manually sync from the CVS repository

[pf3gnuchains/pf3gnuchains4x.git] / gdb / infrun.c

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

   Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
   1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007,
   2008, 2009 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 "gdb_string.h"
#include <ctype.h>
#include "symtab.h"
#include "frame.h"
#include "inferior.h"
#include "exceptions.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 "gdb_assert.h"
#include "mi/mi-common.h"
#include "event-top.h"
#include "record.h"
#include "inline-frame.h"
#include "jit.h"

/* Prototypes for local functions */

static void signals_info (char *, int);

static void handle_command (char *, int);

static void sig_print_info (enum target_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 void build_infrun (void);

static int follow_fork (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 int currently_stepping_or_nexting_callback (struct thread_info *tp,
                                                   void *data);

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

static int prepare_to_proceed (int);

void _initialize_infrun (void);

void nullify_last_target_wait_ptid (void);

/* 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;

/* wait_for_inferior 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;

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);
}

static 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);
}

/* If the program uses ELF-style shared libraries, then calls to
   functions in shared libraries go through stubs, which live in a
   table called the PLT (Procedure Linkage Table).  The first time the
   function is called, the stub sends control to the dynamic linker,
   which looks up the function's real address, patches the stub so
   that future calls will go directly to the function, and then passes
   control to the function.

   If we are stepping at the source level, we don't want to see any of
   this --- we just want to skip over the stub and the dynamic linker.
   The simple approach is to single-step until control leaves the
   dynamic linker.

   However, on some systems (e.g., Red Hat's 5.2 distribution) the
   dynamic linker calls functions in the shared C library, so you
   can't tell from the PC alone whether the dynamic linker is still
   running.  In this case, we use a step-resume breakpoint to get us
   past the dynamic linker, as if we were using "next" to step over a
   function call.

   in_solib_dynsym_resolve_code() says whether we're in the dynamic
   linker code or not.  Normally, this means we single-step.  However,
   if SKIP_SOLIB_RESOLVER then returns non-zero, then its value is an
   address where we can place a step-resume breakpoint to get past the
   linker's symbol resolution function.

   in_solib_dynsym_resolve_code() can generally be implemented in a
   pretty portable way, by comparing the PC against the address ranges
   of the dynamic linker's sections.

   SKIP_SOLIB_RESOLVER is generally going to be system-specific, since
   it depends on internal details of the dynamic linker.  It's usually
   not too hard to figure out where to put a breakpoint, but it
   certainly isn't portable.  SKIP_SOLIB_RESOLVER should do plenty of
   sanity checking.  If it can't figure things out, returning zero and
   getting the (possibly confusing) stepping behavior is better than
   signalling an error, which will obscure the change in the
   inferior's state.  */

/* This function returns TRUE if pc is the address of an instruction
   that lies within the dynamic linker (such as the event hook, or the
   dld itself).

   This function must be used only when a dynamic linker event has
   been caught, and the inferior is being stepped out of the hook, or
   undefined results are guaranteed.  */

#ifndef SOLIB_IN_DYNAMIC_LINKER
#define SOLIB_IN_DYNAMIC_LINKER(pid,pc) 0
#endif


/* Convert the #defines into values.  This is temporary until wfi control
   flow is completely sorted out.  */

#ifndef CANNOT_STEP_HW_WATCHPOINTS
#define CANNOT_STEP_HW_WATCHPOINTS 0
#else
#undef  CANNOT_STEP_HW_WATCHPOINTS
#define CANNOT_STEP_HW_WATCHPOINTS 1
#endif

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

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

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

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

/* 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.  */
static int stop_on_solib_events;
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);

void init_infwait_state (void);

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

static const char *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

/* 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;
  CORE_ADDR step_range_start = 0;
  CORE_ADDR step_range_end = 0;
  struct frame_id step_frame_id = { 0 };

  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->step_resume_breakpoint);
            step_range_start = tp->step_range_start;
            step_range_end = tp->step_range_end;
            step_frame_id = tp->step_frame_id;

            /* 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->step_range_start = 0;
            tp->step_range_end = 0;
            tp->step_frame_id = null_frame_id;
          }

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

        /* Tell the target to do whatever is necessary to follow
           either parent or child.  */
        if (target_follow_fork (follow_child))
          {
            /* 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->step_resume_breakpoint = step_resume_breakpoint;
                    tp->step_range_start = step_range_start;
                    tp->step_range_end = step_range_end;
                    tp->step_frame_id = step_frame_id;
                  }
                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;
}

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.

     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->step_resume_breakpoint)
    breakpoint_re_set_thread (tp->step_resume_breakpoint);

  /* 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 ();
}

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

static void
follow_exec (ptid_t pid, char *execd_pathname)
{
  struct target_ops *tgt;
  struct thread_info *th = inferior_thread ();

  /* 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. */
  update_breakpoints_after_exec ();

  /* If there was one, it's gone now.  We cannot truly step-to-next
     statement through an exec(). */
  th->step_resume_breakpoint = NULL;
  th->step_range_start = 0;
  th->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 (_("Executing new program: %s\n"), 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;
    }

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

  /* 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);

  /* Load the main file's symbols.  */
  symbol_file_add_main (execd_pathname, 0);

#ifdef SOLIB_CREATE_INFERIOR_HOOK
  SOLIB_CREATE_INFERIOR_HOOK (PIDGET (inferior_ptid));
#else
  solib_create_inferior_hook ();
#endif

  jit_inferior_created_hook ();

  /* 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.) */
}

/* Non-zero if we just simulating a single-step.  This is needed
   because we cannot remove the breakpoints in the inferior process
   until after the `wait' in `wait_for_inferior'.  */
static int singlestep_breakpoints_inserted_p = 0;

/* The thread we inserted single-step breakpoints for.  */
static ptid_t singlestep_ptid;

/* PC when we started this single-step.  */
static CORE_ADDR singlestep_pc;

/* If another thread hit the singlestep breakpoint, we save the original
   thread here so that we can resume single-stepping it later.  */
static ptid_t saved_singlestep_ptid;
static int stepping_past_singlestep_breakpoint;

/* If not equal to null_ptid, this means that after stepping over breakpoint
   is finished, we need to switch to deferred_step_ptid, and step it.

   The use case is when one thread has hit a breakpoint, and then the user 
   has switched to another thread and issued 'step'. We need to step over
   breakpoint in the thread which hit the breakpoint, but then continue
   stepping the thread user has selected.  */
static ptid_t deferred_step_ptid;
\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.  */

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

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

/* A queue of pending displaced stepping requests.  */
struct displaced_step_request *displaced_step_request_queue;

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

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

/* The address of the original instruction, and the copy we made.  */
static CORE_ADDR displaced_step_original, displaced_step_copy;

/* Saved contents of copy area.  */
static gdb_byte *displaced_step_saved_copy;

/* Enum strings for "set|show displaced-stepping".  */

static const char can_use_displaced_stepping_auto[] = "auto";
static const char can_use_displaced_stepping_on[] = "on";
static const char can_use_displaced_stepping_off[] = "off";
static const char *can_use_displaced_stepping_enum[] =
{
  can_use_displaced_stepping_auto,
  can_use_displaced_stepping_on,
  can_use_displaced_stepping_off,
  NULL,
};

/* 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 const char *can_use_displaced_stepping =
  can_use_displaced_stepping_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 == can_use_displaced_stepping_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 == can_use_displaced_stepping_auto
            && non_stop)
           || can_use_displaced_stepping == can_use_displaced_stepping_on)
          && gdbarch_displaced_step_copy_insn_p (gdbarch)
          && !RECORD_IS_USED);
}

/* Clean out any stray displaced stepping state.  */
static void
displaced_step_clear (void)
{
  /* 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 *ignore)
{
  displaced_step_clear ();
}

/* 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 regcache *regcache = get_thread_regcache (ptid);
  struct gdbarch *gdbarch = get_regcache_arch (regcache);
  CORE_ADDR original, copy;
  ULONGEST len;
  struct displaced_step_closure *closure;

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

  /* For the first cut, we're displaced stepping one thread at a
     time.  */

  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 ();

  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);
  read_memory (copy, displaced_step_saved_copy, len);
  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, 0);

  /* 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);
}

static void
displaced_step_fixup (ptid_t event_ptid, enum target_signal signal)
{
  struct cleanup *old_cleanups;

  /* 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, 0);

  /* Restore the contents of the copy area.  */
  {
    ULONGEST len = gdbarch_max_insn_length (displaced_step_gdbarch);
    write_memory_ptid (displaced_step_ptid, displaced_step_copy,
                       displaced_step_saved_copy, len);
    if (debug_displaced)
      fprintf_unfiltered (gdb_stdlog, "displaced: restored %s\n",
                          paddress (displaced_step_gdbarch,
                                    displaced_step_copy));
  }

  /* Did the instruction complete successfully?  */
  if (signal == TARGET_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.  */
  while (displaced_step_request_queue)
    {
      struct displaced_step_request *head;
      ptid_t ptid;
      struct regcache *regcache;
      struct gdbarch *gdbarch;
      CORE_ADDR actual_pc;

      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);

      if (breakpoint_here_p (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, TARGET_SIGNAL_0);
          else
            target_resume (ptid, 0, TARGET_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->trap_expected = 0;

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

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

          target_resume (ptid, step, TARGET_SIGNAL_0);
          tp->stop_signal = TARGET_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;

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

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

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

  if (ptid_equal (deferred_step_ptid, old_ptid))
    deferred_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)
{
  normal_stop ();
}

static const char schedlock_off[] = "off";
static const char schedlock_on[] = "on";
static const char schedlock_step[] = "step";
static const char *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 (gdbarch_software_single_step_p (gdbarch)
      && gdbarch_software_single_step (gdbarch, get_current_frame ()))
    {
      hw_step = 0;
      /* Do not pull these breakpoints until after a `wait' in
         `wait_for_inferior' */
      singlestep_breakpoints_inserted_p = 1;
      singlestep_ptid = inferior_ptid;
      singlestep_pc = pc;
    }
  return hw_step;
}

/* 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 target_signal sig)
{
  int should_resume = 1;
  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);

  QUIT;

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: resume (step=%d, signal=%d), "
                        "trap_expected=%d\n",
                        step, sig, tp->trap_expected);

  /* Some targets (e.g. Solaris x86) have a kernel bug when stepping
     over an instruction that causes a page fault without triggering
     a hardware watchpoint. The kernel properly notices that it shouldn't
     stop, because the hardware watchpoint is not triggered, but it forgets
     the step request and continues the program normally.
     Work around the problem by removing hardware watchpoints if a step is
     requested, GDB will check for a hardware watchpoint trigger after the
     step anyway.  */
  if (CANNOT_STEP_HW_WATCHPOINTS && step)
    remove_hw_watchpoints ();


  /* 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 (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 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.  */
  if (use_displaced_stepping (gdbarch)
      && (tp->trap_expected
          || (step && gdbarch_software_single_step_p (gdbarch)))
      && sig == TARGET_SIGNAL_0)
    {
      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 frontend point of view,
             the thread is running.  */
          set_running (inferior_ptid, 1);
          discard_cleanups (old_cleanups);
          return;
        }

      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);

  if (should_resume)
    {
      ptid_t resume_ptid;

      /* 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 (!(singlestep_breakpoints_inserted_p && 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.  */

      /* By default, resume all threads of all processes.  */
      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 (singlestep_breakpoints_inserted_p
          && stepping_past_singlestep_breakpoint)
        {
          /* The situation here is as follows.  In thread T1 we wanted to
             single-step.  Lacking hardware single-stepping we've
             set breakpoint at the PC of the next instruction -- call it
             P.  After resuming, we've hit that breakpoint in thread T2.
             Now we've removed original breakpoint, inserted breakpoint
             at P+1, and try to step to advance T2 past breakpoint.
             We need to step only T2, as if T1 is allowed to freely run,
             it can run past P, and if other threads are allowed to run,
             they can hit breakpoint at P+1, and nested hits of single-step
             breakpoints is not something we'd want -- that's complicated
             to support, and has no value.  */
          resume_ptid = inferior_ptid;
        }
      else if ((step || singlestep_breakpoints_inserted_p)
               && tp->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.

             The current code actually removes all breakpoints when
             doing this, not just the one being stepped over, so if we
             let other threads run, we can actually miss any
             breakpoint, not just the one at PC.  */
          resume_ptid = inferior_ptid;
        }
      else 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 || singlestep_breakpoints_inserted_p)))
        {
          /* User-settable 'scheduler' mode requires solo thread resume. */
          resume_ptid = inferior_ptid;
        }

      if (gdbarch_cannot_step_breakpoint (gdbarch))
        {
          /* Most targets can step a breakpoint instruction, thus
             executing it normally.  But if this one cannot, just
             continue and we will hit it anyway.  */
          if (step && breakpoint_inserted_here_p (pc))
            step = 0;
        }

      if (debug_displaced
          && use_displaced_stepping (gdbarch)
          && tp->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));
        }

      /* 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->stop_signal = TARGET_SIGNAL_0;

      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));

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

  tp->stop_step = 0;

  tp->proceed_to_finish = 0;

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

static int
clear_proceed_status_callback (struct thread_info *tp, void *data)
{
  if (is_exited (tp->ptid))
    return 0;

  clear_proceed_status_thread (tp);
  return 0;
}

void
clear_proceed_status (void)
{
  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 ());
        }
      else
        {
          /* In all-stop mode, delete the per-thread status of
             *all* threads.  */
          iterate_over_threads (clear_proceed_status_callback, NULL);
        }
  
      inferior = current_inferior ();
      inferior->stop_soon = NO_STOP_QUIETLY;
    }

  stop_after_trap = 0;

  observer_notify_about_to_proceed ();

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

/* Check the current thread against the thread that reported the most recent
   event.  If a step-over is required return TRUE and set the current thread
   to the old thread.  Otherwise return FALSE.

   This should be suitable for any targets that support threads. */

static int
prepare_to_proceed (int step)
{
  ptid_t wait_ptid;
  struct target_waitstatus wait_status;
  int schedlock_enabled;

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

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

  /* Make sure we were stopped at a breakpoint.  */
  if (wait_status.kind != TARGET_WAITKIND_STOPPED
      || wait_status.value.sig != TARGET_SIGNAL_TRAP)
    {
      return 0;
    }

  schedlock_enabled = (scheduler_mode == schedlock_on
                       || (scheduler_mode == schedlock_step
                           && step));

  /* Don't switch over to WAIT_PTID if scheduler locking is on.  */
  if (schedlock_enabled)
    return 0;

  /* Don't switch over if we're about to resume some other process
     other than WAIT_PTID's, and schedule-multiple is off.  */
  if (!sched_multi
      && ptid_get_pid (wait_ptid) != ptid_get_pid (inferior_ptid))
    return 0;

  /* Switched over from WAIT_PID.  */
  if (!ptid_equal (wait_ptid, minus_one_ptid)
      && !ptid_equal (inferior_ptid, wait_ptid))
    {
      struct regcache *regcache = get_thread_regcache (wait_ptid);

      if (breakpoint_here_p (regcache_read_pc (regcache)))
        {
          /* If stepping, remember current thread to switch back to.  */
          if (step)
            deferred_step_ptid = inferior_ptid;

          /* Switch back to WAIT_PID thread.  */
          switch_to_thread (wait_ptid);

          /* We return 1 to indicate that there is a breakpoint here,
             so we need to step over it before continuing to avoid
             hitting it straight away. */
          return 1;
        }
    }

  return 0;
}

/* 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 target_signal siggnal, int step)
{
  struct regcache *regcache;
  struct gdbarch *gdbarch;
  struct thread_info *tp;
  CORE_ADDR pc;
  int oneproc = 0;

  /* 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 ();
      return;
    }

  regcache = get_current_regcache ();
  gdbarch = get_regcache_arch (regcache);
  pc = regcache_read_pc (regcache);

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

  if (addr == (CORE_ADDR) -1)
    {
      if (pc == stop_pc && breakpoint_here_p (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.  */

        oneproc = 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.  */
        oneproc = 1;
    }
  else
    {
      regcache_write_pc (regcache, addr);
    }

  if (debug_infrun)
    fprintf_unfiltered (gdb_stdlog,
                        "infrun: proceed (addr=%s, signal=%d, step=%d)\n",
                        paddress (gdbarch, addr), 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
    {
      /* 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.

         prepare_to_proceed checks the current thread against the
         thread that reported the most recent event.  If a step-over
         is required it returns TRUE and sets the current thread to
         the old thread. */
      if (prepare_to_proceed (step))
        oneproc = 1;
    }

  /* prepare_to_proceed may change the current thread.  */
  tp = inferior_thread ();

  if (oneproc)
    {
      tp->trap_expected = 1;
      /* If displaced stepping is enabled, we can step over the
         breakpoint without hitting it, so leave all breakpoints
         inserted.  Otherwise we need to disable all breakpoints, step
         one instruction, and then re-add them when that step is
         finished.  */
      if (!use_displaced_stepping (gdbarch))
        remove_breakpoints ();
    }

  /* We can insert breakpoints if we're not trying to step over one,
     or if we are stepping over one but we're using displaced stepping
     to do so.  */
  if (! tp->trap_expected || use_displaced_stepping (gdbarch))
    insert_breakpoints ();

  if (!non_stop)
    {
      /* Pass the last stop signal to the thread we're resuming,
         irrespective of whether the current thread is the thread that
         got the last event or not.  This was historically GDB's
         behaviour before keeping a stop_signal per thread.  */

      struct thread_info *last_thread;
      ptid_t last_ptid;
      struct target_waitstatus last_status;

      get_last_target_status (&last_ptid, &last_status);
      if (!ptid_equal (inferior_ptid, last_ptid)
          && !ptid_equal (last_ptid, null_ptid)
          && !ptid_equal (last_ptid, minus_one_ptid))
        {
          last_thread = find_thread_ptid (last_ptid);
          if (last_thread)
            {
              tp->stop_signal = last_thread->stop_signal;
              last_thread->stop_signal = TARGET_SIGNAL_0;
            }
        }
    }

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

  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_stepping, 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 have init_execution_control_state () refresh
     the prev_pc value before calculating the line number.  This approach
     did not work because on platforms that use ptrace, 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 ());

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

  /* Reset to normal state.  */
  init_infwait_state ();

  /* Resume inferior.  */
  resume (oneproc || step || bpstat_should_step (), tp->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 (0);
      normal_stop ();
    }
}
\f

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

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

  inferior = current_inferior ();
  inferior->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 (0);

  /* 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 ();

  stepping_past_singlestep_breakpoint = 0;
  deferred_step_ptid = null_ptid;

  target_last_wait_ptid = minus_one_ptid;

  previous_inferior_ptid = null_ptid;
  init_infwait_state ();

  displaced_step_clear ();

  /* 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_thread_hop_state,
  infwait_step_watch_state,
  infwait_nonstep_watch_state
};

/* Why did the inferior stop? Used to print the appropriate messages
   to the interface from within handle_inferior_event(). */
enum inferior_stop_reason
{
  /* Step, next, nexti, stepi finished. */
  END_STEPPING_RANGE,
  /* Inferior terminated by signal. */
  SIGNAL_EXITED,
  /* Inferior exited. */
  EXITED,
  /* Inferior received signal, and user asked to be notified. */
  SIGNAL_RECEIVED,
  /* Reverse execution -- target ran out of history info.  */
  NO_HISTORY
};

/* The PTID we'll do a target_wait on.*/
ptid_t waiton_ptid;

/* Current inferior wait state.  */
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 random_signal;
  CORE_ADDR stop_func_start;
  CORE_ADDR stop_func_end;
  char *stop_func_name;
  int new_thread_event;
  int wait_some_more;
};

static void init_execution_control_state (struct execution_control_state *ecs);

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 insert_step_resume_breakpoint_at_frame (struct frame_info *step_frame);
static void insert_step_resume_breakpoint_at_caller (struct frame_info *);
static void insert_step_resume_breakpoint_at_sal (struct gdbarch *gdbarch,
                                                  struct symtab_and_line sr_sal,
                                                  struct frame_id sr_id);
static void insert_longjmp_resume_breakpoint (struct gdbarch *, CORE_ADDR);

static void stop_stepping (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 print_stop_reason (enum inferior_stop_reason stop_reason,
                               int stop_info);

/* 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 ();

      switch_to_thread (info->ptid);

      /* 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 = TARGET_SIGNAL_0;

      handle_inferior_event (ecs);

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

          normal_stop ();

          /* Finish off the continuations.  The continations
             themselves are responsible for realising the thread
             didn't finish what it was supposed to do.  */
          tp = inferior_thread ();
          do_all_intermediate_continuations_thread (tp);
          do_all_continuations_thread (tp);
        }

      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_request *it, *next, *prev = NULL;

  /* PTID was requested to stop.  Remove it from the displaced
     stepping queue, so we don't try to resume it automatically.  */
  for (it = displaced_step_request_queue; it; it = next)
    {
      next = it->next;

      if (ptid_equal (it->ptid, ptid)
          || ptid_equal (minus_one_ptid, ptid)
          || (ptid_is_pid (ptid)
              && ptid_get_pid (ptid) == ptid_get_pid (it->ptid)))
        {
          if (displaced_step_request_queue == it)
            displaced_step_request_queue = it->next;
          else
            prev->next = it->next;

          xfree (it);
        }
      else
        prev = it;
    }

  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 ();
}

/* Callback for iterate_over_threads.  */

static int
delete_step_resume_breakpoint_callback (struct thread_info *info, void *data)
{
  if (is_exited (info->ptid))
    return 0;

  delete_step_resume_breakpoint (info);
  return 0;
}

/* In all-stop, delete the step resume breakpoint of any thread that
   had one.  In non-stop, delete the step resume breakpoint of the
   thread that just stopped.  */

static void
delete_step_thread_step_resume_breakpoint (void)
{
  if (!target_has_execution
      || ptid_equal (inferior_ptid, null_ptid))
    /* If the inferior has exited, we have already deleted the step
       resume breakpoints out of GDB's lists.  */
    return;

  if (non_stop)
    {
      /* If in non-stop mode, only delete the step-resume or
         longjmp-resume breakpoint of the thread that just stopped
         stepping.  */
      struct thread_info *tp = inferior_thread ();
      delete_step_resume_breakpoint (tp);
    }
  else
    /* In all-stop mode, delete all step-resume and longjmp-resume
       breakpoints of any thread that had them.  */
    iterate_over_threads (delete_step_resume_breakpoint_callback, NULL);
}

/* A cleanup wrapper. */

static void
delete_step_thread_step_resume_breakpoint_cleanup (void *arg)
{
  delete_step_thread_step_resume_breakpoint ();
}

/* 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", PIDGET (waiton_ptid));
  if (PIDGET (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",
                      PIDGET (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);
}

/* Wait for control to return from inferior to debugger.

   If TREAT_EXEC_AS_SIGTRAP is non-zero, then handle EXEC signals
   as if they were SIGTRAP signals.  This can be useful during
   the startup sequence on some targets such as HP/UX, where
   we receive an EXEC event instead of the expected SIGTRAP.

   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 (int treat_exec_as_sigtrap)
{
  struct cleanup *old_cleanups;
  struct execution_control_state ecss;
  struct execution_control_state *ecs;

  if (debug_infrun)
    fprintf_unfiltered
      (gdb_stdlog, "infrun: wait_for_inferior (treat_exec_as_sigtrap=%d)\n",
       treat_exec_as_sigtrap);

  old_cleanups =
    make_cleanup (delete_step_thread_step_resume_breakpoint_cleanup, NULL);

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

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

  while (1)
    {
      struct cleanup *old_chain;

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

      overlay_cache_invalid = 1;
      registers_changed ();

      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 (treat_exec_as_sigtrap && ecs->ws.kind == TARGET_WAITKIND_EXECD)
        {
          xfree (ecs->ws.value.execd_pathname);
          ecs->ws.kind = TARGET_WAITKIND_STOPPED;
          ecs->ws.value.sig = TARGET_SIGNAL_TRAP;
        }

      /* 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);

      if (ecs->ws.kind == TARGET_WAITKIND_SYSCALL_ENTRY
          || ecs->ws.kind == TARGET_WAITKIND_SYSCALL_RETURN)
        ecs->ws.value.syscall_number = UNKNOWN_SYSCALL;

      /* 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);
}

/* 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;

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

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

  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 ();

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

  overlay_cache_invalid = 1;
  registers_changed ();

  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 (non_stop
      && ecs->ws.kind != TARGET_WAITKIND_IGNORE
      && ecs->ws.kind != TARGET_WAITKIND_EXITED
      && ecs->ws.kind != TARGET_WAITKIND_SIGNALLED)
    /* In non-stop mode, each thread is handled individually.  Switch
       early, so the global state is set correctly for this
       thread.  */
    context_switch (ecs->ptid);

  /* 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);

  /* 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_step_thread_step_resume_breakpoint ();

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

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

  /* 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.  */
  if (was_sync && !sync_execution)
    display_gdb_prompt (0);
}

/* 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->step_frame_id = get_frame_id (frame);
  tp->step_stack_frame_id = get_stack_frame_id (frame);

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

/* Prepare an execution control state for looping through a
   wait_for_inferior-type loop.  */

static void
init_execution_control_state (struct execution_control_state *ecs)
{
  ecs->random_signal = 0;
}

/* Clear context switchable stepping state.  */

void
init_thread_stepping_state (struct thread_info *tss)
{
  tss->stepping_over_breakpoint = 0;
  tss->step_after_step_resume_breakpoint = 0;
  tss->stepping_through_solib_after_catch = 0;
  tss->stepping_through_solib_catchpoints = NULL;
}

/* 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)
    {
      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;
  CORE_ADDR breakpoint_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 != TARGET_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);
  if (gdbarch_decr_pc_after_break (gdbarch) == 0)
    return;

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

  /* 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 (breakpoint_pc)
      || (non_stop && moribund_breakpoint_here_p (breakpoint_pc)))
    {
      struct cleanup *old_cleanups = NULL;
      if (RECORD_IS_USED)
        old_cleanups = record_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 (singlestep_breakpoints_inserted_p
          || !ptid_equal (ecs->ptid, inferior_ptid)
          || !currently_stepping (ecs->event_thread)
          || ecs->event_thread->prev_pc == breakpoint_pc)
        regcache_write_pc (regcache, breakpoint_pc);

      if (RECORD_IS_USED)
        do_cleanups (old_cleanups);
    }
}

void
init_infwait_state (void)
{
  waiton_ptid = pid_to_ptid (-1);
  infwait_state = infwait_normal_state;
}

void
error_is_running (void)
{
  error (_("\
Cannot execute this command while the selected thread is running."));
}

void
ensure_not_running (void)
{
  if (is_running (inferior_ptid))
    error_is_running ();
}

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;
  struct gdbarch *gdbarch;
  int syscall_number;

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

  regcache = get_thread_regcache (ecs->ptid);
  gdbarch = get_regcache_arch (regcache);
  syscall_number = gdbarch_get_syscall_number (gdbarch, ecs->ptid);
  stop_pc = regcache_read_pc (regcache);

  target_last_waitstatus.value.syscall_number = syscall_number;

  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->stop_bpstat = bpstat_stop_status (stop_pc, ecs->ptid);
      ecs->random_signal = !bpstat_explains_signal (ecs->event_thread->stop_bpstat);

      if (!ecs->random_signal)
        {
          /* Catchpoint hit.  */
          ecs->event_thread->stop_signal = TARGET_SIGNAL_TRAP;
          return 0;
        }
    }

  /* If no catchpoint triggered for this, then keep going.  */
  ecs->event_thread->stop_signal = TARGET_SIGNAL_0;
  keep_going (ecs);
  return 1;
}

/* 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.  */

static void
handle_inferior_event (struct execution_control_state *ecs)
{
  struct frame_info *frame;
  struct gdbarch *gdbarch;
  int sw_single_step_trap_p = 0;
  int stopped_by_watchpoint;
  int stepped_after_stopped_by_watchpoint = 0;
  struct symtab_and_line stop_pc_sal;
  enum stop_kind stop_soon;

  if (ecs->ws.kind != TARGET_WAITKIND_EXITED
      && ecs->ws.kind != TARGET_WAITKIND_SIGNALLED
      && ecs->ws.kind != TARGET_WAITKIND_IGNORE)
    {
      struct inferior *inf = find_inferior_pid (ptid_get_pid (ecs->ptid));
      gdb_assert (inf);
      stop_soon = inf->stop_soon;
    }
  else
    stop_soon = NO_STOP_QUIETLY;

  /* Cache the last pid/waitstatus. */
  target_last_wait_ptid = ecs->ptid;
  target_last_waitstatus = ecs->ws;

  /* Always clear state belonging to the previous time we stopped.  */
  stop_stack_dummy = 0;

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

  ecs->new_thread_event = (!ptid_equal (ecs->ptid, inferior_ptid)
                           && !ptid_equal (ecs->ptid, minus_one_ptid)
                           && !in_thread_list (ecs->ptid));

  if (ecs->ws.kind != TARGET_WAITKIND_EXITED
      && ecs->ws.kind != TARGET_WAITKIND_SIGNALLED && ecs->new_thread_event)
    add_thread (ecs->ptid);

  ecs->event_thread = find_thread_ptid (ecs->ptid);

  /* 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 ();

  if (ecs->ws.kind != TARGET_WAITKIND_IGNORE)
    {
      breakpoint_retire_moribund ();

      /* 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 (inferior_ptid, 0);
    }

  switch (infwait_state)
    {
    case infwait_thread_hop_state:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: infwait_thread_hop_state\n");
      break;

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

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

      stepped_after_stopped_by_watchpoint = 1;
      break;

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

      /* FIXME-maybe: is this cleaner than setting a flag?  Does it
         handle things like signals arriving and other things happening
         in combination correctly?  */
      stepped_after_stopped_by_watchpoint = 1;
      break;

    default:
      internal_error (__FILE__, __LINE__, _("bad switch"));
    }

  infwait_state = infwait_normal_state;
  waiton_ptid = pid_to_ptid (-1);

  switch (ecs->ws.kind)
    {
    case TARGET_WAITKIND_LOADED:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_LOADED\n");
      /* 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.  */
      if (stop_soon == NO_STOP_QUIETLY)
        {
          /* Check for any newly added shared libraries if we're
             supposed to be adding them automatically.  Switch
             terminal for any messages produced by
             breakpoint_re_set.  */
          target_terminal_ours_for_output ();
          /* NOTE: cagney/2003-11-25: Make certain that the target
             stack's section table is kept up-to-date.  Architectures,
             (e.g., PPC64), use the section table to perform
             operations such as address => section name and hence
             require the table to contain all sections (including
             those found in shared libraries).  */
#ifdef SOLIB_ADD
          SOLIB_ADD (NULL, 0, &current_target, auto_solib_add);
#else
          solib_add (NULL, 0, &current_target, auto_solib_add);
#endif
          target_terminal_inferior ();

          /* If requested, stop when the dynamic linker notifies
             gdb of events.  This allows the user to get control
             and place breakpoints in initializer routines for
             dynamically loaded objects (among other things).  */
          if (stop_on_solib_events)
            {
              stop_stepping (ecs);
              return;
            }

          /* NOTE drow/2007-05-11: This might be a good place to check
             for "catch load".  */
        }

      /* 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.  But stop if
         we're attaching or setting up a remote connection.  */
      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
              && !breakpoints_always_inserted_mode ())
            insert_breakpoints ();
          resume (0, TARGET_SIGNAL_0);
          prepare_to_wait (ecs);
          return;
        }

      break;

    case TARGET_WAITKIND_SPURIOUS:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_SPURIOUS\n");
      resume (0, TARGET_SIGNAL_0);
      prepare_to_wait (ecs);
      return;

    case TARGET_WAITKIND_EXITED:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_EXITED\n");
      inferior_ptid = ecs->ptid;
      target_terminal_ours ();  /* Must do this before mourn anyway */
      print_stop_reason (EXITED, ecs->ws.value.integer);

      /* 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);
      gdb_flush (gdb_stdout);
      target_mourn_inferior ();
      singlestep_breakpoints_inserted_p = 0;
      stop_print_frame = 0;
      stop_stepping (ecs);
      return;

    case TARGET_WAITKIND_SIGNALLED:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_SIGNALLED\n");
      inferior_ptid = ecs->ptid;
      stop_print_frame = 0;
      target_terminal_ours ();  /* Must do this before mourn anyway */

      /* Note: By definition of TARGET_WAITKIND_SIGNALLED, we shouldn't
         reach here unless the inferior is dead.  However, for years
         target_kill() was called here, which hints that fatal signals aren't
         really fatal on some systems.  If that's true, then some changes
         may be needed. */
      target_mourn_inferior ();

      print_stop_reason (SIGNAL_EXITED, ecs->ws.value.sig);
      singlestep_breakpoints_inserted_p = 0;
      stop_stepping (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)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_FORKED\n");

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

      /* 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)
        {
          int child_pid = ptid_get_pid (ecs->ws.value.related_pid);

          /* This won't actually modify the breakpoint list, but will
             physically remove the breakpoints from the child.  */
          detach_breakpoints (child_pid);
        }

      /* 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->stop_bpstat = bpstat_stop_status (stop_pc, ecs->ptid);

      ecs->random_signal = !bpstat_explains_signal (ecs->event_thread->stop_bpstat);

      /* If no catchpoint triggered for this, then keep going.  */
      if (ecs->random_signal)
        {
          int should_resume;

          ecs->event_thread->stop_signal = TARGET_SIGNAL_0;

          should_resume = follow_fork ();

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

          if (should_resume)
            keep_going (ecs);
          else
            stop_stepping (ecs);
          return;
        }
      ecs->event_thread->stop_signal = TARGET_SIGNAL_TRAP;
      goto process_event_stop_test;

    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);
          reinit_frame_cache ();
        }

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

      /* 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->stop_bpstat = bpstat_stop_status (stop_pc, ecs->ptid);
      ecs->random_signal = !bpstat_explains_signal (ecs->event_thread->stop_bpstat);

      /* 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 (ecs->random_signal)
        {
          ecs->event_thread->stop_signal = TARGET_SIGNAL_0;
          keep_going (ecs);
          return;
        }
      ecs->event_thread->stop_signal = TARGET_SIGNAL_TRAP;
      goto process_event_stop_test;

      /* 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)
        return;
      goto process_event_stop_test;

      /* 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)
        return;
      goto process_event_stop_test;

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

    case TARGET_WAITKIND_NO_HISTORY:
      /* Reverse execution: target ran out of history info.  */
      stop_pc = regcache_read_pc (get_thread_regcache (ecs->ptid));
      print_stop_reason (NO_HISTORY, 0);
      stop_stepping (ecs);
      return;

      /* 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.  */
    case TARGET_WAITKIND_IGNORE:
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog, "infrun: TARGET_WAITKIND_IGNORE\n");
      prepare_to_wait (ecs);
      return;
    }

  if (ecs->new_thread_event)
    {
      if (non_stop)
        /* Non-stop assumes that the target handles adding new threads
           to the thread list.  */
        internal_error (__FILE__, __LINE__, "\
targets should add new threads to the thread list themselves in non-stop mode.");

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

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

      if (!ptid_equal (ecs->ptid, inferior_ptid))
        context_switch (ecs->ptid);
      target_resume (RESUME_ALL, 0, TARGET_SIGNAL_0);
      prepare_to_wait (ecs);
      return;
    }

  if (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->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->stop_signal == TARGET_SIGNAL_TRAP)
        ecs->event_thread->stop_signal = TARGET_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);

      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");
        }
    }

  if (stepping_past_singlestep_breakpoint)
    {
      gdb_assert (singlestep_breakpoints_inserted_p);
      gdb_assert (ptid_equal (singlestep_ptid, ecs->ptid));
      gdb_assert (!ptid_equal (singlestep_ptid, saved_singlestep_ptid));

      stepping_past_singlestep_breakpoint = 0;

      /* We've either finished single-stepping past the single-step
         breakpoint, or stopped for some other reason.  It would be nice if
         we could tell, but we can't reliably.  */
      if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP)
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog, "infrun: stepping_past_singlestep_breakpoint\n");
          /* Pull the single step breakpoints out of the target.  */
          remove_single_step_breakpoints ();
          singlestep_breakpoints_inserted_p = 0;

          ecs->random_signal = 0;
          ecs->event_thread->trap_expected = 0;

          context_switch (saved_singlestep_ptid);
          if (deprecated_context_hook)
            deprecated_context_hook (pid_to_thread_id (ecs->ptid));

          resume (1, TARGET_SIGNAL_0);
          prepare_to_wait (ecs);
          return;
        }
    }

  if (!ptid_equal (deferred_step_ptid, null_ptid))
    {
      /* In non-stop mode, there's never a deferred_step_ptid set.  */
      gdb_assert (!non_stop);

      /* If we stopped for some other reason than single-stepping, ignore
         the fact that we were supposed to switch back.  */
      if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP)
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog,
                                "infrun: handling deferred step\n");

          /* Pull the single step breakpoints out of the target.  */
          if (singlestep_breakpoints_inserted_p)
            {
              remove_single_step_breakpoints ();
              singlestep_breakpoints_inserted_p = 0;
            }

          /* Note: We do not call context_switch at this point, as the
             context is already set up for stepping the original thread.  */
          switch_to_thread (deferred_step_ptid);
          deferred_step_ptid = null_ptid;
          /* Suppress spurious "Switching to ..." message.  */
          previous_inferior_ptid = inferior_ptid;

          resume (1, TARGET_SIGNAL_0);
          prepare_to_wait (ecs);
          return;
        }

      deferred_step_ptid = null_ptid;
    }

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

  if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP)
    {
      int thread_hop_needed = 0;

      /* Check if a regular breakpoint has been hit before checking
         for a potential single step breakpoint. Otherwise, GDB will
         not see this breakpoint hit when stepping onto breakpoints.  */
      if (regular_breakpoint_inserted_here_p (stop_pc))
        {
          ecs->random_signal = 0;
          if (!breakpoint_thread_match (stop_pc, ecs->ptid))
            thread_hop_needed = 1;
        }
      else if (singlestep_breakpoints_inserted_p)
        {
          /* We have not context switched yet, so this should be true
             no matter which thread hit the singlestep breakpoint.  */
          gdb_assert (ptid_equal (inferior_ptid, singlestep_ptid));
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog, "infrun: software single step "
                                "trap for %s\n",
                                target_pid_to_str (ecs->ptid));

          ecs->random_signal = 0;
          /* The call to in_thread_list is necessary because PTIDs sometimes
             change when we go from single-threaded to multi-threaded.  If
             the singlestep_ptid is still in the list, assume that it is
             really different from ecs->ptid.  */
          if (!ptid_equal (singlestep_ptid, ecs->ptid)
              && in_thread_list (singlestep_ptid))
            {
              /* If the PC of the thread we were trying to single-step
                 has changed, discard this event (which we were going
                 to ignore anyway), and pretend we saw that thread
                 trap.  This prevents us continuously moving the
                 single-step breakpoint forward, one instruction at a
                 time.  If the PC has changed, then the thread we were
                 trying to single-step has trapped or been signalled,
                 but the event has not been reported to GDB yet.

                 There might be some cases where this loses signal
                 information, if a signal has arrived at exactly the
                 same time that the PC changed, but this is the best
                 we can do with the information available.  Perhaps we
                 should arrange to report all events for all threads
                 when they stop, or to re-poll the remote looking for
                 this particular thread (i.e. temporarily enable
                 schedlock).  */

             CORE_ADDR new_singlestep_pc
               = regcache_read_pc (get_thread_regcache (singlestep_ptid));

             if (new_singlestep_pc != singlestep_pc)
               {
                 enum target_signal stop_signal;

                 if (debug_infrun)
                   fprintf_unfiltered (gdb_stdlog, "infrun: unexpected thread,"
                                       " but expected thread advanced also\n");

                 /* The current context still belongs to
                    singlestep_ptid.  Don't swap here, since that's
                    the context we want to use.  Just fudge our
                    state and continue.  */
                 stop_signal = ecs->event_thread->stop_signal;
                 ecs->event_thread->stop_signal = TARGET_SIGNAL_0;
                 ecs->ptid = singlestep_ptid;
                 ecs->event_thread = find_thread_ptid (ecs->ptid);
                 ecs->event_thread->stop_signal = stop_signal;
                 stop_pc = new_singlestep_pc;
               }
             else
               {
                 if (debug_infrun)
                   fprintf_unfiltered (gdb_stdlog,
                                       "infrun: unexpected thread\n");

                 thread_hop_needed = 1;
                 stepping_past_singlestep_breakpoint = 1;
                 saved_singlestep_ptid = singlestep_ptid;
               }
            }
        }

      if (thread_hop_needed)
        {
          struct regcache *thread_regcache;
          int remove_status = 0;

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

          /* Switch context before touching inferior memory, the
             previous thread may have exited.  */
          if (!ptid_equal (inferior_ptid, ecs->ptid))
            context_switch (ecs->ptid);

          /* Saw a breakpoint, but it was hit by the wrong thread.
             Just continue. */

          if (singlestep_breakpoints_inserted_p)
            {
              /* Pull the single step breakpoints out of the target. */
              remove_single_step_breakpoints ();
              singlestep_breakpoints_inserted_p = 0;
            }

          /* If the arch can displace step, don't remove the
             breakpoints.  */
          thread_regcache = get_thread_regcache (ecs->ptid);
          if (!use_displaced_stepping (get_regcache_arch (thread_regcache)))
            remove_status = remove_breakpoints ();

          /* Did we fail to remove breakpoints?  If so, try
             to set the PC past the bp.  (There's at least
             one situation in which we can fail to remove
             the bp's: On HP-UX's that use ttrace, we can't
             change the address space of a vforking child
             process until the child exits (well, okay, not
             then either :-) or execs. */
          if (remove_status != 0)
            error (_("Cannot step over breakpoint hit in wrong thread"));
          else
            {                   /* Single step */
              if (!non_stop)
                {
                  /* Only need to require the next event from this
                     thread in all-stop mode.  */
                  waiton_ptid = ecs->ptid;
                  infwait_state = infwait_thread_hop_state;
                }

              ecs->event_thread->stepping_over_breakpoint = 1;
              keep_going (ecs);
              return;
            }
        }
      else if (singlestep_breakpoints_inserted_p)
        {
          sw_single_step_trap_p = 1;
          ecs->random_signal = 0;
        }
    }
  else
    ecs->random_signal = 1;

  /* 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);

  if (singlestep_breakpoints_inserted_p)
    {
      /* Pull the single step breakpoints out of the target. */
      remove_single_step_breakpoints ();
      singlestep_breakpoints_inserted_p = 0;
    }

  if (stepped_after_stopped_by_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 stop 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 and breakpoints.  */
      int hw_step = 1;

      if (!target_have_steppable_watchpoint)
        remove_breakpoints ();
        /* Single step */
      hw_step = maybe_software_singlestep (gdbarch, stop_pc);
      target_resume (ecs->ptid, hw_step, TARGET_SIGNAL_0);
      waiton_ptid = ecs->ptid;
      if (target_have_steppable_watchpoint)
        infwait_state = infwait_step_watch_state;
      else
        infwait_state = infwait_nonstep_watch_state;
      prepare_to_wait (ecs);
      return;
    }

  ecs->stop_func_start = 0;
  ecs->stop_func_end = 0;
  ecs->stop_func_name = 0;
  /* Don't care about return value; stop_func_start and stop_func_name
     will both be 0 if it doesn't work.  */
  find_pc_partial_function (stop_pc, &ecs->stop_func_name,
                            &ecs->stop_func_start, &ecs->stop_func_end);
  ecs->stop_func_start
    += gdbarch_deprecated_function_start_offset (gdbarch);
  ecs->event_thread->stepping_over_breakpoint = 0;
  bpstat_clear (&ecs->event_thread->stop_bpstat);
  ecs->event_thread->stop_step = 0;
  stop_print_frame = 1;
  ecs->random_signal = 0;
  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->step_range_end != 1)
    skip_inline_frames (ecs->ptid);

  if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP
      && ecs->event_thread->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->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;
        }
    }

  /* Look at the cause of the stop, and decide what to do.
     The alternatives are:
     1) stop_stepping and return; to really stop and return to the debugger,
     2) keep_going and return to start up again
     (set ecs->event_thread->stepping_over_breakpoint to 1 to single step once)
     3) set ecs->random_signal to 1, and the decision between 1 and 2
     will be made according to the signal handling tables.  */

  /* First, distinguish signals caused by the debugger from signals
     that have to do with the program's own actions.  Note that
     breakpoint insns may cause SIGTRAP or SIGILL or SIGEMT, depending
     on the operating system version.  Here we detect when a SIGILL or
     SIGEMT is really a breakpoint and change it to SIGTRAP.  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 we're doing a displaced step past a breakpoint, then the
     breakpoint is always inserted at the original instruction;
     non-standard signals can't be explained by the breakpoint.  */
  if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP
      || (! ecs->event_thread->trap_expected
          && breakpoint_inserted_here_p (stop_pc)
          && (ecs->event_thread->stop_signal == TARGET_SIGNAL_ILL
              || ecs->event_thread->stop_signal == TARGET_SIGNAL_SEGV
              || ecs->event_thread->stop_signal == TARGET_SIGNAL_EMT))
      || stop_soon == STOP_QUIETLY || stop_soon == STOP_QUIETLY_NO_SIGSTOP
      || stop_soon == STOP_QUIETLY_REMOTE)
    {
      if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP && stop_after_trap)
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog, "infrun: stopped\n");
          stop_print_frame = 0;
          stop_stepping (ecs);
          return;
        }

      /* This is originated from start_remote(), start_inferior() and
         shared libraries hook functions.  */
      if (stop_soon == STOP_QUIETLY || stop_soon == STOP_QUIETLY_REMOTE)
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog, "infrun: quietly stopped\n");
          stop_stepping (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
         TARGET_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
         TARGET_SIGNAL_0, meaning: stopped for no particular reason
         other than GDB's request.  */
      if (stop_soon == STOP_QUIETLY_NO_SIGSTOP
          && (ecs->event_thread->stop_signal == TARGET_SIGNAL_STOP
              || ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP
              || ecs->event_thread->stop_signal == TARGET_SIGNAL_0))
        {
          stop_stepping (ecs);
          ecs->event_thread->stop_signal = TARGET_SIGNAL_0;
          return;
        }

      /* See if there is a breakpoint at the current PC.  */
      ecs->event_thread->stop_bpstat = bpstat_stop_status (stop_pc, ecs->ptid);
      
      /* Following in case break condition called a
         function.  */
      stop_print_frame = 1;

      /* NOTE: cagney/2003-03-29: These two 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.  */

      if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP)
        ecs->random_signal
          = !(bpstat_explains_signal (ecs->event_thread->stop_bpstat)
              || ecs->event_thread->trap_expected
              || (ecs->event_thread->step_range_end
                  && ecs->event_thread->step_resume_breakpoint == NULL));
      else
        {
          ecs->random_signal = !bpstat_explains_signal (ecs->event_thread->stop_bpstat);
          if (!ecs->random_signal)
            ecs->event_thread->stop_signal = TARGET_SIGNAL_TRAP;
        }
    }

  /* When we reach this point, we've pretty much decided
     that the reason for stopping must've been a random
     (unexpected) signal. */

  else
    ecs->random_signal = 1;

process_event_stop_test:

  /* Re-fetch current thread's frame in case we did a
     "goto process_event_stop_test" above.  */
  frame = get_current_frame ();
  gdbarch = get_frame_arch (frame);

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

  if (ecs->random_signal)
    {
      /* Signal not for debugging purposes.  */
      int printed = 0;

      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog, "infrun: random signal %d\n",
                             ecs->event_thread->stop_signal);

      stopped_by_random_signal = 1;

      if (signal_print[ecs->event_thread->stop_signal])
        {
          printed = 1;
          target_terminal_ours_for_output ();
          print_stop_reason (SIGNAL_RECEIVED, ecs->event_thread->stop_signal);
        }
      /* 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
          || signal_stop_state (ecs->event_thread->stop_signal))
        {
          stop_stepping (ecs);
          return;
        }
      /* If not going to stop, give terminal back
         if we took it away.  */
      else if (printed)
        target_terminal_inferior ();

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

      if (ecs->event_thread->prev_pc == stop_pc
          && ecs->event_thread->trap_expected
          && ecs->event_thread->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_step_resume_breakpoint_at_frame (frame);
          ecs->event_thread->step_after_step_resume_breakpoint = 1;
          keep_going (ecs);
          return;
        }

      if (ecs->event_thread->step_range_end != 0
          && ecs->event_thread->stop_signal != TARGET_SIGNAL_0
          && (ecs->event_thread->step_range_start <= stop_pc
              && stop_pc < ecs->event_thread->step_range_end)
          && frame_id_eq (get_stack_frame_id (frame),
                          ecs->event_thread->step_stack_frame_id)
          && ecs->event_thread->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_step_resume_breakpoint_at_frame (frame);
          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.  */
      keep_going (ecs);
      return;
    }

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

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

    if (what.call_dummy)
      {
        stop_stack_dummy = 1;
      }

    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 (!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;
          }

        /* We're going to replace the current step-resume breakpoint
           with a longjmp-resume breakpoint.  */
        delete_step_resume_breakpoint (ecs->event_thread);

        /* Insert a breakpoint at resume address.  */
        insert_longjmp_resume_breakpoint (gdbarch, jmp_buf_pc);

        keep_going (ecs);
        return;

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

        gdb_assert (ecs->event_thread->step_resume_breakpoint != NULL);
        delete_step_resume_breakpoint (ecs->event_thread);

        ecs->event_thread->stop_step = 1;
        print_stop_reason (END_STEPPING_RANGE, 0);
        stop_stepping (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_STOP_NOISY:
        if (debug_infrun)
          fprintf_unfiltered (gdb_stdlog, "infrun: BPSTAT_WHAT_STOP_NOISY\n");
        stop_print_frame = 1;

        /* We are about to nuke the step_resume_breakpointt via the
           cleanup chain, so no need to worry about it here.  */

        stop_stepping (ecs);
        return;

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

        /* We are about to nuke the step_resume_breakpoin via the
           cleanup chain, so no need to worry about it here.  */

        stop_stepping (ecs);
        return;

      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->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;
          }
        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_CHECK_SHLIBS:
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog, "infrun: BPSTAT_WHAT_CHECK_SHLIBS\n");

          /* Check for any newly added shared libraries if we're
             supposed to be adding them automatically.  Switch
             terminal for any messages produced by
             breakpoint_re_set.  */
          target_terminal_ours_for_output ();
          /* NOTE: cagney/2003-11-25: Make certain that the target
             stack's section table is kept up-to-date.  Architectures,
             (e.g., PPC64), use the section table to perform
             operations such as address => section name and hence
             require the table to contain all sections (including
             those found in shared libraries).  */
#ifdef SOLIB_ADD
          SOLIB_ADD (NULL, 0, &current_target, auto_solib_add);
#else
          solib_add (NULL, 0, &current_target, auto_solib_add);
#endif
          target_terminal_inferior ();

          /* If requested, stop when the dynamic linker notifies
             gdb of events.  This allows the user to get control
             and place breakpoints in initializer routines for
             dynamically loaded objects (among other things).  */
          if (stop_on_solib_events || stop_stack_dummy)
            {
              stop_stepping (ecs);
              return;
            }
          else
            {
              /* We want to step over this breakpoint, then keep going.  */
              ecs->event_thread->stepping_over_breakpoint = 1;
              break;
            }
        }
        break;

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

        /* Switch terminal for any messages produced by breakpoint_re_set.  */
        target_terminal_ours_for_output ();

        jit_event_handler (gdbarch);

        target_terminal_inferior ();

        /* We want to step over this breakpoint, then keep going.  */
        ecs->event_thread->stepping_over_breakpoint = 1;

        break;

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

      case BPSTAT_WHAT_KEEP_CHECKING:
        break;
      }
  }

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

  /* 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 (!non_stop)
    {
      struct thread_info *tp;
      tp = iterate_over_threads (currently_stepping_or_nexting_callback,
                                 ecs->event_thread);
      if (tp)
        {
          /* However, if the current thread is blocked on some internal
             breakpoint, and we simply need to step over that breakpoint
             to get it going again, do that first.  */
          if ((ecs->event_thread->trap_expected
               && ecs->event_thread->stop_signal != TARGET_SIGNAL_TRAP)
              || ecs->event_thread->stepping_over_breakpoint)
            {
              keep_going (ecs);
              return;
            }

          /* 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;
            }

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

          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);
          keep_going (ecs);
          return;
        }
    }

  /* Are we stepping to get the inferior out of the dynamic linker's
     hook (and possibly the dld itself) after catching a shlib
     event?  */
  if (ecs->event_thread->stepping_through_solib_after_catch)
    {
#if defined(SOLIB_ADD)
      /* Have we reached our destination?  If not, keep going. */
      if (SOLIB_IN_DYNAMIC_LINKER (PIDGET (ecs->ptid), stop_pc))
        {
          if (debug_infrun)
            fprintf_unfiltered (gdb_stdlog, "infrun: stepping in dynamic linker\n");
          ecs->event_thread->stepping_over_breakpoint = 1;
          keep_going (ecs);
          return;
        }
#endif
      if (debug_infrun)
         fprintf_unfiltered (gdb_stdlog, "infrun: step past dynamic linker\n");
      /* Else, stop and report the catchpoint(s) whose triggering
         caused us to begin stepping. */
      ecs->event_thread->stepping_through_solib_after_catch = 0;
      bpstat_clear (&ecs->event_thread->stop_bpstat);
      ecs->event_thread->stop_bpstat
        = bpstat_copy (ecs->event_thread->stepping_through_solib_catchpoints);
      bpstat_clear (&ecs->event_thread->stepping_through_solib_catchpoints);
      stop_print_frame = 1;
      stop_stepping (ecs);
      return;
    }

  if (ecs->event_thread->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->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;
    }

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

      /* 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->step_range_start
          && stop_pc != ecs->stop_func_start
          && execution_direction == EXEC_REVERSE)
        {
          ecs->event_thread->stop_step = 1;
          print_stop_reason (END_STEPPING_RANGE, 0);
          stop_stepping (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->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;

          insert_step_resume_breakpoint_at_sal (gdbarch,
                                                sr_sal, null_frame_id);
        }

      keep_going (ecs);
      return;
    }

  if (ecs->event_thread->step_range_end != 1
      && (ecs->event_thread->step_over_calls == STEP_OVER_UNDEBUGGABLE
          || ecs->event_thread->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;
    }

  /* 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 commend in frame_id_eq
     for more.  */
  if (!frame_id_eq (get_stack_frame_id (frame),
                    ecs->event_thread->step_stack_frame_id)
      && (frame_id_eq (frame_unwind_caller_id (get_current_frame ()),
                       ecs->event_thread->step_stack_frame_id)
          && (!frame_id_eq (ecs->event_thread->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->step_over_calls == STEP_OVER_NONE)
          || ((ecs->event_thread->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 */
          ecs->event_thread->stop_step = 1;
          print_stop_reason (END_STEPPING_RANGE, 0);
          stop_stepping (ecs);
          return;
        }

      /* Reverse stepping through solib trampolines.  */

      if (execution_direction == EXEC_REVERSE
          && ecs->event_thread->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->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)
            {
              struct symtab_and_line sr_sal;

              /* Normal function call return (static or dynamic).  */
              init_sal (&sr_sal);
              sr_sal.pc = ecs->stop_func_start;
                  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;

          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, 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)
          {
            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->step_over_calls == STEP_OVER_UNDEBUGGABLE
          && step_stop_if_no_debug)
        {
          ecs->event_thread->stop_step = 1;
          print_stop_reason (END_STEPPING_RANGE, 0);
          stop_stepping (ecs);
          return;
        }

      if (execution_direction == EXEC_REVERSE)
        {
          /* 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;
          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->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;
          insert_step_resume_breakpoint_at_sal (gdbarch, 
                                                sr_sal, null_frame_id);
          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.  */
  if (gdbarch_in_solib_return_trampoline (gdbarch,
                                          stop_pc, ecs->stop_func_name))
    {
      /* 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);

          /* 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;
        }
    }

  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->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.  */
          ecs->event_thread->stop_step = 1;
          print_stop_reason (END_STEPPING_RANGE, 0);
          stop_stepping (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->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");
      ecs->event_thread->stop_step = 1;
      print_stop_reason (END_STEPPING_RANGE, 0);
      stop_stepping (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");
      ecs->event_thread->stop_step = 1;
      print_stop_reason (END_STEPPING_RANGE, 0);
      stop_stepping (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->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->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);

          ecs->event_thread->stop_step = 1;
          print_stop_reason (END_STEPPING_RANGE, 0);
          stop_stepping (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
            {
              ecs->event_thread->stop_step = 1;
              print_stop_reason (END_STEPPING_RANGE, 0);
              stop_stepping (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->step_frame_id)
      && stepped_in_from (get_current_frame (),
                          ecs->event_thread->step_frame_id))
    {
      if (debug_infrun)
        fprintf_unfiltered (gdb_stdlog,
                            "infrun: stepping through inlined function\n");

      if (ecs->event_thread->step_over_calls == STEP_OVER_ALL)
        keep_going (ecs);
      else
        {
          ecs->event_thread->stop_step = 1;
          print_stop_reason (END_STEPPING_RANGE, 0);
          stop_stepping (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");
      ecs->event_thread->stop_step = 1;
      print_stop_reason (END_STEPPING_RANGE, 0);
      stop_stepping (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->step_range_start = stop_pc_sal.pc;
  ecs->event_thread->step_range_end = stop_pc_sal.end;
  set_step_info (frame, stop_pc_sal);

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

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

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

/* Returns true if any thread *but* the one passed in "data" is in the
   middle of stepping or of handling a "next".  */

static int
currently_stepping_or_nexting_callback (struct thread_info *tp, void *data)
{
  if (tp == data)
    return 0;

  return (tp->step_range_end
          || tp->trap_expected
          || tp->stepping_through_solib_after_catch);
}

/* 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;

  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.  */
      ecs->event_thread->stop_step = 1;
      print_stop_reason (END_STEPPING_RANGE, 0);
      stop_stepping (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);

      /* 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->step_range_end = ecs->event_thread->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, sr_sal;

  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.  */
      ecs->event_thread->stop_step = 1;
      print_stop_reason (END_STEPPING_RANGE, 0);
      stop_stepping (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->step_range_start = stop_func_sal.pc;
      ecs->event_thread->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 (struct gdbarch *gdbarch,
                                      struct symtab_and_line sr_sal,
                                      struct frame_id sr_id)
{
  /* 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 ()->step_resume_breakpoint == NULL);

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

  inferior_thread ()->step_resume_breakpoint
    = set_momentary_breakpoint (gdbarch, sr_sal, sr_id, bp_step_resume);
}

/* Insert a "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_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);

  insert_step_resume_breakpoint_at_sal (gdbarch, sr_sal,
                                        get_stack_frame_id (return_frame));
}

/* Similar to insert_step_resume_breakpoint_at_frame, except
   but a 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_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);

  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 step-resume or 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 ()->step_resume_breakpoint == NULL);

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

  inferior_thread ()->step_resume_breakpoint =
    set_momentary_breakpoint_at_pc (gdbarch, pc, bp_longjmp_resume);
}

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

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

/* This function handles various cases where we need to continue
   waiting for the inferior.  */
/* (Used to be the keep_going: label in the old wait_for_inferior) */

static void
keep_going (struct execution_control_state *ecs)
{
  /* 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 we did not do break;, it means we should keep running the
     inferior and not return to debugger.  */

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

         We're going to run this baby now!  

         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 (ecs->event_thread->stepping_over_breakpoint)
        {
          struct regcache *thread_regcache = get_thread_regcache (ecs->ptid);
          if (!use_displaced_stepping (get_regcache_arch (thread_regcache)))
            /* Since we can't do a displaced step, we have to remove
               the breakpoint while we step it.  To keep things
               simple, we remove them all.  */
            remove_breakpoints ();
        }
      else
        {
          struct gdb_exception e;
          /* Stop stepping when inserting breakpoints
             has failed.  */
          TRY_CATCH (e, RETURN_MASK_ERROR)
            {
              insert_breakpoints ();
            }
          if (e.reason < 0)
            {
              stop_stepping (ecs);
              return;
            }
        }

      ecs->event_thread->trap_expected = ecs->event_thread->stepping_over_breakpoint;

      /* Do not deliver SIGNAL_TRAP (except when the user explicitly
         specifies that such a signal should be delivered to the
         target program).

         Typically, this would occure when a user is debugging a
         target monitor on a simulator: the target monitor sets a
         breakpoint; the simulator encounters this break-point and
         halts the simulation handing control to GDB; GDB, noteing
         that the break-point isn't valid, returns control back to the
         simulator; the simulator then delivers the hardware
         equivalent of a SIGNAL_TRAP to the program being debugged. */

      if (ecs->event_thread->stop_signal == TARGET_SIGNAL_TRAP
          && !signal_program[ecs->event_thread->stop_signal])
        ecs->event_thread->stop_signal = TARGET_SIGNAL_0;

      resume (currently_stepping (ecs->event_thread),
              ecs->event_thread->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;
}

/* 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 this function from handle_inferior_event()
   each time stop_stepping() is called.*/
static void
print_stop_reason (enum inferior_stop_reason stop_reason, int stop_info)
{
  switch (stop_reason)
    {
    case END_STEPPING_RANGE:
      /* We are done with a step/next/si/ni command. */
      /* For now print nothing. */
      /* Print a message only if not in the middle of doing a "step n"
         operation for n > 1 */
      if (!inferior_thread ()->step_multi
          || !inferior_thread ()->stop_step)
        if (ui_out_is_mi_like_p (uiout))
          ui_out_field_string
            (uiout, "reason",
             async_reason_lookup (EXEC_ASYNC_END_STEPPING_RANGE));
      break;
    case SIGNAL_EXITED:
      /* The inferior was terminated by a signal. */
      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",
                           target_signal_to_name (stop_info));
      annotate_signal_name_end ();
      ui_out_text (uiout, ", ");
      annotate_signal_string ();
      ui_out_field_string (uiout, "signal-meaning",
                           target_signal_to_string (stop_info));
      annotate_signal_string_end ();
      ui_out_text (uiout, ".\n");
      ui_out_text (uiout, "The program no longer exists.\n");
      break;
    case EXITED:
      /* The inferior program is finished. */
      annotate_exited (stop_info);
      if (stop_info)
        {
          if (ui_out_is_mi_like_p (uiout))
            ui_out_field_string (uiout, "reason", 
                                 async_reason_lookup (EXEC_ASYNC_EXITED));
          ui_out_text (uiout, "\nProgram exited with code ");
          ui_out_field_fmt (uiout, "exit-code", "0%o",
                            (unsigned int) stop_info);
          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, "\nProgram exited normally.\n");
        }
      /* Support the --return-child-result option.  */
      return_child_result_value = stop_info;
      break;
    case SIGNAL_RECEIVED:
      /* Signal received.  The signal table tells us to print about
         it. */
      annotate_signal ();

      if (stop_info == TARGET_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",
                               target_signal_to_name (stop_info));
          annotate_signal_name_end ();
          ui_out_text (uiout, ", ");
          annotate_signal_string ();
          ui_out_field_string (uiout, "signal-meaning",
                               target_signal_to_string (stop_info));
          annotate_signal_string_end ();
        }
      ui_out_text (uiout, ".\n");
      break;
    case NO_HISTORY:
      /* Reverse execution: target ran out of history info.  */
      ui_out_text (uiout, "\nNo more reverse-execution history.\n");
      break;
    default:
      internal_error (__FILE__, __LINE__,
                      _("print_stop_reason: unrecognized enum value"));
      break;
    }
}
\f

/* Here to return control to GDB when the inferior stops for real.
   Print appropriate messages, remove breakpoints, give terminal our modes.

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

void
normal_stop (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)
    make_cleanup (finish_thread_state_cleanup, &inferior_ptid);

  /* In non-stop mode, 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.  */

  /* 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".  */
  if (!non_stop
      && !ptid_equal (previous_inferior_ptid, inferior_ptid)
      && target_has_execution
      && last.kind != TARGET_WAITKIND_SIGNALLED
      && last.kind != TARGET_WAITKIND_EXITED)
    {
      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 (!breakpoints_always_inserted_mode () && target_has_execution)
    {
      if (remove_breakpoints ())
        {
          target_terminal_ours_for_output ();
          printf_filtered (_("\
Cannot remove breakpoints because program is no longer writable.\n\
Further 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 ();

  /* Don't print a message if in the middle of doing a "step n"
     operation for n > 1 */
  if (target_has_execution
      && last.kind != TARGET_WAITKIND_SIGNALLED
      && last.kind != TARGET_WAITKIND_EXITED
      && inferior_thread ()->step_multi
      && inferior_thread ()->stop_step)
    goto done;

  target_terminal_ours ();

  /* 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 (), 1);

  /* Let the user/frontend see the threads as stopped.  */
  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 ());

      /* 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. */

      /* 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)
        {
          int bpstat_ret;
          int source_flag;
          int do_frame_printing = 1;
          struct thread_info *tp = inferior_thread ();

          bpstat_ret = bpstat_print (tp->stop_bpstat);
          switch (bpstat_ret)
            {
            case PRINT_UNKNOWN:
              /* If we had hit a shared library event breakpoint,
                 bpstat_print would print out this message.  If we hit
                 an OS-level shared library event, do the same
                 thing.  */
              if (last.kind == TARGET_WAITKIND_LOADED)
                {
                  printf_filtered (_("Stopped due to shared library event\n"));
                  source_flag = SRC_LINE;       /* something bogus */
                  do_frame_printing = 0;
                  break;
                }

              /* 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->stop_step
                  && frame_id_eq (tp->step_frame_id,
                                  get_frame_id (get_current_frame ()))
                  && step_start_function == find_pc_function (stop_pc))
                source_flag = SRC_LINE; /* finished step, just print source line */
              else
                source_flag = SRC_AND_LOC;      /* print location and source line */
              break;
            case PRINT_SRC_AND_LOC:
              source_flag = SRC_AND_LOC;        /* print location and source line */
              break;
            case PRINT_SRC_ONLY:
              source_flag = SRC_LINE;
              break;
            case PRINT_NOTHING:
              source_flag = SRC_LINE;   /* something bogus */
              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);

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

  /* Save the function value return registers, if we care.
     We might be about to restore their previous contents.  */
  if (inferior_thread ()->proceed_to_finish)
    {
      /* 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)
    {
      /* Pop the empty frame that contains the stack dummy.
         This also restores inferior state prior to the call
         (struct inferior_thread_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_inferior_status.  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
      || (!inferior_thread ()->step_multi
          && !(inferior_thread ()->stop_bpstat
               && inferior_thread ()->proceed_to_finish)
          && !inferior_thread ()->in_infcall))
    {
      if (!ptid_equal (inferior_ptid, null_ptid))
        observer_notify_normal_stop (inferior_thread ()->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 ()->stop_bpstat);
    }
}

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];
}

int
signal_stop_update (int signo, int state)
{
  int ret = signal_stop[signo];
  signal_stop[signo] = state;
  return ret;
}

int
signal_print_update (int signo, int state)
{
  int ret = signal_print[signo];
  signal_print[signo] = state;
  return ret;
}

int
signal_pass_update (int signo, int state)
{
  int ret = signal_program[signo];
  signal_program[signo] = state;
  return ret;
}

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

static void
sig_print_info (enum target_signal oursig)
{
  const char *name = target_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", target_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 target_signal oursig;
  int allsigs;
  int nsigs;
  unsigned char *sigs;
  struct cleanup *old_chain;

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

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

  nsigs = (int) TARGET_SIGNAL_LAST;
  sigs = (unsigned char *) alloca (nsigs);
  memset (sigs, 0, nsigs);

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

  argv = 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)
            target_signal_from_command (atoi (*argv));
          if ((*argv)[digits] == '-')
            {
              siglast = (int)
                target_signal_from_command (atoi ((*argv) + digits + 1));
            }
          if (sigfirst > siglast)
            {
              /* Bet he didn't figure we'd think of this case... */
              signum = sigfirst;
              sigfirst = siglast;
              siglast = signum;
            }
        }
      else
        {
          oursig = target_signal_from_name (*argv);
          if (oursig != TARGET_SIGNAL_UNKNOWN)
            {
              sigfirst = siglast = (int) oursig;
            }
          else
            {
              /* Not a number and not a recognized flag word => complain.  */
              error (_("Unrecognized or ambiguous flag word: \"%s\"."), *argv);
            }
        }

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

      for (signum = sigfirst; signum >= 0 && signum <= siglast; signum++)
        {
          switch ((enum target_signal) signum)
            {
            case TARGET_SIGNAL_TRAP:
            case TARGET_SIGNAL_INT:
              if (!allsigs && !sigs[signum])
                {
                  if (query (_("%s is used by the debugger.\n\
Are you sure you want to change it? "), target_signal_to_name ((enum target_signal) signum)))
                    {
                      sigs[signum] = 1;
                    }
                  else
                    {
                      printf_unfiltered (_("Not confirmed, unchanged.\n"));
                      gdb_flush (gdb_stdout);
                    }
                }
              break;
            case TARGET_SIGNAL_0:
            case TARGET_SIGNAL_DEFAULT:
            case TARGET_SIGNAL_UNKNOWN:
              /* Make sure that "all" doesn't print these.  */
              break;
            default:
              sigs[signum] = 1;
              break;
            }
        }

      argv++;
    }

  for (signum = 0; signum < nsigs; signum++)
    if (sigs[signum])
      {
        target_notice_signals (inferior_ptid);

        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);
}

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 target_signal oursig;

          oursig = target_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);
}

/* 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 target_signal oursig;
  sig_print_header ();

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

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

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

  printf_filtered (_("\nUse the \"handle\" command to change these tables.\n"));
}

/* 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 it
   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;

  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;

  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 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)
{
  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
/* Inferior thread state.
   These are details related to the inferior itself, and don't include
   things like what frame the user had selected or what gdb was doing
   with the target at the time.
   For inferior function calls these are things we want to restore
   regardless of whether the function call successfully completes
   or the dummy frame has to be manually popped.  */

struct inferior_thread_state
{
  enum target_signal stop_signal;
  CORE_ADDR stop_pc;
  struct regcache *registers;
};

struct inferior_thread_state *
save_inferior_thread_state (void)
{
  struct inferior_thread_state *inf_state = XMALLOC (struct inferior_thread_state);
  struct thread_info *tp = inferior_thread ();

  inf_state->stop_signal = tp->stop_signal;
  inf_state->stop_pc = stop_pc;

  inf_state->registers = regcache_dup (get_current_regcache ());

  return inf_state;
}

/* Restore inferior session state to INF_STATE.  */

void
restore_inferior_thread_state (struct inferior_thread_state *inf_state)
{
  struct thread_info *tp = inferior_thread ();

  tp->stop_signal = inf_state->stop_signal;
  stop_pc = inf_state->stop_pc;

  /* 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 (get_current_regcache (), inf_state->registers);
  regcache_xfree (inf_state->registers);
  xfree (inf_state);
}

static void
do_restore_inferior_thread_state_cleanup (void *state)
{
  restore_inferior_thread_state (state);
}

struct cleanup *
make_cleanup_restore_inferior_thread_state (struct inferior_thread_state *inf_state)
{
  return make_cleanup (do_restore_inferior_thread_state_cleanup, inf_state);
}

void
discard_inferior_thread_state (struct inferior_thread_state *inf_state)
{
  regcache_xfree (inf_state->registers);
  xfree (inf_state);
}

struct regcache *
get_inferior_thread_state_regcache (struct inferior_thread_state *inf_state)
{
  return inf_state->registers;
}

/* Session related state for inferior function calls.
   These are the additional bits of state that need to be restored
   when an inferior function call successfully completes.  */

struct inferior_status
{
  bpstat stop_bpstat;
  int stop_step;
  int stop_stack_dummy;
  int stopped_by_random_signal;
  int stepping_over_breakpoint;
  CORE_ADDR step_range_start;
  CORE_ADDR step_range_end;
  struct frame_id step_frame_id;
  struct frame_id step_stack_frame_id;
  enum step_over_calls_kind step_over_calls;
  CORE_ADDR step_resume_break_address;
  int stop_after_trap;
  int stop_soon;

  /* ID if the selected frame when the inferior function call was made.  */
  struct frame_id selected_frame_id;

  int proceed_to_finish;
  int in_infcall;
};

/* Save all of the information associated with the inferior<==>gdb
   connection.  */

struct inferior_status *
save_inferior_status (void)
{
  struct inferior_status *inf_status = XMALLOC (struct inferior_status);
  struct thread_info *tp = inferior_thread ();
  struct inferior *inf = current_inferior ();

  inf_status->stop_step = tp->stop_step;
  inf_status->stop_stack_dummy = stop_stack_dummy;
  inf_status->stopped_by_random_signal = stopped_by_random_signal;
  inf_status->stepping_over_breakpoint = tp->trap_expected;
  inf_status->step_range_start = tp->step_range_start;
  inf_status->step_range_end = tp->step_range_end;
  inf_status->step_frame_id = tp->step_frame_id;
  inf_status->step_stack_frame_id = tp->step_stack_frame_id;
  inf_status->step_over_calls = tp->step_over_calls;
  inf_status->stop_after_trap = stop_after_trap;
  inf_status->stop_soon = inf->stop_soon;
  /* Save original bpstat chain here; replace it with copy of chain.
     If caller's caller is walking the chain, they'll be happier if we
     hand them back the original chain when restore_inferior_status is
     called.  */
  inf_status->stop_bpstat = tp->stop_bpstat;
  tp->stop_bpstat = bpstat_copy (tp->stop_bpstat);
  inf_status->proceed_to_finish = tp->proceed_to_finish;
  inf_status->in_infcall = tp->in_infcall;

  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_inferior_status (struct inferior_status *inf_status)
{
  struct thread_info *tp = inferior_thread ();
  struct inferior *inf = current_inferior ();

  tp->stop_step = inf_status->stop_step;
  stop_stack_dummy = inf_status->stop_stack_dummy;
  stopped_by_random_signal = inf_status->stopped_by_random_signal;
  tp->trap_expected = inf_status->stepping_over_breakpoint;
  tp->step_range_start = inf_status->step_range_start;
  tp->step_range_end = inf_status->step_range_end;
  tp->step_frame_id = inf_status->step_frame_id;
  tp->step_stack_frame_id = inf_status->step_stack_frame_id;
  tp->step_over_calls = inf_status->step_over_calls;
  stop_after_trap = inf_status->stop_after_trap;
  inf->stop_soon = inf_status->stop_soon;
  bpstat_clear (&tp->stop_bpstat);
  tp->stop_bpstat = inf_status->stop_bpstat;
  inf_status->stop_bpstat = NULL;
  tp->proceed_to_finish = inf_status->proceed_to_finish;
  tp->in_infcall = inf_status->in_infcall;

  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_inferior_status_cleanup (void *sts)
{
  restore_inferior_status (sts);
}

struct cleanup *
make_cleanup_restore_inferior_status (struct inferior_status *inf_status)
{
  return make_cleanup (do_restore_inferior_status_cleanup, inf_status);
}

void
discard_inferior_status (struct inferior_status *inf_status)
{
  /* See save_inferior_status for info on stop_bpstat. */
  bpstat_clear (&inf_status->stop_bpstat);
  xfree (inf_status);
}
\f
int
inferior_has_forked (ptid_t pid, ptid_t *child_pid)
{
  struct target_waitstatus last;
  ptid_t last_ptid;

  get_last_target_status (&last_ptid, &last);

  if (last.kind != TARGET_WAITKIND_FORKED)
    return 0;

  if (!ptid_equal (last_ptid, pid))
    return 0;

  *child_pid = last.value.related_pid;
  return 1;
}

int
inferior_has_vforked (ptid_t pid, ptid_t *child_pid)
{
  struct target_waitstatus last;
  ptid_t last_ptid;

  get_last_target_status (&last_ptid, &last);

  if (last.kind != TARGET_WAITKIND_VFORKED)
    return 0;

  if (!ptid_equal (last_ptid, pid))
    return 0;

  *child_pid = last.value.related_pid;
  return 1;
}

int
inferior_has_execd (ptid_t pid, char **execd_pathname)
{
  struct target_waitstatus last;
  ptid_t last_ptid;

  get_last_target_status (&last_ptid, &last);

  if (last.kind != TARGET_WAITKIND_EXECD)
    return 0;

  if (!ptid_equal (last_ptid, pid))
    return 0;

  *execd_pathname = xstrdup (last.value.execd_pathname);
  return 1;
}

int
inferior_has_called_syscall (ptid_t pid, int *syscall_number)
{
  struct target_waitstatus last;
  ptid_t last_ptid;

  get_last_target_status (&last_ptid, &last);

  if (last.kind != TARGET_WAITKIND_SYSCALL_ENTRY &&
      last.kind != TARGET_WAITKIND_SYSCALL_RETURN)
    return 0;

  if (!ptid_equal (last_ptid, pid))
    return 0;

  *syscall_number = last.value.syscall_number;
  return 1;
}

/* Oft used ptids */
ptid_t null_ptid;
ptid_t minus_one_ptid;

/* Create a ptid given the necessary PID, LWP, and TID components.  */

ptid_t
ptid_build (int pid, long lwp, long tid)
{
  ptid_t ptid;

  ptid.pid = pid;
  ptid.lwp = lwp;
  ptid.tid = tid;
  return ptid;
}

/* Create a ptid from just a pid.  */

ptid_t
pid_to_ptid (int pid)
{
  return ptid_build (pid, 0, 0);
}

/* Fetch the pid (process id) component from a ptid.  */

int
ptid_get_pid (ptid_t ptid)
{
  return ptid.pid;
}

/* Fetch the lwp (lightweight process) component from a ptid.  */

long
ptid_get_lwp (ptid_t ptid)
{
  return ptid.lwp;
}

/* Fetch the tid (thread id) component from a ptid.  */

long
ptid_get_tid (ptid_t ptid)
{
  return ptid.tid;
}

/* ptid_equal() is used to test equality of two ptids.  */

int
ptid_equal (ptid_t ptid1, ptid_t ptid2)
{
  return (ptid1.pid == ptid2.pid && ptid1.lwp == ptid2.lwp
          && ptid1.tid == ptid2.tid);
}

/* Returns true if PTID represents a process.  */

int
ptid_is_pid (ptid_t ptid)
{
  if (ptid_equal (minus_one_ptid, ptid))
    return 0;
  if (ptid_equal (null_ptid, ptid))
    return 0;

  return (ptid_get_lwp (ptid) == 0 && ptid_get_tid (ptid) == 0);
}

/* 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);
}
\f

/* User interface for reverse debugging:
   Set exec-direction / show exec-direction commands
   (returns error unless target implements to_set_exec_direction method).  */

enum exec_direction_kind 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 *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;
    }
}

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;
  case EXEC_ERROR:
  default:
    fprintf_filtered (out, 
                      _("Forward (target `%s' does not support exec-direction).\n"),
                      target_shortname);
    break;
  }
}

/* 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);
}

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);
}

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);

  add_com ("handle", class_run, 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 \"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."));
  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_zinteger_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) TARGET_SIGNAL_LAST;
  signal_stop = (unsigned char *) xmalloc (sizeof (signal_stop[0]) * numsigs);
  signal_print = (unsigned char *)
    xmalloc (sizeof (signal_print[0]) * numsigs);
  signal_program = (unsigned char *)
    xmalloc (sizeof (signal_program[0]) * numsigs);
  for (i = 0; i < numsigs; i++)
    {
      signal_stop[i] = 1;
      signal_print[i] = 1;
      signal_program[i] = 1;
    }

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

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

  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."),
                            NULL,
                            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 ("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_enum_cmd ("displaced-stepping", class_run,
                        can_use_displaced_stepping_enum,
                        &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);

  /* ptid initializations */
  null_ptid = ptid_build (0, 0, 0);
  minus_one_ptid = ptid_build (-1, 0, 0);
  inferior_ptid = null_ptid;
  target_last_wait_ptid = minus_one_ptid;
  displaced_step_ptid = null_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);

  /* 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_make_value);
}