From 00f8319faf95e53333a9573fdc9e49df23238607 Mon Sep 17 00:00:00 2001
From: obscuren <geffobscura@gmail.com>
Date: Fri, 27 Mar 2015 14:22:38 +0100
Subject: [PATCH] Explicitly check memory's data store. #515

---
 core/vm/memory.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/core/vm/memory.go b/core/vm/memory.go
index dd47fa1b5..f5984d82f 100644
--- a/core/vm/memory.go
+++ b/core/vm/memory.go
@@ -15,10 +15,17 @@ func NewMemory() *Memory {
 }
 
 func (m *Memory) Set(offset, size uint64, value []byte) {
+	// If the length of the store is 0 this is a complete failure
+	// memory size is set prior to calling this method so enough size
+	// should always be available.
+	if len(m.store) == 0 {
+		panic("INVALID memory: store empty")
+	}
+
 	value = common.RightPadBytes(value, int(size))
 
 	totSize := offset + size
-	lenSize := uint64(len(m.store) - 1)
+	lenSize := int64(len(m.store) - 1)
 	if totSize > lenSize {
 		// Calculate the diff between the sizes
 		diff := totSize - lenSize