diff --git a/clang/include/clang/AST/StmtIterator.h b/clang/include/clang/AST/StmtIterator.h
--- a/clang/include/clang/AST/StmtIterator.h
+++ b/clang/include/clang/AST/StmtIterator.h
@@ -104,12 +104,13 @@
     return tmp;
   }
 
-  bool operator==(const DERIVED& RHS) const {
-    return stmt == RHS.stmt && DGI == RHS.DGI && RawVAPtr == RHS.RawVAPtr;
+  friend bool operator==(const DERIVED &LHS, const DERIVED &RHS) {
+    return LHS.stmt == RHS.stmt && LHS.DGI == RHS.DGI &&
+           LHS.RawVAPtr == RHS.RawVAPtr;
   }
 
-  bool operator!=(const DERIVED& RHS) const {
-    return stmt != RHS.stmt || DGI != RHS.DGI || RawVAPtr != RHS.RawVAPtr;
+  friend bool operator!=(const DERIVED &LHS, const DERIVED &RHS) {
+    return !(LHS == RHS);
   }
 
   REFERENCE operator*() const {
diff --git a/clang/lib/Parse/ParseOpenMP.cpp b/clang/lib/Parse/ParseOpenMP.cpp
--- a/clang/lib/Parse/ParseOpenMP.cpp
+++ b/clang/lib/Parse/ParseOpenMP.cpp
@@ -60,6 +60,12 @@
 struct OpenMPDirectiveKindExWrapper {
   OpenMPDirectiveKindExWrapper(unsigned Value) : Value(Value) {}
   OpenMPDirectiveKindExWrapper(OpenMPDirectiveKind DK) : Value(unsigned(DK)) {}
+  bool operator==(OpenMPDirectiveKindExWrapper V) const {
+    return Value == V.Value;
+  }
+  bool operator!=(OpenMPDirectiveKindExWrapper V) const {
+    return Value != V.Value;
+  }
   bool operator==(OpenMPDirectiveKind V) const { return Value == unsigned(V); }
   bool operator!=(OpenMPDirectiveKind V) const { return Value != unsigned(V); }
   bool operator<(OpenMPDirectiveKind V) const { return Value < unsigned(V); }
diff --git a/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp b/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp
--- a/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp
+++ b/clang/lib/StaticAnalyzer/Checkers/GenericTaintChecker.cpp
@@ -102,7 +102,10 @@
   }
 
   struct FunctionData {
-    FunctionData() = delete;
+    FunctionData(const FunctionDecl *FDecl, StringRef Name,
+                 std::string FullName)
+        : FDecl(FDecl), Name(Name), FullName(std::move(FullName)) {}
+
     FunctionData(const FunctionData &) = default;
     FunctionData(FunctionData &&) = default;
     FunctionData &operator=(const FunctionData &) = delete;
diff --git a/llvm/include/llvm/ADT/AllocatorList.h b/llvm/include/llvm/ADT/AllocatorList.h
--- a/llvm/include/llvm/ADT/AllocatorList.h
+++ b/llvm/include/llvm/ADT/AllocatorList.h
@@ -118,13 +118,6 @@
 
     reference operator*() const { return base_type::wrapped()->V; }
     pointer operator->() const { return &operator*(); }
-
-    friend bool operator==(const IteratorImpl &L, const IteratorImpl &R) {
-      return L.wrapped() == R.wrapped();
-    }
-    friend bool operator!=(const IteratorImpl &L, const IteratorImpl &R) {
-      return !(L == R);
-    }
   };
 
 public:
diff --git a/llvm/include/llvm/ADT/DenseMap.h b/llvm/include/llvm/ADT/DenseMap.h
--- a/llvm/include/llvm/ADT/DenseMap.h
+++ b/llvm/include/llvm/ADT/DenseMap.h
@@ -1244,19 +1244,18 @@
     return Ptr;
   }
 
-  bool operator==(const ConstIterator &RHS) const {
-    assert((!Ptr || isHandleInSync()) && "handle not in sync!");
+  friend bool operator==(const DenseMapIterator &LHS,
+                         const DenseMapIterator &RHS) {
+    assert((!LHS.Ptr || LHS.isHandleInSync()) && "handle not in sync!");
     assert((!RHS.Ptr || RHS.isHandleInSync()) && "handle not in sync!");
-    assert(getEpochAddress() == RHS.getEpochAddress() &&
+    assert(LHS.getEpochAddress() == RHS.getEpochAddress() &&
            "comparing incomparable iterators!");
-    return Ptr == RHS.Ptr;
+    return LHS.Ptr == RHS.Ptr;
   }
-  bool operator!=(const ConstIterator &RHS) const {
-    assert((!Ptr || isHandleInSync()) && "handle not in sync!");
-    assert((!RHS.Ptr || RHS.isHandleInSync()) && "handle not in sync!");
-    assert(getEpochAddress() == RHS.getEpochAddress() &&
-           "comparing incomparable iterators!");
-    return Ptr != RHS.Ptr;
+
+  friend bool operator!=(const DenseMapIterator &LHS,
+                         const DenseMapIterator &RHS) {
+    return !(LHS == RHS);
   }
 
   inline DenseMapIterator& operator++() {  // Preincrement
diff --git a/llvm/include/llvm/ADT/DenseSet.h b/llvm/include/llvm/ADT/DenseSet.h
--- a/llvm/include/llvm/ADT/DenseSet.h
+++ b/llvm/include/llvm/ADT/DenseSet.h
@@ -124,8 +124,12 @@
 
     Iterator& operator++() { ++I; return *this; }
     Iterator operator++(int) { auto T = *this; ++I; return T; }
-    bool operator==(const ConstIterator& X) const { return I == X.I; }
-    bool operator!=(const ConstIterator& X) const { return I != X.I; }
+    friend bool operator==(const Iterator &X, const Iterator &Y) {
+      return X.I == Y.I;
+    }
+    friend bool operator!=(const Iterator &X, const Iterator &Y) {
+      return X.I != Y.I;
+    }
   };
 
   class ConstIterator {
@@ -149,8 +153,12 @@
 
     ConstIterator& operator++() { ++I; return *this; }
     ConstIterator operator++(int) { auto T = *this; ++I; return T; }
-    bool operator==(const ConstIterator& X) const { return I == X.I; }
-    bool operator!=(const ConstIterator& X) const { return I != X.I; }
+    friend bool operator==(const ConstIterator &X, const ConstIterator &Y) {
+      return X.I == Y.I;
+    }
+    friend bool operator!=(const ConstIterator &X, const ConstIterator &Y) {
+      return X.I != Y.I;
+    }
   };
 
   using iterator = Iterator;
diff --git a/llvm/include/llvm/ADT/DirectedGraph.h b/llvm/include/llvm/ADT/DirectedGraph.h
--- a/llvm/include/llvm/ADT/DirectedGraph.h
+++ b/llvm/include/llvm/ADT/DirectedGraph.h
@@ -38,8 +38,10 @@
 
   /// Static polymorphism: delegate implementation (via isEqualTo) to the
   /// derived class.
-  bool operator==(const EdgeType &E) const { return getDerived().isEqualTo(E); }
-  bool operator!=(const EdgeType &E) const { return !operator==(E); }
+  bool operator==(const DGEdge &E) const {
+    return getDerived().isEqualTo(E.getDerived());
+  }
+  bool operator!=(const DGEdge &E) const { return !operator==(E); }
 
   /// Retrieve the target node this edge connects to.
   const NodeType &getTargetNode() const { return TargetNode; }
@@ -91,8 +93,12 @@
 
   /// Static polymorphism: delegate implementation (via isEqualTo) to the
   /// derived class.
-  bool operator==(const NodeType &N) const { return getDerived().isEqualTo(N); }
-  bool operator!=(const NodeType &N) const { return !operator==(N); }
+  friend bool operator==(const NodeType &M, const NodeType &N) {
+    return M.isEqualTo(N);
+  }
+  friend bool operator!=(const NodeType &M, const NodeType &N) {
+    return !(M == N);
+  }
 
   const_iterator begin() const { return Edges.begin(); }
   const_iterator end() const { return Edges.end(); }
diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -558,12 +558,12 @@
     return *this;
   }
 
-  using BaseT::operator==;
-  bool operator==(const early_inc_iterator_impl &RHS) const {
+  friend bool operator==(const early_inc_iterator_impl &LHS,
+                         const early_inc_iterator_impl &RHS) {
 #if LLVM_ENABLE_ABI_BREAKING_CHECKS
-    assert(!IsEarlyIncremented && "Cannot compare after dereferencing!");
+    assert(!LHS.IsEarlyIncremented && "Cannot compare after dereferencing!");
 #endif
-    return BaseT::operator==(RHS);
+    return (const BaseT &)LHS == (const BaseT &)RHS;
   }
 };
 
diff --git a/llvm/include/llvm/ADT/StringMap.h b/llvm/include/llvm/ADT/StringMap.h
--- a/llvm/include/llvm/ADT/StringMap.h
+++ b/llvm/include/llvm/ADT/StringMap.h
@@ -367,7 +367,9 @@
     return static_cast<DerivedTy &>(*this);
   }
 
-  bool operator==(const DerivedTy &RHS) const { return Ptr == RHS.Ptr; }
+  friend bool operator==(const DerivedTy &LHS, const DerivedTy &RHS) {
+    return LHS.Ptr == RHS.Ptr;
+  }
 
   DerivedTy &operator++() { // Preincrement
     ++Ptr;
diff --git a/llvm/include/llvm/ADT/iterator.h b/llvm/include/llvm/ADT/iterator.h
--- a/llvm/include/llvm/ADT/iterator.h
+++ b/llvm/include/llvm/ADT/iterator.h
@@ -142,28 +142,24 @@
     return tmp;
   }
 
-  bool operator!=(const DerivedT &RHS) const {
-    return !static_cast<const DerivedT *>(this)->operator==(RHS);
-  }
-
   bool operator>(const DerivedT &RHS) const {
     static_assert(
         IsRandomAccess,
         "Relational operators are only defined for random access iterators.");
-    return !static_cast<const DerivedT *>(this)->operator<(RHS) &&
-           !static_cast<const DerivedT *>(this)->operator==(RHS);
+    return !(static_cast<const DerivedT &>(*this) < RHS) &&
+           !(static_cast<const DerivedT &>(*this) == RHS);
   }
   bool operator<=(const DerivedT &RHS) const {
     static_assert(
         IsRandomAccess,
         "Relational operators are only defined for random access iterators.");
-    return !static_cast<const DerivedT *>(this)->operator>(RHS);
+    return !(static_cast<const DerivedT &>(*this) > RHS);
   }
   bool operator>=(const DerivedT &RHS) const {
     static_assert(
         IsRandomAccess,
         "Relational operators are only defined for random access iterators.");
-    return !static_cast<const DerivedT *>(this)->operator<(RHS);
+    return !(static_cast<const DerivedT &>(*this) < RHS);
   }
 
   PointerT operator->() { return &static_cast<DerivedT *>(this)->operator*(); }
@@ -260,12 +256,20 @@
     return *static_cast<DerivedT *>(this);
   }
 
-  bool operator==(const DerivedT &RHS) const { return I == RHS.I; }
-  bool operator<(const DerivedT &RHS) const {
+  friend bool operator==(const iterator_adaptor_base &LHS,
+                         const iterator_adaptor_base &RHS) {
+    return LHS.I == RHS.I;
+  }
+  friend bool operator!=(const iterator_adaptor_base &LHS,
+                         const iterator_adaptor_base &RHS) {
+    return !(LHS == RHS);
+  }
+  friend bool operator<(const iterator_adaptor_base &LHS,
+                        const iterator_adaptor_base &RHS) {
     static_assert(
         BaseT::IsRandomAccess,
         "Relational operators are only defined for random access iterators.");
-    return I < RHS.I;
+    return LHS.I < RHS.I;
   }
 
   ReferenceT operator*() const { return *I; }
diff --git a/llvm/include/llvm/CodeGen/LiveInterval.h b/llvm/include/llvm/CodeGen/LiveInterval.h
--- a/llvm/include/llvm/CodeGen/LiveInterval.h
+++ b/llvm/include/llvm/CodeGen/LiveInterval.h
@@ -731,10 +731,10 @@
         ++*this;
         return res;
       }
-      bool operator!=(const SingleLinkedListIterator<T> &Other) {
+      bool operator!=(const SingleLinkedListIterator<T> &Other) const {
         return P != Other.operator->();
       }
-      bool operator==(const SingleLinkedListIterator<T> &Other) {
+      bool operator==(const SingleLinkedListIterator<T> &Other) const {
         return P == Other.operator->();
       }
       T &operator*() const {
diff --git a/llvm/include/llvm/IR/Attributes.h b/llvm/include/llvm/IR/Attributes.h
--- a/llvm/include/llvm/IR/Attributes.h
+++ b/llvm/include/llvm/IR/Attributes.h
@@ -874,10 +874,8 @@
 
   bool td_empty() const { return TargetDepAttrs.empty(); }
 
-  bool operator==(const AttrBuilder &B);
-  bool operator!=(const AttrBuilder &B) {
-    return !(*this == B);
-  }
+  bool operator==(const AttrBuilder &B) const;
+  bool operator!=(const AttrBuilder &B) const { return !(*this == B); }
 };
 
 namespace AttributeFuncs {
diff --git a/llvm/include/llvm/IR/BasicBlock.h b/llvm/include/llvm/IR/BasicBlock.h
--- a/llvm/include/llvm/IR/BasicBlock.h
+++ b/llvm/include/llvm/IR/BasicBlock.h
@@ -313,7 +313,9 @@
     phi_iterator_impl() = default;
 
     // Allow conversion between instantiations where valid.
-    template <typename PHINodeU, typename BBIteratorU>
+    template <typename PHINodeU, typename BBIteratorU,
+              typename = std::enable_if_t<
+                  std::is_convertible<PHINodeU *, PHINodeT *>::value>>
     phi_iterator_impl(const phi_iterator_impl<PHINodeU, BBIteratorU> &Arg)
         : PN(Arg.PN) {}
 
diff --git a/llvm/include/llvm/Object/StackMapParser.h b/llvm/include/llvm/Object/StackMapParser.h
--- a/llvm/include/llvm/Object/StackMapParser.h
+++ b/llvm/include/llvm/Object/StackMapParser.h
@@ -35,11 +35,13 @@
       return tmp;
     }
 
-    bool operator==(const AccessorIterator &Other) {
+    bool operator==(const AccessorIterator &Other) const {
       return A.P == Other.A.P;
     }
 
-    bool operator!=(const AccessorIterator &Other) { return !(*this == Other); }
+    bool operator!=(const AccessorIterator &Other) const {
+      return !(*this == Other);
+    }
 
     AccessorT& operator*() { return A; }
     AccessorT* operator->() { return &A; }
diff --git a/llvm/include/llvm/ProfileData/Coverage/CoverageMappingReader.h b/llvm/include/llvm/ProfileData/Coverage/CoverageMappingReader.h
--- a/llvm/include/llvm/ProfileData/Coverage/CoverageMappingReader.h
+++ b/llvm/include/llvm/ProfileData/Coverage/CoverageMappingReader.h
@@ -67,10 +67,10 @@
     increment();
     return *this;
   }
-  bool operator==(const CoverageMappingIterator &RHS) {
+  bool operator==(const CoverageMappingIterator &RHS) const {
     return Reader == RHS.Reader;
   }
-  bool operator!=(const CoverageMappingIterator &RHS) {
+  bool operator!=(const CoverageMappingIterator &RHS) const {
     return Reader != RHS.Reader;
   }
   Expected<CoverageMappingRecord &> operator*() {
diff --git a/llvm/include/llvm/ProfileData/InstrProfReader.h b/llvm/include/llvm/ProfileData/InstrProfReader.h
--- a/llvm/include/llvm/ProfileData/InstrProfReader.h
+++ b/llvm/include/llvm/ProfileData/InstrProfReader.h
@@ -50,8 +50,12 @@
   InstrProfIterator(InstrProfReader *Reader) : Reader(Reader) { Increment(); }
 
   InstrProfIterator &operator++() { Increment(); return *this; }
-  bool operator==(const InstrProfIterator &RHS) { return Reader == RHS.Reader; }
-  bool operator!=(const InstrProfIterator &RHS) { return Reader != RHS.Reader; }
+  bool operator==(const InstrProfIterator &RHS) const {
+    return Reader == RHS.Reader;
+  }
+  bool operator!=(const InstrProfIterator &RHS) const {
+    return Reader != RHS.Reader;
+  }
   value_type &operator*() { return Record; }
   value_type *operator->() { return &Record; }
 };
diff --git a/llvm/include/llvm/Support/BinaryStreamRef.h b/llvm/include/llvm/Support/BinaryStreamRef.h
--- a/llvm/include/llvm/Support/BinaryStreamRef.h
+++ b/llvm/include/llvm/Support/BinaryStreamRef.h
@@ -121,12 +121,12 @@
 
   bool valid() const { return BorrowedImpl != nullptr; }
 
-  bool operator==(const RefType &Other) const {
-    if (BorrowedImpl != Other.BorrowedImpl)
+  friend bool operator==(const RefType &Self, const RefType &Other) {
+    if (Self.BorrowedImpl != Other.BorrowedImpl)
       return false;
-    if (ViewOffset != Other.ViewOffset)
+    if (Self.ViewOffset != Other.ViewOffset)
       return false;
-    if (Length != Other.Length)
+    if (Self.Length != Other.Length)
       return false;
     return true;
   }
diff --git a/llvm/lib/CodeGen/MachineOutliner.cpp b/llvm/lib/CodeGen/MachineOutliner.cpp
--- a/llvm/lib/CodeGen/MachineOutliner.cpp
+++ b/llvm/lib/CodeGen/MachineOutliner.cpp
@@ -590,10 +590,10 @@
       return It;
     }
 
-    bool operator==(const RepeatedSubstringIterator &Other) {
+    bool operator==(const RepeatedSubstringIterator &Other) const {
       return N == Other.N;
     }
-    bool operator!=(const RepeatedSubstringIterator &Other) {
+    bool operator!=(const RepeatedSubstringIterator &Other) const {
       return !(*this == Other);
     }
 
diff --git a/llvm/lib/CodeGen/PeepholeOptimizer.cpp b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
--- a/llvm/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
@@ -330,7 +330,7 @@
       return RegSrcs[Idx].SubReg;
     }
 
-    bool operator==(const ValueTrackerResult &Other) {
+    bool operator==(const ValueTrackerResult &Other) const {
       if (Other.getInst() != getInst())
         return false;
 
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -1729,7 +1729,7 @@
   return Alignment != 0;
 }
 
-bool AttrBuilder::operator==(const AttrBuilder &B) {
+bool AttrBuilder::operator==(const AttrBuilder &B) const {
   if (Attrs != B.Attrs)
     return false;
 
diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
--- a/llvm/lib/IR/DebugInfo.cpp
+++ b/llvm/lib/IR/DebugInfo.cpp
@@ -665,7 +665,7 @@
           if (auto *T = dyn_cast_or_null<MDTuple>(Attachment.second))
             for (unsigned N = 0; N < T->getNumOperands(); ++N)
               if (auto *Loc = dyn_cast_or_null<DILocation>(T->getOperand(N)))
-                if (Loc != DebugLoc())
+                if (Loc != DebugLoc().get())
                   T->replaceOperandWith(N, remapDebugLoc(Loc));
       }
     }
diff --git a/llvm/lib/Transforms/Scalar/GVNHoist.cpp b/llvm/lib/Transforms/Scalar/GVNHoist.cpp
--- a/llvm/lib/Transforms/Scalar/GVNHoist.cpp
+++ b/llvm/lib/Transforms/Scalar/GVNHoist.cpp
@@ -149,8 +149,8 @@
   // The instruction (VN) which uses the values flowing out of CHI.
   Instruction *I;
 
-  bool operator==(const CHIArg &A) { return VN == A.VN; }
-  bool operator!=(const CHIArg &A) { return !(*this == A); }
+  bool operator==(const CHIArg &A) const { return VN == A.VN; }
+  bool operator!=(const CHIArg &A) const { return !(*this == A); }
 };
 
 using CHIIt = SmallVectorImpl<CHIArg>::iterator;
diff --git a/llvm/unittests/ADT/STLExtrasTest.cpp b/llvm/unittests/ADT/STLExtrasTest.cpp
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -463,21 +463,21 @@
 
   // Check fancy pointer overload for unique_ptr
   std::unique_ptr<int> V2 = std::make_unique<int>(0);
-  EXPECT_EQ(V2.get(), to_address(V2));
+  EXPECT_EQ(V2.get(), (to_address)(V2));
 
   V2.reset(V1);
-  EXPECT_EQ(V1, to_address(V2));
+  EXPECT_EQ(V1, (to_address)(V2));
   V2.release();
 
   // Check fancy pointer overload for shared_ptr
   std::shared_ptr<int> V3 = std::make_shared<int>(0);
   std::shared_ptr<int> V4 = V3;
   EXPECT_EQ(V3.get(), V4.get());
-  EXPECT_EQ(V3.get(), to_address(V3));
-  EXPECT_EQ(V4.get(), to_address(V4));
+  EXPECT_EQ(V3.get(), (to_address)(V3));
+  EXPECT_EQ(V4.get(), (to_address)(V4));
 
   V3.reset(V1);
-  EXPECT_EQ(V1, to_address(V3));
+  EXPECT_EQ(V1, (to_address)(V3));
 }
 
 TEST(STLExtrasTest, partition_point) {
diff --git a/llvm/unittests/Support/DJBTest.cpp b/llvm/unittests/Support/DJBTest.cpp
--- a/llvm/unittests/Support/DJBTest.cpp
+++ b/llvm/unittests/Support/DJBTest.cpp
@@ -24,6 +24,7 @@
       {{"qqqqqqqqqqqqqqqqqqqq"}, {"QQQQQQQQQQQQQQQQQQQQ"}},
 
       {{"I"}, {"i"}},
+#ifndef __cpp_char8_t
       // Latin Small Letter Dotless I
       {{u8"\u0130"}, {"i"}},
       // Latin Capital Letter I With Dot Above
@@ -47,6 +48,7 @@
       {{u8"\uff2d"}, {u8"\uff4d"}},
       // Old Hungarian Capital Letter Ej
       {{u8"\U00010c92"}, {u8"\U00010cd2"}},
+#endif
   };
 
   for (const TestCase &T : Tests) {
@@ -79,6 +81,7 @@
   }
 }
 
+#ifndef __cpp_char8_t
 TEST(DJBTest, knownValuesUnicode) {
   EXPECT_EQ(5866553u, djbHash(u8"\u0130"));
   EXPECT_EQ(177678u, caseFoldingDjbHash(u8"\u0130"));
@@ -93,3 +96,4 @@
           u8"\u0130\u0131\u00c0\u00e0\u0100\u0101\u0139\u013a\u0415\u0435\u1ea6"
           u8"\u1ea7\u212a\u006b\u2c1d\u2c4d\uff2d\uff4d\U00010c92\U00010cd2"));
 }
+#endif
\ No newline at end of file
diff --git a/llvm/unittests/Support/JSONTest.cpp b/llvm/unittests/Support/JSONTest.cpp
--- a/llvm/unittests/Support/JSONTest.cpp
+++ b/llvm/unittests/Support/JSONTest.cpp
@@ -173,12 +173,14 @@
   Compare(R"("\"\\\b\f\n\r\t")", "\"\\\b\f\n\r\t");
   Compare(R"("\u0000")", llvm::StringRef("\0", 1));
   Compare("\"\x7f\"", "\x7f");
+#ifndef __cpp_char8_t
   Compare(R"("\ud801\udc37")", u8"\U00010437"); // UTF16 surrogate pair escape.
   Compare("\"\xE2\x82\xAC\xF0\x9D\x84\x9E\"", u8"\u20ac\U0001d11e"); // UTF8
   Compare(
       R"("LoneLeading=\ud801, LoneTrailing=\udc01, LeadingLeadingTrailing=\ud801\ud801\udc37")",
       u8"LoneLeading=\ufffd, LoneTrailing=\ufffd, "
       u8"LeadingLeadingTrailing=\ufffd\U00010437"); // Invalid unicode.
+#endif
 
   Compare(R"({"":0,"":0})", Object{{"", 0}});
   Compare(R"({"obj":{},"arr":[]})", Object{{"obj", Object{}}, {"arr", {}}});