PR 10979

* common.cc (Sort_commons::operator()): Stabilize sort when both
	entries are NULL.
	(Symbol_table::do_allocate_commons_list): When allocating common
	symbols, skip a symbol which is no longer common.
	* symtab.h (Symbol::is_common): Test whether the symbol comes from
	an object before checking its type.
	* testsuite/common_test_2.c: New file.
	* testsuite/common_test_3.c: New file.
	* testsuite/Makefile.am (check_PROGRAMS): Add common_test_2.
	(common_test_2_SOURCES, common_test_2_DEPENDENCIES): Define.
	(common_test_2_LDFLAGS, common_test_2_LDADD): Define.
	(common_test_2_pic.o, common_test_2.so): New targets.
	(common_test_3_pic.o, common_test_3.so): New targets.
	* testsuite/Makefile.in: Rebuild.

gold/testsuite/common_test_2.c

@@ -0,0 +1,33 @@
+/* common_test_2.c -- test common symbol name conflicts
+
+   Copyright 2009 Free Software Foundation, Inc.
+   Written by Ian Lance Taylor <iant@google.com>
+
+   This file is part of gold.
+
+   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, write to the Free Software
+   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+   MA 02110-1301, USA.  */
+
+/* Call a function.  The function will come from a shared library.  */
+
+extern void c1 (void);
+
+void fn (void);
+
+void
+fn (void)
+{
+  c1 ();
+}