[RFC] Allow disabling the default run target.

diff --git a/gdb/NEWS b/gdb/NEWS
index 2a384ba..3bf059c 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -43,6 +43,12 @@  maint ada show ignore-descriptive-types
   the user manual for more details on descriptive types and the intended
   usage of this option.
 
+set auto-connect-native-target
+
+  Control whether GDB is allowed to automatically connect to the
+  native target for the run, attach, etc. commands when not connected
+  to any target yet.  See also "target native" below.
+
 * New features in the GDB remote stub, GDBserver
 
   ** New option --debug-format=option1[,option2,...] allows one to add
@@ -76,6 +82,10 @@  maint ada show ignore-descriptive-types
 
 * The "catch syscall" command now works on s390*-linux* targets.
 
+* The "target native" command now connects to the native instead of
+  erroring out.  This can be used to launch native programs when "set
+  auto-connect-native-target" is set to off.
+
 * New remote packets
 
 qXfer:btrace:read's annex
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index de5ac63..edf77f8 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -2146,6 +2146,57 @@  initialization file---such as @file{.cshrc} for C-shell,
 $@file{.zshenv} for the Z shell, or the file specified in the
 @samp{BASH_ENV} environment variable for BASH.
 
+@anchor{set auto-connect-native-target}
+@kindex set auto-connect-native-target
+@item set auto-connect-native-target
+@itemx set auto-connect-native-target on
+@itemx set auto-connect-native-target off
+@itemx show auto-connect-native-target
+
+By default, if not connected to any target yet (e.g., with
+@code{target remote}), the @code{run} command starts your program as a
+native process under @value{GDBN}, on your local machine.  If you're
+sure you don't want to debug programs on your local machine, you can
+tell @value{GDBN} to not connect to the native target automatically
+with the @code{set auto-connect-native-target off} command.
+
+If @code{on}, which is the default, and if @value{GDBN} is not
+connected to a target already, the @code{run} command automaticaly
+connects to the native target, if one is available.
+
+If @code{off}, and if @value{GDBN} is not connected to a target
+already, the @code{run} command fail with an error:
+
+@smallexample
+(@value{GDBP}) run
+Don't know how to run.  Try "help target".
+@end smallexample
+
+If @value{GDBN} is already connected to a target, @value{GDBN} always
+uses it with the @code{run} command.
+
+In any case, you can explicitly connect to the native target with the
+@code{target native} command.  For example,
+
+@smallexample
+(@value{GDBP}) set auto-connect-native-target off
+(@value{GDBP}) run
+Don't know how to run.  Try "help target".
+(@value{GDBP}) target native
+(@value{GDBP}) run
+Starting program: ./a.out
+[Inferior 1 (process 10421) exited normally]
+@end smallexample
+
+In case you connected explicitly to the @code{native} target,
+@value{GDBN} remains connected even if all inferiors exit, ready for
+the next @code{run} command.  Use the @code{disconnect} command to
+disconnect.
+
+Examples of other commands that likewise respect the
+@code{auto-connect-native-target} setting: @code{run}, @code{attach},
+@code{info proc}, @code{info os}.
+
 @kindex set disable-randomization
 @item set disable-randomization
 @itemx set disable-randomization on
@@ -18050,6 +18101,13 @@  provide these.  For info about any processor-specific simulator details,
 see the appropriate section in @ref{Embedded Processors, ,Embedded
 Processors}.
 
+@item target native
+@cindex native target
+Setup for local/native process debugging.  Useful to make the
+@code{run}, @code{attach}, etc.@: commands spawn native processes even
+when @code{set auto-connect-native-target} is @code{off} (@pxref{set
+auto-connect-native-target}).
+
 @end table
 
 Different targets are available on different configurations of @value{GDBN};
diff --git a/gdb/inf-child.c b/gdb/inf-child.c
index df52992..6ed216e 100644
--- a/gdb/inf-child.c
+++ b/gdb/inf-child.c
@@ -40,6 +40,10 @@ 
 #include <fcntl.h>
 #include <unistd.h>
 
+/* A pointer to what is returned by inf_child_target.  Used to be able
+   to push the most-derived target in reaction to "target child".  */
+static struct target_ops *inf_child_ops = NULL;
+
 /* Helper function for child_wait and the derivatives of child_wait.
    HOSTSTATUS is the waitstatus from wait() or the equivalent; store our
    translation of that in OURSTATUS.  */
@@ -109,10 +113,41 @@  inf_child_prepare_to_store (struct target_ops *self,
 {
 }
 
+/* True if the user did "target child".  In that case, we won't unpush
+   the child target automatically when the last inferior is gone.  */
+static int inf_child_explicitly_opened;
+
 static void
 inf_child_open (char *arg, int from_tty)
 {
-  error (_("Use the \"run\" command to start a process."));
+  target_preopen (from_tty);
+  push_target (inf_child_ops);
+  inf_child_explicitly_opened = 1;
+}
+
+static void
+inf_child_disconnect (struct target_ops *target, char *args, int from_tty)
+{
+  if (args != NULL)
+    error (_("Argument given to \"disconnect\"."));
+
+  /* This offers to detach/kill current inferiors, and then pops all
+     targets.  */
+  target_preopen (from_tty);
+}
+
+static void
+inf_child_close (struct target_ops *target)
+{
+  /* In case we were forcibly closed.  */
+  inf_child_explicitly_opened = 0;
+}
+
+void
+inf_child_maybe_unpush (struct target_ops *ops)
+{
+  if (!inf_child_explicitly_opened && !have_inferiors ())
+    unpush_target (ops);
 }
 
 static void
@@ -410,6 +445,8 @@  inf_child_target (void)
   t->to_longname = "Native process";
   t->to_doc = "Native process (started by the \"run\" command).";
   t->to_open = inf_child_open;
+  t->to_close = inf_child_close;
+  t->to_disconnect = inf_child_disconnect;
   t->to_post_attach = inf_child_post_attach;
   t->to_fetch_registers = inf_child_fetch_inferior_registers;
   t->to_store_registers = inf_child_store_inferior_registers;
@@ -445,5 +482,10 @@  inf_child_target (void)
   t->to_magic = OPS_MAGIC;
   t->to_use_agent = inf_child_use_agent;
   t->to_can_use_agent = inf_child_can_use_agent;
+
+  /* Store a pointer so we can push the target from
+     inf_child_open.  */
+  inf_child_ops = t;
+
   return t;
 }
diff --git a/gdb/inf-child.h b/gdb/inf-child.h
index 4473cff..56c69fe 100644
--- a/gdb/inf-child.h
+++ b/gdb/inf-child.h
@@ -25,6 +25,8 @@ 
 
 extern struct target_ops *inf_child_target (void);
 
+extern void inf_child_maybe_unpush (struct target_ops *ops);
+
 /* Functions for helping to write a native target.  */
 
 /* This is for native targets which use a unix/POSIX-style waitstatus.  */
diff --git a/gdb/inf-ptrace.c b/gdb/inf-ptrace.c
index bffb4ba..7d077b8 100644
--- a/gdb/inf-ptrace.c
+++ b/gdb/inf-ptrace.c
@@ -176,8 +176,7 @@  inf_ptrace_mourn_inferior (struct target_ops *ops)
 
   generic_mourn_inferior ();
 
-  if (!have_inferiors ())
-    unpush_target (ops);
+  inf_child_maybe_unpush (ops);
 }
 
 /* Attach to the process specified by ARGS.  If FROM_TTY is non-zero,
@@ -297,8 +296,7 @@  inf_ptrace_detach (struct target_ops *ops, const char *args, int from_tty)
   inferior_ptid = null_ptid;
   detach_inferior (pid);
 
-  if (!have_inferiors ())
-    unpush_target (ops);
+  inf_child_maybe_unpush (ops);
 }
 
 /* Kill the inferior.  */
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 5535462..f9b0ed0 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -201,6 +201,10 @@  static int (*linux_nat_siginfo_fixup) (siginfo_t *,
    Called by our to_xfer_partial.  */
 static target_xfer_partial_ftype *super_xfer_partial;
 
+/* The saved to_close method, inherited from inf-ptrace.c.
+   Called by our to_close.  */
+static void (*super_close) (struct target_ops *);
+
 static unsigned int debug_linux_nat;
 static void
 show_debug_linux_nat (struct ui_file *file, int from_tty,
@@ -4776,6 +4780,8 @@  linux_nat_close (struct target_ops *self)
 
   if (linux_ops->to_close)
     linux_ops->to_close (linux_ops);
+
+  super_close (self);
 }
 
 /* When requests are passed down from the linux-nat layer to the
@@ -4857,6 +4863,8 @@  linux_nat_add_target (struct target_ops *t)
   t->to_async = linux_nat_async;
   t->to_terminal_inferior = linux_nat_terminal_inferior;
   t->to_terminal_ours = linux_nat_terminal_ours;
+
+  super_close = t->to_close;
   t->to_close = linux_nat_close;
 
   /* Methods for non-stop support.  */
diff --git a/gdb/target.c b/gdb/target.c
index 0d22297..bbb8e5e 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -2574,6 +2574,20 @@  target_require_runnable (void)
   internal_error (__FILE__, __LINE__, _("No targets found"));
 }
 
+/* Whether GDB is allowed to fall back to the default run target for
+   "run", "attach", etc. when no target is connected yet.  */
+static int auto_connect_native_target = 1;
+
+static void
+show_auto_connect_native_target (struct ui_file *file, int from_tty,
+				 struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file,
+		    _("Whether GDB may automatically connect to the "
+		      "native target is %s.\n"),
+		    value);
+}
+
 /* Look through the list of possible targets for a target that can
    execute a run or attach command without any other data.  This is
    used to locate the default process stratum.
@@ -2584,23 +2598,28 @@  target_require_runnable (void)
 static struct target_ops *
 find_default_run_target (char *do_mesg)
 {
-  struct target_ops **t;
   struct target_ops *runable = NULL;
-  int count;
 
-  count = 0;
-
-  for (t = target_structs; t < target_structs + target_struct_size;
-       ++t)
+  if (auto_connect_native_target)
     {
-      if ((*t)->to_can_run != delegate_can_run && target_can_run (*t))
+      struct target_ops **t;
+      int count = 0;
+
+      for (t = target_structs; t < target_structs + target_struct_size;
+	   ++t)
 	{
-	  runable = *t;
-	  ++count;
+	  if ((*t)->to_can_run != delegate_can_run && target_can_run (*t))
+	    {
+	      runable = *t;
+	      ++count;
+	    }
 	}
+
+      if (count != 1)
+	runable = NULL;
     }
 
-  if (count != 1)
+  if (runable == NULL)
     {
       if (do_mesg)
 	error (_("Don't know how to %s.  Try \"help target\"."), do_mesg);
@@ -4369,4 +4388,13 @@  When this permission is on, GDB may interrupt/stop the target's execution.\n\
 Otherwise, any attempt to interrupt or stop will be ignored."),
 			   set_target_permissions, NULL,
 			   &setlist, &showlist);
+
+  add_setshow_boolean_cmd ("auto-connect-native-target", class_support,
+			   &auto_connect_native_target, _("\
+Set whether GDB may automatically connect to the native target."), _("\
+Show whether GDB may automatically connect to the native target."), _("\
+When on, and GDB is not connected to a target yet, GDB\n\
+attempts \"run\" and other commands with the native target."),
+			   NULL, show_auto_connect_native_target,
+			   &setlist, &showlist);
 }
diff --git a/gdb/testsuite/boards/native-extended-gdbserver.exp b/gdb/testsuite/boards/native-extended-gdbserver.exp
index 8bb95db..080a22e 100644
--- a/gdb/testsuite/boards/native-extended-gdbserver.exp
+++ b/gdb/testsuite/boards/native-extended-gdbserver.exp
@@ -36,6 +36,8 @@  set_board_info gdb_protocol "extended-remote"
 
 send_user "configuring for gdbserver local testing (extended-remote)\n"
 
+set GDBFLAGS "${GDBFLAGS} -ex \"set auto-connect-native-target off\""
+
 # We must load this explicitly here, and rename the procedures we want
 # to override.  If we didn't do this, given that mi-support.exp is
 # loaded later in the test files, the procedures loaded then would