diff --git a/libcxx/test/libcxx/assertions/single_expression.sh.cpp b/libcxx/test/libcxx/assertions/single_expression.sh.cpp
--- a/libcxx/test/libcxx/assertions/single_expression.sh.cpp
+++ b/libcxx/test/libcxx/assertions/single_expression.sh.cpp
@@ -9,13 +9,13 @@
 // Make sure that _LIBCPP_ASSERT is a single expression. This is useful so we can use
 // it in places that require an expression, such as in a constructor initializer list.
 
-// RUN: %{build} -Wno-macro-redefined -D_LIBCPP_ENABLE_ASSERTIONS=1
+// RUN: %{build} -Wno-macro-redefined -Wno-comma -D_LIBCPP_ENABLE_ASSERTIONS=1
 // RUN: %{run}
 
-// RUN: %{build} -Wno-macro-redefined -D_LIBCPP_ENABLE_ASSERTIONS=0
+// RUN: %{build} -Wno-macro-redefined -Wno-comma -D_LIBCPP_ENABLE_ASSERTIONS=0
 // RUN: %{run}
 
-// RUN: %{build} -Wno-macro-redefined -D_LIBCPP_ENABLE_ASSERTIONS=0 -D_LIBCPP_ASSERTIONS_DISABLE_ASSUME
+// RUN: %{build} -Wno-macro-redefined -Wno-comma -D_LIBCPP_ENABLE_ASSERTIONS=0 -D_LIBCPP_ASSERTIONS_DISABLE_ASSUME
 // RUN: %{run}
 
 // We flag uses of the assertion handler in older dylibs at compile-time to avoid runtime
diff --git a/libcxx/test/libcxx/atomics/bit-int.verify.cpp b/libcxx/test/libcxx/atomics/bit-int.verify.cpp
--- a/libcxx/test/libcxx/atomics/bit-int.verify.cpp
+++ b/libcxx/test/libcxx/atomics/bit-int.verify.cpp
@@ -17,6 +17,8 @@
 
 // UNSUPPORTED: c++03
 
+// ADDITIONAL_COMPILE_FLAGS: -Wno-bit-int-extension
+
 #include <atomic>
 
 int main(int, char**)
diff --git a/libcxx/test/libcxx/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/move_reentrant.pass.cpp b/libcxx/test/libcxx/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/move_reentrant.pass.cpp
--- a/libcxx/test/libcxx/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/move_reentrant.pass.cpp
+++ b/libcxx/test/libcxx/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/move_reentrant.pass.cpp
@@ -25,6 +25,8 @@
   static std::function<void()> global;
   static bool cancel;
 
+  A() = default;
+  A(const A&) = default;
   ~A() {
     DoNotOptimize(cancel);
     if (cancel)
diff --git a/libcxx/test/libcxx/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/nullptr_t_assign_reentrant.pass.cpp b/libcxx/test/libcxx/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/nullptr_t_assign_reentrant.pass.cpp
--- a/libcxx/test/libcxx/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/nullptr_t_assign_reentrant.pass.cpp
+++ b/libcxx/test/libcxx/utilities/function.objects/func.wrap/func.wrap.func/func.wrap.func.con/nullptr_t_assign_reentrant.pass.cpp
@@ -25,6 +25,8 @@
   static std::function<void()> global;
   static bool cancel;
 
+  A() = default;
+  A(const A&) = default;
   ~A() {
     DoNotOptimize(cancel);
     if (cancel)
diff --git a/libcxx/test/std/concepts/concepts.lang/concept.constructible/constructible_from.compile.pass.cpp b/libcxx/test/std/concepts/concepts.lang/concept.constructible/constructible_from.compile.pass.cpp
--- a/libcxx/test/std/concepts/concepts.lang/concept.constructible/constructible_from.compile.pass.cpp
+++ b/libcxx/test/std/concepts/concepts.lang/concept.constructible/constructible_from.compile.pass.cpp
@@ -106,9 +106,6 @@
   test<void (Empty::*)(const int&)&, void (Empty::*)(const int&) &&>();
   test<void (Empty::*)(const int&) &&>();
   test<void (Empty::*)(const int&)&&, void (Empty::*)(const int&)>();
-  test<void (Empty::*)(const int&) throw()>();
-  test<void (Empty::*)(const int&) throw(),
-       void(Empty::*)(const int&) noexcept(true)>();
   test<void (Empty::*)(const int&) noexcept>();
   test<void (Empty::*)(const int&) noexcept(true)>();
   test<void (Empty::*)(const int&) noexcept(true),
diff --git a/libcxx/test/std/containers/sequences/array/array.creation/to_array.pass.cpp b/libcxx/test/std/containers/sequences/array/array.creation/to_array.pass.cpp
--- a/libcxx/test/std/containers/sequences/array/array.creation/to_array.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.creation/to_array.pass.cpp
@@ -84,10 +84,13 @@
 
   // Test C99 compound literal.
   {
+TEST_DIAGNOSTIC_PUSH
+TEST_CLANG_DIAGNOSTIC_IGNORED("-Wc99-extensions")
     auto arr = std::to_array((int[]){3, 4});
     ASSERT_SAME_TYPE(decltype(arr), std::array<int, 2>);
     assert(arr[0] == 3);
     assert(arr[1] == 4);
+TEST_DIAGNOSTIC_POP
   }
 
   //  Test explicit type.
diff --git a/libcxx/test/std/iterators/predef.iterators/insert.iterators/back.insert.iter.ops/back.insert.iter.op=/lv_value.pass.cpp b/libcxx/test/std/iterators/predef.iterators/insert.iterators/back.insert.iter.ops/back.insert.iter.op=/lv_value.pass.cpp
--- a/libcxx/test/std/iterators/predef.iterators/insert.iterators/back.insert.iter.ops/back.insert.iter.op=/lv_value.pass.cpp
+++ b/libcxx/test/std/iterators/predef.iterators/insert.iterators/back.insert.iter.ops/back.insert.iter.op=/lv_value.pass.cpp
@@ -37,6 +37,7 @@
     int data_;
 public:
     Copyable() : data_(0) {}
+    Copyable(const Copyable&) = default;
     ~Copyable() {data_ = -1;}
 
     friend bool operator==(const Copyable& x, const Copyable& y)
diff --git a/libcxx/test/std/iterators/predef.iterators/insert.iterators/front.insert.iter.ops/front.insert.iter.op=/lv_value.pass.cpp b/libcxx/test/std/iterators/predef.iterators/insert.iterators/front.insert.iter.ops/front.insert.iter.op=/lv_value.pass.cpp
--- a/libcxx/test/std/iterators/predef.iterators/insert.iterators/front.insert.iter.ops/front.insert.iter.op=/lv_value.pass.cpp
+++ b/libcxx/test/std/iterators/predef.iterators/insert.iterators/front.insert.iter.ops/front.insert.iter.op=/lv_value.pass.cpp
@@ -37,6 +37,7 @@
     int data_;
 public:
     Copyable() : data_(0) {}
+    Copyable(const Copyable&) = default;
     ~Copyable() {data_ = -1;}
 
     friend bool operator==(const Copyable& x, const Copyable& y)
diff --git a/libcxx/test/std/iterators/predef.iterators/move.iterators/move.iter.ops/move.iter.op.star/op_star.pass.cpp b/libcxx/test/std/iterators/predef.iterators/move.iterators/move.iter.ops/move.iter.op.star/op_star.pass.cpp
--- a/libcxx/test/std/iterators/predef.iterators/move.iterators/move.iter.ops/move.iter.op.star/op_star.pass.cpp
+++ b/libcxx/test/std/iterators/predef.iterators/move.iterators/move.iter.ops/move.iter.op.star/op_star.pass.cpp
@@ -25,6 +25,7 @@
     int data_;
 public:
     A() : data_(1) {}
+    A(const A&) = default;
     ~A() {data_ = -1;}
 
     friend bool operator==(const A& x, const A& y)
diff --git a/libcxx/test/std/iterators/predef.iterators/reverse.iterators/reverse.iter.elem/arrow.pass.cpp b/libcxx/test/std/iterators/predef.iterators/reverse.iterators/reverse.iter.elem/arrow.pass.cpp
--- a/libcxx/test/std/iterators/predef.iterators/reverse.iterators/reverse.iter.elem/arrow.pass.cpp
+++ b/libcxx/test/std/iterators/predef.iterators/reverse.iterators/reverse.iter.elem/arrow.pass.cpp
@@ -50,6 +50,7 @@
     int data_;
 public:
     B(int d=1) : data_(d) {}
+    B(const B&) = default;
     ~B() {data_ = -1;}
 
     int get() const {return data_;}
diff --git a/libcxx/test/std/language.support/support.exception/except.nested/rethrow_if_nested.pass.cpp b/libcxx/test/std/language.support/support.exception/except.nested/rethrow_if_nested.pass.cpp
--- a/libcxx/test/std/language.support/support.exception/except.nested/rethrow_if_nested.pass.cpp
+++ b/libcxx/test/std/language.support/support.exception/except.nested/rethrow_if_nested.pass.cpp
@@ -28,6 +28,7 @@
     int data_;
 public:
     explicit A(int data) : data_(data) {}
+    A(const A&) = default;
     virtual ~A() TEST_NOEXCEPT {}
 
     friend bool operator==(const A& x, const A& y) {return x.data_ == y.data_;}
@@ -63,7 +64,6 @@
         {
             A a(3);  // not a polymorphic type --> no effect
             std::rethrow_if_nested(a);
-            assert(true);
         }
         catch (...)
         {
@@ -75,7 +75,6 @@
         {
             D s;  // inaccessible base class --> no effect
             std::rethrow_if_nested(s);
-            assert(true);
         }
         catch (...)
         {
@@ -87,7 +86,6 @@
         {
             E s;  // ambiguous base class --> no effect
             std::rethrow_if_nested(s);
-            assert(true);
         }
         catch (...)
         {
@@ -123,7 +121,6 @@
         try
         {
             std::rethrow_if_nested(C());
-            assert(true);
         }
         catch (...)
         {
diff --git a/libcxx/test/std/language.support/support.start.term/quick_exit.pass.cpp b/libcxx/test/std/language.support/support.start.term/quick_exit.pass.cpp
--- a/libcxx/test/std/language.support/support.start.term/quick_exit.pass.cpp
+++ b/libcxx/test/std/language.support/support.start.term/quick_exit.pass.cpp
@@ -23,5 +23,4 @@
 int main(int, char**) {
     std::at_quick_exit(f);
     std::quick_exit(0);
-    return 0;
 }
diff --git a/libcxx/test/std/ranges/range.adaptors/range.drop/dangling.cache.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.drop/dangling.cache.pass.cpp
--- a/libcxx/test/std/ranges/range.adaptors/range.drop/dangling.cache.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.drop/dangling.cache.pass.cpp
@@ -30,6 +30,9 @@
   constexpr ForwardIter end() { return ForwardIter(buff + 8); }
   constexpr ForwardIter end() const { return ForwardIter(); }
 
+  ZeroOnDestroy() = default;
+  ZeroOnDestroy(const ZeroOnDestroy&) = default;
+
   ~ZeroOnDestroy() {
     std::memset(buff, 0, sizeof(buff));
   }
diff --git a/libcxx/test/std/ranges/range.adaptors/range.zip/iterator/singular.pass.cpp b/libcxx/test/std/ranges/range.adaptors/range.zip/iterator/singular.pass.cpp
--- a/libcxx/test/std/ranges/range.adaptors/range.zip/iterator/singular.pass.cpp
+++ b/libcxx/test/std/ranges/range.adaptors/range.zip/iterator/singular.pass.cpp
@@ -31,8 +31,8 @@
   ThrowOnIncrementIterator& operator++() {
     ++it_;
     throw 5;
-    return *this;
   }
+
   void operator++(int) { ++it_; }
 
   int& operator*() const { return *it_; }
diff --git a/libcxx/test/std/strings/string.view/string.view.cons/from_range.pass.cpp b/libcxx/test/std/strings/string.view/string.view.cons/from_range.pass.cpp
--- a/libcxx/test/std/strings/string.view/string.view.cons/from_range.pass.cpp
+++ b/libcxx/test/std/strings/string.view/string.view.cons/from_range.pass.cpp
@@ -161,7 +161,7 @@
   struct ThrowingData {
     char* begin() const { return nullptr; }
     char* end() const { return nullptr; }
-    char* data() const { throw 42; return nullptr; }
+    char* data() const { throw 42; }
   };
   try {
     ThrowingData x;
@@ -174,7 +174,7 @@
   struct ThrowingSize {
     char* begin() const { return nullptr; }
     char* end() const { return nullptr; }
-    size_t size() const { throw 42; return 0; }
+    size_t size() const { throw 42; }
   };
   try {
     ThrowingSize x;
@@ -195,4 +195,3 @@
 
   return 0;
 }
-
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock.algorithm/lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock.algorithm/lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock.algorithm/lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock.algorithm/lock.pass.cpp
@@ -88,7 +88,6 @@
     bool try_lock()
     {
         TEST_THROW(1);
-        return locked_;
     }
 
     void unlock() {locked_ = false;}
diff --git a/libcxx/test/std/thread/thread.mutex/thread.lock.algorithm/try_lock.pass.cpp b/libcxx/test/std/thread/thread.mutex/thread.lock.algorithm/try_lock.pass.cpp
--- a/libcxx/test/std/thread/thread.mutex/thread.lock.algorithm/try_lock.pass.cpp
+++ b/libcxx/test/std/thread/thread.mutex/thread.lock.algorithm/try_lock.pass.cpp
@@ -64,7 +64,6 @@
     bool try_lock()
     {
         TEST_THROW(1);
-        return locked_;
     }
 
     void unlock() {locked_ = false;}
diff --git a/libcxx/test/std/utilities/any/any.class/any.modifiers/emplace.pass.cpp b/libcxx/test/std/utilities/any/any.class/any.modifiers/emplace.pass.cpp
--- a/libcxx/test/std/utilities/any/any.class/any.modifiers/emplace.pass.cpp
+++ b/libcxx/test/std/utilities/any/any.class/any.modifiers/emplace.pass.cpp
@@ -27,6 +27,7 @@
 struct Tracked {
   static int count;
   Tracked()  {++count;}
+  Tracked(const Tracked&) = default;
   ~Tracked() { --count; }
 };
 int Tracked::count = 0;
diff --git a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp
--- a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace.pass.cpp
@@ -40,6 +40,7 @@
     static bool dtor_called;
     Y() = default;
     Y(int) { TEST_THROW(6);}
+    Y(const Y&) = default;
     ~Y() {dtor_called = true;}
 };
 
diff --git a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace_initializer_list.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace_initializer_list.pass.cpp
--- a/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace_initializer_list.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.object/optional.object.assign/emplace_initializer_list.pass.cpp
@@ -31,6 +31,7 @@
     constexpr X(int i, bool& dtor_called) : i_(i), dtor_called_(&dtor_called) {}
     constexpr X(std::initializer_list<int> il, bool& dtor_called)
     : i_(il.begin()[0]), j_(il.begin()[1]), dtor_called_(&dtor_called) {}
+    constexpr X(const X&) = default;
     TEST_CONSTEXPR_CXX20 ~X() {*dtor_called_ = true;}
 
     friend constexpr bool operator==(const X& x, const X& y)
@@ -57,6 +58,7 @@
 public:
     static bool dtor_called;
     Z() : i_(0) {}
+    Z(const Z&) = default;
     Z(int i) : i_(i) {}
     Z(std::initializer_list<int> il) : i_(il.begin()[0]), j_(il.begin()[1])
         { TEST_THROW(6);}
diff --git a/libcxx/test/std/utilities/optional/optional.object/optional.object.dtor/dtor.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/optional.object.dtor/dtor.pass.cpp
--- a/libcxx/test/std/utilities/optional/optional.object/optional.object.dtor/dtor.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.object/optional.object.dtor/dtor.pass.cpp
@@ -29,6 +29,7 @@
 public:
     static bool dtor_called;
     X() = default;
+    X(const X&) = default;
     ~X() {dtor_called = true;}
 };
 
diff --git a/libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp b/libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp
--- a/libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.object/optional.object.mod/reset.pass.cpp
@@ -23,6 +23,8 @@
 struct X
 {
     static bool dtor_called;
+    X() = default;
+    X(const X&) = default;
     ~X() {dtor_called = true;}
 };
 
diff --git a/libcxx/test/std/utilities/tuple/tuple.tuple/alloc_first.h b/libcxx/test/std/utilities/tuple/tuple.tuple/alloc_first.h
--- a/libcxx/test/std/utilities/tuple/tuple.tuple/alloc_first.h
+++ b/libcxx/test/std/utilities/tuple/tuple.tuple/alloc_first.h
@@ -22,6 +22,7 @@
     int data_;
 
     alloc_first() : data_(0) {}
+    alloc_first(const alloc_first&) = default;
     alloc_first(int d) : data_(d) {}
     alloc_first(std::allocator_arg_t, const A1<int>& a)
         : data_(0)
diff --git a/libcxx/test/std/utilities/tuple/tuple.tuple/alloc_last.h b/libcxx/test/std/utilities/tuple/tuple.tuple/alloc_last.h
--- a/libcxx/test/std/utilities/tuple/tuple.tuple/alloc_last.h
+++ b/libcxx/test/std/utilities/tuple/tuple.tuple/alloc_last.h
@@ -22,6 +22,7 @@
     int data_;
 
     alloc_last() : data_(0) {}
+    alloc_last(const alloc_last&) = default;
     alloc_last(int d) : data_(d) {}
     alloc_last(const A1<int>& a)
         : data_(0)
diff --git a/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.assign/convert_move.pass.cpp b/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.assign/convert_move.pass.cpp
--- a/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.assign/convert_move.pass.cpp
+++ b/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.assign/convert_move.pass.cpp
@@ -26,6 +26,8 @@
 struct B {
     int id_;
     explicit B(int i = 0) : id_(i) {}
+    B(const B&) = default;
+    B& operator=(const B&) = default;
     virtual ~B() {}
 };
 
diff --git a/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/convert_move.pass.cpp b/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/convert_move.pass.cpp
--- a/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/convert_move.pass.cpp
+++ b/libcxx/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/convert_move.pass.cpp
@@ -36,7 +36,7 @@
     int id_;
 
     explicit B(int i) : id_(i) {}
-
+    B(const B&) = default;
     virtual ~B() {}
 };
 
diff --git a/libcxx/test/std/utilities/variant/variant.visit/visit_return_type.pass.cpp b/libcxx/test/std/utilities/variant/variant.visit/visit_return_type.pass.cpp
--- a/libcxx/test/std/utilities/variant/variant.visit/visit_return_type.pass.cpp
+++ b/libcxx/test/std/utilities/variant/variant.visit/visit_return_type.pass.cpp
@@ -233,18 +233,18 @@
   }
 }
 
-void test_constexpr_void() {
+constexpr bool test_constexpr_void() {
   constexpr ReturnFirst obj{};
   constexpr ReturnArity aobj{};
   {
     using V = std::variant<int>;
     constexpr V v(42);
-    static_assert((std::visit<void>(obj, v), 42) == 42, "");
+    std::visit<void>(obj, v);
   }
   {
     using V = std::variant<short, long, char>;
     constexpr V v(42l);
-    static_assert((std::visit<void>(obj, v), 42) == 42, "");
+    std::visit<void>(obj, v);
   }
   {
     using V1 = std::variant<int>;
@@ -253,7 +253,7 @@
     constexpr V1 v1;
     constexpr V2 v2(nullptr);
     constexpr V3 v3;
-    static_assert((std::visit<void>(aobj, v1, v2, v3), 3) == 3, "");
+    std::visit<void>(aobj, v1, v2, v3);
   }
   {
     using V1 = std::variant<int>;
@@ -262,18 +262,20 @@
     constexpr V1 v1;
     constexpr V2 v2(nullptr);
     constexpr V3 v3;
-    static_assert((std::visit<void>(aobj, v1, v2, v3), 3) == 3, "");
+    std::visit<void>(aobj, v1, v2, v3);
   }
   {
     using V = std::variant<int, long, double, int *>;
     constexpr V v1(42l), v2(101), v3(nullptr), v4(1.1);
-    static_assert((std::visit<void>(aobj, v1, v2, v3, v4), 4) == 4, "");
+    std::visit<void>(aobj, v1, v2, v3, v4);
   }
   {
     using V = std::variant<int, long, double, long long, int *>;
     constexpr V v1(42l), v2(101), v3(nullptr), v4(1.1);
-    static_assert((std::visit<void>(aobj, v1, v2, v3, v4), 4) == 4, "");
+    std::visit<void>(aobj, v1, v2, v3, v4);
   }
+
+  return true;
 }
 
 void test_constexpr_int() {
@@ -504,7 +506,7 @@
   test_call_operator_forwarding<void>();
   test_argument_forwarding<void>();
   test_return_type<void>();
-  test_constexpr_void();
+  static_assert(test_constexpr_void());
   test_exceptions<void>();
   test_caller_accepts_nonconst<void>();
   test_call_operator_forwarding<int>();
diff --git a/libcxx/test/support/any_helpers.h b/libcxx/test/support/any_helpers.h
--- a/libcxx/test/support/any_helpers.h
+++ b/libcxx/test/support/any_helpers.h
@@ -286,7 +286,7 @@
         throwMyAnyExpression();
     }
 
-    small_throws_on_copy(small_throws_on_copy && other) throw() {
+    small_throws_on_copy(small_throws_on_copy && other) noexcept {
         value = other.value;
         ++count; ++moved;
     }
@@ -326,7 +326,7 @@
          throwMyAnyExpression();
     }
 
-    large_throws_on_copy(large_throws_on_copy && other) throw() {
+    large_throws_on_copy(large_throws_on_copy && other) noexcept {
         value = other.value;
         ++count; ++moved;
     }
diff --git a/libcxx/test/support/counting_predicates.h b/libcxx/test/support/counting_predicates.h
--- a/libcxx/test/support/counting_predicates.h
+++ b/libcxx/test/support/counting_predicates.h
@@ -18,6 +18,7 @@
     typedef bool result_type;
 
     unary_counting_predicate(Predicate p) : p_(p), count_(0) {}
+    unary_counting_predicate(const unary_counting_predicate&) = default;
     ~unary_counting_predicate() {}
 
     bool operator () (const Arg &a) const { ++count_; return p_(a); }
diff --git a/libcxx/test/support/deleter_types.h b/libcxx/test/support/deleter_types.h
--- a/libcxx/test/support/deleter_types.h
+++ b/libcxx/test/support/deleter_types.h
@@ -170,6 +170,8 @@
 public:
 
     CDeleter() : state_(0) {}
+    CDeleter(const CDeleter&) = default;
+    CDeleter& operator=(const CDeleter&) = default;
     explicit CDeleter(int s) : state_(s) {}
     ~CDeleter() {assert(state_ >= 0); state_ = -1;}
 
@@ -191,6 +193,8 @@
 public:
 
     CDeleter() : state_(0) {}
+    CDeleter(const CDeleter&) = default;
+    CDeleter& operator=(const CDeleter&) = default;
     explicit CDeleter(int s) : state_(s) {}
     template <class U>
         CDeleter(const CDeleter<U>& d)
diff --git a/libcxx/test/support/nasty_containers.h b/libcxx/test/support/nasty_containers.h
--- a/libcxx/test/support/nasty_containers.h
+++ b/libcxx/test/support/nasty_containers.h
@@ -41,6 +41,8 @@
 #if TEST_STD_VER >= 11
     nasty_vector(std::initializer_list<value_type> il) : v_(il) {}
 #endif
+    nasty_vector(const nasty_vector&) = default;
+    nasty_vector& operator=(const nasty_vector&) = default;
     ~nasty_vector() {}
 
     template <class InputIterator>
diff --git a/libcxx/utils/libcxx/test/params.py b/libcxx/utils/libcxx/test/params.py
--- a/libcxx/utils/libcxx/test/params.py
+++ b/libcxx/utils/libcxx/test/params.py
@@ -7,22 +7,38 @@
 #===----------------------------------------------------------------------===##
 
 from libcxx.test.dsl import *
-from libcxx.test.features import _isMSVC
+from libcxx.test.features import _isMSVC, _isClang
 import re
 
 _warningFlags = [
-  '-Werror',
   '-Wall',
+  '-Walloca',
+  '-Wcomma',
+  '-Wdeprecated',
   '-Wextra',
+  '-Werror',
   '-Wshadow',
   '-Wundef',
+  '-Wunreachable-code-aggressive',
+  '-Wvla',
+
+  # GCC doesn't support -Wno-gnu-include-next, so we can't enable -Wpedantic for it
+  lambda cfg: '-Wpedantic' if _isClang(cfg) else '',
+
+  # We use these extensions in the code base
+  '-Wno-gnu-include-next',
+  '-Wno-c11-extensions',
+  '-Wno-zero-length-array',
+
   '-Wno-unused-command-line-argument',
   '-Wno-attributes',
-  '-Wno-pessimizing-move',
-  '-Wno-c++11-extensions',
   '-Wno-noexcept-type',
   '-Wno-aligned-allocation-unavailable',
   '-Wno-atomic-alignment',
+  '-Wno-unused-local-typedef',
+
+  # We only support C++03 with Clang extensions
+  '-Wno-c++11-extensions',
 
   # GCC warns about places where we might want to add sized allocation/deallocation
   # functions, but we know better what we're doing/testing in the test suite.
@@ -39,8 +55,6 @@
   '-Wsign-compare',
   '-Wunused-variable',
   '-Wunused-parameter',
-  '-Wunreachable-code',
-  '-Wno-unused-local-typedef',
 ]
 
 _allStandards = ['c++03', 'c++11', 'c++14', 'c++17', 'c++20', 'c++2b']