Restrict access to the virtual functions move and copy

* These are meant to be used by detail::STVar only and
  are otherwise error-prone to call.

src/ripple/protocol/STAccount.h

@@ -46,11 +46,6 @@ public:
     STAccount(SerialIter& sit, SField const& name);
     STAccount(SField const& n, AccountID const& v);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     SerializedTypeID
     getSType() const override;
 
@@ -74,6 +69,14 @@ public:
 
     void
     setValue(AccountID const& v);
+
+private:
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 inline STAccount&

src/ripple/protocol/STAmount.h

@@ -144,11 +144,6 @@ public:
     STAmount(IOUAmount const& amount, Issue const& issue);
     STAmount(XRPAmount const& amount);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     //--------------------------------------------------------------------------
     //
     // Observers
@@ -273,6 +268,13 @@ private:
     set(std::int64_t v);
     void
     canonicalize();
+
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 //------------------------------------------------------------------------------

src/ripple/protocol/STArray.h

@@ -50,12 +50,6 @@ public:
     explicit STArray(int n);
     explicit STArray(SField const& f);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     STObject&
     operator[](std::size_t j);
 
@@ -134,6 +128,14 @@ public:
 
     bool
     isDefault() const override;
+
+private:
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 inline STObject&

src/ripple/protocol/STBase.h

@@ -33,6 +33,10 @@ namespace ripple {
 
 enum class JsonOptions { none = 0, include_date = 1 };
 
+namespace detail {
+class STVar;
+}
+
 // VFALCO TODO fix this restriction on copy assignment.
 //
 // CAUTION: Do not create a vector (or similar container) of any object derived
@@ -77,11 +81,6 @@ public:
     bool
     operator!=(const STBase& t) const;
 
-    virtual STBase*
-    copy(std::size_t n, void* buf) const;
-    virtual STBase*
-    move(std::size_t n, void* buf);
-
     template <class D>
     D&
     downcast();
@@ -126,6 +125,14 @@ protected:
     template <class T>
     static STBase*
     emplace(std::size_t n, void* buf, T&& val);
+
+private:
+    virtual STBase*
+    copy(std::size_t n, void* buf) const;
+    virtual STBase*
+    move(std::size_t n, void* buf);
+
+    friend class detail::STVar;
 };
 
 //------------------------------------------------------------------------------

src/ripple/protocol/STBitString.h

@@ -42,12 +42,6 @@ public:
     STBitString(SField const& n, const value_type& v);
     STBitString(SerialIter& sit, SField const& name);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     SerializedTypeID
     getSType() const override;
 
@@ -71,6 +65,14 @@ public:
     value() const;
 
     operator value_type() const;
+
+private:
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 using STHash128 = STBitString<128>;

src/ripple/protocol/STBlob.h

@@ -45,12 +45,6 @@ public:
     STBlob(SField const& n);
     STBlob(SerialIter&, SField const& name = sfGeneric);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     std::size_t
     size() const;
 
@@ -83,6 +77,14 @@ public:
 
     void
     setValue(Buffer&& b);
+
+private:
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 inline STBlob::STBlob(STBlob const& rhs)

src/ripple/protocol/STInteger.h

@@ -38,12 +38,6 @@ public:
     STInteger(SField const& n, Integer v = 0);
     STInteger(SerialIter& sit, SField const& name);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     SerializedTypeID
     getSType() const override;
 
@@ -71,6 +65,14 @@ public:
     setValue(Integer v);
 
     operator Integer() const;
+
+private:
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 using STUInt8 = STInteger<unsigned char>;

src/ripple/protocol/STLedgerEntry.h

@@ -43,12 +43,6 @@ public:
     STLedgerEntry(SerialIter&& sit, uint256 const& index);
     STLedgerEntry(STObject const& object, uint256 const& index);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     SerializedTypeID
     getSType() const override;
 
@@ -90,6 +84,13 @@ private:
     setSLEType();
 
     friend Invariants_test;  // this test wants access to the private type_
+
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 using SLE = STLedgerEntry;

src/ripple/protocol/STObject.h

@@ -92,12 +92,6 @@ public:
     STObject(SerialIter&& sit, SField const& name);
     explicit STObject(SField const& name);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     iterator
     begin() const;
 
@@ -448,6 +442,13 @@ private:
     template <typename T>
     T&
     peekField(SField const& field);
+
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 //------------------------------------------------------------------------------

src/ripple/protocol/STPathSet.h

@@ -182,12 +182,6 @@ public:
     STPathSet(SField const& n);
     STPathSet(SerialIter& sit, SField const& name);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     void
     add(Serializer& s) const override;
 
@@ -230,6 +224,14 @@ public:
     template <typename... Args>
     void
     emplace_back(Args&&... args);
+
+private:
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 // ------------ STPathElement ------------

src/ripple/protocol/STTx.h

@@ -66,12 +66,6 @@ public:
     */
     STTx(TxType type, std::function<void(STObject&)> assembler);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     // STObject functions.
     SerializedTypeID
     getSType() const override;
@@ -137,6 +131,13 @@ private:
 
     Expected<void, std::string>
     checkMultiSign(RequireFullyCanonicalSig requireCanonicalSig) const;
+
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 bool

src/ripple/protocol/STValidation.h

@@ -94,12 +94,6 @@ public:
         NodeID const& nodeID,
         F&& f);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     // Hash of the validated ledger
     uint256
     getLedgerHash() const;
@@ -150,6 +144,13 @@ public:
 private:
     static SOTemplate const&
     validationFormat();
+
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 template <class LookupNodeID>

src/ripple/protocol/STVector256.h

@@ -40,12 +40,6 @@ public:
     STVector256(SField const& n, std::vector<uint256> const& vector);
     STVector256(SerialIter& sit, SField const& name);
 
-    STBase*
-    copy(std::size_t n, void* buf) const override;
-
-    STBase*
-    move(std::size_t n, void* buf) override;
-
     SerializedTypeID
     getSType() const override;
 
@@ -116,6 +110,14 @@ public:
 
     void
     clear() noexcept;
+
+private:
+    STBase*
+    copy(std::size_t n, void* buf) const override;
+    STBase*
+    move(std::size_t n, void* buf) override;
+
+    friend class detail::STVar;
 };
 
 inline STVector256::STVector256(SField const& n) : STBase(n)