From 61b8d5e4e4b27010f5dd757a34e7295bb5dd10ff Mon Sep 17 00:00:00 2001
From: Andreas Sandberg <Andreas.Sandberg@ARM.com>
Date: Tue, 26 Aug 2014 10:13:28 -0400
Subject: [PATCH] base: Add a static assert to check bit union ranges

If a bit field in a bit union specified as Bitfield<LSB, MSB> instead
of Bitfield<MSB, LSB> the code silently fails and the field is read as
zero. This changeset introduces a static assert that tests, at compile
time, that the bit order is correct.
---
 src/base/bitunion.hh | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/base/bitunion.hh b/src/base/bitunion.hh
index f640fa3b1..190c1a5e1 100644
--- a/src/base/bitunion.hh
+++ b/src/base/bitunion.hh
@@ -85,6 +85,9 @@ namespace BitfieldBackend
         template<int first, int last=first>
         class Bitfield : public BitfieldBase<Type>
         {
+            static_assert(first >= last,
+                          "Bitfield ranges must be specified as <msb, lsb>");
+
           public:
             operator const uint64_t () const
             {
-- 
2.30.2