refactor: wrap CCoinsViewCursor in unique_ptr

Specifically with CCoinsViewDB, if a raw cursor is allocated and
not freed, a cryptic leveldb assertion failure occurs on
CCoinsViewDB destruction.

See: https://github.com/google/leveldb/issues/142#issuecomment-414418135

1 files changed, 3 insertions, 3 deletions

diff --git a/src/coins.h b/src/coins.h
index 816b4864a3..3151a260d9 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -180,7 +180,7 @@ public:
     virtual bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock);
 
     //! Get a cursor to iterate over the whole state
-    virtual CCoinsViewCursor *Cursor() const;
+    virtual std::unique_ptr<CCoinsViewCursor> Cursor() const;
 
     //! As we use CCoinsViews polymorphically, have a virtual destructor
     virtual ~CCoinsView() {}
@@ -204,7 +204,7 @@ public:
     std::vector<uint256> GetHeadBlocks() const override;
     void SetBackend(CCoinsView &viewIn);
     bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
-    CCoinsViewCursor *Cursor() const override;
+    std::unique_ptr<CCoinsViewCursor> Cursor() const override;
     size_t EstimateSize() const override;
 };
 
@@ -237,7 +237,7 @@ public:
     uint256 GetBestBlock() const override;
     void SetBestBlock(const uint256 &hashBlock);
     bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
-    CCoinsViewCursor* Cursor() const override {
+    std::unique_ptr<CCoinsViewCursor> Cursor() const override {
         throw std::logic_error("CCoinsViewCache cursor iteration not supported.");
     }