[patch] Fix symtab/14601

[dje at google dot com]

Hi.

This patch fixes a gdb segv a user was tripping over.
Not all code paths to handle DW_TAG_imported_{declaration,module}
ensure using_directives is reset to NULL.
This patch fixes things by "going with the flow" and resetting
using_directives to NULL in buildsym_init along with the others.
[A discussion of buildsym.c itself is for another day. :-)]

I will check this in in a few days if there are no objections.

2012-09-20  Doug Evans  <dje@google.com>

	symtab/14601
	* buildsym.c (buildsym_init): Reset using_directives to NULL.

	testsuite/
	* gdb.cp/using-crash.exp: New file.
	* gdb.cp/using-crash.cc: New file.

Index: buildsym.c
===================================================================
RCS file: /cvs/src/src/gdb/buildsym.c,v
retrieving revision 1.103
diff -u -p -r1.103 buildsym.c
--- buildsym.c	19 Sep 2012 20:06:47 -0000	1.103
+++ buildsym.c	20 Sep 2012 22:19:07 -0000
@@ -1488,6 +1488,7 @@ buildsym_init (void)
   global_symbols = NULL;
   pending_blocks = NULL;
   pending_macros = NULL;
+  using_directives = NULL;
 
   /* We shouldn't have any address map at this point.  */
   gdb_assert (! pending_addrmap);

Index: testsuite/gdb.cp/using-crash.cc
===================================================================
RCS file: testsuite/gdb.cp/using-crash.cc
diff -N testsuite/gdb.cp/using-crash.cc
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/using-crash.cc	20 Sep 2012 22:34:54 -0000
@@ -0,0 +1,43 @@
+/* Copyright 2012 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 <iostream>
+using namespace std;
+
+class c1;
+
+void foo ();
+
+int
+main ()
+{
+  foo ();
+  return 0;
+}
+
+void
+foo ()
+{
+  c1 *p = 0;
+}
+
+class b1 { public: int x; };
+
+class c1 : public b1
+{
+ public:
+  using b1::x;
+  c1 () {}
+};
Index: testsuite/gdb.cp/using-crash.exp
===================================================================
RCS file: testsuite/gdb.cp/using-crash.exp
diff -N testsuite/gdb.cp/using-crash.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.cp/using-crash.exp	20 Sep 2012 22:34:54 -0000
@@ -0,0 +1,32 @@
+# Copyright 2012 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/>.
+
+standard_testfile .cc
+
+if {[prepare_for_testing $testfile.exp $testfile $srcfile {debug c++}]} {
+    return -1
+}
+
+runto "foo"
+
+# This would cause reading debug info with using_directives pointing to
+# freed memory.
+# http://sourceware.org/bugzilla/show_bug.cgi?id=14601
+# Note: You may need to compile with -fdebug-types-section to see the crash.
+set test "reload file"
+if { [gdb_file_cmd "$binfile"] == 0 } {
+    pass $test
+} else {
+    fail $test
+}