Add remove-inferiors test

I noticed that the remove-inferiors command was not tested, and as I am
doing some changes related to the user selection, I want to make sure I
don't break it.  For example, I want to make sure it's not possible to
remove the current inferior.

gdb/testsuite/ChangeLog:

	* gdb.multi/remove-inferiors.exp: New file.
	* gdb.multi/remove-inferiors.c: New file.

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2016-08-17  Simon Marchi  <simon.marchi@ericsson.com>
+
+	* gdb.multi/remove-inferiors.exp: New file.
+	* gdb.multi/remove-inferiors.c: New file.
+
 2016-08-12  Yao Qi  <yao.qi@linaro.org>
 
 	* gdb.base/signals-state-child.c (main): Remove "i" from fprintf's

gdb/testsuite/gdb.multi/remove-inferiors.c

@@ -0,0 +1,23 @@
+/* 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/>.  */
+
+int
+main (void)
+{
+  return 0;
+}
+

gdb/testsuite/gdb.multi/remove-inferiors.exp

@@ -0,0 +1,70 @@
+# 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/>.
+
+standard_testfile
+
+if { [build_executable ${testfile}.exp ${binfile} "${srcfile}" {debug}] != 0 } {
+    return -1
+}
+
+proc switch_to_inferior { num message } {
+    gdb_test "inferior ${num}" \
+	     "\\\[Switching to inferior ${num} \\\[<null>\\\] \\\(<noexec>\\\)\\\]" \
+	     "${message}"
+}
+
+proc add_inferior { expected_num message } {
+    gdb_test "add-inferior" "Added inferior ${expected_num}" "${message}"
+}
+
+proc test_remove_inferiors { } {
+    global binfile
+
+    clean_restart ${binfile}
+
+    # Add another inferior and switch to it.
+    add_inferior 2 "add second inferior"
+    switch_to_inferior 2 "switch to second inferior"
+
+    # Test that it is not possible to remove the current inferior.
+    gdb_test "remove-inferiors 2" \
+	     "warning: Can not remove current symbol inferior 2." \
+	     "can't remove current inferior"
+
+    # Test that it is possible to remove a non-active non-current inferior.
+    gdb_test_no_output "remove-inferiors 1" "remove non-current inferior"
+
+    # Load binfile and start the inferior.
+    set binfile_re [string_to_regexp ${binfile}]
+    gdb_test "file ${binfile}" \
+	     "Reading symbols from ${binfile_re}...done." \
+	     "load binary"
+
+    if {![runto_main]} {
+	fail "Couldn't run to main."
+	return
+    }
+
+    # Add another inferior and switch to it.
+    add_inferior 3 "add third inferior"
+    switch_to_inferior 3 "switch to third inferior"
+
+    # Test that it is not possible to remove an active non-current inferior.
+    gdb_test "remove-inferiors 2" \
+	     "warning: Can not remove active inferior 2." \
+	     "can't remove active inferior"
+}
+
+test_remove_inferiors