Simplify starting the command event loop

All interpreter types (CLI/TUI/MI) print the prompt, and then call
start_event_loop.

Because we'll need an interpreter hook to display the
interpreter-specific prompt before going back to the event loop,
without actually starting an event loop, this patch moves the
start_event_loop call to common code, and replaces the command_loop
hook with a pre_command_look hook, that now just prints the prompt.

Turns out to be a cleanup on its own right anyway.

gdb/ChangeLog:
2016-06-21  Pedro Alves  <palves@redhat.com>

	* cli/cli-interp.c (cli_interpreter_pre_command_loop): New
	function.
	(cli_interp_procs): Install it instead of cli_command_loop.
	* cli/cli-interp.h (cli_interpreter_pre_command_loop): Declare.
	* event-top.c (cli_command_loop): Delete.
	* interps.c (interp_new): Remove reference to command_loop_proc.
	(current_interp_command_loop): Delete.
	(interp_pre_command_loop): New function.
	(interp_command_loop_ftype): Delete.
	* interps.h (interp_pre_command_loop_ftype): New typedef.
	(struct interp_procs) <command_loop_proc>: Delele field.
	<pre_command_loop_proc>: New field.
	(current_interp_command_loop): Delete declaration.
	(interp_pre_command_loop): New declaration.
	* main.c (captured_command_loop): Call interp_pre_command_loop
	instead of current_interp_command_loop and start an event loop.
	* mi/mi-interp.c (mi_command_loop): Delete.
	(mi_interpreter_pre_command_loop): New.
	(mi_interp_procs): Update.
	* tui/tui-interp.c (tui_interp_procs): Install
	cli_interpreter_pre_command_loop instead of cli_command_loop.

gdb/ChangeLog

@@ -1,3 +1,27 @@
+2016-06-21  Pedro Alves  <palves@redhat.com>
+
+	* cli/cli-interp.c (cli_interpreter_pre_command_loop): New
+	function.
+	(cli_interp_procs): Install it instead of cli_command_loop.
+	* cli/cli-interp.h (cli_interpreter_pre_command_loop): Declare.
+	* event-top.c (cli_command_loop): Delete.
+	* interps.c (interp_new): Remove reference to command_loop_proc.
+	(current_interp_command_loop): Delete.
+	(interp_pre_command_loop): New function.
+	(interp_command_loop_ftype): Delete.
+	* interps.h (interp_pre_command_loop_ftype): New typedef.
+	(struct interp_procs) <command_loop_proc>: Delele field.
+	<pre_command_loop_proc>: New field.
+	(current_interp_command_loop): Delete declaration.
+	(interp_pre_command_loop): New declaration.
+	* main.c (captured_command_loop): Call interp_pre_command_loop
+	instead of current_interp_command_loop and start an event loop.
+	* mi/mi-interp.c (mi_command_loop): Delete.
+	(mi_interpreter_pre_command_loop): New.
+	(mi_interp_procs): Update.
+	* tui/tui-interp.c (tui_interp_procs): Install
+	cli_interpreter_pre_command_loop instead of cli_command_loop.
+
 2016-06-21  Pedro Alves  <palves@redhat.com>
 
 	* interps.c (current_interpreter): New function.

gdb/cli/cli-interp.c

@@ -190,6 +190,14 @@ cli_on_command_error (void)
   display_gdb_prompt (NULL);
 }
 
+/* pre_command_loop implementation.  */
+
+void
+cli_interpreter_pre_command_loop (struct interp *self)
+{
+  display_gdb_prompt (0);
+}
+
 /* These implement the cli out interpreter: */
 
 static void *
@@ -312,7 +320,7 @@ static const struct interp_procs cli_interp_procs = {
   cli_interpreter_exec,		/* exec_proc */
   cli_ui_out,			/* ui_out_proc */
   NULL,                       	/* set_logging_proc */
-  cli_command_loop,		/* command_loop_proc */
+  cli_interpreter_pre_command_loop, /* pre_command_loop_proc */
   cli_interpreter_supports_command_editing, /* supports_command_editing_proc */
 };
 

gdb/cli/cli-interp.h

@@ -22,4 +22,6 @@ struct interp;
 
 extern int cli_interpreter_supports_command_editing (struct interp *interp);
 
+extern void cli_interpreter_pre_command_loop (struct interp *self);
+
 #endif

gdb/event-top.c

@@ -216,19 +216,6 @@ gdb_rl_callback_handler (char *rl)
     throw_exception_sjlj (gdb_rl_expt);
 }
 
-/* Initialize all the necessary variables, start the event loop,
-   register readline, and stdin, start the loop.  The DATA is the
-   interpreter data cookie, ignored for now.  */
-
-void
-cli_command_loop (void *data)
-{
-  display_gdb_prompt (0);
-
-  /* Now it's time to start the event loop.  */
-  start_event_loop ();
-}
-
 /* Change the function to be invoked every time there is a character
    ready on stdin.  This is used when the user sets the editing off,
    therefore bypassing readline, and letting gdb handle the input

gdb/interps.c

@@ -117,9 +117,6 @@ interp_new (const char *name, const struct interp_procs *procs, void *data)
   new_interp->procs = procs;
   new_interp->inited = 0;
 
-  /* Check for required procs.  */
-  gdb_assert (procs->command_loop_proc != NULL);
-
   return new_interp;
 }
 
@@ -411,16 +408,15 @@ command_interp (void)
     return ui_interp->current_interpreter;
 }
 
-/* Run the current command interpreter's main loop.  */
+/* See interps.h.  */
+
 void
-current_interp_command_loop (void)
+interp_pre_command_loop (struct interp *interp)
 {
-  struct ui_interp_info *ui_interp = get_current_interp_info ();
+  gdb_assert (interp != NULL);
-  struct interp *interp = ui_interp->current_interpreter;
 
-  gdb_assert (ui_interp->current_interpreter != NULL);
+  if (interp->procs->pre_command_loop_proc != NULL)
-
+    interp->procs->pre_command_loop_proc (interp);
-  interp->procs->command_loop_proc (interp->data);
 }
 
 /* See interp.h  */

gdb/interps.h

@@ -46,7 +46,7 @@ typedef int (interp_resume_ftype) (void *data);
 typedef int (interp_suspend_ftype) (void *data);
 typedef struct gdb_exception (interp_exec_ftype) (void *data,
 						  const char *command);
-typedef void (interp_command_loop_ftype) (void *data);
+typedef void (interp_pre_command_loop_ftype) (struct interp *self);
 typedef struct ui_out *(interp_ui_out_ftype) (struct interp *self);
 
 typedef int (interp_set_logging_ftype) (struct interp *self, int start_log,
@@ -73,7 +73,9 @@ struct interp_procs
      disabled.  */
   interp_set_logging_ftype *set_logging_proc;
 
-  interp_command_loop_ftype *command_loop_proc;
+  /* Called before starting an event loop, to give the interpreter a
+     chance to e.g., print a prompt.  */
+  interp_pre_command_loop_ftype *pre_command_loop_proc;
 
   /* Returns true if this interpreter supports using the readline
      library; false if it uses GDB's own simplified readline
@@ -100,8 +102,6 @@ extern struct interp *interp_set_temp (const char *name);
 
 extern int current_interp_named_p (const char *name);
 
-extern void current_interp_command_loop (void);
-
 /* Call this function to give the current interpreter an opportunity
    to do any special handling of streams when logging is enabled or
    disabled.  START_LOG is 1 when logging is starting, 0 when it ends,
@@ -127,6 +127,10 @@ extern void clear_interpreter_hooks (void);
    if it uses GDB's own simplified form of readline.  */
 extern int interp_supports_command_editing (struct interp *interp);
 
+/* Called before starting an event loop, to give the interpreter a
+   chance to e.g., print a prompt.  */
+extern void interp_pre_command_loop (struct interp *interp);
+
 /* well-known interpreters */
 #define INTERP_CONSOLE		"console"
 #define INTERP_MI1             "mi1"

gdb/main.c

@@ -315,7 +315,12 @@ captured_command_loop (void *data)
      here on.  */
   current_ui->async = 1;
 
-  current_interp_command_loop ();
+  /* Give the interpreter a chance to print a prompt.  */
+  interp_pre_command_loop (top_level_interpreter ());
+
+  /* Now it's time to start the event loop.  */
+  start_event_loop ();
+
   /* FIXME: cagney/1999-11-05: A correct command_loop() implementaton
      would clean things up (restoring the cleanup chain) to the state
      they were just prior to the call.  Technically, this means that

gdb/mi/mi-interp.c

@@ -44,7 +44,6 @@
 
 static void mi_execute_command_wrapper (const char *cmd);
 static void mi_execute_command_input_handler (char *cmd);
-static void mi_command_loop (void *data);
 
 /* These are hooks that we put in place while doing interpreter_exec
    so we can report interesting things that happened "behind the MI's
@@ -329,9 +328,9 @@ mi_execute_command_input_handler (char *cmd)
 }
 
 static void
-mi_command_loop (void *data)
+mi_interpreter_pre_command_loop (struct interp *self)
 {
-  struct mi_interp *mi = (struct mi_interp *) data;
+  struct mi_interp *mi = (struct mi_interp *) interp_data (self);
 
   /* Turn off 8 bit strings in quoted output.  Any character with the
      high bit set is printed using C's octal format.  */
@@ -339,8 +338,6 @@ mi_command_loop (void *data)
 
   /* Tell the world that we're alive.  */
   display_mi_prompt (mi);
-
-  start_event_loop ();
 }
 
 static void
@@ -1442,7 +1439,7 @@ static const struct interp_procs mi_interp_procs =
   mi_interpreter_exec,		/* exec_proc */
   mi_ui_out, 			/* ui_out_proc */
   mi_set_logging,		/* set_logging_proc */
-  mi_command_loop		/* command_loop_proc */
+  mi_interpreter_pre_command_loop /* pre_command_loop_proc */
 };
 
 /* Factory for MI interpreters.  */

gdb/tui/tui-interp.c

@@ -278,7 +278,7 @@ static const struct interp_procs tui_interp_procs = {
   tui_exec,
   tui_ui_out,
   NULL,
-  cli_command_loop,
+  cli_interpreter_pre_command_loop,
   cli_interpreter_supports_command_editing,
 };