PR gdb/17300: Input after "c -a" crashes readline/GDB

If all threads in the target were already running when the user does
"c -a", nothing puts the inferior's terminal settings in effect and
removes stdin from the event loop, which we must when running a
foreground command.  The result is that user input afterwards crashes
readline/gdb:

 (gdb) start
 Temporary breakpoint 1 at 0x4005d4: file continue-all-already-running.c, line 23.
 Starting program: continue-all-already-running

 Temporary breakpoint 1, main () at continue-all-already-running.c:23
 23        sleep (10);
 (gdb) c -a&
 Continuing.
 (gdb) c -a
 Continuing.
 p 1
 readline: readline_callback_read_char() called with no handler!
 Aborted (core dumped)
 $

Backtrace:

 Program received signal SIGABRT, Aborted.
 0x0000003b36a35877 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
 56        return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);
 (top-gdb) p 1
 $1 = 1
 (top-gdb) bt
 #0  0x0000003b36a35877 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
 #1  0x0000003b36a36f68 in __GI_abort () at abort.c:89
 #2  0x0000000000784aa9 in rl_callback_read_char () at readline/callback.c:116
 #3  0x0000000000619181 in rl_callback_read_char_wrapper (client_data=0x0) at gdb/event-top.c:167
 #4  0x0000000000619557 in stdin_event_handler (error=0, client_data=0x0) at gdb/event-top.c:373
 #5  0x000000000061814a in handle_file_event (data=...) at gdb/event-loop.c:763
 #6  0x0000000000617631 in process_event () at gdb/event-loop.c:340
 #7  0x00000000006176f8 in gdb_do_one_event () at gdb/event-loop.c:404
 #8  0x0000000000617748 in start_event_loop () at gdb/event-loop.c:429
 #9  0x00000000006191b3 in cli_command_loop (data=0x0) at gdb/event-top.c:182
 #10 0x000000000060f538 in current_interp_command_loop () at gdb/interps.c:318
 #11 0x0000000000610701 in captured_command_loop (data=0x0) at gdb/main.c:323
 #12 0x000000000060c3f5 in catch_errors (func=0x6106e6 <captured_command_loop>, func_args=0x0, errstring=0x9002c1 "", mask=RETURN_MASK_ALL)
     at gdb/exceptions.c:237
 #13 0x0000000000611bff in captured_main (data=0x7fffffffd780) at gdb/main.c:1151
 #14 0x000000000060c3f5 in catch_errors (func=0x610afe <captured_main>, func_args=0x7fffffffd780, errstring=0x9002c1 "", mask=RETURN_MASK_ALL)
     at gdb/exceptions.c:237
 #15 0x0000000000611c28 in gdb_main (args=0x7fffffffd780) at gdb/main.c:1159
 #16 0x000000000045ef97 in main (argc=5, argv=0x7fffffffd888) at gdb/gdb.c:32
 (top-gdb)

Tested on x86_64 Fedora 20, native and gdbserver.

gdb/
2014-10-17  Pedro Alves  <palves@redhat.com>

	PR gdb/17300
	* infcmd.c (continue_1): If continuing all threads in the
	foreground, make sure the inferior's terminal settings are put in
	effect.

gdb/testsuite/
2014-10-17  Pedro Alves  <palves@redhat.com>

	PR gdb/17300
	* gdb.base/continue-all-already-running.c: New file.
	* gdb.base/continue-all-already-running.exp: New file.

gdb/ChangeLog

@@ -1,3 +1,10 @@
+2014-10-17  Pedro Alves  <palves@redhat.com>
+
+	PR gdb/17300
+	* infcmd.c (continue_1): If continuing all threads in the
+	foreground, make sure the inferior's terminal settings are put in
+	effect.
+
 2014-10-17  Pedro Alves  <palves@redhat.com>
 
 	PR gdb/17472

gdb/infcmd.c

@@ -735,6 +735,24 @@ continue_1 (int all_threads)
 
       iterate_over_threads (proceed_thread_callback, NULL);
 
+      if (sync_execution)
+	{
+	  /* If all threads in the target were already running,
+	     proceed_thread_callback ends up never calling proceed,
+	     and so nothing calls this to put the inferior's terminal
+	     settings in effect and remove stdin from the event loop,
+	     which we must when running a foreground command.  E.g.:
+
+	      (gdb) c -a&
+	      Continuing.
+	      <all threads are running now>
+	      (gdb) c -a
+	      Continuing.
+	      <no thread was resumed, but the inferior now owns the terminal>
+	  */
+	  target_terminal_inferior ();
+	}
+
       /* Restore selected ptid.  */
       do_cleanups (old_chain);
     }

gdb/testsuite/ChangeLog

@@ -1,3 +1,9 @@
+2014-10-17  Pedro Alves  <palves@redhat.com>
+
+	PR gdb/17300
+	* gdb.base/continue-all-already-running.c: New file.
+	* gdb.base/continue-all-already-running.exp: New file.
+
 2014-10-17  Pedro Alves  <palves@redhat.com>
 
 	PR gdb/17472

gdb/testsuite/gdb.base/continue-all-already-running.c

@@ -0,0 +1,25 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2014 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 (10);
+  return 0; /* set break here */
+}

gdb/testsuite/gdb.base/continue-all-already-running.exp

@@ -0,0 +1,79 @@
+# Copyright (C) 2014 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 "c -a" doesn't leave GDB processing input, even if all
+# threads were already running.  PR gdb/17300.
+
+standard_testfile
+
+if { [prepare_for_testing ${testfile}.exp ${testfile} $srcfile] } {
+    return -1
+}
+
+gdb_test_no_output "set non-stop on"
+
+if ![runto_main] {
+    return
+}
+
+set linenum [gdb_get_line_number "set break here"]
+gdb_breakpoint "$linenum"
+
+gdb_test "c -a&" "Continuing\\."
+
+set test "no stop"
+gdb_test_multiple "" $test {
+    -timeout 1
+    timeout {
+	pass $test
+    }
+}
+
+# Paranoia.  Check that input works after bg command.
+gdb_test "print 1" " = 1"
+
+# Continue in the foreground, and wait one second to make sure the
+# inferior really starts running.  If we get a prompt to soon (e.g.,
+# the program stops), this issues a fail.
+set saw_continuing 0
+set test "c -a"
+gdb_test_multiple "c -a" $test {
+    -timeout 1
+    -re "Continuing\\." {
+	set saw_continuing 1
+	exp_continue
+    }
+    timeout {
+	gdb_assert $saw_continuing $test
+    }
+}
+
+# Type something while the inferior is running in the foreground.
+send_gdb "print 2\n"
+
+# Poor buggy GDB would crash before the breakpoint was hit.
+set test "breakpoint hit"
+gdb_test_multiple "" $test {
+    -re "set break here ..\r\n$gdb_prompt " {
+	pass $test
+    }
+}
+
+set test "print command result"
+gdb_test_multiple "" $test {
+    -re " = 2\r\n$gdb_prompt $" {
+	pass $test
+    }
+}