Fix PR gdb/20418 - Problems with synchronous commands and new-ui

When executing commands on a secondary UI running the MI interpreter,
some commands that should be synchronous are not.  MI incorrectly
continues processing input right after the synchronous command is
sent, before the target stops.

The problem happens when we emit MI async events (=library-loaded,
etc.), and we go about restoring the previous terminal state, we end
up calling target_terminal_ours, which incorrectly always installs the
current UI's input_fd in the event loop...  That is, code like this:

   old_chain = make_cleanup_restore_target_terminal ();
   target_terminal_ours_for_output ();

   fprintf_unfiltered (mi->event_channel, "library-loaded");

...

   do_cleanups (old_chain);

The fix is to move the add_file_handler/delete_file_handler calls out
of target_terminal_$foo, making these completely no-ops unless called
with the main UI as current UI.

gdb/ChangeLog:
2016-08-09  Pedro Alves  <palves@redhat.com>

	PR gdb/20418
	* event-top.c (ui_register_input_event_handler)
	(ui_unregister_input_event_handler): New functions.
	(async_enable_stdin): Register input in the event loop.
	(async_disable_stdin): Unregister input from the event loop.
	(gdb_setup_readline): Register input in the event loop.
	* infrun.c (check_curr_ui_sync_execution_done): Register input in
	the event loop.
	* target.c (target_terminal_inferior): Don't unregister input from
	the event loop.
	(target_terminal_ours): Don't register input in the event loop.
	* target.h (target_terminal_inferior)
	(target_terminal_ours_for_output, target_terminal_ours): Update
	comments.
	* top.h (ui_register_input_event_handler)
	(ui_unregister_input_event_handler): New declarations.
	* utils.c (ui_unregister_input_event_handler_cleanup)
	(prepare_to_handle_input): New functions.
	(defaulted_query, prompt_for_continue): Use
	prepare_to_handle_input.

gdb/testsuite/ChangeLog:
2016-08-09  Pedro Alves  <palves@redhat.com>
	    Simon Marchi  <simon.marchi@ericsson.com>

	PR gdb/20418
	* gdb.mi/new-ui-mi-sync.c, gdb.mi/new-ui-mi-sync.exp: New files.
	* lib/mi-support.exp (mi_expect_interrupt): Remove anchors.

1 files changed, 8 insertions, 6 deletions

diff --git a/gdb/target.h b/gdb/target.h
index 15fd806ad9..7091360260 100644
--- a/gdb/target.h
+++ b/gdb/target.h
@@ -1523,21 +1523,23 @@ extern int target_terminal_is_ours (void);
 
 extern void target_terminal_init (void);
 
-/* Put the inferior's terminal settings into effect.
-   This is preparation for starting or resuming the inferior.  */
+/* Put the inferior's terminal settings into effect.  This is
+   preparation for starting or resuming the inferior.  This is a no-op
+   unless called with the main UI as current UI.  */
 
 extern void target_terminal_inferior (void);
 
 /* Put some of our terminal settings into effect, enough to get proper
    results from our output, but do not change into or out of RAW mode
    so that no input is discarded.  This is a no-op if terminal_ours
-   was most recently called.  */
+   was most recently called.  This is a no-op unless called with the main
+   UI as current UI.  */
 
 extern void target_terminal_ours_for_output (void);
 
-/* Put our terminal settings into effect.
-   First record the inferior's terminal settings
-   so they can be restored properly later.  */
+/* Put our terminal settings into effect.  First record the inferior's
+   terminal settings so they can be restored properly later.  This is
+   a no-op unless called with the main UI as current UI.  */
 
 extern void target_terminal_ours (void);