Test GDB connection to GDBserver with no symbol files

This test exercises the scenarios where we attempt to connect GDB to GDBserver
in standard remote mode, query the symbol file path, attempt to open said
symbol file on GDB's end and fail, causing the connection to drop abruptly.

Regression-tested on x86-64/Ubuntu.

With an unpatched GDB we should see this:

FAIL: gdb.server/connect-with-no-symbol-file.exp: sysroot=: action=permission: connection to GDBserver succeeded (the program is no longer running)
FAIL: gdb.server/connect-with-no-symbol-file.exp: sysroot=: action=delete: connection to GDBserver succeeded (the program is no longer running)
FAIL: gdb.server/connect-with-no-symbol-file.exp: sysroot=target:: action=permission: connection to GDBserver succeeded (the program is no longer running)
FAIL: gdb.server/connect-with-no-symbol-file.exp: sysroot=target:: action=delete: connection to GDBserver succeeded (the program is no longer running)

A patched GDB should have full passes.

gdb/testsuite/ChangeLog:

2016-04-13  Luis Machado  <lgustavo@codesourcery.com>

	* gdb.server/connect-with-no-symbol-file.c: New file.
	* gdb.server/connect-with-no-symbol-file.exp: New file.

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2016-04-13  Luis Machado  <lgustavo@codesourcery.com>
+
+	* gdb.server/connect-with-no-symbol-file.c: New file.
+	* gdb.server/connect-with-no-symbol-file.exp: New file.
+
 2016-04-13  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* lib/gdb.exp (gdb_remote_download): Fix and extend comment.

gdb/testsuite/gdb.server/connect-with-no-symbol-file.c

@@ -0,0 +1,22 @@
+/* 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 (int argc, char **argv)
+{
+  return 0;
+}

gdb/testsuite/gdb.server/connect-with-no-symbol-file.exp

@@ -0,0 +1,97 @@
+# 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/>.
+
+# Test GDB's ability to properly connect to GDBserver with no pre-opened
+# symbol file.  If GDB is buggy, it will drop the connection when
+# it attempts to open the symbol file indicated by GDBserver and fails.
+#
+# This test is only meaningful for standard remote connections.
+
+load_lib gdbserver-support.exp
+
+standard_testfile
+
+if { [skip_gdbserver_tests] } {
+    return 0
+}
+
+if { [prepare_for_testing $testfile.exp $testfile $srcfile debug] } {
+    return -1
+}
+
+# Test connecting GDB to GDBserver without loading a symbol file.
+#
+# SYSROOT is the desired sysroot string
+#
+# ACTION is the action to perform to the symbol file on the target.
+# It can be either "permission" to deny access to the file or "delete"
+# to remove the file.
+#
+proc connect_no_symbol_file { sysroot action } {
+    global binfile
+
+    with_test_prefix "setup" {
+	# Copy the symbol file to the target.
+	gdb_remote_download target $binfile.bak $binfile 
+
+	# Make sure we're disconnected, in case we're testing with an
+	# extended-remote board, therefore already connected.
+	gdb_test "disconnect" ".*" "disconnect"
+
+	# Discard any symbol files that we have opened.
+	gdb_test "file" ".*" "discard symbol table" \
+	    {Discard symbol table from `.*'\? \(y or n\) } "y"
+
+	# Set sysroot to something non-target and possibly also invalid so that
+	# GDB is unable to open the symbol file.
+	gdb_test_no_output "set sysroot $sysroot" "adjust sysroot"
+
+	set target_exec [gdbserver_download_current_prog]
+
+	# Start GDBserver.
+	set res [gdbserver_start "" $target_exec]
+
+	set gdbserver_protocol [lindex $res 0]
+	set gdbserver_gdbport [lindex $res 1]
+
+	# Perform test actions to the symbol file on the target.
+	if { $action == "delete" } then {
+	  remote_file target delete $binfile
+	} elseif { $action == "permission" } {
+	  remote_spawn target "chmod 000 $binfile"
+	}
+       
+	# Connect to GDBserver.
+	gdb_target_cmd $gdbserver_protocol $gdbserver_gdbport
+    }
+
+    # Check if GDB succeeded connecting to GDBserver by attempting to detach
+    # from the process.
+    gdb_test "detach" \
+	".*Detaching from program: , process.*Ending remote debugging.*" \
+	"connection to GDBserver succeeded"
+}
+
+# Make sure we have the original symbol file in a safe place to copy from.
+gdb_remote_download host $binfile $binfile.bak
+
+# Run the test with different permutations.
+foreach_with_prefix sysroot {"" "target:"} {
+    foreach_with_prefix action {"permission" "delete"} {
+	connect_no_symbol_file $sysroot $action
+    }
+}