us out of "
                                "single-step range\n");

          insert_hp_step_resume_breakpoint_at_frame (frame);
          ecs->event_thread->step_after_step_resume_breakpoint = 1;
          /* Reset trap_expected to ensure breakpoints are re-inserted.  */
          ecs->event_thread->control.trap_expected = 0;
          keep_going (ecs);
          return;
        }

      /* Note: step_resume_breakpoint may be non-NULL.  This occures
         when either there's a nested signal, or when there's a
         pending signal enabled just as the signal handler returns
         (leaving the inferior at the step-resume-breakpoint without
         actually executing it).  Either way continue until the
         breakpoint is really hit.  */

      if (!switch_back_to_stepped_thread (ecs))
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: random signal, keep going\n");

          keep_going (ecs);
        }
      return;
    }

  process_event_stop_test (ecs);
}

/* Come here when we've got some debug event / signal we can explain
   (IOW, not a random signal), and test whether it should cause a
   stop, or whether we should resume the inferior (transparently).
   E.g., could be a breakpoint whose condition evaluates false; we
   could be still stepping within the line; etc.  */

static void
process_event_stop_test (struct execution_control_state *ecs)
{
  struct symtab_and_line stop_pc_sal;
  struct frame_info *frame;
  struct gdbarch *gdbarch;
  CORE_ADDR jmp_buf_pc;
  struct bpstat_what what;

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

  frame = get_current_frame ();
  gdbarch = get_frame_arch (frame);

  what = bpstat_what (ecs->event_thread->control.stop_bpstat);

  if (what.call_dummy)
    {
      stop_stack_dummy = what.call_dummy;
    }

  /* If we hit an internal event that triggers symbol changes, the
     current frame will be invalidated within bpstat_what (e.g., if we
     hit an internal solib event).  Re-fetch it.  */
  frame = get_current_frame ();
  gdbarch = get_frame_arch (frame);

  switch (what.main_action)
    {
    case BPSTAT_WHAT_SET_LONGJMP_RESUME:
      /* If we hit the breakpoint at longjmp while stepping, we
         install a momentary breakpoint at the target of the
         jmp_buf.  */

      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: BPSTAT_WHAT_SET_LONGJMP_RESUME\n");

      ecs->event_thread->stepping_over_breakpoint = 1;

      if (what.is_longjmp)
        {
          struct value *arg_value;

          /* If we set the longjmp breakpoint via a SystemTap probe,
             then use it to extract the arguments.  The destination PC
             is the third argument to the probe.  */
          arg_value = probe_safe_evaluate_at_pc (frame, 2);
          if (arg_value)
            {
              jmp_buf_pc = value_as_address (arg_value);
              jmp_buf_pc = gdbarch_addr_bits_remove (gdbarch, jmp_buf_pc);
            }
          else if (!gdbarch_get_longjmp_target_p (gdbarch)
                   || !gdbarch_get_longjmp_target (gdbarch,
                                                   frame, &jmp_buf_pc))
            {
              if (debug_infrun)
                fprintf_unfiltered (gdb_stdlog,
                                    "infrun: BPSTAT_WHAT_SET_LONGJMP_RESUME "
                                    "(!gdbarch_get_longjmp_target)\n");
              keep_going (ecs);
              return;
            }

          /* Insert a breakpoint at resume address.  */
          insert_longjmp_resume_breakpoint (gdbarch, jmp_buf_pc);
        }
      else
        check_exception_resume (ecs, frame);
      keep_going (ecs);
      return;

    case BPSTAT_WHAT_CLEAR_LONGJMP_RESUME:
      {
        struct frame_info *init_frame;

        /* There are several cases to consider.

           1. The initiating frame no longer exists.  In this case we
           must stop, because the exception or longjmp has gone too
           far.

           2. The initiating frame exists, and is the same as the
           current frame.  We stop, because the exception or longjmp
           has been caught.

           3. The initiating frame exists and is different from the
           current frame.  This means the exception or longjmp has
           been caught beneath the initiating frame, so keep going.

           4. longjmp breakpoint has been placed just to protect
           against stale dummy frames and user is not interested in
           stopping around longjmps.  */

        if (debug_infrun)
          fprintf_unfiltered (gdb_stdlog,
                              "infrun: BPSTAT_WHAT_CLEAR_LONGJMP_RESUME\n");

        gdb_assert (ecs->event_thread->control.exception_resume_breakpoint
                    != NULL);
        delete_exception_resume_breakpoint (ecs->event_thread);

        if (what.is_longjmp)
          {
            check_longjmp_breakpoint_for_call_dummy (ecs->event_thread);

            if (!frame_id_p (ecs->event_thread->initiating_frame))
              {
                /* Case 4.  */
                keep_going (ecs);
                return;
              }
          }

        init_frame = frame_find_by_id (ecs->event_thread->initiating_frame);

        if (init_frame)
          {
            struct frame_id current_id
              = get_frame_id (get_current_frame ());
            if (frame_id_eq (current_id,
                             ecs->event_thread->initiating_frame))
              {
                /* Case 2.  Fall through.  */
              }
            else
              {
                /* Case 3.  */
                keep_going (ecs);
                return;
              }
          }

        /* For Cases 1 and 2, remove the step-resume breakpoint, if it
           exists.  */
        delete_step_resume_breakpoint (ecs->event_thread);

        end_stepping_range (ecs);
      }
      return;

    case BPSTAT_WHAT_SINGLE:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: BPSTAT_WHAT_SINGLE\n");
      ecs->event_thread->stepping_over_breakpoint = 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_STEP_RESUME:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: BPSTAT_WHAT_STEP_RESUME\n");

      delete_step_resume_breakpoint (ecs->event_thread);
      if (ecs->event_thread->control.proceed_to_finish
          && execution_direction == EXEC_REVERSE)
        {
          struct thread_info *tp = ecs->event_thread;

          /* We are finishing a function in reverse, and just hit the
             step-resume breakpoint at the start address of the
             function, and we're almost there -- just need to back up
             by one more single-step, which should take us back to the
             function call.  */
          tp->control.step_range_start = tp->control.step_range_end = 1;
          keep_going (ecs);
          return;
        }
      fill_in_stop_func (gdbarch, ecs);
      if (stop_pc == ecs->stop_func_start
          && execution_direction == EXEC_REVERSE)
        {
          /* We are stepping over a function call in reverse, and just
             hit the step-resume breakpoint at the start address of
             the function.  Go back to single-stepping, which should
             take us back to the function call.  */
          ecs->event_thread->stepping_over_breakpoint = 1;
          keep_going (ecs);
          return;
        }
      break;

    case BPSTAT_WHAT_STOP_NOISY:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: BPSTAT_WHAT_STOP_NOISY\n");
      stop_print_frame = 1;

      /* Assume the thread stopped for a breapoint.  We'll still check
         whether a/the breakpoint is there when the thread is next
         resumed.  */
      ecs->event_thread->stepping_over_breakpoint = 1;

      stop_waiting (ecs);
      return;

    case BPSTAT_WHAT_STOP_SILENT:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: BPSTAT_WHAT_STOP_SILENT\n");
      stop_print_frame = 0;

      /* Assume the thread stopped for a breapoint.  We'll still check
         whether a/the breakpoint is there when the thread is next
         resumed.  */
      ecs->event_thread->stepping_over_breakpoint = 1;
      stop_waiting (ecs);
      return;

    case BPSTAT_WHAT_HP_STEP_RESUME:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: BPSTAT_WHAT_HP_STEP_RESUME\n");

      delete_step_resume_breakpoint (ecs->event_thread);
      if (ecs->event_thread->step_after_step_resume_breakpoint)
        {
          /* Back when the step-resume breakpoint was inserted, we
             were trying to single-step off a breakpoint.  Go back to
             doing that.  */
          ecs->event_thread->step_after_step_resume_breakpoint = 0;
          ecs->event_thread->stepping_over_breakpoint = 1;
          keep_going (ecs);
          return;
        }
      break;

    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.  */

  /* In all-stop mode, if we're currently stepping but have stopped in
     some other thread, we need to switch back to the stepped thread.  */
  if (switch_back_to_stepped_thread (ecs))
    return;

  if (ecs->event_thread->control.step_resume_breakpoint)
    {
      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog,
                             "infrun: step-resume breakpoint is inserted\n");

      /* Having a step-resume breakpoint overrides anything
         else having to do with stepping commands until
         that breakpoint is reached.  */
      keep_going (ecs);
      return;
    }

  if (ecs->event_thread->control.step_range_end == 0)
    {
      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog, "infrun: no stepping, continue\n");
      /* Likewise if we aren't even stepping.  */
      keep_going (ecs);
      return;
    }

  /* Re-fetch current thread's frame in case the code above caused
     the frame cache to be re-initialized, making our FRAME variable
     a dangling pointer.  */
  frame = get_current_frame ();
  gdbarch = get_frame_arch (frame);
  fill_in_stop_func (gdbarch, ecs);

  /* If stepping through a line, keep going if still within it.

     Note that step_range_end is the address of the first instruction
     beyond the step range, and NOT the address of the last instruction
     within it!

     Note also that during reverse execution, we may be stepping
     through a function epilogue and therefore must detect when
     the current-frame changes in the middle of a line.  */

  if (pc_in_thread_step_range (stop_pc, ecs->event_thread)
      && (execution_direction != EXEC_REVERSE
          || frame_id_eq (get_frame_id (frame),
                          ecs->event_thread->control.step_frame_id)))
    {
      if (debug_infrun)
        fprintf_unfiltered
          (gdb_stdlog, "infrun: stepping inside range [%s-%s]\n",
           paddress (gdbarch, ecs->event_thread->control.step_range_start),
           paddress (gdbarch, ecs->event_thread->control.step_range_end));

      /* Tentatively re-enable range stepping; `resume' disables it if
         necessary (e.g., if we're stepping over a breakpoint or we
         have software watchpoints).  */
      ecs->event_thread->control.may_range_step = 1;

      /* When stepping backward, stop at beginning of line range
         (unless it's the function entry point, in which case
         keep going back to the call point).  */
      if (stop_pc == ecs->event_thread->control.step_range_start
          && stop_pc != ecs->stop_func_start
          && execution_direction == EXEC_REVERSE)
        end_stepping_range (ecs);
      else
        keep_going (ecs);

      return;
    }

  /* We stepped out of the stepping range.  */

  /* If we are stepping at the source level and entered the runtime
     loader dynamic symbol resolution code...

     EXEC_FORWARD: we keep on single stepping until we exit the run
     time loader code and reach the callee's address.

     EXEC_REVERSE: we've already executed the callee (backward), and
     the runtime loader code is handled just like any other
     undebuggable function call.  Now we need only keep stepping
     backward through the trampoline code, and that's handled further
     down, so there is nothing for us to do here.  */

  if (execution_direction != EXEC_REVERSE
      && ecs->event_thread->control.step_over_calls == STEP_OVER_UNDEBUGGABLE
      && in_solib_dynsym_resolve_code (stop_pc))
    {
      CORE_ADDR pc_after_resolver =
        gdbarch_skip_solib_resolver (gdbarch, stop_pc);

      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog,
                             "infrun: stepped into dynsym resolve code\n");

      if (pc_after_resolver)
        {
          /* Set up a step-resume breakpoint at the address
             indicated by SKIP_SOLIB_RESOLVER.  */
          struct symtab_and_line sr_sal;

          init_sal (&sr_sal);
          sr_sal.pc = pc_after_resolver;
          sr_sal.pspace = get_frame_program_space (frame);

          insert_step_resume_breakpoint_at_sal (gdbarch,
                                                sr_sal, null_frame_id);
        }

      keep_going (ecs);
      return;
    }

  if (ecs->event_thread->control.step_range_end != 1
      && (ecs->event_thread->control.step_over_calls == STEP_OVER_UNDEBUGGABLE
          || ecs->event_thread->control.step_over_calls == STEP_OVER_ALL)
      && get_frame_type (frame) == SIGTRAMP_FRAME)
    {
      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog,
                             "infrun: stepped into signal trampoline\n");
      /* The inferior, while doing a "step" or "next", has ended up in
         a signal trampoline (either by a signal being delivered or by
         the signal handler returning).  Just single-step until the
         inferior leaves the trampoline (either by calling the handler
         or returning).  */
      keep_going (ecs);
      return;
    }

  /* If we're in the return path from a shared library trampoline,
     we want to proceed through the trampoline when stepping.  */
  /* macro/2012-04-25: This needs to come before the subroutine
     call check below as on some targets return trampolines look
     like subroutine calls (MIPS16 return thunks).  */
  if (gdbarch_in_solib_return_trampoline (gdbarch,
                                          stop_pc, ecs->stop_func_name)
      && ecs->event_thread->control.step_over_calls != STEP_OVER_NONE)
    {
      /* Determine where this trampoline returns.  */
      CORE_ADDR real_stop_pc;

      real_stop_pc = gdbarch_skip_trampoline_code (gdbarch, frame, stop_pc);

      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog,
                             "infrun: stepped into solib return tramp\n");

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

          init_sal (&sr_sal);   /* initialize to zeroes */
          sr_sal.pc = real_stop_pc;
          sr_sal.section = find_pc_overlay (sr_sal.pc);
          sr_sal.pspace = get_frame_program_space (frame);

          /* 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.  */
          insert_step_resume_breakpoint_at_sal (gdbarch,
                                                sr_sal, null_frame_id);

          /* Restart without fiddling with the step ranges or
             other state.  */
          keep_going (ecs);
          return;
        }
    }

  /* Check for subroutine calls.  The check for the current frame
     equalling the step ID is not necessary - the check of the
     previous frame's ID is sufficient - but it is a common case and
     cheaper than checking the previous frame's ID.

     NOTE: frame_id_eq will never report two invalid frame IDs as
     being equal, so to get into this block, both the current and
     previous frame must have valid frame IDs.  */
  /* The outer_frame_id check is a heuristic to detect stepping
     through startup code.  If we step over an instruction which
     sets the stack pointer from an invalid value to a valid value,
     we may detect that as a subroutine call from the mythical
     "outermost" function.  This could be fixed by marking
     outermost frames as !stack_p,code_p,special_p.  Then the
     initial outermost frame, before sp was valid, would
     have code_addr == &_start.  See the comment in frame_id_eq
     for more.  */
  if (!frame_id_eq (get_stack_frame_id (frame),
                    ecs->event_thread->control.step_stack_frame_id)
      && (frame_id_eq (frame_unwind_caller_id (get_current_frame ()),
                       ecs->event_thread->control.step_stack_frame_id)
          && (!frame_id_eq (ecs->event_thread->control.step_stack_frame_id,
                            outer_frame_id)
              || step_start_function != find_pc_function (stop_pc))))
    {
      CORE_ADDR real_stop_pc;

      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog, "infrun: stepped into subroutine\n");

      if ((ecs->event_thread->control.step_over_calls == STEP_OVER_NONE)
          || ((ecs->event_thread->control.step_range_end == 1)
              && in_prologue (gdbarch, ecs->event_thread->prev_pc,
                              ecs->stop_func_start)))
        {
          /* I presume that step_over_calls is only 0 when we're
             supposed to be stepping at the assembly language level
             ("stepi").  Just stop.  */
          /* Also, maybe we just did a "nexti" inside a prolog, so we
             thought it was a subroutine call but it was not.  Stop as
             well.  FENN */
          /* And this works the same backward as frontward.  MVS */
          end_stepping_range (ecs);
          return;
        }

      /* Reverse stepping through solib trampolines.  */

      if (execution_direction == EXEC_REVERSE
          && ecs->event_thread->control.step_over_calls != STEP_OVER_NONE
          && (gdbarch_skip_trampoline_code (gdbarch, frame, stop_pc)
              || (ecs->stop_func_start == 0
                  && in_solib_dynsym_resolve_code (stop_pc))))
        {
          /* Any solib trampoline code can be handled in reverse
             by simply continuing to single-step.  We have already
             executed the solib function (backwards), and a few 
             steps will take us back through the trampoline to the
             caller.  */
          keep_going (ecs);
          return;
        }

      if (ecs->event_thread->control.step_over_calls == STEP_OVER_ALL)
        {
          /* We're doing a "next".

             Normal (forward) execution: set a breakpoint at the
             callee's return address (the address at which the caller
             will resume).

             Reverse (backward) execution.  set the step-resume
             breakpoint at the start of the function that we just
             stepped into (backwards), and continue to there.  When we
             get there, we'll need to single-step back to the caller.  */

          if (execution_direction == EXEC_REVERSE)
            {
              /* If we're already at the start of the function, we've either
                 just stepped backward into a single instruction function,
                 or stepped back out of a signal handler to the first instruction
                 of the function.  Just keep going, which will single-step back
                 to the caller.  */
              if (ecs->stop_func_start != stop_pc && ecs->stop_func_start != 0)
                {
                  struct symtab_and_line sr_sal;

                  /* Normal function call return (static or dynamic).  */
                  init_sal (&sr_sal);
                  sr_sal.pc = ecs->stop_func_start;
                  sr_sal.pspace = get_frame_program_space (frame);
                  insert_step_resume_breakpoint_at_sal (gdbarch,
                                                        sr_sal, null_frame_id);
                }
            }
          else
            insert_step_resume_breakpoint_at_caller (frame);

          keep_going (ecs);
          return;
        }

      /* 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.  */
      real_stop_pc = skip_language_trampoline (frame, stop_pc);
      if (real_stop_pc == 0)
        real_stop_pc = gdbarch_skip_trampoline_code (gdbarch, frame, stop_pc);
      if (real_stop_pc != 0)
        ecs->stop_func_start = real_stop_pc;

      if (real_stop_pc != 0 && in_solib_dynsym_resolve_code (real_stop_pc))
        {
          struct symtab_and_line sr_sal;

          init_sal (&sr_sal);
          sr_sal.pc = ecs->stop_func_start;
          sr_sal.pspace = get_frame_program_space (frame);

          insert_step_resume_breakpoint_at_sal (gdbarch,
                                                sr_sal, null_frame_id);
          keep_going (ecs);
          return;
        }

      /* If we have line number information for the function we are
         thinking of stepping into and the function isn't on the skip
         list, 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 (ecs->stop_func_start, 0);
        if (tmp_sal.line != 0
            && !function_name_is_marked_for_skip (ecs->stop_func_name,
                                                  &tmp_sal))
          {
            if (execution_direction == EXEC_REVERSE)
              handle_step_into_function_backward (gdbarch, ecs);
            else
              handle_step_into_function (gdbarch, ecs);
            return;
          }
      }

      /* If we have no line number and the step-stop-if-no-debug is
         set, we stop the step so that the user has a chance to switch
         in assembly mode.  */
      if (ecs->event_thread->control.step_over_calls == STEP_OVER_UNDEBUGGABLE
          && step_stop_if_no_debug)
        {
          end_stepping_range (ecs);
          return;
        }

      if (execution_direction == EXEC_REVERSE)
        {
          /* If we're already at the start of the function, we've either just
             stepped backward into a single instruction function without line
             number info, or stepped back out of a signal handler to the first
             instruction of the function without line number info.  Just keep
             going, which will single-step back to the caller.  */
          if (ecs->stop_func_start != stop_pc)
            {
              /* Set a breakpoint at callee's start address.
                 From there we can step once and be back in the caller.  */
              struct symtab_and_line sr_sal;

              init_sal (&sr_sal);
              sr_sal.pc = ecs->stop_func_start;
              sr_sal.pspace = get_frame_program_space (frame);
              insert_step_resume_breakpoint_at_sal (gdbarch,
                                                    sr_sal, null_frame_id);
            }
        }
      else
        /* Set a breakpoint at callee's return address (the address
           at which the caller will resume).  */
        insert_step_resume_breakpoint_at_caller (frame);

      keep_going (ecs);
      return;
    }

  /* Reverse stepping through solib trampolines.  */

  if (execution_direction == EXEC_REVERSE
      && ecs->event_thread->control.step_over_calls != STEP_OVER_NONE)
    {
      if (gdbarch_skip_trampoline_code (gdbarch, frame, stop_pc)
          || (ecs->stop_func_start == 0
              && in_solib_dynsym_resolve_code (stop_pc)))
        {
          /* Any solib trampoline code can be handled in reverse
             by simply continuing to single-step.  We have already
             executed the solib function (backwards), and a few 
             steps will take us back through the trampoline to the
             caller.  */
          keep_going (ecs);
          return;
        }
      else if (in_solib_dynsym_resolve_code (stop_pc))
        {
          /* Stepped backward into the solib dynsym resolver.
             Set a breakpoint at its start and continue, then
             one more step will take us out.  */
          struct symtab_and_line sr_sal;

          init_sal (&sr_sal);
          sr_sal.pc = ecs->stop_func_start;
          sr_sal.pspace = get_frame_program_space (frame);
          insert_step_resume_breakpoint_at_sal (gdbarch, 
                                                sr_sal, null_frame_id);
          keep_going (ecs);
          return;
        }
    }

  stop_pc_sal = find_pc_line (stop_pc, 0);

  /* NOTE: tausq/2004-05-24: This if block used to be done before all
     the trampoline processing logic, however, there are some trampolines 
     that have no names, so we should do trampoline handling first.  */
  if (ecs->event_thread->control.step_over_calls == STEP_OVER_UNDEBUGGABLE
      && ecs->stop_func_name == NULL
      && stop_pc_sal.line == 0)
    {
      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog,
                             "infrun: stepped into undebuggable function\n");

      /* The inferior just stepped into, or returned to, an
         undebuggable function (where there is no debugging information
         and no line number corresponding to the address where the
         inferior stopped).  Since we want to skip this kind of code,
         we keep going until the inferior returns from this
         function - unless the user has asked us not to (via
         set step-mode) or we no longer know how to get back
         to the call site.  */
      if (step_stop_if_no_debug
          || !frame_id_p (frame_unwind_caller_id (frame)))
        {
          /* If we have no line number and the step-stop-if-no-debug
             is set, we stop the step so that the user has a chance to
             switch in assembly mode.  */
          end_stepping_range (ecs);
          return;
        }
      else
        {
          /* Set a breakpoint at callee's return address (the address
             at which the caller will resume).  */
          insert_step_resume_breakpoint_at_caller (frame);
          keep_going (ecs);
          return;
        }
    }

  if (ecs->event_thread->control.step_range_end == 1)
    {
      /* It is stepi or nexti.  We always want to stop stepping after
         one instruction.  */
      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog, "infrun: stepi/nexti\n");
      end_stepping_range (ecs);
      return;
    }

  if (stop_pc_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?).  */
      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog, "infrun: no line number info\n");
      end_stepping_range (ecs);
      return;
    }

  /* Look for "calls" to inlined functions, part one.  If the inline
     frame machinery detected some skipped call sites, we have entered
     a new inline function.  */

  if (frame_id_eq (get_frame_id (get_current_frame ()),
                   ecs->event_thread->control.step_frame_id)
      && inline_skipped_frames (ecs->ptid))
    {
      struct symtab_and_line call_sal;

      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: stepped into inlined function\n");

      find_frame_sal (get_current_frame (), &call_sal);

      if (ecs->event_thread->control.step_over_calls != STEP_OVER_ALL)
        {
          /* For "step", we're going to stop.  But if the call site
             for this inlined function is on the same source line as
             we were previously stepping, go down into the function
             first.  Otherwise stop at the call site.  */

          if (call_sal.line == ecs->event_thread->current_line
              && call_sal.symtab == ecs->event_thread->current_symtab)
            step_into_inline_frame (ecs->ptid);

          end_stepping_range (ecs);
          return;
        }
      else
        {
          /* For "next", we should stop at the call site if it is on a
             different source line.  Otherwise continue through the
             inlined function.  */
          if (call_sal.line == ecs->event_thread->current_line
              && call_sal.symtab == ecs->event_thread->current_symtab)
            keep_going (ecs);
          else
            end_stepping_range (ecs);
          return;
        }
    }

  /* Look for "calls" to inlined functions, part two.  If we are still
     in the same real function we were stepping through, but we have
     to go further up to find the exact frame ID, we are stepping
     through a more inlined call beyond its call site.  */

  if (get_frame_type (get_current_frame ()) == INLINE_FRAME
      && !frame_id_eq (get_frame_id (get_current_frame ()),
                       ecs->event_thread->control.step_frame_id)
      && stepped_in_from (get_current_frame (),
                          ecs->event_thread->control.step_frame_id))
    {
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: stepping through inlined function\n");

      if (ecs->event_thread->control.step_over_calls == STEP_OVER_ALL)
        keep_going (ecs);
      else
        end_stepping_range (ecs);
      return;
    }

  if ((stop_pc == stop_pc_sal.pc)
      && (ecs->event_thread->current_line != stop_pc_sal.line
          || ecs->event_thread->current_symtab != stop_pc_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.  */
      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog,
                             "infrun: stepped to a different line\n");
      end_stepping_range (ecs);
      return;
    }

  /* 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.)  */

  ecs->event_thread->control.step_range_start = stop_pc_sal.pc;
  ecs->event_thread->control.step_range_end = stop_pc_sal.end;
  ecs->event_thread->control.may_range_step = 1;
  set_step_info (frame, stop_pc_sal);

  if (debug_infrun)
     fprintf_unfiltered (gdb_stdlog, "infrun: keep going\n");
  keep_going (ecs);
}

/* In all-stop mode, if we're currently stepping but have stopped in
   some other thread, we may need to switch back to the stepped
   thread.  Returns true we set the inferior running, false if we left
   it stopped (and the event needs further processing).  */

static int
switch_back_to_stepped_thread (struct execution_control_state *ecs)
{
  if (!non_stop)
    {
      struct thread_info *tp;
      struct thread_info *stepping_thread;
      struct thread_info *step_over;

      /* If any thread is blocked on some internal breakpoint, and we
         simply need to step over that breakpoint to get it going
         again, do that first.  */

      /* However, if we see an event for the stepping thread, then we
         know all other threads have been moved past their breakpoints
         already.  Let the caller check whether the step is finished,
         etc., before deciding to move it past a breakpoint.  */
      if (ecs->event_thread->control.step_range_end != 0)
        return 0;

      /* Check if the current thread is blocked on an incomplete
         step-over, interrupted by a random signal.  */
      if (ecs->event_thread->control.trap_expected
          && ecs->event_thread->suspend.stop_signal != GDB_SIGNAL_TRAP)
        {
          if (debug_infrun)
            {
              fprintf_unfiltered (gdb_stdlog,
                                  "infrun: need to finish step-over of [%s]\n",
                                  target_pid_to_str (ecs->event_thread->ptid));
            }
          keep_going (ecs);
          return 1;
        }

      /* Check if the current thread is blocked by a single-step
         breakpoint of another thread.  */
      if (ecs->hit_singlestep_breakpoint)
       {
         if (debug_infrun)
           {
             fprintf_unfiltered (gdb_stdlog,
                                 "infrun: need to step [%s] over single-step "
                                 "breakpoint\n",
                                 target_pid_to_str (ecs->ptid));
           }
         keep_going (ecs);
         return 1;
       }

      /* Otherwise, we no longer expect a trap in the current thread.
         Clear the trap_expected flag before switching back -- this is
         what keep_going does as well, if we call it.  */
      ecs->event_thread->control.trap_expected = 0;

      /* Likewise, clear the signal if it should not be passed.  */
      if (!signal_program[ecs->event_thread->suspend.stop_signal])
        ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;

      /* If scheduler locking applies even if not stepping, there's no
         need to walk over threads.  Above we've checked whether the
         current thread is stepping.  If some other thread not the
         event thread is stepping, then it must be that scheduler
         locking is not in effect.  */
      if (schedlock_applies (0))
        return 0;

      /* Look for the stepping/nexting thread, and check if any other
         thread other than the stepping thread needs to start a
         step-over.  Do all step-overs before actually proceeding with
         step/next/etc.  */
      stepping_thread = NULL;
      step_over = NULL;
      ALL_NON_EXITED_THREADS (tp)
        {
          /* Ignore threads of processes we're not resuming.  */
          if (!sched_multi
              && ptid_get_pid (tp->ptid) != ptid_get_pid (inferior_ptid))
            continue;

          /* When stepping over a breakpoint, we lock all threads
             except the one that needs to move past the breakpoint.
             If a non-event thread has this set, the "incomplete
             step-over" check above should have caught it earlier.  */
          gdb_assert (!tp->control.trap_expected);

          /* Did we find the stepping thread?  */
          if (tp->control.step_range_end)
            {
              /* Yep.  There should only one though.  */
              gdb_assert (stepping_thread == NULL);

              /* The event thread is handled at the top, before we
                 enter this loop.  */
              gdb_assert (tp != ecs->event_thread);

              /* If some thread other than the event thread is
                 stepping, then scheduler locking can't be in effect,
                 otherwise we wouldn't have resumed the current event
                 thread in the first place.  */
              gdb_assert (!schedlock_applies (1));

              stepping_thread = tp;
            }
          else if (thread_still_needs_step_over (tp))
            {
              step_over = tp;

              /* At the top we've returned early if the event thread
                 is stepping.  If some other thread not the event
                 thread is stepping, then scheduler locking can't be
                 in effect, and we can resume this thread.  No need to
                 keep looking for the stepping thread then.  */
              break;
            }
        }

      if (step_over != NULL)
        {
          tp = step_over;
          if (debug_infrun)
            {
              fprintf_unfiltered (gdb_stdlog,
                                  "infrun: need to step-over [%s]\n",
                                  target_pid_to_str (tp->ptid));
            }

          /* Only the stepping thread should have this set.  */
          gdb_assert (tp->control.step_range_end == 0);

          ecs->ptid = tp->ptid;
          ecs->event_thread = tp;
          switch_to_thread (ecs->ptid);
          keep_going (ecs);
          return 1;
        }

      if (stepping_thread != NULL)
        {
          struct frame_info *frame;
          struct gdbarch *gdbarch;

          tp = stepping_thread;

          /* If the stepping thread exited, then don't try to switch
             back and resume it, which could fail in several different
             ways depending on the target.  Instead, just keep going.

             We can find a stepping dead thread in the thread list in
             two cases:

             - The target supports thread exit events, and when the
             target tries to delete the thread from the thread list,
             inferior_ptid pointed at the exiting thread.  In such
             case, calling delete_thread does not really remove the
             thread from the list; instead, the thread is left listed,
             with 'exited' state.

             - The target's debug interface does not support thread
             exit events, and so we have no idea whatsoever if the
             previously stepping thread is still alive.  For that
             reason, we need to synchronously query the target
             now.  */
          if (is_exited (tp->ptid)
              || !target_thread_alive (tp->ptid))
            {
              if (debug_infrun)
                fprintf_unfiltered (gdb_stdlog,
                                    "infrun: not switching back to "
                                    "stepped thread, it has vanished\n");

              delete_thread (tp->ptid);
              keep_going (ecs);
              return 1;
            }

          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: switching back to stepped thread\n");

          ecs->event_thread = tp;
          ecs->ptid = tp->ptid;
          context_switch (ecs->ptid);

          stop_pc = regcache_read_pc (get_thread_regcache (ecs->ptid));
          frame = get_current_frame ();
          gdbarch = get_frame_arch (frame);

          /* If the PC of the thread we were trying to single-step has
             changed, then that thread has trapped or been signaled,
             but the event has not been reported to GDB yet.  Re-poll
             the target looking for this particular thread's event
             (i.e. temporarily enable schedlock) by:

               - setting a break at the current PC
               - resuming that particular thread, only (by setting
                 trap expected)

             This prevents us continuously moving the single-step
             breakpoint forward, one instruction at a time,
             overstepping.  */

          if (gdbarch_software_single_step_p (gdbarch)
              && stop_pc != tp->prev_pc)
            {
              if (debug_infrun)
                fprintf_unfiltered (gdb_stdlog,
                                    "infrun: expected thread advanced also\n");

              /* Clear the info of the previous step-over, as it's no
                 longer valid.  It's what keep_going would do too, if
                 we called it.  Must do this before trying to insert
                 the sss breakpoint, otherwise if we were previously
                 trying to step over this exact address in another
                 thread, the breakpoint ends up not installed.  */
              clear_step_over_info ();

              insert_single_step_breakpoint (get_frame_arch (frame),
                                             get_frame_address_space (frame),
                                             stop_pc);
              ecs->event_thread->control.trap_expected = 1;

              resume (0, GDB_SIGNAL_0);
              prepare_to_wait (ecs);
            }
          else
            {
              if (debug_infrun)
                fprintf_unfiltered (gdb_stdlog,
                                    "infrun: expected thread still "
                                    "hasn't advanced\n");
              keep_going (ecs);
            }

          return 1;
        }
    }
  return 0;
}

/* Is thread TP in the middle of single-stepping?  */

static int
currently_stepping (struct thread_info *tp)
{
  return ((tp->control.step_range_end
           && tp->control.step_resume_breakpoint == NULL)
          || tp->control.trap_expected
          || bpstat_should_step ());
}

/* Inferior has stepped into a subroutine call with source code that
   we should not step over.  Do step to the first line of code in
   it.  */

static void
handle_step_into_function (struct gdbarch *gdbarch,
                           struct execution_control_state *ecs)
{
  struct symtab *s;
  struct symtab_and_line stop_func_sal, sr_sal;

  fill_in_stop_func (gdbarch, ecs);

  s = find_pc_symtab (stop_pc);
  if (s && s->language != language_asm)
    ecs->stop_func_start = gdbarch_skip_prologue (gdbarch,
                                                  ecs->stop_func_start);

  stop_func_sal = find_pc_line (ecs->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.  */
  if (stop_func_sal.end
      && stop_func_sal.pc != ecs->stop_func_start
      && stop_func_sal.end < ecs->stop_func_end)
    ecs->stop_func_start = stop_func_sal.end;

  /* Architectures which require breakpoint adjustment might not be able
     to place a breakpoint at the computed address.  If so, the test
     ``ecs->stop_func_start == stop_pc'' will never succeed.  Adjust
     ecs->stop_func_start to an address at which a breakpoint may be
     legitimately placed.

     Note:  kevinb/2004-01-19:  On FR-V, if this adjustment is not
     made, GDB will enter an infinite loop when stepping through
     optimized code consisting of VLIW instructions which contain
     subinstructions corresponding to different source lines.  On
     FR-V, it's not permitted to place a breakpoint on any but the
     first subinstruction of a VLIW instruction.  When a breakpoint is
     set, GDB will adjust the breakpoint address to the beginning of
     the VLIW instruction.  Thus, we need to make the corresponding
     adjustment here when computing the stop address.  */

  if (gdbarch_adjust_breakpoint_address_p (gdbarch))
    {
      ecs->stop_func_start
        = gdbarch_adjust_breakpoint_address (gdbarch,
                                             ecs->stop_func_start);
    }

  if (ecs->stop_func_start == stop_pc)
    {
      /* We are already there: stop now.  */
      end_stepping_range (ecs);
      return;
    }
  else
    {
      /* Put the step-breakpoint there and go until there.  */
      init_sal (&sr_sal);       /* initialize to zeroes */
      sr_sal.pc = ecs->stop_func_start;
      sr_sal.section = find_pc_overlay (ecs->stop_func_start);
      sr_sal.pspace = get_frame_program_space (get_current_frame ());

      /* 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.  */
      insert_step_resume_breakpoint_at_sal (gdbarch, sr_sal, null_frame_id);

      /* And make sure stepping stops right away then.  */
      ecs->event_thread->control.step_range_end
        = ecs->event_thread->control.step_range_start;
    }
  keep_going (ecs);
}

/* Inferior has stepped backward into a subroutine call with source
   code that we should not step over.  Do step to the beginning of the
   last line of code in it.  */

static void
handle_step_into_function_backward (struct gdbarch *gdbarch,
                                    struct execution_control_state *ecs)
{
  struct symtab *s;
  struct symtab_and_line stop_func_sal;

  fill_in_stop_func (gdbarch, ecs);

  s = find_pc_symtab (stop_pc);
  if (s && s->language != language_asm)
    ecs->stop_func_start = gdbarch_skip_prologue (gdbarch,
                                                  ecs->stop_func_start);

  stop_func_sal = find_pc_line (stop_pc, 0);

  /* OK, we're just going to keep stepping here.  */
  if (stop_func_sal.pc == stop_pc)
    {
      /* We're there already.  Just stop stepping now.  */
      end_stepping_range (ecs);
    }
  else
    {
      /* Else just reset the step range and keep going.
         No step-resume breakpoint, they don't work for
         epilogues, which can have multiple entry paths.  */
      ecs->event_thread->control.step_range_start = stop_func_sal.pc;
      ecs->event_thread->control.step_range_end = stop_func_sal.end;
      keep_going (ecs);
    }
  return;
}

/* Insert a "step-resume breakpoint" at SR_SAL with frame ID SR_ID.
   This is used to both functions and to skip over code.  */

static void
insert_step_resume_breakpoint_at_sal_1 (struct gdbarch *gdbarch,
                                        struct symtab_and_line sr_sal,
                                        struct frame_id sr_id,
                                        enum bptype sr_type)
{
  /* There should never be more than one step-resume or longjmp-resume
     breakpoint per thread, so we should never be setting a new
     step_resume_breakpoint when one is already active.  */
  gdb_assert (inferior_thread ()->control.step_resume_breakpoint == NULL);
  gdb_assert (sr_type == bp_step_resume || sr_type == bp_hp_step_resume);

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: inserting step-resume breakpoint at %s\n",
                        paddress (gdbarch, sr_sal.pc));

  inferior_thread ()->control.step_resume_breakpoint
    = set_momentary_breakpoint (gdbarch, sr_sal, sr_id, sr_type);
}

void
insert_step_resume_breakpoint_at_sal (struct gdbarch *gdbarch,
                                      struct symtab_and_line sr_sal,
                                      struct frame_id sr_id)
{
  insert_step_resume_breakpoint_at_sal_1 (gdbarch,
                                          sr_sal, sr_id,
                                          bp_step_resume);
}

/* Insert a "high-priority step-resume breakpoint" at RETURN_FRAME.pc.
   This is used to skip a potential signal handler.

   This is called with the interrupted function's frame.  The signal
   handler, when it returns, will resume the interrupted function at
   RETURN_FRAME.pc.  */

static void
insert_hp_step_resume_breakpoint_at_frame (struct frame_info *return_frame)
{
  struct symtab_and_line sr_sal;
  struct gdbarch *gdbarch;

  gdb_assert (return_frame != NULL);
  init_sal (&sr_sal);           /* initialize to zeros */

  gdbarch = get_frame_arch (return_frame);
  sr_sal.pc = gdbarch_addr_bits_remove (gdbarch, get_frame_pc (return_frame));
  sr_sal.section = find_pc_overlay (sr_sal.pc);
  sr_sal.pspace = get_frame_program_space (return_frame);

  insert_step_resume_breakpoint_at_sal_1 (gdbarch, sr_sal,
                                          get_stack_frame_id (return_frame),
                                          bp_hp_step_resume);
}

/* Insert a "step-resume breakpoint" at the previous frame's PC.  This
   is used to skip a function after stepping into it (for "next" or if
   the called function has no debugging information).

   The current function has almost always been reached by single
   stepping a call or return instruction.  NEXT_FRAME belongs to the
   current function, and the breakpoint will be set at the caller's
   resume address.

   This is a separate function rather than reusing
   insert_hp_step_resume_breakpoint_at_frame in order to avoid
   get_prev_frame, which may stop prematurely (see the implementation
   of frame_unwind_caller_id for an example).  */

static void
insert_step_resume_breakpoint_at_caller (struct frame_info *next_frame)
{
  struct symtab_and_line sr_sal;
  struct gdbarch *gdbarch;

  /* We shouldn't have gotten here if we don't know where the call site
     is.  */
  gdb_assert (frame_id_p (frame_unwind_caller_id (next_frame)));

  init_sal (&sr_sal);           /* initialize to zeros */

  gdbarch = frame_unwind_caller_arch (next_frame);
  sr_sal.pc = gdbarch_addr_bits_remove (gdbarch,
                                        frame_unwind_caller_pc (next_frame));
  sr_sal.section = find_pc_overlay (sr_sal.pc);
  sr_sal.pspace = frame_unwind_program_space (next_frame);

  insert_step_resume_breakpoint_at_sal (gdbarch, sr_sal,
                                        frame_unwind_caller_id (next_frame));
}

/* Insert a "longjmp-resume" breakpoint at PC.  This is used to set a
   new breakpoint at the target of a jmp_buf.  The handling of
   longjmp-resume uses the same mechanisms used for handling
   "step-resume" breakpoints.  */

static void
insert_longjmp_resume_breakpoint (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  /* There should never be more than one longjmp-resume breakpoint per
     thread, so we should never be setting a new
     longjmp_resume_breakpoint when one is already active.  */
  gdb_assert (inferior_thread ()->control.exception_resume_breakpoint == NULL);

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: inserting longjmp-resume breakpoint at %s\n",
                        paddress (gdbarch, pc));

  inferior_thread ()->control.exception_resume_breakpoint =
    set_momentary_breakpoint_at_pc (gdbarch, pc, bp_longjmp_resume);
}

/* Insert an exception resume breakpoint.  TP is the thread throwing
   the exception.  The block B is the block of the unwinder debug hook
   function.  FRAME is the frame corresponding to the call to this
   function.  SYM is the symbol of the function argument holding the
   target PC of the exception.  */

static void
insert_exception_resume_breakpoint (struct thread_info *tp,
                                    const struct block *b,
                                    struct frame_info *frame,
                                    struct symbol *sym)
{
  volatile struct gdb_exception e;

  /* We want to ignore errors here.  */
  TRY_CATCH (e, RETURN_MASK_ERROR)
    {
      struct symbol *vsym;
      struct value *value;
      CORE_ADDR handler;
      struct breakpoint *bp;

      vsym = lookup_symbol (SYMBOL_LINKAGE_NAME (sym), b, VAR_DOMAIN, NULL);
      value = read_var_value (vsym, frame);
      /* If the value was optimized out, revert to the old behavior.  */
      if (! value_optimized_out (value))
        {
          handler = value_as_address (value);

          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: exception resume at %lx\n",
                                (unsigned long) handler);

          bp = set_momentary_breakpoint_at_pc (get_frame_arch (frame),
                                               handler, bp_exception_resume);

          /* set_momentary_breakpoint_at_pc invalidates FRAME.  */
          frame = NULL;

          bp->thread = tp->num;
          inferior_thread ()->control.exception_resume_breakpoint = bp;
        }
    }
}

/* A helper for check_exception_resume that sets an
   exception-breakpoint based on a SystemTap probe.  */

static void
insert_exception_resume_from_probe (struct thread_info *tp,
                                    const struct bound_probe *probe,
                                    struct frame_info *frame)
{
  struct value *arg_value;
  CORE_ADDR handler;
  struct breakpoint *bp;

  arg_value = probe_safe_evaluate_at_pc (frame, 1);
  if (!arg_value)
    return;

  handler = value_as_address (arg_value);

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: exception resume at %s\n",
                        paddress (get_objfile_arch (probe->objfile),
                                  handler));

  bp = set_momentary_breakpoint_at_pc (get_frame_arch (frame),
                                       handler, bp_exception_resume);
  bp->thread = tp->num;
  inferior_thread ()->control.exception_resume_breakpoint = bp;
}

/* This is called when an exception has been intercepted.  Check to
   see whether the exception's destination is of interest, and if so,
   set an exception resume breakpoint there.  */

static void
check_exception_resume (struct execution_control_state *ecs,
                        struct frame_info *frame)
{
  volatile struct gdb_exception e;
  struct bound_probe probe;
  struct symbol *func;

  /* First see if this exception unwinding breakpoint was set via a
     SystemTap probe point.  If so, the probe has two arguments: the
     CFA and the HANDLER.  We ignore the CFA, extract the handler, and
     set a breakpoint there.  */
  probe = find_probe_by_pc (get_frame_pc (frame));
  if (probe.probe)
    {
      insert_exception_resume_from_probe (ecs->event_thread, &probe, frame);
      return;
    }

  func = get_frame_function (frame);
  if (!func)
    return;

  TRY_CATCH (e, RETURN_MASK_ERROR)
    {
      const struct block *b;
      struct block_iterator iter;
      struct symbol *sym;
      int argno = 0;

      /* The exception breakpoint is a thread-specific breakpoint on
         the unwinder's debug hook, declared as:
         
         void _Unwind_DebugHook (void *cfa, void *handler);
         
         The CFA argument indicates the frame to which control is
         about to be transferred.  HANDLER is the destination PC.
         
         We ignore the CFA and set a temporary breakpoint at HANDLER.
         This is not extremely efficient but it avoids issues in gdb
         with computing the DWARF CFA, and it also works even in weird
         cases such as throwing an exception from inside a signal
         handler.  */

      b = SYMBOL_BLOCK_VALUE (func);
      ALL_BLOCK_SYMBOLS (b, iter, sym)
        {
          if (!SYMBOL_IS_ARGUMENT (sym))
            continue;

          if (argno == 0)
            ++argno;
          else
            {
              insert_exception_resume_breakpoint (ecs->event_thread,
                                                  b, frame, sym);
              break;
            }
        }
    }
}

static void
stop_waiting (struct execution_control_state *ecs)
{
  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog, "infrun: stop_waiting\n");

  clear_step_over_info ();

  /* Let callers know we don't want to wait for the inferior anymore.  */
  ecs->wait_some_more = 0;
}

/* Called when we should continue running the inferior, because the
   current event doesn't cause a user visible stop.  This does the
   resuming part; waiting for the next event is done elsewhere.  */

static void
keep_going (struct execution_control_state *ecs)
{
  /* Make sure normal_stop is called if we get a QUIT handled before
     reaching resume.  */
  struct cleanup *old_cleanups = make_cleanup (resume_cleanups, 0);

  /* Save the pc before execution, to compare with pc after stop.  */
  ecs->event_thread->prev_pc
    = regcache_read_pc (get_thread_regcache (ecs->ptid));

  if (ecs->event_thread->control.trap_expected
      && ecs->event_thread->suspend.stop_signal != GDB_SIGNAL_TRAP)
    {
      /* We haven't yet gotten our trap, and either: intercepted a
         non-signal event (e.g., a fork); or took a signal which we
         are supposed to pass through to the inferior.  Simply
         continue.  */
      discard_cleanups (old_cleanups);
      resume (currently_stepping (ecs->event_thread),
              ecs->event_thread->suspend.stop_signal);
    }
  else
    {
      volatile struct gdb_exception e;
      struct regcache *regcache = get_current_regcache ();
      int remove_bp;
      int remove_wps;

      /* Either the trap was not expected, but we are continuing
         anyway (if we got a signal, the user asked it be passed to
         the child)
         -- or --
         We got our expected trap, but decided we should resume from
         it.

         We're going to run this baby now!

         Note that insert_breakpoints won't try to re-insert
         already inserted breakpoints.  Therefore, we don't
         care if breakpoints were already inserted, or not.  */

      /* If we need to step over a breakpoint, and we're not using
         displaced stepping to do so, insert all breakpoints
         (watchpoints, etc.) but the one we're stepping over, step one
         instruction, and then re-insert the breakpoint when that step
         is finished.  */

      remove_bp = (ecs->hit_singlestep_breakpoint
                   || thread_still_needs_step_over (ecs->event_thread));
      remove_wps = (ecs->event_thread->stepping_over_watchpoint
                    && !target_have_steppable_watchpoint);

      if (remove_bp && !use_displaced_stepping (get_regcache_arch (regcache)))
        {
          set_step_over_info (get_regcache_aspace (regcache),
                              regcache_read_pc (regcache), remove_wps);
        }
      else if (remove_wps)
        set_step_over_info (NULL, 0, remove_wps);
      else
        clear_step_over_info ();

      /* Stop stepping if inserting breakpoints fails.  */
      TRY_CATCH (e, RETURN_MASK_ERROR)
        {
          insert_breakpoints ();
        }
      if (e.reason < 0)
        {
          exception_print (gdb_stderr, e);
          stop_waiting (ecs);
          return;
        }

      ecs->event_thread->control.trap_expected = (remove_bp || remove_wps);

      /* Do not deliver GDB_SIGNAL_TRAP (except when the user
         explicitly specifies that such a signal should be delivered
         to the target program).  Typically, that would occur when a
         user is debugging a target monitor on a simulator: the target
         monitor sets a breakpoint; the simulator encounters this
         breakpoint and halts the simulation handing control to GDB;
         GDB, noting that the stop address doesn't map to any known
         breakpoint, returns control back to the simulator; the
         simulator then delivers the hardware equivalent of a
         GDB_SIGNAL_TRAP to the program being debugged.  */
      if (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP
          && !signal_program[ecs->event_thread->suspend.stop_signal])
        ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;

      discard_cleanups (old_cleanups);
      resume (currently_stepping (ecs->event_thread),
              ecs->event_thread->suspend.stop_signal);
    }

  prepare_to_wait (ecs);
}

/* This function normally comes after a resume, before
   handle_inferior_event exits.  It takes care of any last bits of
   housekeeping, and sets the all-important wait_some_more flag.  */

static void
prepare_to_wait (struct execution_control_state *ecs)
{
  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog, "infrun: prepare_to_wait\n");

  /* This is the old end of the while loop.  Let everybody know we
     want to wait for the inferior some more and get called again
     soon.  */
  ecs->wait_some_more = 1;
}

/* We are done with the step range of a step/next/si/ni command.
   Called once for each n of a "step n" operation.  */

static void
end_stepping_range (struct execution_control_state *ecs)
{
  ecs->event_thread->control.stop_step = 1;
  stop_waiting (ecs);
}

/* Several print_*_reason functions to print why the inferior has stopped.
   We always print something when the inferior exits, or receives a signal.
   The rest of the cases are dealt with later on in normal_stop and
   print_it_typical.  Ideally there should be a call to one of these
   print_*_reason functions functions from handle_inferior_event each time
   stop_waiting is called.

   Note that we don't call these directly, instead we delegate that to
   the interpreters, through observers.  Interpreters then call these
   with whatever uiout is right.  */

void
print_end_stepping_range_reason (struct ui_out *uiout)
{
  /* For CLI-like interpreters, print nothing.  */

  if (ui_out_is_mi_like_p (uiout))
    {
      ui_out_field_string (uiout, "reason",
                           async_reason_lookup (EXEC_ASYNC_END_STEPPING_RANGE));
    }
}

void
print_signal_exited_reason (struct ui_out *uiout, enum gdb_signal siggnal)
{
  annotate_signalled ();
  if (ui_out_is_mi_like_p (uiout))
    ui_out_field_string
      (uiout, "reason", async_reason_lookup (EXEC_ASYNC_EXITED_SIGNALLED));
  ui_out_text (uiout, "\nProgram terminated with signal ");
  annotate_signal_name ();
  ui_out_field_string (uiout, "signal-name",
                       gdb_signal_to_name (siggnal));
  annotate_signal_name_end ();
  ui_out_text (uiout, ", ");
  annotate_signal_string ();
  ui_out_field_string (uiout, "signal-meaning",
                       gdb_signal_to_string (siggnal));
  annotate_signal_string_end ();
  ui_out_text (uiout, ".\n");
  ui_out_text (uiout, "The program no longer exists.\n");
}

void
print_exited_reason (struct ui_out *uiout, int exitstatus)
{
  struct inferior *inf = current_inferior ();
  const char *pidstr = target_pid_to_str (pid_to_ptid (inf->pid));

  annotate_exited (exitstatus);
  if (exitstatus)
    {
      if (ui_out_is_mi_like_p (uiout))
        ui_out_field_string (uiout, "reason", 
                             async_reason_lookup (EXEC_ASYNC_EXITED));
      ui_out_text (uiout, "[Inferior ");
      ui_out_text (uiout, plongest (inf->num));
      ui_out_text (uiout, " (");
      ui_out_text (uiout, pidstr);
      ui_out_text (uiout, ") exited with code ");
      ui_out_field_fmt (uiout, "exit-code", "0%o", (unsigned int) exitstatus);
      ui_out_text (uiout, "]\n");
    }
  else
    {
      if (ui_out_is_mi_like_p (uiout))
        ui_out_field_string
          (uiout, "reason", async_reason_lookup (EXEC_ASYNC_EXITED_NORMALLY));
      ui_out_text (uiout, "[Inferior ");
      ui_out_text (uiout, plongest (inf->num));
      ui_out_text (uiout, " (");
      ui_out_text (uiout, pidstr);
      ui_out_text (uiout, ") exited normally]\n");
    }
}

void
print_signal_received_reason (struct ui_out *uiout, enum gdb_signal siggnal)
{
  annotate_signal ();

  if (siggnal == GDB_SIGNAL_0 && !ui_out_is_mi_like_p (uiout))
    {
      struct thread_info *t = inferior_thread ();

      ui_out_text (uiout, "\n[");
      ui_out_field_string (uiout, "thread-name",
                           target_pid_to_str (t->ptid));
      ui_out_field_fmt (uiout, "thread-id", "] #%d", t->num);
      ui_out_text (uiout, " stopped");
    }
  else
    {
      ui_out_text (uiout, "\nProgram received signal ");
      annotate_signal_name ();
      if (ui_out_is_mi_like_p (uiout))
        ui_out_field_string
          (uiout, "reason", async_reason_lookup (EXEC_ASYNC_SIGNAL_RECEIVED));
      ui_out_field_string (uiout, "signal-name",
                           gdb_signal_to_name (siggnal));
      annotate_signal_name_end ();
      ui_out_text (uiout, ", ");
      annotate_signal_string ();
      ui_out_field_string (uiout, "signal-meaning",
                           gdb_signal_to_string (siggnal));
      annotate_signal_string_end ();
    }
  ui_out_text (uiout, ".\n");
}

void
print_no_history_reason (struct ui_out *uiout)
{
  ui_out_text (uiout, "\nNo more reverse-execution history.\n");
}

/* Print current location without a level number, if we have changed
   functions or hit a breakpoint.  Print source line if we have one.
   bpstat_print contains the logic deciding in detail what to print,
   based on the event(s) that just occurred.  */

void
print_stop_event (struct target_waitstatus *ws)
{
  int bpstat_ret;
  int source_flag;
  int do_frame_printing = 1;
  struct thread_info *tp = inferior_thread ();

  bpstat_ret = bpstat_print (tp->control.stop_bpstat, ws->kind);
  switch (bpstat_ret)
    {
    case PRINT_UNKNOWN:
      /* FIXME: cagney/2002-12-01: Given that a frame ID does (or
         should) carry around the function and does (or should) use
         that when doing a frame comparison.  */
      if (tp->control.stop_step
          && frame_id_eq (tp->control.step_frame_id,
                          get_frame_id (get_current_frame ()))
          && step_start_function == find_pc_function (stop_pc))
        {
          /* Finished step, just print source line.  */
          source_flag = SRC_LINE;
        }
      else
        {
          /* Print location and source line.  */
          source_flag = SRC_AND_LOC;
        }
      break;
    case PRINT_SRC_AND_LOC:
      /* Print location and source line.  */
      source_flag = SRC_AND_LOC;
      break;
    case PRINT_SRC_ONLY:
      source_flag = SRC_LINE;
      break;
    case PRINT_NOTHING:
      /* Something bogus.  */
      source_flag = SRC_LINE;
      do_frame_printing = 0;
      break;
    default:
      internal_error (__FILE__, __LINE__, _("Unknown value."));
    }

  /* The behavior of this routine with respect to the source
     flag is:
     SRC_LINE: Print only source line
     LOCATION: Print only location
     SRC_AND_LOC: Print location and source line.  */
  if (do_frame_printing)
    print_stack_frame (get_selected_frame (NULL), 0, source_flag, 1);

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

/* 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 (void)
{
  struct target_waitstatus last;
  ptid_t last_ptid;
  struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);

  get_last_target_status (&last_ptid, &last);

  /* If an exception is thrown from this point on, make sure to
     propagate GDB's knowledge of the executing state to the
     frontend/user running state.  A QUIT is an easy exception to see
     here, so do this before any filtered output.  */
  if (!non_stop)
    make_cleanup (finish_thread_state_cleanup, &minus_one_ptid);
  else if (last.kind != TARGET_WAITKIND_SIGNALLED
           && last.kind != TARGET_WAITKIND_EXITED
           && last.kind != TARGET_WAITKIND_NO_RESUMED)
    make_cleanup (finish_thread_state_cleanup, &inferior_ptid);

  /* As we're presenting a stop, and potentially removing breakpoints,
     update the thread list so we can tell whether there are threads
     running on the target.  With target remote, for example, we can
     only learn about new threads when we explicitly update the thread
     list.  Do this before notifying the interpreters about signal
     stops, end of stepping ranges, etc., so that the "new thread"
     output is emitted before e.g., "Program received signal FOO",
     instead of after.  */
  update_thread_list ();

  if (last.kind == TARGET_WAITKIND_STOPPED && stopped_by_random_signal)
    observer_notify_signal_received (inferior_thread ()->suspend.stop_signal);

  /* As with the notification of thread events, we want to delay
     notifying the user that we've switched thread context until
     the inferior actually stops.

     There's no point in saying anything if the inferior has exited.
     Note that SIGNALLED here means "exited with a signal", not
     "received a signal".

     Also skip saying anything in non-stop mode.  In that mode, as we
     don't want GDB to switch threads behind the user's back, to avoid
     races where the user is typing a command to apply to thread x,
     but GDB switches to thread y before the user finishes entering
     the command, fetch_inferior_event installs a cleanup to restore
     the current thread back to the thread the user had selected right
     after this event is handled, so we're not really switching, only
     informing of a stop.  */
  if (!non_stop
      && !ptid_equal (previous_inferior_ptid, inferior_ptid)
      && target_has_execution
      && last.kind != TARGET_WAITKIND_SIGNALLED
      && last.kind != TARGET_WAITKIND_EXITED
      && last.kind != TARGET_WAITKIND_NO_RESUMED)
    {
      target_terminal_ours_for_output ();
      printf_filtered (_("[Switching to %s]\n"),
                       target_pid_to_str (inferior_ptid));
      annotate_thread_changed ();
      previous_inferior_ptid = inferior_ptid;
    }

  if (last.kind == TARGET_WAITKIND_NO_RESUMED)
    {
      gdb_assert (sync_execution || !target_can_async_p ());

      target_terminal_ours_for_output ();
      printf_filtered (_("No unwaited-for children left.\n"));
    }

  /* Note: this depends on the update_thread_list call above.  */
  if (!breakpoints_should_be_inserted_now () && target_has_execution)
    {
      if (remove_breakpoints ())
        {
          target_terminal_ours_for_output ();
          printf_filtered (_("Cannot remove breakpoints because "
                             "program is no longer writable.\nFurther "
                             "execution is probably impossible.\n"));
        }
    }

  /* 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 ();

  /* Notify observers if we finished a "step"-like command, etc.  */
  if (target_has_execution
      && last.kind != TARGET_WAITKIND_SIGNALLED
      && last.kind != TARGET_WAITKIND_EXITED
      && inferior_thread ()->control.stop_step)
    {
      /* But not if in the middle of doing a "step n" operation for
         n > 1 */
      if (inferior_thread ()->step_multi)
        goto done;

      observer_notify_end_stepping_range ();
    }

  target_terminal_ours ();
  async_enable_stdin ();

  /* Set the current source location.  This will also happen if we
     display the frame below, but the current SAL will be incorrect
     during a user hook-stop function.  */
  if (has_stack_frames () && !stop_stack_dummy)
    set_current_sal_from_frame (get_current_frame ());

  /* Let the user/frontend see the threads as stopped, but do nothing
     if the thread was running an infcall.  We may be e.g., evaluating
     a breakpoint condition.  In that case, the thread had state
     THREAD_RUNNING before the infcall, and shall remain set to
     running, all without informing the user/frontend about state
     transition changes.  If this is actually a call command, then the
     thread was originally already stopped, so there's no state to
     finish either.  */
  if (target_has_execution && inferior_thread ()->control.in_infcall)
    discard_cleanups (old_chain);
  else
    do_cleanups (old_chain);

  /* Look up the hook_stop and run it (CLI internally handles problem
     of stop_command's pre-hook not existing).  */
  if (stop_command)
    catch_errors (hook_stop_stub, stop_command,
                  "Error while running hook_stop:\n", RETURN_MASK_ALL);

  if (!has_stack_frames ())
    goto done;

  if (last.kind == TARGET_WAITKIND_SIGNALLED
      || last.kind == TARGET_WAITKIND_EXITED)
    goto done;

  /* Select innermost stack frame - i.e., current frame is frame 0,
     and current location is based on that.
     Don't do this on return from a stack dummy routine,
     or if the program has exited.  */

  if (!stop_stack_dummy)
    {
      select_frame (get_current_frame ());

      /* If --batch-silent is enabled then there's no need to print the current
         source location, and to try risks causing an error message about
         missing source files.  */
      if (stop_print_frame && !batch_silent)
        print_stop_event (&last);
    }

  /* Save the function value return registers, if we care.
     We might be about to restore their previous contents.  */
  if (inferior_thread ()->control.proceed_to_finish
      && execution_direction != EXEC_REVERSE)
    {
      /* This should not be necessary.  */
      if (stop_registers)
        regcache_xfree (stop_registers);

      /* NB: The copy goes through to the target picking up the value of
         all the registers.  */
      stop_registers = regcache_dup (get_current_regcache ());
    }

  if (stop_stack_dummy == STOP_STACK_DUMMY)
    {
      /* Pop the empty frame that contains the stack dummy.
         This also restores inferior state prior to the call
         (struct infcall_suspend_state).  */
      struct frame_info *frame = get_current_frame ();

      gdb_assert (get_frame_type (frame) == DUMMY_FRAME);
      frame_pop (frame);
      /* frame_pop() calls reinit_frame_cache as the last thing it
         does which means there's currently no selected frame.  We
         don't need to re-establish a selected frame if the dummy call
         returns normally, that will be done by
         restore_infcall_control_state.  However, we do have to handle
         the case where the dummy call is returning after being
         stopped (e.g. the dummy call previously hit a breakpoint).
         We can't know which case we have so just always re-establish
         a selected frame here.  */
      select_frame (get_current_frame ());
    }

done:
  annotate_stopped ();

  /* Suppress the stop observer if we're in the middle of:

     - a step n (n > 1), as there still more steps to be done.

     - a "finish" command, as the observer will be called in
       finish_command_continuation, so it can include the inferior
       function's return value.

     - calling an inferior function, as we pretend we inferior didn't
       run at all.  The return value of the call is handled by the
       expression evaluator, through call_function_by_hand.  */

  if (!target_has_execution
      || last.kind == TARGET_WAITKIND_SIGNALLED
      || last.kind == TARGET_WAITKIND_EXITED
      || last.kind == TARGET_WAITKIND_NO_RESUMED
      || (!(inferior_thread ()->step_multi
            && inferior_thread ()->control.stop_step)
          && !(inferior_thread ()->control.stop_bpstat
               && inferior_thread ()->control.proceed_to_finish)
          && !inferior_thread ()->control.in_infcall))
    {
      if (!ptid_equal (inferior_ptid, null_ptid))
        observer_notify_normal_stop (inferior_thread ()->control.stop_bpstat,
                                     stop_print_frame);
      else
        observer_notify_normal_stop (NULL, stop_print_frame);
    }

  if (target_has_execution)
    {
      if (last.kind != TARGET_WAITKIND_SIGNALLED
          && last.kind != TARGET_WAITKIND_EXITED)
        /* 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 (inferior_thread ()->control.stop_bpstat);
    }

  /* Try to get rid of automatically added inferiors that are no
     longer needed.  Keeping those around slows down things linearly.
     Note that this never removes the current inferior.  */
  prune_inferiors ();
}

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

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

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

static void
signal_cache_update (int signo)
{
  if (signo == -1)
    {
      for (signo = 0; signo < (int) GDB_SIGNAL_LAST; signo++)
        signal_cache_update (signo);

      return;
    }

  signal_pass[signo] = (signal_stop[signo] == 0
                        && signal_print[signo] == 0
                        && signal_program[signo] == 1
                        && signal_catch[signo] == 0);
}

int
signal_stop_update (int signo, int state)
{
  int ret = signal_stop[signo];

  signal_stop[signo] = state;
  signal_cache_update (signo);
  return ret;
}

int
signal_print_update (int signo, int state)
{
  int ret = signal_print[signo];

  signal_print[signo] = state;
  signal_cache_update (signo);
  return ret;
}

int
signal_pass_update (int signo, int state)
{
  int ret = signal_program[signo];

  signal_program[signo] = state;
  signal_cache_update (signo);
  return ret;
}

/* Update the global 'signal_catch' from INFO and notify the
   target.  */

void
signal_catch_update (const unsigned int *info)
{
  int i;

  for (i = 0; i < GDB_SIGNAL_LAST; ++i)
    signal_catch[i] = info[i] > 0;
  signal_cache_update (-1);
  target_pass_signals ((int) GDB_SIGNAL_LAST, signal_pass);
}

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

static void
sig_print_info (enum gdb_signal oursig)
{
  const char *name = gdb_signal_to_name (oursig);
  int name_padding = 13 - strlen (name);

  if (name_padding <= 0)
    name_padding = 0;

  printf_filtered ("%s", name);
  printf_filtered ("%*.*s ", name_padding, name_padding, "                 ");
  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", gdb_signal_to_string (oursig));
}

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

static void
handle_command (char *args, int from_tty)
{
  char **argv;
  int digits, wordlen;
  int sigfirst, signum, siglast;
  enum gdb_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) GDB_SIGNAL_LAST;
  sigs = (unsigned char *) alloca (nsigs);
  memset (sigs, 0, nsigs);

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

  argv = gdb_buildargv (args);
  old_chain = make_cleanup_freeargv (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)
            gdb_signal_from_command (atoi (*argv));
          if ((*argv)[digits] == '-')
            {
              siglast = (int)
                gdb_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 = gdb_signal_from_name (*argv);
          if (oursig != GDB_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 gdb_signal) signum)
            {
            case GDB_SIGNAL_TRAP:
            case GDB_SIGNAL_INT:
              if (!allsigs && !sigs[signum])
                {
                  if (query (_("%s is used by the debugger.\n\
Are you sure you want to change it? "),
                             gdb_signal_to_name ((enum gdb_signal) signum)))
                    {
                      sigs[signum] = 1;
                    }
                  else
                    {
                      printf_unfiltered (_("Not confirmed, unchanged.\n"));
                      gdb_flush (gdb_stdout);
                    }
                }
              break;
            case GDB_SIGNAL_0:
            case GDB_SIGNAL_DEFAULT:
            case GDB_SIGNAL_UNKNOWN:
              /* Make sure that "all" doesn't print these.  */
              break;
            default:
              sigs[signum] = 1;
              break;
            }
        }

      argv++;
    }

  for (signum = 0; signum < nsigs; signum++)
    if (sigs[signum])
      {
        signal_cache_update (-1);
        target_pass_signals ((int) GDB_SIGNAL_LAST, signal_pass);
        target_program_signals ((int) GDB_SIGNAL_LAST, signal_program);

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

        break;
      }

  do_cleanups (old_chain);
}

/* Complete the "handle" command.  */

static VEC (char_ptr) *
handle_completer (struct cmd_list_element *ignore,
                  const char *text, const char *word)
{
  VEC (char_ptr) *vec_signals, *vec_keywords, *return_val;
  static const char * const keywords[] =
    {
      "all",
      "stop",
      "ignore",
      "print",
      "pass",
      "nostop",
      "noignore",
      "noprint",
      "nopass",
      NULL,
    };

  vec_signals = signal_completer (ignore, text, word);
  vec_keywords = complete_on_enum (keywords, word, word);

  return_val = VEC_merge (char_ptr, vec_signals, vec_keywords);
  VEC_free (char_ptr, vec_signals);
  VEC_free (char_ptr, vec_keywords);
  return return_val;
}

static void
xdb_handle_command (char *args, int from_tty)
{
  char **argv;
  struct cleanup *old_chain;

  if (args == NULL)
    error_no_arg (_("xdb command"));

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

  argv = gdb_buildargv (args);
  old_chain = make_cleanup_freeargv (argv);
  if (argv[1] != (char *) NULL)
    {
      char *argBuf;
      int bufLen;

      bufLen = strlen (argv[0]) + 20;
      argBuf = (char *) xmalloc (bufLen);
      if (argBuf)
        {
          int validFlag = 1;
          enum gdb_signal oursig;

          oursig = gdb_signal_from_name (argv[0]);
          memset (argBuf, 0, bufLen);
          if (strcmp (argv[1], "Q") == 0)
            sprintf (argBuf, "%s %s", argv[0], "noprint");
          else
            {
              if (strcmp (argv[1], "s") == 0)
                {
                  if (!signal_stop[oursig])
                    sprintf (argBuf, "%s %s", argv[0], "stop");
                  else
                    sprintf (argBuf, "%s %s", argv[0], "nostop");
                }
              else if (strcmp (argv[1], "i") == 0)
                {
                  if (!signal_program[oursig])
                    sprintf (argBuf, "%s %s", argv[0], "pass");
                  else
                    sprintf (argBuf, "%s %s", argv[0], "nopass");
                }
              else if (strcmp (argv[1], "r") == 0)
                {
                  if (!signal_print[oursig])
                    sprintf (argBuf, "%s %s", argv[0], "print");
                  else
                    sprintf (argBuf, "%s %s", argv[0], "noprint");
                }
              else
                validFlag = 0;
            }
          if (validFlag)
            handle_command (argBuf, from_tty);
          else
            printf_filtered (_("Invalid signal handling flag.\n"));
          if (argBuf)
            xfree (argBuf);
        }
    }
  do_cleanups (old_chain);
}

enum gdb_signal
gdb_signal_from_command (int num)
{
  if (num >= 1 && num <= 15)
    return (enum gdb_signal) num;
  error (_("Only signals 1-15 are valid as numeric signals.\n\
Use \"info signals\" for a list of symbolic signals."));
}

/* 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 (char *signum_exp, int from_tty)
{
  enum gdb_signal oursig;

  sig_print_header ();

  if (signum_exp)
    {
      /* First see if this is a symbol name.  */
      oursig = gdb_signal_from_name (signum_exp);
      if (oursig == GDB_SIGNAL_UNKNOWN)
        {
          /* No, try numeric.  */
          oursig =
            gdb_signal_from_command (parse_and_eval_long (signum_exp));
        }
      sig_print_info (oursig);
      return;
    }

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

      if (oursig != GDB_SIGNAL_UNKNOWN
          && oursig != GDB_SIGNAL_DEFAULT && oursig != GDB_SIGNAL_0)
        sig_print_info (oursig);
    }

  printf_filtered (_("\nUse the \"handle\" command "
                     "to change these tables.\n"));
}

/* Check if it makes sense to read $_siginfo from the current thread
   at this point.  If not, throw an error.  */

static void
validate_siginfo_access (void)
{
  /* No current inferior, no siginfo.  */
  if (ptid_equal (inferior_ptid, null_ptid))
    error (_("No thread selected."));

  /* Don't try to read from a dead thread.  */
  if (is_exited (inferior_ptid))
    error (_("The current thread has terminated"));

  /* ... or from a spinning thread.  */
  if (is_running (inferior_ptid))
    error (_("Selected thread is running."));
}

/* The $_siginfo convenience variable is a bit special.  We don't know
   for sure the type of the value until we actually have a chance to
   fetch the data.  The type can change depending on gdbarch, so it is
   also dependent on which thread you have selected.

     1. making $_siginfo be an internalvar that creates a new value on
     access.

     2. making the value of $_siginfo be an lval_computed value.  */

/* This function implements the lval_computed support for reading a
   $_siginfo value.  */

static void
siginfo_value_read (struct value *v)
{
  LONGEST transferred;

  validate_siginfo_access ();

  transferred =
    target_read (&current_target, TARGET_OBJECT_SIGNAL_INFO,
                 NULL,
                 value_contents_all_raw (v),
                 value_offset (v),
                 TYPE_LENGTH (value_type (v)));

  if (transferred != TYPE_LENGTH (value_type (v)))
    error (_("Unable to read siginfo"));
}

/* This function implements the lval_computed support for writing a
   $_siginfo value.  */

static void
siginfo_value_write (struct value *v, struct value *fromval)
{
  LONGEST transferred;

  validate_siginfo_access ();

  transferred = target_write (&current_target,
                              TARGET_OBJECT_SIGNAL_INFO,
                              NULL,
                              value_contents_all_raw (fromval),
                              value_offset (v),
                              TYPE_LENGTH (value_type (fromval)));

  if (transferred != TYPE_LENGTH (value_type (fromval)))
    error (_("Unable to write siginfo"));
}

static const struct lval_funcs siginfo_value_funcs =
  {
    siginfo_value_read,
    siginfo_value_write
  };

/* Return a new value with the correct type for the siginfo object of
   the current thread using architecture GDBARCH.  Return a void value
   if there's no object available.  */

static struct value *
siginfo_make_value (struct gdbarch *gdbarch, struct internalvar *var,
                    void *ignore)
{
  if (target_has_stack
      && !ptid_equal (inferior_ptid, null_ptid)
      && gdbarch_get_siginfo_type_p (gdbarch))
    {
      struct type *type = gdbarch_get_siginfo_type (gdbarch);

      return allocate_computed_value (type, &siginfo_value_funcs, NULL);
    }

  return allocate_value (builtin_type (gdbarch)->builtin_void);
}

\f
/* infcall_suspend_state contains state about the program itself like its
   registers and any signal it received when it last stopped.
   This state must be restored regardless of how the inferior function call
   ends (either successfully, or after it hits a breakpoint or signal)
   if the program is to properly continue where it left off.  */

struct infcall_suspend_state
{
  struct thread_suspend_state thread_suspend;
#if 0 /* Currently unused and empty structures are not valid C.  */
  struct inferior_suspend_state inferior_suspend;
#endif

  /* Other fields:  */
  CORE_ADDR stop_pc;
  struct regcache *registers;

  /* Format of SIGINFO_DATA or NULL if it is not present.  */
  struct gdbarch *siginfo_gdbarch;

  /* The inferior format depends on SIGINFO_GDBARCH and it has a length of
     TYPE_LENGTH (gdbarch_get_siginfo_type ()).  For different gdbarch the
     content would be invalid.  */
  gdb_byte *siginfo_data;
};

struct infcall_suspend_state *
save_infcall_suspend_state (void)
{
  struct infcall_suspend_state *inf_state;
  struct thread_info *tp = inferior_thread ();
#if 0
  struct inferior *inf = current_inferior ();
#endif
  struct regcache *regcache = get_current_regcache ();
  struct gdbarch *gdbarch = get_regcache_arch (regcache);
  gdb_byte *siginfo_data = NULL;

  if (gdbarch_get_siginfo_type_p (gdbarch))
    {
      struct type *type = gdbarch_get_siginfo_type (gdbarch);
      size_t len = TYPE_LENGTH (type);
      struct cleanup *back_to;

      siginfo_data = xmalloc (len);
      back_to = make_cleanup (xfree, siginfo_data);

      if (target_read (&current_target, TARGET_OBJECT_SIGNAL_INFO, NULL,
                       siginfo_data, 0, len) == len)
        discard_cleanups (back_to);
      else
        {
          /* Errors ignored.  */
          do_cleanups (back_to);
          siginfo_data = NULL;
        }
    }

  inf_state = XCNEW (struct infcall_suspend_state);

  if (siginfo_data)
    {
      inf_state->siginfo_gdbarch = gdbarch;
      inf_state->siginfo_data = siginfo_data;
    }

  inf_state->thread_suspend = tp->suspend;
#if 0 /* Currently unused and empty structures are not valid C.  */
  inf_state->inferior_suspend = inf->suspend;
#endif

  /* run_inferior_call will not use the signal due to its `proceed' call with
     GDB_SIGNAL_0 anyway.  */
  tp->suspend.stop_signal = GDB_SIGNAL_0;

  inf_state->stop_pc = stop_pc;

  inf_state->registers = regcache_dup (regcache);

  return inf_state;
}

/* Restore inferior session state to INF_STATE.  */

void
restore_infcall_suspend_state (struct infcall_suspend_state *inf_state)
{
  struct thread_info *tp = inferior_thread ();
#if 0
  struct inferior *inf = current_inferior ();
#endif
  struct regcache *regcache = get_current_regcache ();
  struct gdbarch *gdbarch = get_regcache_arch (regcache);

  tp->suspend = inf_state->thread_suspend;
#if 0 /* Currently unused and empty structures are not valid C.  */
  inf->suspend = inf_state->inferior_suspend;
#endif

  stop_pc = inf_state->stop_pc;

  if (inf_state->siginfo_gdbarch == gdbarch)
    {
      struct type *type = gdbarch_get_siginfo_type (gdbarch);

      /* Errors ignored.  */
      target_write (&current_target, TARGET_OBJECT_SIGNAL_INFO, NULL,
                    inf_state->siginfo_data, 0, TYPE_LENGTH (type));
    }

  /* The inferior can be gone if the user types "print exit(0)"
     (and perhaps other times).  */
  if (target_has_execution)
    /* NB: The register write goes through to the target.  */
    regcache_cpy (regcache, inf_state->registers);

  discard_infcall_suspend_state (inf_state);
}

static void
do_restore_infcall_suspend_state_cleanup (void *state)
{
  restore_infcall_suspend_state (state);
}

struct cleanup *
make_cleanup_restore_infcall_suspend_state
  (struct infcall_suspend_state *inf_state)
{
  return make_cleanup (do_restore_infcall_suspend_state_cleanup, inf_state);
}

void
discard_infcall_suspend_state (struct infcall_suspend_state *inf_state)
{
  regcache_xfree (inf_state->registers);
  xfree (inf_state->siginfo_data);
  xfree (inf_state);
}

struct regcache *
get_infcall_suspend_state_regcache (struct infcall_suspend_state *inf_state)
{
  return inf_state->registers;
}

/* infcall_control_state contains state regarding gdb's control of the
   inferior itself like stepping control.  It also contains session state like
   the user's currently selected frame.  */

struct infcall_control_state
{
  struct thread_control_state thread_control;
  struct inferior_control_state inferior_control;

  /* Other fields:  */
  enum stop_stack_kind stop_stack_dummy;
  int stopped_by_random_signal;
  int stop_after_trap;

  /* ID if the selected frame when the inferior function call was made.  */
  struct frame_id selected_frame_id;
};

/* Save all of the information associated with the inferior<==>gdb
   connection.  */

struct infcall_control_state *
save_infcall_control_state (void)
{
  struct infcall_control_state *inf_status = xmalloc (sizeof (*inf_status));
  struct thread_info *tp = inferior_thread ();
  struct inferior *inf = current_inferior ();

  inf_status->thread_control = tp->control;
  inf_status->inferior_control = inf->control;

  tp->control.step_resume_breakpoint = NULL;
  tp->control.exception_resume_breakpoint = NULL;

  /* Save original bpstat chain to INF_STATUS; replace it in TP 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_infcall_control_state is
     called.  */
  tp->control.stop_bpstat = bpstat_copy (tp->control.stop_bpstat);

  /* Other fields:  */
  inf_status->stop_stack_dummy = stop_stack_dummy;
  inf_status->stopped_by_random_signal = stopped_by_random_signal;
  inf_status->stop_after_trap = stop_after_trap;

  inf_status->selected_frame_id = get_frame_id (get_selected_frame (NULL));

  return inf_status;
}

static int
restore_selected_frame (void *args)
{
  struct frame_id *fid = (struct frame_id *) args;
  struct frame_info *frame;

  frame = frame_find_by_id (*fid);

  /* If inf_status->selected_frame_id is NULL, there was no previously
     selected frame.  */
  if (frame == NULL)
    {
      warning (_("Unable to restore previously selected frame."));
      return 0;
    }

  select_frame (frame);

  return (1);
}

/* Restore inferior session state to INF_STATUS.  */

void
restore_infcall_control_state (struct infcall_control_state *inf_status)
{
  struct thread_info *tp = inferior_thread ();
  struct inferior *inf = current_inferior ();

  if (tp->control.step_resume_breakpoint)
    tp->control.step_resume_breakpoint->disposition = disp_del_at_next_stop;

  if (tp->control.exception_resume_breakpoint)
    tp->control.exception_resume_breakpoint->disposition
      = disp_del_at_next_stop;

  /* Handle the bpstat_copy of the chain.  */
  bpstat_clear (&tp->control.stop_bpstat);

  tp->control = inf_status->thread_control;
  inf->control = inf_status->inferior_control;

  /* Other fields:  */
  stop_stack_dummy = inf_status->stop_stack_dummy;
  stopped_by_random_signal = inf_status->stopped_by_random_signal;
  stop_after_trap = inf_status->stop_after_trap;

  if (target_has_stack)
    {
      /* 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, &inf_status->selected_frame_id,
           "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 ());
    }

  xfree (inf_status);
}

static void
do_restore_infcall_control_state_cleanup (void *sts)
{
  restore_infcall_control_state (sts);
}

struct cleanup *
make_cleanup_restore_infcall_control_state
  (struct infcall_control_state *inf_status)
{
  return make_cleanup (do_restore_infcall_control_state_cleanup, inf_status);
}

void
discard_infcall_control_state (struct infcall_control_state *inf_status)
{
  if (inf_status->thread_control.step_resume_breakpoint)
    inf_status->thread_control.step_resume_breakpoint->disposition
      = disp_del_at_next_stop;

  if (inf_status->thread_control.exception_resume_breakpoint)
    inf_status->thread_control.exception_resume_breakpoint->disposition
      = disp_del_at_next_stop;

  /* See save_infcall_control_state for info on stop_bpstat.  */
  bpstat_clear (&inf_status->thread_control.stop_bpstat);

  xfree (inf_status);
}
\f
/* restore_inferior_ptid() will be used by the cleanup machinery
   to restore the inferior_ptid value saved in a call to
   save_inferior_ptid().  */

static void
restore_inferior_ptid (void *arg)
{
  ptid_t *saved_ptid_ptr = arg;

  inferior_ptid = *saved_ptid_ptr;
  xfree (arg);
}

/* Save the value of inferior_ptid so that it may be restored by a
   later call to do_cleanups().  Returns the struct cleanup pointer
   needed for later doing the cleanup.  */

struct cleanup *
save_inferior_ptid (void)
{
  ptid_t *saved_ptid_ptr;

  saved_ptid_ptr = xmalloc (sizeof (ptid_t));
  *saved_ptid_ptr = inferior_ptid;
  return make_cleanup (restore_inferior_ptid, saved_ptid_ptr);
}

/* See infrun.h.  */

void
clear_exit_convenience_vars (void)
{
  clear_internalvar (lookup_internalvar ("_exitsignal"));
  clear_internalvar (lookup_internalvar ("_exitcode"));
}
\f

/* User interface for reverse debugging:
   Set exec-direction / show exec-direction commands
   (returns error unless target implements to_set_exec_direction method).  */

int execution_direction = EXEC_FORWARD;
static const char exec_forward[] = "forward";
static const char exec_reverse[] = "reverse";
static const char *exec_direction = exec_forward;
static const char *const exec_direction_names[] = {
  exec_forward,
  exec_reverse,
  NULL
};

static void
set_exec_direction_func (char *args, int from_tty,
                         struct cmd_list_element *cmd)
{
  if (target_can_execute_reverse)
    {
      if (!strcmp (exec_direction, exec_forward))
        execution_direction = EXEC_FORWARD;
      else if (!strcmp (exec_direction, exec_reverse))
        execution_direction = EXEC_REVERSE;
    }
  else
    {
      exec_direction = exec_forward;
      error (_("Target does not support this operation."));
    }
}

static void
show_exec_direction_func (struct ui_file *out, int from_tty,
                          struct cmd_list_element *cmd, const char *value)
{
  switch (execution_direction) {
  case EXEC_FORWARD:
    fprintf_filtered (out, _("Forward.\n"));
    break;
  case EXEC_REVERSE:
    fprintf_filtered (out, _("Reverse.\n"));
    break;
  default:
    internal_error (__FILE__, __LINE__,
                    _("bogus execution_direction value: %d"),
                    (int) execution_direction);
  }
}

static void
show_schedule_multiple (struct ui_file *file, int from_tty,
                        struct cmd_list_element *c, const char *value)
{
  fprintf_filtered (file, _("Resuming the execution of threads "
                            "of all processes is %s.\n"), value);
}

/* Implementation of `siginfo' variable.  */

static const struct internalvar_funcs siginfo_funcs =
{
  siginfo_make_value,
  NULL,
  NULL
};

void
_initialize_infrun (void)
{
  int i;
  int numsigs;
  struct cmd_list_element *c;

  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);

  c = add_com ("handle", class_run, handle_command, _("\
Specify how to handle signals.\n\
Usage: handle SIGNAL [ACTIONS]\n\
Args are signals and actions to apply to those signals.\n\
If no actions are specified, the current settings for the specified signals\n\
will be displayed instead.\n\
\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\
\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.\n\
\n\
Multiple signals may be specified.  Signal numbers and signal names\n\
may be interspersed with actions, with the actions being performed for\n\
all signals cumulatively specified."));
  set_cmd_completer (c, handle_completer);

  if (xdb_commands)
    {
      add_com ("lz", class_info, signals_info, _("\
What debugger does when program gets various signals.\n\
Specify a signal as argument to print info on that signal only."));
      add_com ("z", class_run, xdb_handle_command, _("\
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 \"s\" (toggles between stop and nostop),\n\
\"r\" (toggles between print and noprint), \"i\" (toggles between pass and \
nopass), \"Q\" (noprint)\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."));
    }

  if (!dbx_commands)
    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);

  add_setshow_zuinteger_cmd ("infrun", class_maintenance, &debug_infrun, _("\
Set inferior debugging."), _("\
Show inferior debugging."), _("\
When non-zero, inferior specific debugging is enabled."),
                             NULL,
                             show_debug_infrun,
                             &setdebuglist, &showdebuglist);

  add_setshow_boolean_cmd ("displaced", class_maintenance,
                           &debug_displaced, _("\
Set displaced stepping debugging."), _("\
Show displaced stepping debugging."), _("\
When non-zero, displaced stepping specific debugging is enabled."),
                            NULL,
                            show_debug_displaced,
                            &setdebuglist, &showdebuglist);

  add_setshow_boolean_cmd ("non-stop", no_class,
                           &non_stop_1, _("\
Set whether gdb controls the inferior in non-stop mode."), _("\
Show whether gdb controls the inferior in non-stop mode."), _("\
When debugging a multi-threaded program and this setting is\n\
off (the default, also called all-stop mode), when one thread stops\n\
(for a breakpoint, watchpoint, exception, or similar events), GDB stops\n\
all other threads in the program while you interact with the thread of\n\
interest.  When you continue or step a thread, you can allow the other\n\
threads to run, or have them remain stopped, but while you inspect any\n\
thread's state, all threads stop.\n\
\n\
In non-stop mode, when one thread stops, other threads can continue\n\
to run freely.  You'll be able to step each thread independently,\n\
leave it stopped or free to run as needed."),
                           set_non_stop,
                           show_non_stop,
                           &setlist,
                           &showlist);

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

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

  /* Signals that are not errors should not normally enter the debugger.  */
  signal_stop[GDB_SIGNAL_ALRM] = 0;
  signal_print[GDB_SIGNAL_ALRM] = 0;
  signal_stop[GDB_SIGNAL_VTALRM] = 0;
  signal_print[GDB_SIGNAL_VTALRM] = 0;
  signal_stop[GDB_SIGNAL_PROF] = 0;
  signal_print[GDB_SIGNAL_PROF] = 0;
  signal_stop[GDB_SIGNAL_CHLD] = 0;
  signal_print[GDB_SIGNAL_CHLD] = 0;
  signal_stop[GDB_SIGNAL_IO] = 0;
  signal_print[GDB_SIGNAL_IO] = 0;
  signal_stop[GDB_SIGNAL_POLL] = 0;
  signal_print[GDB_SIGNAL_POLL] = 0;
  signal_stop[GDB_SIGNAL_URG] = 0;
  signal_print[GDB_SIGNAL_URG] = 0;
  signal_stop[GDB_SIGNAL_WINCH] = 0;
  signal_print[GDB_SIGNAL_WINCH] = 0;
  signal_stop[GDB_SIGNAL_PRIO] = 0;
  signal_print[GDB_SIGNAL_PRIO] = 0;

  /* These signals are used internally by user-level thread
     implementations.  (See signal(5) on Solaris.)  Like the above
     signals, a healthy program receives and handles them as part of
     its normal operation.  */
  signal_stop[GDB_SIGNAL_LWP] = 0;
  signal_print[GDB_SIGNAL_LWP] = 0;
  signal_stop[GDB_SIGNAL_WAITING] = 0;
  signal_print[GDB_SIGNAL_WAITING] = 0;
  signal_stop[GDB_SIGNAL_CANCEL] = 0;
  signal_print[GDB_SIGNAL_CANCEL] = 0;

  /* Update cached state.  */
  signal_cache_update (-1);

  add_setshow_zinteger_cmd ("stop-on-solib-events", class_support,
                            &stop_on_solib_events, _("\
Set stopping for shared library events."), _("\
Show stopping for shared library events."), _("\
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."),
                            set_stop_on_solib_events,
                            show_stop_on_solib_events,
                            &setlist, &showlist);

  add_setshow_enum_cmd ("follow-fork-mode", class_run,
                        follow_fork_mode_kind_names,
                        &follow_fork_mode_string, _("\
Set debugger response to a program call of fork or vfork."), _("\
Show debugger response to a program call of fork or vfork."), _("\
A fork or vfork creates a new process.  follow-fork-mode can be:\n\
  parent  - the original process is debugged after a fork\n\
  child   - the new process is debugged after a fork\n\
The unfollowed process will continue to run.\n\
By default, the debugger will follow the parent process."),
                        NULL,
                        show_follow_fork_mode_string,
                        &setlist, &showlist);

  add_setshow_enum_cmd ("follow-exec-mode", class_run,
                        follow_exec_mode_names,
                        &follow_exec_mode_string, _("\
Set debugger response to a program call of exec."), _("\
Show debugger response to a program call of exec."), _("\
An exec call replaces the program image of a process.\n\
\n\
follow-exec-mode can be:\n\
\n\
  new - the debugger creates a new inferior and rebinds the process\n\
to this new inferior.  The program the process was running before\n\
the exec call can be restarted afterwards by restarting the original\n\
inferior.\n\
\n\
  same - the debugger keeps the process bound to the same inferior.\n\
The new executable image replaces the previous executable loaded in\n\
the inferior.  Restarting the inferior after the exec call restarts\n\
the executable the process was running after the exec call.\n\
\n\
By default, the debugger will use the same inferior."),
                        NULL,
                        show_follow_exec_mode_string,
                        &setlist, &showlist);

  add_setshow_enum_cmd ("scheduler-locking", class_run, 
                        scheduler_enums, &scheduler_mode, _("\
Set mode for locking scheduler during execution."), _("\
Show mode for locking scheduler during execution."), _("\
off  == no locking (threads may preempt at any time)\n\
on   == full locking (no thread except the current thread may run)\n\
step == scheduler locked during every single-step operation.\n\
        In this mode, no other thread may run during a step command.\n\
        Other threads may run while stepping over a function call ('next')."), 
                        set_schedlock_func,     /* traps on target vector */
                        show_scheduler_mode,
                        &setlist, &showlist);

  add_setshow_boolean_cmd ("schedule-multiple", class_run, &sched_multi, _("\
Set mode for resuming threads of all processes."), _("\
Show mode for resuming threads of all processes."), _("\
When on, execution commands (such as 'continue' or 'next') resume all\n\
threads of all processes.  When off (which is the default), execution\n\
commands only resume the threads of the current process.  The set of\n\
threads that are resumed is further refined by the scheduler-locking\n\
mode (see help set scheduler-locking)."),
                           NULL,
                           show_schedule_multiple,
                           &setlist, &showlist);

  add_setshow_boolean_cmd ("step-mode", class_run, &step_stop_if_no_debug, _("\
Set mode of the step operation."), _("\
Show mode of the step operation."), _("\
When set, doing a step over a function without debug line information\n\
will stop at the first instruction of that function. Otherwise, the\n\
function is skipped and the step command stops at a different source line."),
                           NULL,
                           show_step_stop_if_no_debug,
                           &setlist, &showlist);

  add_setshow_auto_boolean_cmd ("displaced-stepping", class_run,
                                &can_use_displaced_stepping, _("\
Set debugger's willingness to use displaced stepping."), _("\
Show debugger's willingness to use displaced stepping."), _("\
If on, gdb will use displaced stepping to step over breakpoints if it is\n\
supported by the target architecture.  If off, gdb will not use displaced\n\
stepping to step over breakpoints, even if such is supported by the target\n\
architecture.  If auto (which is the default), gdb will use displaced stepping\n\
if the target architecture supports it and non-stop mode is active, but will not\n\
use it in all-stop mode (see help set non-stop)."),
                                NULL,
                                show_can_use_displaced_stepping,
                                &setlist, &showlist);

  add_setshow_enum_cmd ("exec-direction", class_run, exec_direction_names,
                        &exec_direction, _("Set direction of execution.\n\
Options are 'forward' or 'reverse'."),
                        _("Show direction of execution (forward/reverse)."),
                        _("Tells gdb whether to execute forward or backward."),
                        set_exec_direction_func, show_exec_direction_func,
                        &setlist, &showlist);

  /* Set/show detach-on-fork: user-settable mode.  */

  add_setshow_boolean_cmd ("detach-on-fork", class_run, &detach_fork, _("\
Set whether gdb will detach the child of a fork."), _("\
Show whether gdb will detach the child of a fork."), _("\
Tells gdb whether to detach the child of a fork."),
                           NULL, NULL, &setlist, &showlist);

  /* Set/show disable address space randomization mode.  */

  add_setshow_boolean_cmd ("disable-randomization", class_support,
                           &disable_randomization, _("\
Set disabling of debuggee's virtual address space randomization."), _("\
Show disabling of debuggee's virtual address space randomization."), _("\
When this mode is on (which is the default), randomization of the virtual\n\
address space is disabled.  Standalone programs run with the randomization\n\
enabled by default on some platforms."),
                           &set_disable_randomization,
                           &show_disable_randomization,
                           &setlist, &showlist);

  /* ptid initializations */
  inferior_ptid = null_ptid;
  target_last_wait_ptid = minus_one_ptid;

  observer_attach_thread_ptid_changed (infrun_thread_ptid_changed);
  observer_attach_thread_stop_requested (infrun_thread_stop_requested);
  observer_attach_thread_exit (infrun_thread_thread_exit);
  observer_attach_inferior_exit (infrun_inferior_exit);

  /* Explicitly create without lookup, since that tries to create a
     value with a void typed value, and when we get here, gdbarch
     isn't initialized yet.  At this point, we're quite sure there
     isn't another convenience variable of the same name.  */
  create_internalvar_type_lazy ("_siginfo", &siginfo_funcs, NULL);

  add_setshow_boolean_cmd ("observer", no_class,
                           &observer_mode_1, _("\
Set whether gdb controls the inferior in observer mode."), _("\
Show whether gdb controls the inferior in observer mode."), _("\
In observer mode, GDB can get data from the inferior, but not\n\
affect its execution.  Registers and memory may not be changed,\n\
breakpoints may not be set, and the program cannot be interrupted\n\
or signalled."),
                           set_observer_mode,
                           show_observer_mode,
                           &setlist,
                           &showlist);
}