FYI: fix bit field bug

[Tom Tromey <tromey at redhat dot com>]

I'm checking this in.

A user on irc pointed out a case where gdb printed the wrong value of a
bit field.  It can happen when the bit field is a member of an anonymous
union in a struct.

This patch fixes the problem.

Built and regtested on x86-64 (compile farm).
Regression test included.

Tom

2010-09-30  Tom Tromey  <tromey@redhat.com>

	* value.c (value_primitive_field): Take 'offset' into account for
	packed field.

2010-09-30  Tom Tromey  <tromey@redhat.com>

	* gdb.base/anon.exp: New file.
	* gdb.base/anon.c: New file.

Index: value.c
===================================================================
RCS file: /cvs/src/src/gdb/value.c,v
retrieving revision 1.112
diff -u -r1.112 value.c
--- value.c	14 Sep 2010 19:08:30 -0000	1.112
+++ value.c	30 Sep 2010 18:54:48 -0000
@@ -1973,8 +1973,9 @@
 	v->bitpos = bitpos % container_bitsize;
       else
 	v->bitpos = bitpos % 8;
-      v->offset = value_embedded_offset (arg1)
-	+ (bitpos - v->bitpos) / 8;
+      v->offset = (value_embedded_offset (arg1)
+		   + offset
+		   + (bitpos - v->bitpos) / 8);
       v->parent = arg1;
       value_incref (v->parent);
       if (!value_lazy (arg1))
Index: testsuite/gdb.base/anon.c
===================================================================
RCS file: testsuite/gdb.base/anon.c
diff -N testsuite/gdb.base/anon.c
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/anon.c	30 Sep 2010 18:54:50 -0000
@@ -0,0 +1,32 @@
+/* Test of anonymous union in a struct.  */
+
+#include <string.h>
+
+struct outer
+{
+  int one;
+  int two;
+
+  struct
+  {
+    union {
+      int three : 3;
+      int four : 4;
+    };
+
+    union {
+      int five : 3;
+      int six : 4;
+    };
+  } data;
+};
+
+int main ()
+{
+  struct outer val;
+
+  memset (&val, 0, sizeof (val));
+  val.data.six = 6;
+
+  return 0;			/* break here */
+}
Index: testsuite/gdb.base/anon.exp
===================================================================
RCS file: testsuite/gdb.base/anon.exp
diff -N testsuite/gdb.base/anon.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ testsuite/gdb.base/anon.exp	30 Sep 2010 18:54:50 -0000
@@ -0,0 +1,32 @@
+# Copyright 2010 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/>.
+#
+
+set testfile "anon"
+set srcfile $testfile.c
+if { [prepare_for_testing $testfile.exp $testfile $srcfile {debug}] } {
+    return -1
+}
+
+if { ![runto main] } then {
+    fail "run to main"
+    return
+}
+
+set loc [gdb_get_line_number "break here"]
+gdb_test "break $loc" ".*Breakpoint 2 .*" "set breakpoint in anon.c"
+gdb_continue_to_breakpoint "continue to breakpoint in anon.c"
+
+gdb_test "print val.data.six" " = 6" "print val.data.six"