X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=gdb%2Finferior.c;h=17d28c4cf5486f594fb2713238350701c41e860b;hb=e98ee8c458f3a8405eb93e71b00f801b4bbe3635;hp=e19a8985d05e6f51f9f0391ef62b2ca6d6ce8335;hpb=a562dc8f5a5930afaa5ffb3e98200e21dd8b724a;p=deliverable%2Fbinutils-gdb.git

diff --git a/gdb/inferior.c b/gdb/inferior.c
index e19a8985d0..17d28c4cf5 100644
--- a/gdb/inferior.c
+++ b/gdb/inferior.c
@@ -1,6 +1,6 @@
 /* Multi-process control for GDB, the GNU debugger.
 
-   Copyright (C) 2008, 2009 Free Software Foundation, Inc.
+   Copyright (C) 2008-2018 Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -18,73 +18,100 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "defs.h"
+#include "exec.h"
 #include "inferior.h"
 #include "target.h"
 #include "command.h"
+#include "completer.h"
 #include "gdbcmd.h"
 #include "gdbthread.h"
 #include "ui-out.h"
-#include "observer.h"
-
-void _initialize_inferiors (void);
-
-static struct inferior *inferior_list = NULL;
+#include "observable.h"
+#include "gdbcore.h"
+#include "symfile.h"
+#include "environ.h"
+#include "cli/cli-utils.h"
+#include "continuations.h"
+#include "arch-utils.h"
+#include "target-descriptions.h"
+#include "readline/tilde.h"
+#include "progspace-and-thread.h"
+
+/* Keep a registry of per-inferior data-pointers required by other GDB
+   modules.  */
+
+DEFINE_REGISTRY (inferior, REGISTRY_ACCESS_FIELD)
+
+struct inferior *inferior_list = NULL;
 static int highest_inferior_num;
 
-/* Print notices on inferior events (attach, detach, etc.), set with
-   `set print inferior-events'.  */
-static int print_inferior_events = 0;
+/* See inferior.h.  */
+int print_inferior_events = 1;
+
+/* The Current Inferior.  This is a strong reference.  I.e., whenever
+   an inferior is the current inferior, its refcount is
+   incremented.  */
+static struct inferior *current_inferior_ = NULL;
 
 struct inferior*
 current_inferior (void)
 {
-  struct inferior *inf = find_inferior_pid (ptid_get_pid (inferior_ptid));
-  gdb_assert (inf);
-  return inf;
+  return current_inferior_;
 }
 
-static void
-free_inferior (struct inferior *inf)
+void
+set_current_inferior (struct inferior *inf)
 {
-  discard_all_inferior_continuations (inf);
-  xfree (inf->private);
-  xfree (inf);
+  /* There's always an inferior.  */
+  gdb_assert (inf != NULL);
+
+  inf->incref ();
+  current_inferior_->decref ();
+  current_inferior_ = inf;
 }
 
-void
-init_inferior_list (void)
-{
-  struct inferior *inf, *infnext;
+private_inferior::~private_inferior () = default;
 
-  highest_inferior_num = 0;
-  if (!inferior_list)
-    return;
+inferior::~inferior ()
+{
+  inferior *inf = this;
 
-  for (inf = inferior_list; inf; inf = infnext)
-    {
-      infnext = inf->next;
-      free_inferior (inf);
-    }
+  discard_all_inferior_continuations (inf);
+  inferior_free_data (inf);
+  xfree (inf->args);
+  xfree (inf->terminal);
+  target_desc_info_free (inf->tdesc_info);
+}
 
-  inferior_list = NULL;
+inferior::inferior (int pid_)
+  : num (++highest_inferior_num),
+    pid (pid_),
+    environment (gdb_environ::from_host_environ ()),
+    registry_data ()
+{
+  inferior_alloc_data (this);
 }
 
 struct inferior *
 add_inferior_silent (int pid)
 {
-  struct inferior *inf;
+  inferior *inf = new inferior (pid);
 
-  inf = xmalloc (sizeof (*inf));
-  memset (inf, 0, sizeof (*inf));
-  inf->pid = pid;
+  if (inferior_list == NULL)
+    inferior_list = inf;
+  else
+    {
+      inferior *last;
 
-  inf->stop_soon = NO_STOP_QUIETLY;
+      for (last = inferior_list; last->next != NULL; last = last->next)
+	;
+      last->next = inf;
+    }
 
-  inf->num = ++highest_inferior_num;
-  inf->next = inferior_list;
-  inferior_list = inf;
+  gdb::observers::inferior_added.notify (inf);
 
-  observer_notify_new_inferior (pid);
+  if (pid != 0)
+    inferior_appeared (inf, pid);
 
   return inf;
 }
@@ -95,7 +122,9 @@ add_inferior (int pid)
   struct inferior *inf = add_inferior_silent (pid);
 
   if (print_inferior_events)
-    printf_unfiltered (_("[New inferior %d]\n"), pid);
+    printf_unfiltered (_("[New inferior %d (%s)]\n"),
+		       inf->num,
+		       target_pid_to_str (ptid_t (pid)));
 
   return inf;
 }
@@ -109,88 +138,156 @@ struct delete_thread_of_inferior_arg
 static int
 delete_thread_of_inferior (struct thread_info *tp, void *data)
 {
-  struct delete_thread_of_inferior_arg *arg = data;
+  struct delete_thread_of_inferior_arg *arg
+    = (struct delete_thread_of_inferior_arg *) data;
 
-  if (ptid_get_pid (tp->ptid) == arg->pid)
+  if (tp->ptid.pid () == arg->pid)
     {
       if (arg->silent)
-	delete_thread_silent (tp->ptid);
+	delete_thread_silent (tp);
       else
-	delete_thread (tp->ptid);
+	delete_thread (tp);
     }
 
   return 0;
 }
 
-/* If SILENT then be quiet -- don't announce a inferior death, or the
-   exit of its threads.  */
-static void
-delete_inferior_1 (int pid, int silent)
+void
+delete_inferior (struct inferior *todel)
 {
   struct inferior *inf, *infprev;
-  struct delete_thread_of_inferior_arg arg = { pid, silent };
+  struct delete_thread_of_inferior_arg arg;
 
   infprev = NULL;
 
   for (inf = inferior_list; inf; infprev = inf, inf = inf->next)
-    if (inf->pid == pid)
+    if (inf == todel)
       break;
 
   if (!inf)
     return;
 
+  arg.pid = inf->pid;
+  arg.silent = 1;
+
+  iterate_over_threads (delete_thread_of_inferior, &arg);
+
   if (infprev)
     infprev->next = inf->next;
   else
     inferior_list = inf->next;
 
-  free_inferior (inf);
+  gdb::observers::inferior_removed.notify (inf);
+
+  /* If this program space is rendered useless, remove it. */
+  if (program_space_empty_p (inf->pspace))
+    delete_program_space (inf->pspace);
+
+  delete inf;
+}
+
+/* If SILENT then be quiet -- don't announce a inferior exit, or the
+   exit of its threads.  */
+
+static void
+exit_inferior_1 (struct inferior *inftoex, int silent)
+{
+  struct inferior *inf;
+  struct delete_thread_of_inferior_arg arg;
+
+  for (inf = inferior_list; inf; inf = inf->next)
+    if (inf == inftoex)
+      break;
 
-  arg.pid = pid;
+  if (!inf)
+    return;
+
+  arg.pid = inf->pid;
   arg.silent = silent;
 
   iterate_over_threads (delete_thread_of_inferior, &arg);
 
-  observer_notify_inferior_exit (pid);
+  gdb::observers::inferior_exit.notify (inf);
+
+  inf->pid = 0;
+  inf->fake_pid_p = 0;
+  inf->priv = NULL;
+
+  if (inf->vfork_parent != NULL)
+    {
+      inf->vfork_parent->vfork_child = NULL;
+      inf->vfork_parent = NULL;
+    }
+  if (inf->vfork_child != NULL)
+    {
+      inf->vfork_child->vfork_parent = NULL;
+      inf->vfork_child = NULL;
+    }
+
+  inf->pending_detach = 0;
+  /* Reset it.  */
+  inf->control = inferior_control_state (NO_STOP_QUIETLY);
 }
 
 void
-delete_inferior (int pid)
+exit_inferior (inferior *inf)
 {
-  delete_inferior_1 (pid, 0);
+  exit_inferior_1 (inf, 0);
+}
 
-  if (print_inferior_events)
-    printf_unfiltered (_("[Inferior %d exited]\n"), pid);
+void
+exit_inferior_silent (int pid)
+{
+  struct inferior *inf = find_inferior_pid (pid);
+
+  exit_inferior_1 (inf, 1);
 }
 
 void
-delete_inferior_silent (int pid)
+exit_inferior_silent (inferior *inf)
 {
-  delete_inferior_1 (pid, 1);
+  exit_inferior_1 (inf, 1);
 }
 
+/* See inferior.h.  */
+
 void
-detach_inferior (int pid)
+detach_inferior (inferior *inf)
 {
-  delete_inferior_1 (pid, 1);
+  /* Save the pid, since exit_inferior_1 will reset it.  */
+  int pid = inf->pid;
+
+  exit_inferior_1 (inf, 0);
 
   if (print_inferior_events)
-    printf_unfiltered (_("[Inferior %d detached]\n"), pid);
+    printf_unfiltered (_("[Inferior %d (%s) detached]\n"),
+		       inf->num,
+		       target_pid_to_str (ptid_t (pid)));
+}
+
+void
+inferior_appeared (struct inferior *inf, int pid)
+{
+  inf->pid = pid;
+  inf->has_exit_code = 0;
+  inf->exit_code = 0;
+
+  gdb::observers::inferior_appeared.notify (inf);
 }
 
 void
 discard_all_inferiors (void)
 {
-  struct inferior *inf, *infnext;
+  struct inferior *inf;
 
-  for (inf = inferior_list; inf; inf = infnext)
+  for (inf = inferior_list; inf; inf = inf->next)
     {
-      infnext = inf->next;
-      delete_inferior_silent (inf->pid);
+      if (inf->pid != 0)
+	exit_inferior_silent (inf);
     }
 }
 
-static struct inferior *
+struct inferior *
 find_inferior_id (int num)
 {
   struct inferior *inf;
@@ -207,6 +304,11 @@ find_inferior_pid (int pid)
 {
   struct inferior *inf;
 
+  /* Looking for inferior pid == 0 is always wrong, and indicative of
+     a bug somewhere else.  There may be more than one with pid == 0,
+     for instance.  */
+  gdb_assert (pid != 0);
+
   for (inf = inferior_list; inf; inf = inf->next)
     if (inf->pid == pid)
       return inf;
@@ -214,6 +316,33 @@ find_inferior_pid (int pid)
   return NULL;
 }
 
+/* See inferior.h */
+
+struct inferior *
+find_inferior_ptid (ptid_t ptid)
+{
+  return find_inferior_pid (ptid.pid ());
+}
+
+/* See inferior.h.  */
+
+struct inferior *
+find_inferior_for_program_space (struct program_space *pspace)
+{
+  struct inferior *inf = current_inferior ();
+
+  if (inf->pspace == pspace)
+    return inf;
+
+  for (inf = inferior_list; inf != NULL; inf = inf->next)
+    {
+      if (inf->pspace == pspace)
+	return inf;
+    }
+
+  return NULL;
+}
+
 struct inferior *
 iterate_over_inferiors (int (*callback) (struct inferior *, void *),
 			void *data)
@@ -231,101 +360,528 @@ iterate_over_inferiors (int (*callback) (struct inferior *, void *),
 }
 
 int
-valid_gdb_inferior_id (int num)
+have_inferiors (void)
 {
   struct inferior *inf;
 
   for (inf = inferior_list; inf; inf = inf->next)
-    if (inf->num == num)
+    if (inf->pid != 0)
       return 1;
 
   return 0;
 }
 
+/* Return the number of live inferiors.  We account for the case
+   where an inferior might have a non-zero pid but no threads, as
+   in the middle of a 'mourn' operation.  */
+
 int
-pid_to_gdb_inferior_id (int pid)
+number_of_live_inferiors (void)
 {
   struct inferior *inf;
+  int num_inf = 0;
 
   for (inf = inferior_list; inf; inf = inf->next)
-    if (inf->pid == pid)
-      return inf->num;
-
-  return 0;
+    if (inf->pid != 0)
+      {
+	struct thread_info *tp;
+
+	ALL_NON_EXITED_THREADS (tp)
+	 if (tp && tp->ptid.pid () == inf->pid)
+	   if (target_has_execution_1 (tp->ptid))
+	     {
+	       /* Found a live thread in this inferior, go to the next
+		  inferior.  */
+	       ++num_inf;
+	       break;
+	     }
+      }
+
+  return num_inf;
 }
 
+/* Return true if there is at least one live inferior.  */
+
 int
-gdb_inferior_id_to_pid (int num)
+have_live_inferiors (void)
 {
-  struct inferior *inferior = find_inferior_id (num);
-  if (inferior)
-    return inferior->pid;
-  else
-    return -1;
+  return number_of_live_inferiors () > 0;
 }
 
+/* Prune away any unused inferiors, and then prune away no longer used
+   program spaces.  */
+
+void
+prune_inferiors (void)
+{
+  struct inferior *ss, **ss_link;
+
+  ss = inferior_list;
+  ss_link = &inferior_list;
+  while (ss)
+    {
+      if (!ss->deletable ()
+	  || !ss->removable
+	  || ss->pid != 0)
+	{
+	  ss_link = &ss->next;
+	  ss = *ss_link;
+	  continue;
+	}
+
+      *ss_link = ss->next;
+      delete_inferior (ss);
+      ss = *ss_link;
+    }
+}
+
+/* Simply returns the count of inferiors.  */
+
 int
-in_inferior_list (int pid)
+number_of_inferiors (void)
 {
   struct inferior *inf;
+  int count = 0;
 
-  for (inf = inferior_list; inf; inf = inf->next)
-    if (inf->pid == pid)
-      return 1;
+  for (inf = inferior_list; inf != NULL; inf = inf->next)
+    count++;
 
-  return 0;
+  return count;
 }
 
-int
-have_inferiors (void)
+/* Converts an inferior process id to a string.  Like
+   target_pid_to_str, but special cases the null process.  */
+
+static const char *
+inferior_pid_to_str (int pid)
+{
+  if (pid != 0)
+    return target_pid_to_str (ptid_t (pid));
+  else
+    return _("<null>");
+}
+
+/* See inferior.h.  */
+
+void
+print_selected_inferior (struct ui_out *uiout)
 {
-  return inferior_list != NULL;
+  struct inferior *inf = current_inferior ();
+  const char *filename = inf->pspace->pspace_exec_filename;
+
+  if (filename == NULL)
+    filename = _("<noexec>");
+
+  uiout->message (_("[Switching to inferior %d [%s] (%s)]\n"),
+		  inf->num, inferior_pid_to_str (inf->pid), filename);
 }
 
 /* Prints the list of inferiors and their details on UIOUT.  This is a
    version of 'info_inferior_command' suitable for use from MI.
 
-   If REQUESTED_INFERIOR is not -1, it's the GDB id of the inferior that
-   should be printed.  Otherwise, all inferiors are printed.  */
-void
-print_inferior (struct ui_out *uiout, int requested_inferior)
+   If REQUESTED_INFERIORS is not NULL, it's a list of GDB ids of the
+   inferiors that should be printed.  Otherwise, all inferiors are
+   printed.  */
+
+static void
+print_inferior (struct ui_out *uiout, const char *requested_inferiors)
 {
   struct inferior *inf;
-  struct cleanup *old_chain;
-
-  old_chain = make_cleanup_ui_out_list_begin_end (uiout, "inferiors");
+  int inf_count = 0;
 
+  /* Compute number of inferiors we will print.  */
   for (inf = inferior_list; inf; inf = inf->next)
     {
-      struct cleanup *chain2;
+      if (!number_is_in_list (requested_inferiors, inf->num))
+	continue;
+
+      ++inf_count;
+    }
+
+  if (inf_count == 0)
+    {
+      uiout->message ("No inferiors.\n");
+      return;
+    }
+
+  ui_out_emit_table table_emitter (uiout, 4, inf_count, "inferiors");
+  uiout->table_header (1, ui_left, "current", "");
+  uiout->table_header (4, ui_left, "number", "Num");
+  uiout->table_header (17, ui_left, "target-id", "Description");
+  uiout->table_header (17, ui_left, "exec", "Executable");
 
-      if (requested_inferior != -1 && inf->num != requested_inferior)
+  uiout->table_body ();
+  for (inf = inferior_list; inf; inf = inf->next)
+    {
+      if (!number_is_in_list (requested_inferiors, inf->num))
 	continue;
 
-      chain2 = make_cleanup_ui_out_tuple_begin_end (uiout, NULL);
+      ui_out_emit_tuple tuple_emitter (uiout, NULL);
+
+      if (inf == current_inferior ())
+	uiout->field_string ("current", "*");
+      else
+	uiout->field_skip ("current");
+
+      uiout->field_int ("number", inf->num);
 
-      if (inf->pid == ptid_get_pid (inferior_ptid))
-	ui_out_text (uiout, "* ");
+      uiout->field_string ("target-id", inferior_pid_to_str (inf->pid));
+
+      if (inf->pspace->pspace_exec_filename != NULL)
+	uiout->field_string ("exec", inf->pspace->pspace_exec_filename);
       else
-	ui_out_text (uiout, "  ");
+	uiout->field_skip ("exec");
+
+      /* Print extra info that isn't really fit to always present in
+	 tabular form.  Currently we print the vfork parent/child
+	 relationships, if any.  */
+      if (inf->vfork_parent)
+	{
+	  uiout->text (_("\n\tis vfork child of inferior "));
+	  uiout->field_int ("vfork-parent", inf->vfork_parent->num);
+	}
+      if (inf->vfork_child)
+	{
+	  uiout->text (_("\n\tis vfork parent of inferior "));
+	  uiout->field_int ("vfork-child", inf->vfork_child->num);
+	}
+
+      uiout->text ("\n");
+    }
+}
+
+static void
+detach_inferior_command (const char *args, int from_tty)
+{
+  if (!args || !*args)
+    error (_("Requires argument (inferior id(s) to detach)"));
+
+  number_or_range_parser parser (args);
+  while (!parser.finished ())
+    {
+      int num = parser.get_number ();
+
+      inferior *inf = find_inferior_id (num);
+      if (inf == NULL)
+	{
+	  warning (_("Inferior ID %d not known."), num);
+	  continue;
+	}
+
+      if (inf->pid == 0)
+	{
+	  warning (_("Inferior ID %d is not running."), num);
+	  continue;
+	}
+
+      thread_info *tp = any_thread_of_inferior (inf);
+      if (tp == NULL)
+	{
+	  warning (_("Inferior ID %d has no threads."), num);
+	  continue;
+	}
+
+      switch_to_thread (tp);
+
+      detach_command (NULL, from_tty);
+    }
+}
+
+static void
+kill_inferior_command (const char *args, int from_tty)
+{
+  if (!args || !*args)
+    error (_("Requires argument (inferior id(s) to kill)"));
+
+  number_or_range_parser parser (args);
+  while (!parser.finished ())
+    {
+      int num = parser.get_number ();
+
+      inferior *inf = find_inferior_id (num);
+      if (inf == NULL)
+	{
+	  warning (_("Inferior ID %d not known."), num);
+	  continue;
+	}
+
+      if (inf->pid == 0)
+	{
+	  warning (_("Inferior ID %d is not running."), num);
+	  continue;
+	}
+
+      thread_info *tp = any_thread_of_inferior (inf);
+      if (tp == NULL)
+	{
+	  warning (_("Inferior ID %d has no threads."), num);
+	  continue;
+	}
+
+      switch_to_thread (tp);
+
+      target_kill ();
+    }
+
+  bfd_cache_close_all ();
+}
+
+static void
+inferior_command (const char *args, int from_tty)
+{
+  struct inferior *inf;
+  int num;
+
+  num = parse_and_eval_long (args);
 
-      ui_out_field_int (uiout, "id", inf->num);
-      ui_out_text (uiout, " ");
-      ui_out_field_int (uiout, "target-id", inf->pid);
+  inf = find_inferior_id (num);
+  if (inf == NULL)
+    error (_("Inferior ID %d not known."), num);
 
-      ui_out_text (uiout, "\n");
-      do_cleanups (chain2);
+  if (inf->pid != 0)
+    {
+      if (inf != current_inferior ())
+	{
+	  thread_info *tp = any_thread_of_inferior (inf);
+	  if (tp == NULL)
+	    error (_("Inferior has no threads."));
+
+	  switch_to_thread (tp);
+	}
+
+      gdb::observers::user_selected_context_changed.notify
+	(USER_SELECTED_INFERIOR
+	 | USER_SELECTED_THREAD
+	 | USER_SELECTED_FRAME);
     }
+  else
+    {
+      set_current_inferior (inf);
+      switch_to_no_thread ();
+      set_current_program_space (inf->pspace);
 
-  do_cleanups (old_chain);
+      gdb::observers::user_selected_context_changed.notify
+	(USER_SELECTED_INFERIOR);
+    }
 }
 
 /* Print information about currently known inferiors.  */
 
 static void
-info_inferiors_command (char *arg, int from_tty)
+info_inferiors_command (const char *args, int from_tty)
 {
-  print_inferior (uiout, -1);
+  print_inferior (current_uiout, args);
+}
+
+/* remove-inferior ID */
+
+static void
+remove_inferior_command (const char *args, int from_tty)
+{
+  if (args == NULL || *args == '\0')
+    error (_("Requires an argument (inferior id(s) to remove)"));
+
+  number_or_range_parser parser (args);
+  while (!parser.finished ())
+    {
+      int num = parser.get_number ();
+      struct inferior *inf = find_inferior_id (num);
+
+      if (inf == NULL)
+	{
+	  warning (_("Inferior ID %d not known."), num);
+	  continue;
+	}
+
+      if (!inf->deletable ())
+	{
+	  warning (_("Can not remove current inferior %d."), num);
+	  continue;
+	}
+    
+      if (inf->pid != 0)
+	{
+	  warning (_("Can not remove active inferior %d."), num);
+	  continue;
+	}
+
+      delete_inferior (inf);
+    }
+}
+
+struct inferior *
+add_inferior_with_spaces (void)
+{
+  struct address_space *aspace;
+  struct program_space *pspace;
+  struct inferior *inf;
+  struct gdbarch_info info;
+
+  /* If all inferiors share an address space on this system, this
+     doesn't really return a new address space; otherwise, it
+     really does.  */
+  aspace = maybe_new_address_space ();
+  pspace = new program_space (aspace);
+  inf = add_inferior (0);
+  inf->pspace = pspace;
+  inf->aspace = pspace->aspace;
+
+  /* Setup the inferior's initial arch, based on information obtained
+     from the global "set ..." options.  */
+  gdbarch_info_init (&info);
+  inf->gdbarch = gdbarch_find_by_info (info);
+  /* The "set ..." options reject invalid settings, so we should
+     always have a valid arch by now.  */
+  gdb_assert (inf->gdbarch != NULL);
+
+  return inf;
+}
+
+/* add-inferior [-copies N] [-exec FILENAME]  */
+
+static void
+add_inferior_command (const char *args, int from_tty)
+{
+  int i, copies = 1;
+  gdb::unique_xmalloc_ptr<char> exec;
+  symfile_add_flags add_flags = 0;
+
+  if (from_tty)
+    add_flags |= SYMFILE_VERBOSE;
+
+  if (args)
+    {
+      gdb_argv built_argv (args);
+
+      for (char **argv = built_argv.get (); *argv != NULL; argv++)
+	{
+	  if (**argv == '-')
+	    {
+	      if (strcmp (*argv, "-copies") == 0)
+		{
+		  ++argv;
+		  if (!*argv)
+		    error (_("No argument to -copies"));
+		  copies = parse_and_eval_long (*argv);
+		}
+	      else if (strcmp (*argv, "-exec") == 0)
+		{
+		  ++argv;
+		  if (!*argv)
+		    error (_("No argument to -exec"));
+		  exec.reset (tilde_expand (*argv));
+		}
+	    }
+	  else
+	    error (_("Invalid argument"));
+	}
+    }
+
+  scoped_restore_current_pspace_and_thread restore_pspace_thread;
+
+  for (i = 0; i < copies; ++i)
+    {
+      struct inferior *inf = add_inferior_with_spaces ();
+
+      printf_filtered (_("Added inferior %d\n"), inf->num);
+
+      if (exec != NULL)
+	{
+	  /* Switch over temporarily, while reading executable and
+	     symbols.q.  */
+	  set_current_program_space (inf->pspace);
+	  set_current_inferior (inf);
+	  switch_to_no_thread ();
+
+	  exec_file_attach (exec.get (), from_tty);
+	  symbol_file_add_main (exec.get (), add_flags);
+	}
+    }
+}
+
+/* clone-inferior [-copies N] [ID] */
+
+static void
+clone_inferior_command (const char *args, int from_tty)
+{
+  int i, copies = 1;
+  struct inferior *orginf = NULL;
+
+  if (args)
+    {
+      gdb_argv built_argv (args);
+
+      char **argv = built_argv.get ();
+      for (; *argv != NULL; argv++)
+	{
+	  if (**argv == '-')
+	    {
+	      if (strcmp (*argv, "-copies") == 0)
+		{
+		  ++argv;
+		  if (!*argv)
+		    error (_("No argument to -copies"));
+		  copies = parse_and_eval_long (*argv);
+
+		  if (copies < 0)
+		    error (_("Invalid copies number"));
+		}
+	    }
+	  else
+	    {
+	      if (orginf == NULL)
+		{
+		  int num;
+
+		  /* The first non-option (-) argument specified the
+		     program space ID.  */
+		  num = parse_and_eval_long (*argv);
+		  orginf = find_inferior_id (num);
+
+		  if (orginf == NULL)
+		    error (_("Inferior ID %d not known."), num);
+		  continue;
+		}
+	      else
+		error (_("Invalid argument"));
+	    }
+	}
+    }
+
+  /* If no inferior id was specified, then the user wants to clone the
+     current inferior.  */
+  if (orginf == NULL)
+    orginf = current_inferior ();
+
+  scoped_restore_current_pspace_and_thread restore_pspace_thread;
+
+  for (i = 0; i < copies; ++i)
+    {
+      struct address_space *aspace;
+      struct program_space *pspace;
+      struct inferior *inf;
+
+      /* If all inferiors share an address space on this system, this
+	 doesn't really return a new address space; otherwise, it
+	 really does.  */
+      aspace = maybe_new_address_space ();
+      pspace = new program_space (aspace);
+      inf = add_inferior (0);
+      inf->pspace = pspace;
+      inf->aspace = pspace->aspace;
+      inf->gdbarch = orginf->gdbarch;
+
+      /* If the original inferior had a user specified target
+	 description, make the clone use it too.  */
+      if (target_desc_info_from_user_p (inf->tdesc_info))
+	copy_inferior_target_desc_info (inf, orginf);
+
+      printf_filtered (_("Added inferior %d.\n"), inf->num);
+
+      set_current_inferior (inf);
+      switch_to_no_thread ();
+      clone_program_space (pspace, orginf->pspace);
+    }
 }
 
 /* Print notices when new inferiors are created and die.  */
@@ -336,11 +892,87 @@ show_print_inferior_events (struct ui_file *file, int from_tty,
   fprintf_filtered (file, _("Printing of inferior events is %s.\n"), value);
 }
 
+/* Return a new value for the selected inferior's id.  */
+
+static struct value *
+inferior_id_make_value (struct gdbarch *gdbarch, struct internalvar *var,
+			void *ignore)
+{
+  struct inferior *inf = current_inferior ();
+
+  return value_from_longest (builtin_type (gdbarch)->builtin_int, inf->num);
+}
+
+/* Implementation of `$_inferior' variable.  */
+
+static const struct internalvar_funcs inferior_funcs =
+{
+  inferior_id_make_value,
+  NULL,
+  NULL
+};
+
+
+
 void
-_initialize_inferiors (void)
+initialize_inferiors (void)
 {
+  struct cmd_list_element *c = NULL;
+
+  /* There's always one inferior.  Note that this function isn't an
+     automatic _initialize_foo function, since other _initialize_foo
+     routines may need to install their per-inferior data keys.  We
+     can only allocate an inferior when all those modules have done
+     that.  Do this after initialize_progspace, due to the
+     current_program_space reference.  */
+  current_inferior_ = add_inferior_silent (0);
+  current_inferior_->incref ();
+  current_inferior_->pspace = current_program_space;
+  current_inferior_->aspace = current_program_space->aspace;
+  /* The architecture will be initialized shortly, by
+     initialize_current_architecture.  */
+
   add_info ("inferiors", info_inferiors_command,
-	    _("IDs of currently known inferiors."));
+	    _("Print a list of inferiors being managed.\n\
+Usage: info inferiors [ID]...\n\
+If IDs are specified, the list is limited to just those inferiors.\n\
+By default all inferiors are displayed."));
+
+  c = add_com ("add-inferior", no_class, add_inferior_command, _("\
+Add a new inferior.\n\
+Usage: add-inferior [-copies N] [-exec FILENAME]\n\
+N is the optional number of inferiors to add, default is 1.\n\
+FILENAME is the file name of the executable to use\n\
+as main program."));
+  set_cmd_completer (c, filename_completer);
+
+  add_com ("remove-inferiors", no_class, remove_inferior_command, _("\
+Remove inferior ID (or list of IDs).\n\
+Usage: remove-inferiors ID..."));
+
+  add_com ("clone-inferior", no_class, clone_inferior_command, _("\
+Clone inferior ID.\n\
+Usage: clone-inferior [-copies N] [ID]\n\
+Add N copies of inferior ID.  The new inferior has the same\n\
+executable loaded as the copied inferior.  If -copies is not specified,\n\
+adds 1 copy.  If ID is not specified, it is the current inferior\n\
+that is cloned."));
+
+  add_cmd ("inferiors", class_run, detach_inferior_command, _("\
+Detach from inferior ID (or list of IDS).\n\
+Usage; detach inferiors ID..."),
+	   &detachlist);
+
+  add_cmd ("inferiors", class_run, kill_inferior_command, _("\
+Kill inferior ID (or list of IDs).\n\
+Usage: kill inferiors ID..."),
+	   &killlist);
+
+  add_cmd ("inferior", class_run, inferior_command, _("\
+Use this command to switch between inferiors.\n\
+Usage: inferior ID\n\
+The new inferior ID must be currently known."),
+	   &cmdlist);
 
   add_setshow_boolean_cmd ("inferior-events", no_class,
          &print_inferior_events, _("\
@@ -349,4 +981,6 @@ Show printing of inferior events (e.g., inferior start and exit)."), NULL,
          NULL,
          show_print_inferior_events,
          &setprintlist, &showprintlist);
+
+  create_internalvar_type_lazy ("_inferior", &inferior_funcs, NULL);
 }