Fix invoking "[kill|detach] inferiors" on inferiors that are not running

diff --git a/gdb/inferior.c b/gdb/inferior.c
index 5e98df5..2e44f17 100644
--- a/gdb/inferior.c
+++ b/gdb/inferior.c
@@ -625,6 +625,11 @@  detach_inferior_command (char *args, int from_tty)
 	}
 
       pid = gdb_inferior_id_to_pid (num);
+      if (pid == 0)
+	{
+	  warning (_("Inferior ID %d is not running."), num);
+	  continue;
+	}
 
       tp = any_thread_of_process (pid);
       if (!tp)
@@ -661,6 +666,11 @@  kill_inferior_command (char *args, int from_tty)
 	}
 
       pid = gdb_inferior_id_to_pid (num);
+      if (pid == 0)
+	{
+	  warning (_("Inferior ID %d is not running."), num);
+	  continue;
+	}
 
       tp = any_thread_of_process (pid);
       if (!tp)
diff --git a/gdb/testsuite/gdb.base/kill-detach-inferiors-cmd.c b/gdb/testsuite/gdb.base/kill-detach-inferiors-cmd.c
new file mode 100644
index 0000000..2398f00
--- /dev/null
+++ b/gdb/testsuite/gdb.base/kill-detach-inferiors-cmd.c
@@ -0,0 +1,25 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2015 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 (600);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/kill-detach-inferiors-cmd.exp b/gdb/testsuite/gdb.base/kill-detach-inferiors-cmd.exp
new file mode 100644
index 0000000..eb0fd3b
--- /dev/null
+++ b/gdb/testsuite/gdb.base/kill-detach-inferiors-cmd.exp
@@ -0,0 +1,60 @@ 
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2015 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 the basic operation of the "kill inferiors" and "detach inferiors" commands.
+
+if ![can_spawn_for_attach] {
+    return 0
+}
+
+standard_testfile
+set executable $testfile
+
+if [prepare_for_testing $testfile.exp $executable] {
+    return -1
+}
+
+runto_main
+
+# Add another forked inferior process.
+gdb_test "add-inferior" "Added inferior 2" "add inferior 2"
+gdb_test "inferior 2" "Switching to inferior 2.*"
+gdb_test "file $binfile" "Reading symbols from .*done.*" "load binary"
+gdb_test "start" "Temporary breakpoint.*Starting program.*"
+
+# Add an attached inferior process.
+set testpid [spawn_wait_for_attach $binfile]
+gdb_test "add-inferior" "Added inferior 3" "add inferior 3"
+gdb_test "inferior 3" "Switching to inferior 3.*"
+gdb_test "attach $testpid" "Attaching to process.*" "attach to pid"
+
+# Kill the first two inferiors, and detach the third.
+gdb_test_no_output "kill inferiors 1 2"
+gdb_test "inferior 1" "Switching to inferior 1.*"
+gdb_test "kill" "The program is not being run.*"
+gdb_test "detach inferiors 3" "Detaching from program.*process $testpid.*"
+
+# No inferiors should be running anymore.
+gdb_test "kill inferiors 1 2 3" \
+	 "ID 1 is not running.*ID 2 is not running.*ID 3 is not running.*"
+gdb_test "detach inferiors 1 2 3" \
+	 "ID 1 is not running.*ID 2 is not running.*ID 3 is not running.*"
+
+gdb_test "kill inferiors 10" \
+	 "ID 10 not known.*"
+
+remote_exec host "kill $testpid"