From c16cc204d320fb61a462397644ec35c04286182a Mon Sep 17 00:00:00 2001
From: warptangent <warptangent@tutanota.com>
Date: Sat, 13 Feb 2016 03:50:42 -0800
Subject: [PATCH] BlockchainLMDB: Add sanity check for inconsistent state

This hasn't been known to occur in block-level txn abort, but throw
exception if it does.
---
 src/blockchain_db/lmdb/db_lmdb.cpp | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/blockchain_db/lmdb/db_lmdb.cpp b/src/blockchain_db/lmdb/db_lmdb.cpp
index 3b3c5691..7b7af23b 100644
--- a/src/blockchain_db/lmdb/db_lmdb.cpp
+++ b/src/blockchain_db/lmdb/db_lmdb.cpp
@@ -2233,8 +2233,19 @@ void BlockchainLMDB::block_txn_abort()
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   if (! m_batch_active)
   {
-    delete m_write_txn;
-    m_write_txn = nullptr;
+    if (m_write_txn != nullptr)
+    {
+      delete m_write_txn;
+      m_write_txn = nullptr;
+    }
+    else
+    {
+      // This would probably mean an earlier exception was caught, but then we
+      // proceeded further than we should have.
+      throw0(DB_ERROR((std::string("BlockchainLMDB::") + __func__ +
+                       std::string(": block-level DB transaction abort called when write txn doesn't exist")
+                      ).c_str()));
+    }
   }
 }