[PATCH 2/4] Suppress repeated annotations until GDB is ready to accept input.

[Pedro Alves <palves@redhat.com>]

With some changes to how software single-step (SSS) breakpoints are
handled, one of those being to place SSS breakpoints on the breakpoint
chain as all other breakpoints, annota1.exp times out with lots and
lots of breakpoint-invalid and frame-changed annotations.  All those
extra annotations are actually unnecessary.  For one, SSS breakpoints
are internal breakpoints, so the frontend shouldn't care if they were
added, removed or changed.  Then, there's really no point in emitting
"breakpoints-invalid" or "frames-invalid" more than once between times
the frontend/user can actually issues GDB commands; the frontend will
have to wait for the GDB prompt to refresh its state, so emitting
those annotations at most once between prompts is enough.  Non-stop or
async would complicate this, but no frontend will be using annotations
in those modes (one of goes of emacs switching to MI was non-stop mode
support, AFAIK).  The previous patch reveals there has been an
intention in the past to suppress multiple breakpoints-invalid
annotations caused by ignore count changes.  As the previous patch
shows, that's always been broken, but in any case, this patch actually
makes it work.  The next patch will remove several annotation-specific
calls in breakpoint.c in favor of always using the breakpoint modified
& friends observers, and that causes yet more of these annotations,
because several calls to the corresponding annotate_* functions in
breakpoint.c are missing, particularly in newer code.

So all in all, here's a simple mechanism that avoids sending the same
annotation to the frontend more than once until gdb is ready to accept
further commands.

Tested on x86_64 Fedora 17.

2012-11-21  Pedro Alves  <palves@redhat.com>

	* annotate.c (frames_invalid_emitted)
	(breakpoints_invalid_emitted): New globals.
	(annotate_breakpoints_changed, annotate_frames_invalid): Skip
	emitting the annotation if it has already been emitted.
	(annotate_display_prompt): New function.
	* annotate.h (annotate_display_prompt): New declaration.
	* event-top.c: Include annotate.h.
	(display_gdb_prompt): Call annotate_display_prompt.
---
 gdb/annotate.c  |   23 +++++++++++++++++++++--
 gdb/annotate.h  |    2 ++
 gdb/event-top.c |    3 +++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/gdb/annotate.c b/gdb/annotate.c
index a222736..3c7acb9 100644
--- a/gdb/annotate.c
+++ b/gdb/annotate.c
@@ -38,6 +38,12 @@ static void breakpoint_changed (struct breakpoint *b);
 void (*deprecated_annotate_signalled_hook) (void);
 void (*deprecated_annotate_signal_hook) (void);
 
+/* Booleans indicating whether we've emitted certain notifications.
+   Used to suppress useless repeated notifications until the next time
+   we're ready to accept more commands.  */
+static int frames_invalid_emitted;
+static int breakpoints_invalid_emitted;
+
 static void
 print_value_flags (struct type *t)
 {
@@ -50,10 +56,11 @@ print_value_flags (struct type *t)
 void
 annotate_breakpoints_changed (void)
 {
-  if (annotation_level == 2)
+  if (annotation_level == 2 && !breakpoints_invalid_emitted)
     {
       target_terminal_ours ();
       printf_unfiltered (("\n\032\032breakpoints-invalid\n"));
+      breakpoints_invalid_emitted = 1;
     }
 }
 
@@ -185,10 +192,11 @@ annotate_breakpoints_table_end (void)
 void
 annotate_frames_invalid (void)
 {
-  if (annotation_level == 2)
+  if (annotation_level == 2 && !frames_invalid_emitted)
     {
       target_terminal_ours ();
       printf_unfiltered (("\n\032\032frames-invalid\n"));
+      frames_invalid_emitted = 1;
     }
 }
 
@@ -538,6 +546,17 @@ annotate_array_section_end (void)
     printf_filtered (("\n\032\032array-section-end\n"));
 }
 
+/* Called when GDB is about to display the prompt.  Used to reset
+   annotation suppression whenever we're ready to accept new
+   frontend/user commands.  */
+
+void
+annotate_display_prompt (void)
+{
+  frames_invalid_emitted = 0;
+  breakpoints_invalid_emitted = 0;
+}
+
 static void
 breakpoint_changed (struct breakpoint *b)
 {
diff --git a/gdb/annotate.h b/gdb/annotate.h
index 443d892..15064b1 100644
--- a/gdb/annotate.h
+++ b/gdb/annotate.h
@@ -45,6 +45,8 @@ extern void annotate_frames_invalid (void);
 extern void annotate_new_thread (void);
 extern void annotate_thread_changed (void);
 
+extern void annotate_display_prompt (void);
+
 struct type;
 
 extern void annotate_field_begin (struct type *);
diff --git a/gdb/event-top.c b/gdb/event-top.c
index 5c533e4..2f0bbf7 100644
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -36,6 +36,7 @@
 #include "observer.h"
 #include "continuations.h"
 #include "gdbcmd.h"		/* for dont_repeat() */
+#include "annotate.h"
 
 /* readline include files.  */
 #include "readline/readline.h"
@@ -232,6 +233,8 @@ display_gdb_prompt (char *new_prompt)
   char *actual_gdb_prompt = NULL;
   struct cleanup *old_chain;
 
+  annotate_display_prompt ();
+
   /* Reset the nesting depth used when trace-commands is set.  */
   reset_command_nest_depth ();