Fixed a couple incremental merkle tree bugs breaking consistency checks.

src/coins.cpp

@@ -113,14 +113,13 @@ bool CCoinsViewCache::GetAnchorAt(const uint256 &rt, libzerocash::IncrementalMer
         }
     }
 
-    CAnchorsCacheEntry entry;
     if (!base->GetAnchorAt(rt, tree)) {
         return false;
     }
 
-    entry.entered = true;
-    entry.tree.setTo(tree);
-    cacheAnchors.insert(std::make_pair(rt, entry));
+    CAnchorsMap::iterator ret = cacheAnchors.insert(std::make_pair(rt, CAnchorsCacheEntry())).first;
+    ret->second.entered = true;
+    ret->second.tree.setTo(tree);
 
     return true;
 }

src/test/coins_tests.cpp

@@ -93,7 +93,10 @@ public:
         }
         for (CAnchorsMap::iterator it = mapAnchors.begin(); it != mapAnchors.end(); ) {
             if (it->second.entered) {
-                mapAnchors_[it->first] = it->second.tree;
+                std::map<uint256, libzerocash::IncrementalMerkleTree>::iterator ret =
+                    mapAnchors_.insert(std::make_pair(it->first, IncrementalMerkleTree(INCREMENTAL_MERKLE_TREE_DEPTH))).first;
+
+                ret->second.setTo(it->second.tree);
             } else {
                 mapAnchors_.erase(it->first);
             }
@@ -173,6 +176,45 @@ void appendRandomCommitment(IncrementalMerkleTree &tree)
     tree.insertElement(commitment, index);
 }
 
+BOOST_AUTO_TEST_CASE(anchors_flush_test)
+{
+    CCoinsViewTest base;
+    uint256 newrt;
+    {
+        CCoinsViewCacheTest cache(&base);
+        IncrementalMerkleTree tree(INCREMENTAL_MERKLE_TREE_DEPTH);
+        BOOST_CHECK(cache.GetAnchorAt(cache.GetBestAnchor(), tree));
+        appendRandomCommitment(tree);
+
+        {
+            std::vector<unsigned char> newrt_v(32);
+            tree.getRootValue(newrt_v);
+            newrt = uint256(newrt_v);
+        }
+
+        cache.PushAnchor(tree);
+        cache.Flush();
+    }
+    
+    {
+        CCoinsViewCacheTest cache(&base);
+        IncrementalMerkleTree tree(INCREMENTAL_MERKLE_TREE_DEPTH);
+        BOOST_CHECK(cache.GetAnchorAt(cache.GetBestAnchor(), tree));
+
+        // Get the cached entry.
+        BOOST_CHECK(cache.GetAnchorAt(cache.GetBestAnchor(), tree));
+
+        uint256 check_rt;
+        {
+            std::vector<unsigned char> newrt_v(32);
+            tree.getRootValue(newrt_v);
+            check_rt = uint256(newrt_v);
+        }
+
+        BOOST_CHECK(check_rt == newrt);
+    }
+}
+
 BOOST_AUTO_TEST_CASE(anchors_test)
 {
     // TODO: These tests should be more methodical.

src/wallet/wallet.cpp

@@ -1077,12 +1077,11 @@ bool CWallet::WitnessBucketCommitment(uint256 &commitment,
                     std::vector<bool> index;
                     std::vector<unsigned char> commitment_value(bucket_commitment.begin(), bucket_commitment.end());
                     libzerocash::convertBytesVectorToVector(commitment_value, commitment_bv);
-                    tree.insertElement(commitment_bv, index);
+                    assert(tree.insertElement(commitment_bv, index));
 
                     if (bucket_commitment == commitment) {
                         // We've found it! Now, we construct a witness.
                         res = true;
-                        tree.prune();
                         commitment_index = index;
                     }
                 }