Catch exception in lib/gdbserver-support.exp:gdb_exit

I see the error when I run gdb-sigterm.exp with native-gdbserver
on x86_64-linux.

infrun: prepare_to_wait^M
Cannot execute this command while the target is running.^M
Use the "interrupt" command to stop the target^M
and then try again.^M
gdb.base/gdb-sigterm.exp: expect eof #0: got eof
gdb.base/gdb-sigterm.exp: expect eof #0: stepped 12 times
ERROR OCCURED: : spawn id exp8 not open
    while executing
"expect {
-i exp8 -timeout 10
            -re "$gdb_prompt $" {
                exp_continue
            }
            -i "$server_spawn_id" eof {
                wait -i $expect_out(spawn_id)
                unse..."
    ("uplevel" body line 1)
    invoked from within

In gdb-sigterm.exp, SIGTERM is sent to GDB and it exits.  However,
Dejagnu or tcl doesn't know this.

This patch is to catch the exception, but error messages are still
shown in the console and gdb.log.  In order to avoid this, we also
replace gdb_expect with expect.

gdb/testsuite:

2015-04-13  Yao Qi  <yao.qi@linaro.org>

	* lib/gdbserver-support.exp (gdb_exit): Catch exception
	and use expect instead of gdb_expect.

2 files changed, 22 insertions, 9 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index fbb8bc8..55aeecc 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-04-13  Yao Qi  <yao.qi@linaro.org>
+
+	* lib/gdbserver-support.exp (gdb_exit): Catch exception
+	and use expect instead of gdb_expect.
+
 2015-04-13  Sergio Durigan Junior  <sergiodj@redhat.com>
 
 	* gdb.base/coredump-filter.exp: Rename variable "addr" to
diff --git a/gdb/testsuite/lib/gdbserver-support.exp b/gdb/testsuite/lib/gdbserver-support.exp
index 53843b8..b3140c2 100644
--- a/gdb/testsuite/lib/gdbserver-support.exp
+++ b/gdb/testsuite/lib/gdbserver-support.exp
@@ -353,15 +353,23 @@ proc gdb_exit {} {
     global gdb_prompt
 
     if {[info exists gdb_spawn_id] && [info exists server_spawn_id]} {
-	send_gdb "monitor exit\n";
-	gdb_expect {
-	    -re "$gdb_prompt $" {
-		exp_continue
-	    }
-	    -i "$server_spawn_id" eof {
-		wait -i $expect_out(spawn_id)
-		unset server_spawn_id
-		unset inferior_spawn_id
+	# GDB may be terminated in an expected way or an unexpected way,
+	# but DejaGNU doesn't know that, so gdb_spawn_id isn't unset.
+	# Catch the exceptions.
+	catch {
+	    send_gdb "monitor exit\n";
+	    # We use expect rather than gdb_expect because
+	    # we want to suppress printing exception messages, otherwise,
+	    # remote_expect, invoked by gdb_expect, prints the exceptions.
+	    expect {
+		-i "$gdb_spawn_id" -re "$gdb_prompt $" {
+		    exp_continue
+		}
+		-i "$server_spawn_id" eof {
+		    wait -i $expect_out(spawn_id)
+		    unset server_spawn_id
+		    unset inferior_spawn_id
+		}
 	    }
 	}
     }