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.

4 files changed, 148 insertions, 2 deletions

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