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.

11 files changed, 238 insertions, 30 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index b2b518a..17c799e 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,28 @@
 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.
+
+2016-08-09  Pedro Alves  <palves@redhat.com>
+
 	PR mi/20431
 	* mi/mi-main.c (mi_execute_command): Enable input and set prompt
 	state to PROMPT_NEEDED.
diff --git a/gdb/event-top.c b/gdb/event-top.c
index 072ad2a..91b06e6 100644
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -550,6 +550,22 @@ stdin_event_handler (int error, gdb_client_data client_data)
     }
 }
 
+/* See top.h.  */
+
+void
+ui_register_input_event_handler (struct ui *ui)
+{
+  add_file_handler (ui->input_fd, stdin_event_handler, ui);
+}
+
+/* See top.h.  */
+
+void
+ui_unregister_input_event_handler (struct ui *ui)
+{
+  delete_file_handler (ui->input_fd);
+}
+
 /* Re-enable stdin after the end of an execution command in
    synchronous mode, or after an error from the target, and we aborted
    the exec operation.  */
@@ -562,6 +578,7 @@ async_enable_stdin (void)
   if (ui->prompt_state == PROMPT_BLOCKED)
     {
       target_terminal_ours ();
+      ui_register_input_event_handler (ui);
       ui->prompt_state = PROMPT_NEEDED;
     }
 }
@@ -575,6 +592,7 @@ async_disable_stdin (void)
   struct ui *ui = current_ui;
 
   ui->prompt_state = PROMPT_BLOCKED;
+  delete_file_handler (ui->input_fd);
 }
 
 
@@ -1284,7 +1302,7 @@ gdb_setup_readline (int editing)
      Another source is going to be the target program (inferior), but
      that must be registered only when it actually exists (I.e. after
      we say 'run' or after we connect to a remote target.  */
-  add_file_handler (ui->input_fd, stdin_event_handler, ui);
+  ui_register_input_event_handler (ui);
 }
 
 /* Disable command input through the standard CLI channels.  Used in
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 257ac8a..90841f4 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -3848,6 +3848,7 @@ check_curr_ui_sync_execution_done (void)
     {
       target_terminal_ours ();
       observer_notify_sync_execution_done ();
+      ui_register_input_event_handler (ui);
     }
 }
 
diff --git a/gdb/target.c b/gdb/target.c
index 6228361..5603d01 100644
--- a/gdb/target.c
+++ b/gdb/target.c
@@ -486,15 +486,9 @@ target_terminal_inferior (void)
   if (ui->prompt_state != PROMPT_BLOCKED)
     return;
 
-  /* Always delete the current UI's input file handler, regardless of
-     terminal_state, because terminal_state is only valid for the main
-     UI.  */
-  delete_file_handler (ui->input_fd);
-
   /* Since we always run the inferior in the main console (unless "set
      inferior-tty" is in effect), when some UI other than the main one
      calls target_terminal_inferior/target_terminal_inferior, then we
-     only register/unregister the UI's input from the event loop, but
      leave the main UI's terminal settings as is.  */
   if (ui != main_ui)
     return;
@@ -520,11 +514,6 @@ target_terminal_ours (void)
 {
   struct ui *ui = current_ui;
 
-  /* Always add the current UI's input file handler, regardless of
-     terminal_state, because terminal_state is only valid for the main
-     UI.  */
-  add_file_handler (ui->input_fd, stdin_event_handler, ui);
-
   /* See target_terminal_inferior.  */
   if (ui != main_ui)
     return;
diff --git a/gdb/target.h b/gdb/target.h
index 15fd806..7091360 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);
 
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 605802f..1b9ffed 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,4 +1,11 @@
 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.
+
+2016-08-09  Pedro Alves  <palves@redhat.com>
 
 	PR mi/20431
 	* gdb.mi/mi-cmd-error.exp: New file.
diff --git a/gdb/testsuite/gdb.mi/new-ui-mi-sync.c b/gdb/testsuite/gdb.mi/new-ui-mi-sync.c
new file mode 100644
index 0000000..9cc8c90
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/new-ui-mi-sync.c
@@ -0,0 +1,25 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2016 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include <unistd.h>
+
+int
+main (void)
+{
+  sleep (180);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.mi/new-ui-mi-sync.exp b/gdb/testsuite/gdb.mi/new-ui-mi-sync.exp
new file mode 100644
index 0000000..55c66a5
--- /dev/null
+++ b/gdb/testsuite/gdb.mi/new-ui-mi-sync.exp
@@ -0,0 +1,114 @@
+# Copyright 2016 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test that on a separate MI UI (new-ui mi <tty>), the printing of an
+# asynchronous event (e.g. =library-loaded) during the synchronous
+# execution of a command (e.g.  -exec-run or -exec-continue) does not
+# prematurely re-enable MI input.  After executing synchronous
+# commands, MI should not process further commands until the inferior
+# stops again.  See PR gdb/20418.
+
+load_lib mi-support.exp
+
+standard_testfile
+
+if {[build_executable $testfile.exp $testfile ${srcfile} "debug"] == -1} {
+    untested "failed to compile $testfile"
+    return -1
+}
+
+# The test driver.  SYNC_COMMAND specifies which command is used to
+# synchronously start the program running.
+
+proc do_test {sync_command} {
+    global srcdir subdir binfile srcfile
+    global gdb_spawn_id gdb_main_spawn_id mi_spawn_id inferior_spawn_id
+    global gdb_prompt mi_gdb_prompt
+
+    mi_gdb_exit
+
+    if {[mi_gdb_start "separate-mi-tty"] != 0} {
+	fail "Could not start gdb"
+	return
+    }
+
+    mi_delete_breakpoints
+    mi_gdb_reinitialize_dir $srcdir/$subdir
+    mi_gdb_load $binfile
+
+    # Start a synchronous run/continue on the MI UI.
+    set test "send synchronous execution command"
+    if {$sync_command == "run"} {
+	if {[mi_run_cmd] >= 0} {
+	    pass $test
+	} else {
+	    return
+	}
+    } else {
+	if {[mi_runto main] < 0} {
+	    return
+	}
+	if {[mi_send_resuming_command_raw "123-exec-continue" $test] >= 0} {
+	    pass $test
+	} else {
+	    return
+	}
+    }
+
+    # Send -thread-info immediately after.  If everything works
+    # correctly, this is only serviced by GDB when the execution
+    # stops.
+    send_gdb "456-thread-info\n"
+    pass "send -thread-info"
+
+    # Make sure we trigger an asynchronous event (=thread-group-added)
+    # in the separate MI UI.  Note the "run" variant usually triggers
+    # =thread-group-started/=thread-created/=library-loaded as well.
+    with_spawn_id $gdb_main_spawn_id {
+	gdb_test "add-inferior" "Added inferior 2"
+    }
+
+    # Interrupt the program.
+    with_spawn_id $gdb_main_spawn_id {
+	set message "interrupt on the CLI"
+	gdb_test_multiple "interrupt" "$message" {
+	    -re "$gdb_prompt " {
+		gdb_test_multiple "" "$message" {
+		    -re "received signal SIGINT" {
+			pass $message
+		    }
+		}
+	    }
+	}
+    }
+
+    # On the MI channel, we should see the interrupt output _before_
+    # the -thread-info output.
+    with_spawn_id $mi_spawn_id {
+	mi_expect_interrupt "got MI interrupt output"
+    }
+
+    # Look for the result of our -thread-info.  If input were
+    # re-enabled too soon, the thread would incorrectly show up with
+    # state="running".
+    with_spawn_id $mi_spawn_id {
+	mi_gdb_test "" "456\\^.*state=\"stopped\".*" \
+	    "got -thread-info output and thread is stopped"
+    }
+}
+
+foreach_with_prefix sync-command {"run" "continue"} {
+    do_test ${sync-command}
+}
diff --git a/gdb/testsuite/lib/mi-support.exp b/gdb/testsuite/lib/mi-support.exp
index 28af70a..18664c4 100644
--- a/gdb/testsuite/lib/mi-support.exp
+++ b/gdb/testsuite/lib/mi-support.exp
@@ -1272,7 +1272,7 @@ proc mi_expect_interrupt { test } {
     if {$async} {
 	set prompt_re ""
     } else {
-	set prompt_re "$mi_gdb_prompt$"
+	set prompt_re "$mi_gdb_prompt"
     }
 
     set r_nonstop "reason=\"signal-received\",signal-name=\"0\",signal-meaning=\"Signal 0\""
@@ -1287,7 +1287,7 @@ proc mi_expect_interrupt { test } {
 	    pass "$test"
 	    return 0
 	}
-	-re ".*\r\n$mi_gdb_prompt$" {
+	-re ".*\r\n$mi_gdb_prompt" {
 	    verbose -log "got $expect_out(buffer)"
 	    fail "$test (unknown output after running)"
 	    return -1
diff --git a/gdb/top.h b/gdb/top.h
index bdc3529..c5f6bc7 100644
--- a/gdb/top.h
+++ b/gdb/top.h
@@ -191,6 +191,12 @@ extern struct cleanup *make_delete_ui_cleanup (struct ui *ui);
 /* Cleanup that restores the current UI.  */
 extern void restore_ui_cleanup (void *data);
 
+/* Register the UI's input file descriptor in the event loop.  */
+extern void ui_register_input_event_handler (struct ui *ui);
+
+/* Unregister the UI's input file descriptor from the event loop.  */
+extern void ui_unregister_input_event_handler (struct ui *ui);
+
 /* From top.c.  */
 extern char *saved_command_line;
 extern int in_user_command;
diff --git a/gdb/utils.c b/gdb/utils.c
index c70e99c..5188828 100644
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -1209,6 +1209,33 @@ compile_rx_or_error (regex_t *pattern, const char *rx, const char *message)
   return make_regfree_cleanup (pattern);
 }
 
+/* A cleanup that simply calls ui_unregister_input_event_handler.  */
+
+static void
+ui_unregister_input_event_handler_cleanup (void *ui)
+{
+  ui_unregister_input_event_handler ((struct ui *) ui);
+}
+
+/* Set up to handle input.  */
+
+static struct cleanup *
+prepare_to_handle_input (void)
+{
+  struct cleanup *old_chain;
+
+  old_chain = make_cleanup_restore_target_terminal ();
+  target_terminal_ours ();
+
+  ui_register_input_event_handler (current_ui);
+  if (current_ui->prompt_state == PROMPT_BLOCKED)
+    make_cleanup (ui_unregister_input_event_handler_cleanup, current_ui);
+
+  make_cleanup_override_quit_handler (default_quit_handler);
+
+  return old_chain;
+}
+
 
 
 /* This function supports the query, nquery, and yquery functions.
@@ -1265,8 +1292,6 @@ defaulted_query (const char *ctlstr, const char defchar, va_list args)
   if (!confirm || server_command)
     return def_value;
 
-  old_chain = make_cleanup_restore_target_terminal ();
-
   /* If input isn't coming from the user directly, just say what
      question we're asking, and then answer the default automatically.  This
      way, important error messages don't get lost when talking to GDB
@@ -1274,6 +1299,8 @@ defaulted_query (const char *ctlstr, const char defchar, va_list args)
   if (current_ui->instream != current_ui->stdin_stream
       || !input_interactive_p (current_ui))
     {
+      old_chain = make_cleanup_restore_target_terminal ();
+
       target_terminal_ours_for_output ();
       wrap_here ("");
       vfprintf_filtered (gdb_stdout, ctlstr, args);
@@ -1291,6 +1318,7 @@ defaulted_query (const char *ctlstr, const char defchar, va_list args)
     {
       int res;
 
+      old_chain = make_cleanup_restore_target_terminal ();
       res = deprecated_query_hook (ctlstr, args);
       do_cleanups (old_chain);
       return res;
@@ -1298,7 +1326,7 @@ defaulted_query (const char *ctlstr, const char defchar, va_list args)
 
   /* Format the question outside of the loop, to avoid reusing args.  */
   question = xstrvprintf (ctlstr, args);
-  make_cleanup (xfree, question);
+  old_chain = make_cleanup (xfree, question);
   prompt = xstrprintf (_("%s%s(%s or %s) %s"),
 		      annotation_level > 1 ? "\n\032\032pre-query\n" : "",
 		      question, y_string, n_string,
@@ -1308,9 +1336,7 @@ defaulted_query (const char *ctlstr, const char defchar, va_list args)
   /* Used for calculating time spend waiting for user.  */
   gettimeofday (&prompt_started, NULL);
 
-  /* We'll need to handle input.  */
-  target_terminal_ours ();
-  make_cleanup_override_quit_handler (default_quit_handler);
+  prepare_to_handle_input ();
 
   while (1)
     {
@@ -1882,10 +1908,7 @@ prompt_for_continue (void)
      beyond the end of the screen.  */
   reinitialize_more_filter ();
 
-  /* We'll need to handle input.  */
-  make_cleanup_restore_target_terminal ();
-  target_terminal_ours ();
-  make_cleanup_override_quit_handler (default_quit_handler);
+  prepare_to_handle_input ();
 
   /* Call gdb_readline_wrapper, not readline, in order to keep an
      event loop running.  */