This patch adds a new convenience variable called "$_exitsignal", which

will hold the signal number when the inferior terminates due to the
uncaught signal.

I've made modifications on infrun.c:handle_inferior_event such that
$_exitcode gets cleared when the inferior signalled, and vice-versa.
This assumption was made because the variables are mutually
exclusive, i.e., when the inferior terminates because of an uncaught
signal it is not possible for it to return.  I have also made modifications
such that when a corefile is loaded, $_exitsignal gets set to the uncaught
signal that "killed" the inferior, and $_exitcode is cleared.

The patch also adds a NEWS entry, documentation bits, and a testcase.  The
documentation entry explains how to use $_exitsignal and $_exitcode in a
GDB script, by making use of the new $_isvoid convenience function.

gdb/
2013-10-06  Sergio Durigan Junior  <sergiodj@redhat.com>

	* NEWS: Mention new convenience variable $_exitsignal.
	* corelow.c (core_open): Reset exit convenience variables.  Set
	$_exitsignal to the uncaught signal which generated the corefile.
	* infrun.c (handle_inferior_event): Reset exit convenience
	variables.  Set $_exitsignal for TARGET_WAITKIND_SIGNALLED.
	(clear_exit_convenience_vars): New function.
	* inferior.h (clear_exit_convenience_vars): New prototype.

gdb/testsuite/
2013-10-06  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gdb.base/corefile.exp: Test whether $_exitsignal is set and
	$_exitcode is void when opening a corefile.
	* gdb.base/exitsignal.exp: New file.
	* gdb.base/segv.c: Likewise.
	* gdb.base/normal.c: Likewise.

gdb/doc/
2013-10-06  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gdb.texinfo (Convenience Variables): Document $_exitsignal.
	Update entry for $_exitcode.

1 files changed, 24 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/normal.c b/gdb/testsuite/gdb.base/normal.c
new file mode 100644
index 0000000..4aa7c45
--- /dev/null
+++ b/gdb/testsuite/gdb.base/normal.c
@@ -0,0 +1,24 @@
+/* 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/>.  */
+
+/* This test is just a normal return 0.  */
+
+int
+main (int argc, char *argv[])
+{
+  return 0;
+}