Replace "struct continuation" mechanism by something more extensible

This adds an object oriented replacement for the "struct continuation"
mechanism, and converts the stepping commands (step, next, stepi,
nexti) and the "finish" commands to use it.

It adds a new thread "class" (struct thread_fsm) that contains the
necessary info and callbacks to manage the state machine of a thread's
execution command.

This allows getting rid of some hacks.  E.g., in fetch_inferior_event
and normal_stop we no longer need to know whether a thread is doing a
multi-step (e.g., step N).  This effectively makes the
intermediate_continuations unused -- they'll be garbage collected in a
separate patch.  (They were never a proper abstraction, IMO.  See how
fetch_inferior_event needs to check step_multi before knowing whether
to call INF_EXEC_CONTINUE or INF_EXEC_COMPLETE.)

The target async vs !async uiout hacks in mi_on_normal_stop go away
too.

print_stop_event is no longer called from normal_stop.  Instead it is
now called from within each interpreter's normal_stop observer.  This
clears the path to make each interpreter print a stop event the way it
sees fit.  Currently we have some hacks in common code to
differenciate CLI vs TUI vs MI around this area.

The "finish" command's FSM class stores the return value plus that
value's position in the value history, so that those can be printed to
both MI and CLI's streams.  This fixes the CLI "finish" command when
run from MI -- it now also includes the function's return value in the
CLI stream:

  (gdb)
  ~"callee3 (strarg=0x400730 \"A string argument.\") at src/gdb/testsuite/gdb.mi/basics.c:35\n"
  ~"35\t}\n"
 +~"Value returned is $1 = 0\n"
  *stopped,reason="function-finished",frame=...,gdb-result-var="$1",return-value="0",thread-id="1",stopped-threads="all",core="0"
 -FAIL: gdb.mi/mi-cli.exp: CLI finish: check CLI output
 +PASS: gdb.mi/mi-cli.exp: CLI finish: check CLI output

gdb/ChangeLog:
2015-09-09  Pedro Alves  <palves@redhat.com>

	* Makefile.in (COMMON_OBS): Add thread-fsm.o.
	* breakpoint.c (handle_jit_event): Print debug output.
	(bpstat_what): Split event callback handling to ...
	(bpstat_run_callbacks): ... this new function.
	(momentary_bkpt_print_it): No longer handle bp_finish here.
	* breakpoint.h (bpstat_run_callbacks): Declare.
	* gdbthread.h (struct thread_info) <step_multi>: Delete field.
	<thread_fsm>: New field.
	(thread_cancel_execution_command): Declare.
	* infcmd.c: Include thread-fsm.h.
	(struct step_command_fsm): New.
	(step_command_fsm_ops): New global.
	(new_step_command_fsm, step_command_fsm_prepare): New functions.
	(step_1): Adjust to use step_command_fsm_prepare and
	prepare_one_step.
	(struct step_1_continuation_args): Delete.
	(step_1_continuation): Delete.
	(step_command_fsm_should_stop): New function.
	(step_once): Delete.
	(step_command_fsm_clean_up, step_command_fsm_async_reply_reason)
	(prepare_one_step): New function, based on step_once.
	(until_next_command): Remove step_multi reference.
	(struct return_value_info): New.
	(print_return_value): Rename to ...
	(print_return_value_1): ... this.  New struct return_value_info
	parameter.  Adjust.
	(print_return_value): Reimplement as wrapper around
	print_return_value_1.
	(struct finish_command_fsm): New.
	(finish_command_continuation): Delete.
	(finish_command_fsm_ops): New global.
	(new_finish_command_fsm, finish_command_fsm_should_stop): New
	functions.
	(finish_command_fsm_clean_up, finish_command_fsm_return_value):
	New.
	(finish_command_continuation_free_arg): Delete.
	(finish_command_fsm_async_reply_reason): New.
	(finish_backward, finish_forward): Change symbol parameter to a
	finish_command_fsm.  Adjust.
	(finish_command): Create a finish_command_fsm.  Adjust.
	* infrun.c: Include "thread-fsm.h".
	(clear_proceed_status_thread): Delete the thread's FSM.
	(infrun_thread_stop_requested_callback): Cancel the thread's
	execution command.
	(clean_up_just_stopped_threads_fsms): New function.
	(fetch_inferior_event): Handle the event_thread's should_stop
	method saying the command isn't done yet.
	(process_event_stop_test): Run breakpoint callbacks here.
	(print_stop_event): Rename to ...
	(print_stop_location): ... this.
	(restore_current_uiout_cleanup): New function.
	(print_stop_event): Reimplement.
	(normal_stop): No longer notify the end_stepping_range observers
	here handle "step N" nor "finish" here.  No longer call
	print_stop_event here.
	* infrun.h (struct return_value_info): Forward declare.
	(print_return_value): Declare.
	(print_stop_event): Change prototype.
	* thread-fsm.c: New file.
	* thread-fsm.h: New file.
	* thread.c: Include "thread-fsm.h".
	(thread_cancel_execution_command): New function.
	(clear_thread_inferior_resources): Call it.
	* cli/cli-interp.c (cli_on_normal_stop): New function.
	(cli_interpreter_init): Install cli_on_normal_stop as normal_stop
	observer.
	* mi/mi-interp.c: Include "thread-fsm.h".
	(restore_current_uiout_cleanup): Delete.
	(mi_on_normal_stop): If the thread has an FSM associated, and it
	finished, ask it for the async-reply-reason to print.  Always call
	print_stop_event here, regardless of the top-level interpreter.
	Check bpstat_what to tell whether an asynchronous breakpoint hit
	triggered.
	* tui/tui-interp.c (tui_on_normal_stop): New function.
	(tui_init): Install tui_on_normal_stop as normal_stop observer.

gdb/testsuite/ChangeLog:
2015-09-09  Pedro Alves  <palves@redhat.com>

	* gdb.mi/mi-cli.exp: Add CLI finish tests.

1 files changed, 108 insertions, 49 deletions

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 273c2bc..73ac090 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -62,6 +62,7 @@
 #include "terminal.h"
 #include "solist.h"
 #include "event-loop.h"
+#include "thread-fsm.h"
 
 /* Prototypes for local functions */
 
@@ -2749,6 +2750,9 @@ clear_proceed_status_thread (struct thread_info *tp)
   if (!signal_pass_state (tp->suspend.stop_signal))
     tp->suspend.stop_signal = GDB_SIGNAL_0;
 
+  thread_fsm_delete (tp->thread_fsm);
+  tp->thread_fsm = NULL;
+
   tp->control.trap_expected = 0;
   tp->control.step_range_start = 0;
   tp->control.step_range_end = 0;
@@ -3220,7 +3224,7 @@ infrun_thread_stop_requested_callback (struct thread_info *info, void *arg)
 	 have consistent output as if the stop event had been
 	 reported.  */
       ecs->ptid = info->ptid;
-      ecs->event_thread = find_thread_ptid (info->ptid);
+      ecs->event_thread = info;
       ecs->ws.kind = TARGET_WAITKIND_STOPPED;
       ecs->ws.value.sig = GDB_SIGNAL_0;
 
@@ -3230,6 +3234,9 @@ infrun_thread_stop_requested_callback (struct thread_info *info, void *arg)
 	{
 	  struct thread_info *tp;
 
+	  /* Cancel any running execution command.  */
+	  thread_cancel_execution_command (info);
+
 	  normal_stop ();
 
 	  /* Finish off the continuations.  */
@@ -3718,6 +3725,35 @@ reinstall_readline_callback_handler_cleanup (void *arg)
     gdb_rl_callback_handler_reinstall ();
 }
 
+/* Clean up the FSMs of threads that are now stopped.  In non-stop,
+   that's just the event thread.  In all-stop, that's all threads.  */
+
+static void
+clean_up_just_stopped_threads_fsms (struct execution_control_state *ecs)
+{
+  struct thread_info *thr = ecs->event_thread;
+
+  if (thr != NULL && thr->thread_fsm != NULL)
+    thread_fsm_clean_up (thr->thread_fsm);
+
+  if (!non_stop)
+    {
+      ALL_NON_EXITED_THREADS (thr)
+        {
+	  if (thr->thread_fsm == NULL)
+	    continue;
+	  if (thr == ecs->event_thread)
+	    continue;
+
+	  switch_to_thread (thr->ptid);
+	  thread_fsm_clean_up (thr->thread_fsm);
+	}
+
+      if (ecs->event_thread != NULL)
+	switch_to_thread (ecs->event_thread->ptid);
+    }
+}
+
 /* 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
@@ -3796,22 +3832,31 @@ fetch_inferior_event (void *client_data)
   if (!ecs->wait_some_more)
     {
       struct inferior *inf = find_inferior_ptid (ecs->ptid);
+      int should_stop = 1;
+      struct thread_info *thr = ecs->event_thread;
 
       delete_just_stopped_threads_infrun_breakpoints ();
 
-      /* We may not find an inferior if this was a process exit.  */
-      if (inf == NULL || inf->control.stop_soon == NO_STOP_QUIETLY)
-	normal_stop ();
-
-      if (target_has_execution
-	  && ecs->ws.kind != TARGET_WAITKIND_NO_RESUMED
-	  && ecs->ws.kind != TARGET_WAITKIND_EXITED
-	  && ecs->ws.kind != TARGET_WAITKIND_SIGNALLED
-	  && ecs->event_thread->step_multi
-	  && ecs->event_thread->control.stop_step)
-	inferior_event_handler (INF_EXEC_CONTINUE, NULL);
+      if (thr != NULL)
+	{
+	  struct thread_fsm *thread_fsm = thr->thread_fsm;
+
+	  if (thread_fsm != NULL)
+	    should_stop = thread_fsm_should_stop (thread_fsm);
+	}
+
+      if (!should_stop)
+	{
+	  keep_going (ecs);
+	}
       else
 	{
+	  clean_up_just_stopped_threads_fsms (ecs);
+
+	  /* We may not find an inferior if this was a process exit.  */
+	  if (inf == NULL || inf->control.stop_soon == NO_STOP_QUIETLY)
+	    normal_stop ();
+
 	  inferior_event_handler (INF_EXEC_COMPLETE, NULL);
 	  cmd_done = 1;
 	}
@@ -5898,6 +5943,10 @@ process_event_stop_test (struct execution_control_state *ecs)
       stop_stack_dummy = what.call_dummy;
     }
 
+  /* A few breakpoint types have callbacks associated (e.g.,
+     bp_jit_event).  Run them now.  */
+  bpstat_run_callbacks (ecs->event_thread->control.stop_bpstat);
+
   /* If we hit an internal event that triggers symbol changes, the
      current frame will be invalidated within bpstat_what (e.g., if we
      hit an internal solib event).  Re-fetch it.  */
@@ -7663,8 +7712,8 @@ print_no_history_reason (struct ui_out *uiout)
    bpstat_print contains the logic deciding in detail what to print,
    based on the event(s) that just occurred.  */
 
-void
-print_stop_event (struct target_waitstatus *ws)
+static void
+print_stop_location (struct target_waitstatus *ws)
 {
   int bpstat_ret;
   enum print_what source_flag;
@@ -7715,9 +7764,50 @@ print_stop_event (struct target_waitstatus *ws)
      SRC_AND_LOC: Print location and source line.  */
   if (do_frame_printing)
     print_stack_frame (get_selected_frame (NULL), 0, source_flag, 1);
+}
+
+/* Cleanup that restores a previous current uiout.  */
+
+static void
+restore_current_uiout_cleanup (void *arg)
+{
+  struct ui_out *saved_uiout = arg;
+
+  current_uiout = saved_uiout;
+}
+
+/* See infrun.h.  */
+
+void
+print_stop_event (struct ui_out *uiout)
+{
+  struct cleanup *old_chain;
+  struct target_waitstatus last;
+  ptid_t last_ptid;
+  struct thread_info *tp;
+
+  get_last_target_status (&last_ptid, &last);
+
+  old_chain = make_cleanup (restore_current_uiout_cleanup, current_uiout);
+  current_uiout = uiout;
+
+  print_stop_location (&last);
 
   /* Display the auto-display expressions.  */
   do_displays ();
+
+  do_cleanups (old_chain);
+
+  tp = inferior_thread ();
+  if (tp->thread_fsm != NULL
+      && thread_fsm_finished_p (tp->thread_fsm))
+    {
+      struct return_value_info *rv;
+
+      rv = thread_fsm_return_value (tp->thread_fsm);
+      if (rv != NULL)
+	print_return_value (uiout, rv);
+    }
 }
 
 /* Here to return control to GDB when the inferior stops for real.
@@ -7830,20 +7920,6 @@ normal_stop (void)
   if (stopped_by_random_signal)
     disable_current_display ();
 
-  /* Notify observers if we finished a "step"-like command, etc.  */
-  if (target_has_execution
-      && last.kind != TARGET_WAITKIND_SIGNALLED
-      && last.kind != TARGET_WAITKIND_EXITED
-      && inferior_thread ()->control.stop_step)
-    {
-      /* But not if in the middle of doing a "step n" operation for
-	 n > 1 */
-      if (inferior_thread ()->step_multi)
-	goto done;
-
-      observer_notify_end_stepping_range ();
-    }
-
   target_terminal_ours ();
   async_enable_stdin ();
 
@@ -7885,15 +7961,7 @@ normal_stop (void)
      or if the program has exited.  */
 
   if (!stop_stack_dummy)
-    {
-      select_frame (get_current_frame ());
-
-      /* If --batch-silent is enabled then there's no need to print the current
-	 source location, and to try risks causing an error message about
-	 missing source files.  */
-      if (stop_print_frame && !batch_silent)
-	print_stop_event (&last);
-    }
+    select_frame (get_current_frame ());
 
   if (stop_stack_dummy == STOP_STACK_DUMMY)
     {
@@ -7917,16 +7985,9 @@ normal_stop (void)
     }
 
 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.  */
@@ -7935,11 +7996,7 @@ done:
       || last.kind == TARGET_WAITKIND_SIGNALLED
       || last.kind == TARGET_WAITKIND_EXITED
       || last.kind == TARGET_WAITKIND_NO_RESUMED
-      || (!(inferior_thread ()->step_multi
-	    && inferior_thread ()->control.stop_step)
-	  && !(inferior_thread ()->control.stop_bpstat
-	       && inferior_thread ()->control.proceed_to_finish)
-	  && !inferior_thread ()->control.in_infcall))
+      || !inferior_thread ()->control.in_infcall)
     {
       if (!ptid_equal (inferior_ptid, null_ptid))
 	observer_notify_normal_stop (inferior_thread ()->control.stop_bpstat,
@@ -7948,6 +8005,8 @@ done:
 	observer_notify_normal_stop (NULL, stop_print_frame);
     }
 
+  annotate_stopped ();
+
   if (target_has_execution)
     {
       if (last.kind != TARGET_WAITKIND_SIGNALLED