Fix PR cli/15603

This fixes PR cli/15603.

The bug here is that when a software watchpoint is being used, gdb
will stop responding to C-c.  This is a regression caused by the
"catch signal" patch.

The problem is that software watchpoints always end up on the bpstat
list.  However, this makes bpstat_explains_signal return
BPSTAT_SIGNAL_HIDE, causing infrun to think that the signal is not a
"random signal".

The fix is to change bpstat_explains_signal to handle this better.  I
chose to do it in a "clean API" way, by passing the signal value to
bpstat_explains_signal and then adding an explains_signal method for
watchpoints, which handles the specifics.

Built and regtested on x86-64 Fedora 18.
New test case included.

	* break-catch-sig.c (signal_catchpoint_explains_signal): Add 'sig'
	argument.
	* breakpoint.c (bpstat_explains_signal): Add 'sig' argument.
	Special case signals other than GDB_SIGNAL_TRAP.
	(explains_signal_watchpoint): New function.
	(base_breakpoint_explains_signal): Add 'sig' argument.
	(initialize_breakpoint_ops): Set 'explains_signal' method for
	watchpoints.
	* breakpoint.h (struct breakpoint_ops) <explains_signal>: Add
	signal argument.
	(bpstat_explains_signal): Likewise.
	* infrun.c (handle_syscall_event, handle_inferior_event): Update.

	* gdb.base/random-signal.c: New file.
	* gdb.base/random-signal.exp: New file.

2 files changed, 71 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/random-signal.c b/gdb/testsuite/gdb.base/random-signal.c
new file mode 100644
index 0000000..3d23bf7
--- /dev/null
+++ b/gdb/testsuite/gdb.base/random-signal.c
@@ -0,0 +1,29 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2013 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 v;
+
+int main()
+{
+  /* Don't let the test case run forever.  */
+  alarm (60);
+
+  for (;;)
+    ;
+}
diff --git a/gdb/testsuite/gdb.base/random-signal.exp b/gdb/testsuite/gdb.base/random-signal.exp
new file mode 100644
index 0000000..bd23513
--- /dev/null
+++ b/gdb/testsuite/gdb.base/random-signal.exp
@@ -0,0 +1,42 @@
+# Copyright 2013 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/>.
+
+if [target_info exists gdb,nosignals] {
+    verbose "Skipping catch-signal.exp because of nosignals."
+    continue
+}
+
+standard_testfile
+
+if {[prepare_for_testing $testfile.exp $testfile $srcfile debug]} {
+    return -1
+}
+
+if {![runto_main]} {
+    return -1
+}
+
+gdb_test_no_output "set can-use-hw-watchpoints 0"
+gdb_test "watch v" "Watchpoint .*"
+gdb_test_multiple "continue" "continue" {
+    -re "Continuing" {
+	pass "continue"
+    }
+}
+
+# For this to work we must be sure to consume the "Continuing."
+# message first, or GDB's signal handler may not be in place.
+after 500 {send_gdb "\003"}
+gdb_test "" "Program received signal SIGINT.*" "stop with control-c"