Don't return stale data from CCoinsViewCache::Cursor()

CCoinsViewCache doesn't actually support cursor iteration returning the
current contents of the cache, so raise an error when the cursor method is
called instead of returning a cursor that iterates over stale data.

Also update the gettxoutsetinfo RPC which was relying on the old behavior to be
explicit about which view it is returning data about.

src/coins.h

@@ -212,6 +212,9 @@ public:
     uint256 GetBestBlock() const;
     void SetBestBlock(const uint256 &hashBlock);
     bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
+    CCoinsViewCursor* Cursor() const {
+        throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
+    }
 
     /**
      * Check if we have the given utxo already loaded in this cache.

src/init.cpp

@@ -162,7 +162,6 @@ public:
     // Writes do not need similar protection, as failure to write is handled by the caller.
 };
 
-static CCoinsViewDB *pcoinsdbview = NULL;
 static CCoinsViewErrorCatcher *pcoinscatcher = NULL;
 static std::unique_ptr<ECCVerifyHandle> globalVerifyHandle;
 

src/rpc/blockchain.cpp

@@ -19,6 +19,7 @@
 #include "rpc/server.h"
 #include "streams.h"
 #include "sync.h"
+#include "txdb.h"
 #include "txmempool.h"
 #include "util.h"
 #include "utilstrencodings.h"
@@ -917,7 +918,7 @@ UniValue gettxoutsetinfo(const JSONRPCRequest& request)
 
     CCoinsStats stats;
     FlushStateToDisk();
-    if (GetUTXOStats(pcoinsTip, stats)) {
+    if (GetUTXOStats(pcoinsdbview, stats)) {
         ret.push_back(Pair("height", (int64_t)stats.nHeight));
         ret.push_back(Pair("bestblock", stats.hashBlock.GetHex()));
         ret.push_back(Pair("transactions", (int64_t)stats.nTransactions));

src/validation.cpp

@@ -175,6 +175,7 @@ CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& loc
     return chain.Genesis();
 }
 
+CCoinsViewDB *pcoinsdbview = NULL;
 CCoinsViewCache *pcoinsTip = NULL;
 CBlockTreeDB *pblocktree = NULL;
 

src/validation.h

@@ -36,6 +36,7 @@ class CBlockIndex;
 class CBlockTreeDB;
 class CBloomFilter;
 class CChainParams;
+class CCoinsViewDB;
 class CInv;
 class CConnman;
 class CScriptCheck;
@@ -482,6 +483,9 @@ bool ResetBlockFailureFlags(CBlockIndex *pindex);
 /** The currently-connected chain of blocks (protected by cs_main). */
 extern CChain chainActive;
 
+/** Global variable that points to the coins database (protected by cs_main) */
+extern CCoinsViewDB *pcoinsdbview;
+
 /** Global variable that points to the active CCoinsView (protected by cs_main) */
 extern CCoinsViewCache *pcoinsTip;