From 9d11d0ff68c559ff7b2f0b07c6c8a2ad1717233c Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Thu, 4 May 2017 18:09:20 +0100
Subject: [PATCH] Workaround bug in Boost

---
 libevm/VM.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libevm/VM.cpp b/libevm/VM.cpp
index 1ca1d7612ab..d98dc05f758 100755
--- a/libevm/VM.cpp
+++ b/libevm/VM.cpp
@@ -579,8 +579,9 @@ void VM::interpretCases()
 			ON_OP();
 			updateIOGas();
 
-			/// TODO: confirm shift >= 256 results in 0
-			m_SPP[0] = m_SP[0] << m_SP[1];
+			/// This workarounds a bug in Boost, ...
+			u256 mask = u256(1) << (256 - m_SP[1])) - 1;
+			m_SPP[0] = (m_SP[0] & mask) << m_SP[1];
 		}
 		NEXT