Add "signal SIGTRAP" test

Some local changes I was working on related to SIGTRAP handling
resulted in "signal SIGTRAP" no longer passing the SIGTRAP to the
inferior.

Surprisingly, only annota1.exp catches this.  This commit adds a test
that doesn't rely on annotations, so that at the point annotations are
finaly dropped, we still have this use case covered ...

This is a multi-threaded test to also exercise the case of first
needing to do a step-over before delivering the signal.

Tested on x86_64 Fedora 20, native, remote/extended-remote gdbserver.

gdb/testsuite/
2015-02-10  Pedro Alves  <palves@redhat.com>

	* gdb.threads/signal-sigtrap.c: New file.
	* gdb.threads/signal-sigtrap.exp: New file.

gdb/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2015-02-10  Pedro Alves  <palves@redhat.com>
+
+	* gdb.threads/signal-sigtrap.c: New file.
+	* gdb.threads/signal-sigtrap.exp: New file.
+
 2015-02-10  Antoine Tremblay <antoine.tremblay@ericsson.com>
 
 	* gdb.trace/no-attach-trace.c: New file.

gdb/testsuite/gdb.threads/signal-sigtrap.c

@@ -0,0 +1,46 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2014-2015 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>
+#include <stdlib.h>
+#include <pthread.h>
+#include <signal.h>
+
+void
+sigtrap_handler (int sig)
+{
+}
+
+void *
+thread_function (void *arg)
+{
+  return NULL;
+}
+
+int
+main (void)
+{
+  pthread_t child_thread;
+
+  signal (SIGTRAP, sigtrap_handler);
+
+  pthread_create (&child_thread, NULL, thread_function, NULL);
+
+  pthread_join (child_thread, NULL);
+
+  return 0;
+}

gdb/testsuite/gdb.threads/signal-sigtrap.exp

@@ -0,0 +1,67 @@
+# Copyright (C) 2014-2015 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/>.  */
+
+# Check that GDB doesn't forget to pass SIGTRAP to the program when
+# the user explicitly passes it with the signal command.
+
+if [target_info exists gdb,nosignals] {
+    verbose "Skipping ${testfile}.exp because of nosignals."
+    return -1
+}
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug pthreads}]} {
+    return -1
+}
+
+# Run test proper.  SIGTRAP_THREAD is the thread that should get the
+# SIGTRAP.
+
+proc test { sigtrap_thread } {
+    global srcfile binfile
+
+    with_test_prefix "sigtrap thread $sigtrap_thread" {
+	clean_restart ${binfile}
+
+	if ![runto "thread_function"] then {
+	    fail "Can't run to thread_function"
+	    return 0
+	}
+
+	set pattern "\\\* 2\[ \t\]+Thread.*"
+	gdb_test "info threads" $pattern "thread 2 hit breakpoint"
+
+	gdb_test "break sigtrap_handler" "Breakpoint .* at .*$srcfile.*"
+
+	# Thread 2 is stopped at a breakpoint, which must be stepped
+	# over first.  Thus if this is thread 1, then GDB will first
+	# switch back to thread 2 to step it over the breakpoint.
+	gdb_test "thread $sigtrap_thread" \
+	    "Switching to thread $sigtrap_thread.*" \
+	    "switch to sigtrap thread"
+
+	gdb_test "signal SIGTRAP" \
+	    "Continuing with signal SIGTRAP.*Breakpoint .* sigtrap_handler .*" \
+	    "signal SIGTRAP reaches handler"
+
+	set pattern "\\\* $sigtrap_thread\[ \t\]+Thread.*"
+	gdb_test "info threads" $pattern "right thread got the signal"
+    }
+}
+
+foreach sigtrap_thread {1 2} {
+    test $sigtrap_thread
+}