diff --git a/libcxx/test/libcxx/strings/basic.string/string.modifiers/erase_iter_iter_db3.pass.cpp b/libcxx/test/libcxx/strings/basic.string/string.modifiers/erase_iter_iter_db3.pass.cpp
@@ -22,7 +22,7 @@
 #include "test_macros.h"
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     std::string l1("123");
@@ -43,8 +43,10 @@ int main()
 
 #else
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
 
 #endif
diff --git a/libcxx/test/libcxx/strings/basic.string/string.modifiers/erase_iter_iter_db4.pass.cpp b/libcxx/test/libcxx/strings/basic.string/string.modifiers/erase_iter_iter_db4.pass.cpp
@@ -22,7 +22,7 @@
 #include "test_macros.h"
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     std::string l1("123");
@@ -41,8 +41,10 @@ int main()
 
 #else
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
 
 #endif
diff --git a/libcxx/test/libcxx/strings/basic.string/string.modifiers/erase_pop_back_db1.pass.cpp b/libcxx/test/libcxx/strings/basic.string/string.modifiers/erase_pop_back_db1.pass.cpp
@@ -19,7 +19,7 @@
 
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
 #if _LIBCPP_DEBUG >= 1
     {
@@ -28,4 +28,6 @@ int main()
         assert(false);
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/basic.string/string.modifiers/insert_iter_char_db1.pass.cpp b/libcxx/test/libcxx/strings/basic.string/string.modifiers/insert_iter_char_db1.pass.cpp
@@ -19,7 +19,7 @@
 #include <cassert>
 
 
-int main()
+int main(int, char**)
 {
 #if _LIBCPP_DEBUG >= 1
     {
@@ -30,4 +30,6 @@ int main()
         assert(false);
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/basic.string/string.modifiers/insert_iter_size_char_db1.pass.cpp b/libcxx/test/libcxx/strings/basic.string/string.modifiers/insert_iter_size_char_db1.pass.cpp
@@ -17,7 +17,7 @@
 #include <string>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
 #if _LIBCPP_DEBUG >= 1
     {
@@ -27,4 +27,6 @@ int main()
         assert(false);
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/basic.string/string.modifiers/resize_default_initialized.pass.cpp b/libcxx/test/libcxx/strings/basic.string/string.modifiers/resize_default_initialized.pass.cpp
@@ -56,7 +56,9 @@ void test_basic() {
   }
 }
 
-int main() {
+int main(int, char**) {
   test_basic();
   test_buffer_usage();
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/c.strings/version_cctype.pass.cpp b/libcxx/test/libcxx/strings/c.strings/version_cctype.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/c.strings/version_cstring.pass.cpp b/libcxx/test/libcxx/strings/c.strings/version_cstring.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/c.strings/version_cuchar.pass.cpp b/libcxx/test/libcxx/strings/c.strings/version_cuchar.pass.cpp
@@ -16,6 +16,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/c.strings/version_cwchar.pass.cpp b/libcxx/test/libcxx/strings/c.strings/version_cwchar.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/c.strings/version_cwctype.pass.cpp b/libcxx/test/libcxx/strings/c.strings/version_cwctype.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/iterators.exceptions.pass.cpp b/libcxx/test/libcxx/strings/iterators.exceptions.pass.cpp
@@ -33,7 +33,7 @@ static const bool expected = false;
 static const bool expected = true;
 #endif
 
-int main()
+int main(int, char**)
 {
 //  basic tests
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<char *>::value), "");
@@ -84,4 +84,6 @@ int main()
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::initializer_list<char>::iterator>              ::value), "");
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::initializer_list<char>::const_iterator>        ::value), "");
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/iterators.noexcept.pass.cpp b/libcxx/test/libcxx/strings/iterators.noexcept.pass.cpp
@@ -30,7 +30,7 @@
 #include "test_macros.h"
 #include "test_iterators.h"
 
-int main()
+int main(int, char**)
 {
 //  basic tests
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<char *>::value), "");
@@ -77,4 +77,6 @@ int main()
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::initializer_list<char>::iterator>              ::value), "");
     static_assert(( std::__libcpp_string_gets_noexcept_iterator<std::initializer_list<char>::const_iterator>        ::value), "");
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/strings/version.pass.cpp b/libcxx/test/libcxx/strings/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/futures/futures.promise/set_exception.pass.cpp b/libcxx/test/libcxx/thread/futures/futures.promise/set_exception.pass.cpp
@@ -31,7 +31,7 @@
 #include <cassert>
 
 
-int main()
+int main(int, char**)
 {
     typedef std::__libcpp_debug_exception ExType;
     {
@@ -52,4 +52,6 @@ int main()
         } catch (ExType const&) {
         }
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/futures/futures.promise/set_exception_at_thread_exit.pass.cpp b/libcxx/test/libcxx/thread/futures/futures.promise/set_exception_at_thread_exit.pass.cpp
@@ -31,7 +31,7 @@
 #include <cassert>
 
 
-int main()
+int main(int, char**)
 {
     typedef std::__libcpp_debug_exception ExType;
     {
@@ -52,4 +52,6 @@ int main()
         } catch (ExType const& value) {
         }
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/futures/futures.task/types.pass.cpp b/libcxx/test/libcxx/thread/futures/futures.task/types.pass.cpp
@@ -24,7 +24,9 @@
 
 struct A {};
 
-int main()
+int main(int, char**)
 {
     static_assert((std::is_same<std::packaged_task<A(int, char)>::result_type, A>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/futures/version.pass.cpp b/libcxx/test/libcxx/thread/futures/version.pass.cpp
@@ -16,6 +16,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/...x/test/libcxx/thread/thread.condition/PR30202_notify_from_pthread_created_thread.pass.cpp b/...x/test/libcxx/thread/thread.condition/PR30202_notify_from_pthread_created_thread.pass.cpp
@@ -45,7 +45,7 @@ void* func(void*)
     return nullptr;
 }
 
-int main()
+int main(int, char**)
 {
     {
     std::unique_lock<std::mutex> lk(mut);
@@ -72,4 +72,6 @@ int main()
     assert(t1-t0 > ms(250));
     t.join();
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp b/libcxx/test/libcxx/thread/thread.condition/thread.condition.condvar/native_handle.pass.cpp
@@ -20,11 +20,13 @@
 #include <condition_variable>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     static_assert((std::is_same<std::condition_variable::native_handle_type,
                                 pthread_cond_t*>::value), "");
     std::condition_variable cv;
     std::condition_variable::native_handle_type h = cv.native_handle();
     assert(h != nullptr);
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.condition/version.pass.cpp b/libcxx/test/libcxx/thread/thread.condition/version.pass.cpp
@@ -16,6 +16,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/...ex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp b/...ex.requirements/thread.mutex.requirements.mutex/thread.mutex.class/native_handle.pass.cpp
@@ -20,9 +20,11 @@
 #include <mutex>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     std::mutex m;
     pthread_mutex_t* h = m.native_handle();
     assert(h);
+
+  return 0;
 }
diff --git a/...equirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp b/...equirements/thread.mutex.requirements.mutex/thread.mutex.recursive/native_handle.pass.cpp
@@ -20,9 +20,11 @@
 #include <mutex>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     std::recursive_mutex m;
     pthread_mutex_t* h = m.native_handle();
     assert(h);
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_annotations_not_enabled.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_annotations_not_enabled.pass.cpp
@@ -16,10 +16,12 @@
 
 #include <mutex>
 
-int main() {
+int main(int, char**) {
   std::mutex m;
   m.lock();
   {
     std::unique_lock<std::mutex> g(m, std::adopt_lock);
   }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_guard.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_guard.pass.cpp
@@ -32,8 +32,10 @@ static void scoped() {
 #endif
 }
 
-int main() {
+int main(int, char**) {
   scoped();
   std::lock_guard<std::mutex> lock(m);
   foo++;
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_unlock.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_lock_unlock.pass.cpp
@@ -23,8 +23,10 @@
 std::mutex m;
 int foo __attribute__((guarded_by(m)));
 
-int main() {
+int main(int, char**) {
   m.lock();
   foo++;
   m.unlock();
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_missing_unlock.fail.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_missing_unlock.fail.cpp
@@ -22,6 +22,8 @@
 
 std::mutex m;
 
-int main() {
+int main(int, char**) {
   m.lock();
+
+  return 0;
 } // expected-error {{mutex 'm' is still held at the end of function}}
diff --git a/libcxx/test/libcxx/thread/thread.mutex/thread_safety_requires_capability.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/thread_safety_requires_capability.pass.cpp
@@ -27,8 +27,10 @@ void increment() __attribute__((requires_capability(m))) {
   foo++;
 }
 
-int main() {
+int main(int, char**) {
   m.lock();
   increment();
   m.unlock();
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.mutex/version.pass.cpp b/libcxx/test/libcxx/thread/thread.mutex/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/...cxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp b/...cxx/thread/thread.threads/thread.thread.class/thread.thread.member/native_handle.pass.cpp
@@ -43,7 +43,7 @@ class G
 int G::n_alive = 0;
 bool G::op_run = false;
 
-int main()
+int main(int, char**)
 {
     {
         G g;
@@ -52,4 +52,6 @@ int main()
         assert(pid != 0);
         t0.join();
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp b/libcxx/test/libcxx/thread/thread.threads/thread.thread.class/types.pass.cpp
@@ -21,7 +21,9 @@
 #include <thread>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     static_assert((std::is_same<std::thread::native_handle_type, pthread_t>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.threads/thread.thread.this/sleep_for.pass.cpp b/libcxx/test/libcxx/thread/thread.threads/thread.thread.this/sleep_for.pass.cpp
@@ -34,7 +34,7 @@
 
 void sig_action(int) {}
 
-int main()
+int main(int, char**)
 {
     int ec;
     struct sigaction action;
@@ -64,4 +64,6 @@ int main()
     std::chrono::nanoseconds err = 5 * ms / 100;
     // The time slept is within 5% of 500ms
     assert(std::abs(ns.count()) < err.count());
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/thread/thread.threads/version.pass.cpp b/libcxx/test/libcxx/thread/thread.threads/version.pass.cpp
@@ -16,6 +16,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/type_traits/convert_to_integral.pass.cpp b/libcxx/test/libcxx/type_traits/convert_to_integral.pass.cpp
@@ -79,7 +79,7 @@ enum enum2 : unsigned long {
   value = std::numeric_limits<unsigned long>::max()
 };
 
-int main()
+int main(int, char**)
 {
   check_integral_types<bool, int>();
   check_integral_types<char, int>();
@@ -105,4 +105,6 @@ int main()
   check_enum_types<enum1, decltype(((Enum1UT)1) + 1)>();
   typedef std::underlying_type<enum2>::type Enum2UT;
   check_enum_types<enum2, decltype(((Enum2UT)1) + 1)>();
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/type_traits/lazy_metafunctions.pass.cpp b/libcxx/test/libcxx/type_traits/lazy_metafunctions.pass.cpp
@@ -128,9 +128,11 @@ void LazyOrTest() {
 }
 
 
-int main() {
+int main(int, char**) {
     LazyEnableIfTest();
     LazyNotTest();
     LazyAndTest();
     LazyOrTest();
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/any/size_and_alignment.pass.cpp b/libcxx/test/libcxx/utilities/any/size_and_alignment.pass.cpp
@@ -14,9 +14,11 @@
 
 #include <any>
 
-int main()
+int main(int, char**)
 {
     using std::any;
     static_assert(sizeof(any) == sizeof(void*)*4, "");
     static_assert(alignof(any) == alignof(void*), "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/any/small_type.pass.cpp b/libcxx/test/libcxx/utilities/any/small_type.pass.cpp
@@ -54,7 +54,7 @@ struct alignas(DoubleBufferAlignment) OverSizeAndAlignedType {
     char buff[BufferSize + 1];
 };
 
-int main()
+int main(int, char**)
 {
     using std::any;
     using std::__any_imp::_IsSmallObject;
@@ -110,4 +110,6 @@ int main()
         static_assert(alignof(T) > BufferAlignment, "");
         static_assert(!_IsSmallObject<T>::value, "");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/any/version.pass.cpp b/libcxx/test/libcxx/utilities/any/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/function.objects/func.require/bullet_1_2_3.pass.cpp b/libcxx/test/libcxx/utilities/function.objects/func.require/bullet_1_2_3.pass.cpp
@@ -271,7 +271,7 @@ void test_derived_from_ref_wrap() {
 }
 #endif
 
-int main() {
+int main(int, char**) {
     typedef void*& R;
     typedef ArgType A;
     TestCase<R(),                                   0, Q_None>::run();
@@ -367,4 +367,6 @@ int main() {
 
     test_derived_from_ref_wrap();
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/function.objects/func.require/bullet_4_5_6.pass.cpp b/libcxx/test/libcxx/utilities/function.objects/func.require/bullet_4_5_6.pass.cpp
@@ -206,10 +206,12 @@ struct TestCase {
 
 
 
-int main() {
+int main(int, char**) {
     TestCase<ArgType>::run();
     TestCase<ArgType const>::run();
     TestCase<ArgType volatile>::run();
     TestCase<ArgType const volatile>::run();
     TestCase<ArgType*>::run();
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/function.objects/func.require/bullet_7.pass.cpp b/libcxx/test/libcxx/utilities/function.objects/func.require/bullet_7.pass.cpp
@@ -247,7 +247,7 @@ void runTestCase() {
     runFunctorTestCase <Sig, Arity, LValueCaster, ArgCaster>();
 };
 
-int main() {
+int main(int, char**) {
     typedef void*& R;
     typedef ArgType A;
     typedef A const CA;
@@ -323,4 +323,6 @@ int main() {
     runFunctorTestCase11<R(A&&) const volatile &&, 1, MoveCVCaster,       MC>();
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/function.objects/func.require/invoke.pass.cpp b/libcxx/test/libcxx/utilities/function.objects/func.require/invoke.pass.cpp
@@ -31,7 +31,7 @@ struct Type
 #endif
 };
 
-int main()
+int main(int, char**)
 {
     static_assert(sizeof(std::__invoke(&Type::f1, std::declval<Type        >())) == 1, "");
     static_assert(sizeof(std::__invoke(&Type::f2, std::declval<Type const  >())) == 2, "");
@@ -41,4 +41,6 @@ int main()
     static_assert(sizeof(std::__invoke(&Type::g3, std::declval<Type      &&>())) == 3, "");
     static_assert(sizeof(std::__invoke(&Type::g4, std::declval<Type const&&>())) == 4, "");
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/function.objects/refwrap/binary.pass.cpp b/libcxx/test/libcxx/utilities/function.objects/refwrap/binary.pass.cpp
@@ -46,7 +46,7 @@ struct C
     typedef int result_type;
 };
 
-int main()
+int main(int, char**)
 {
     static_assert((!std::is_base_of<std::binary_function<int, char, int>,
                                     std::reference_wrapper<functor1> >::value), "");
@@ -76,4 +76,6 @@ int main()
                                    std::reference_wrapper<float(C::*)(int)> >::value), "");
     static_assert((std::is_base_of<std::binary_function<const volatile C*, int, float>,
                                    std::reference_wrapper<float(C::*)(int) const volatile> >::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/function.objects/refwrap/unary.pass.cpp b/libcxx/test/libcxx/utilities/function.objects/refwrap/unary.pass.cpp
@@ -46,7 +46,7 @@ struct C
     typedef int result_type;
 };
 
-int main()
+int main(int, char**)
 {
     static_assert((std::is_base_of<std::unary_function<int, char>,
                                    std::reference_wrapper<functor1> >::value), "");
@@ -74,4 +74,6 @@ int main()
                                    std::reference_wrapper<float(C::*)() const volatile> >::value), "");
     static_assert((!std::is_base_of<std::unary_function<C*, float>,
                                    std::reference_wrapper<float(C::*)(int)> >::value), "");
+
+  return 0;
 }
diff --git a/.../function.objects/unord.hash/murmur2_or_cityhash_ubsan_unsigned_overflow_ignored.pass.cpp b/.../function.objects/unord.hash/murmur2_or_cityhash_ubsan_unsigned_overflow_ignored.pass.cpp
@@ -28,7 +28,7 @@ void test(const void* key, int len) {
   }
 }
 
-int main() {
+int main(int, char**) {
   const std::string TestCases[] = {
       "abcdaoeuaoeclaoeoaeuaoeuaousaotehu]+}sthoasuthaoesutahoesutaohesutaoeusaoetuhasoetuhaoseutaoseuthaoesutaohes"
       "00000000000000000000000000000000000000000000000000000000000000000000000",
@@ -37,4 +37,6 @@ int main() {
   const size_t NumCases = sizeof(TestCases)/sizeof(TestCases[0]);
   for (size_t i=0; i < NumCases; ++i)
     test(TestCases[i].data(), TestCases[i].length());
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/function.objects/version.pass.cpp b/libcxx/test/libcxx/utilities/function.objects/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/memory/util.dynamic.safety/get_pointer_safety_cxx03.pass.cpp b/libcxx/test/libcxx/utilities/memory/util.dynamic.safety/get_pointer_safety_cxx03.pass.cpp
@@ -28,7 +28,7 @@ void test_pr26961() {
 }
 #endif
 
-int main()
+int main(int, char**)
 {
 #ifndef TEST_IS_UNSUPPORTED
   {
@@ -42,4 +42,6 @@ int main()
     test_pr26961();
   }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/memory/util.dynamic.safety/get_pointer_safety_new_abi.pass.cpp b/libcxx/test/libcxx/utilities/memory/util.dynamic.safety/get_pointer_safety_new_abi.pass.cpp
@@ -18,7 +18,7 @@
 #include <memory>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
   {
     static_assert(std::is_enum<std::pointer_safety>::value, "");
@@ -34,4 +34,6 @@ int main()
            r == std::pointer_safety::preferred ||
            r == std::pointer_safety::strict);
   }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/memory/util.smartptr/race_condition.pass.cpp b/libcxx/test/libcxx/utilities/memory/util.smartptr/race_condition.pass.cpp
@@ -77,7 +77,7 @@ void run_test(Ptr p) {
     assert(p.use_count() == 3);
 }
 
-int main() {
+int main(int, char**) {
   {
     // Test with out-of-place shared_count.
     Ptr p(new int(42));
@@ -91,4 +91,6 @@ int main() {
     run_test(p);
     assert(p.use_count() == 1);
   }
+
+  return 0;
 }
diff --git a/...tilities/memory/util.smartptr/util.smartptr.shared/function_type_default_deleter.fail.cpp b/...tilities/memory/util.smartptr/util.smartptr.shared/function_type_default_deleter.fail.cpp
@@ -29,7 +29,7 @@ struct Deleter {
   }
 };
 
-int main() {
+int main(int, char**) {
   {
     SPtr<0> s; // OK
     SPtr<1> s1(nullptr); // OK
@@ -41,4 +41,6 @@ int main() {
     SPtr<4> s4(getFn<4>()); // expected-note {{requested here}}
     SPtr<5> s5(getFn<5>(), std::default_delete<FnType<5>>{}); // expected-note {{requested here}}
   }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/memory/version.pass.cpp b/libcxx/test/libcxx/utilities/memory/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/meta/is_referenceable.pass.cpp b/libcxx/test/libcxx/utilities/meta/is_referenceable.pass.cpp
@@ -189,4 +189,6 @@ static_assert(( std::__is_referenceable<void (Foo::*)(int, float, Foo &, ...) &&
 static_assert(( std::__is_referenceable<void (Foo::*)(int, float, Foo &, ...) const &&>::value), "");
 #endif
 
-int main () {}
+int main(int, char**) {
+  return 0;
+}
diff --git a/...x/test/libcxx/utilities/meta/meta.unary/meta.unary.prop/__has_operator_addressof.pass.cpp b/...x/test/libcxx/utilities/meta/meta.unary/meta.unary.prop/__has_operator_addressof.pass.cpp
@@ -55,7 +55,7 @@ struct J
 };
 
 
-int main()
+int main(int, char**)
 {
     static_assert(std::__has_operator_addressof<int>::value == false, "");
     static_assert(std::__has_operator_addressof<A>::value == false, "");
@@ -65,4 +65,6 @@ int main()
     static_assert(std::__has_operator_addressof<G>::value == true, "");
     static_assert(std::__has_operator_addressof<H>::value == true, "");
     static_assert(std::__has_operator_addressof<J>::value == true, "");
+
+  return 0;
 }
diff --git a/...test/libcxx/utilities/meta/meta.unary/meta.unary.prop/missing_is_aggregate_trait.fail.cpp b/...test/libcxx/utilities/meta/meta.unary/meta.unary.prop/missing_is_aggregate_trait.fail.cpp
@@ -15,7 +15,7 @@
 
 #include <type_traits>
 
-int main ()
+int main(int, char**)
 {
 #ifdef _LIBCPP_HAS_NO_IS_AGGREGATE
   // This should not compile when _LIBCPP_HAS_NO_IS_AGGREGATE is defined.
@@ -24,4 +24,6 @@ int main ()
 #else
 #error Forcing failure...
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/meta/version.pass.cpp b/libcxx/test/libcxx/utilities/meta/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/optional/optional.object/optional.object.assign/copy.pass.cpp b/libcxx/test/libcxx/utilities/optional/optional.object/optional.object.assign/copy.pass.cpp
@@ -53,7 +53,7 @@ test()
     return true;
 }
 
-int main()
+int main(int, char**)
 {
     {
         using T = int;
@@ -70,4 +70,6 @@ int main()
 
     static_assert(!(std::is_copy_assignable<optional<Z1>>::value), "");
     static_assert(!(std::is_copy_assignable<optional<Z2>>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/optional/optional.object/optional.object.assign/move.pass.cpp b/libcxx/test/libcxx/utilities/optional/optional.object/optional.object.assign/move.pass.cpp
@@ -50,7 +50,7 @@ test()
     return true;
 }
 
-int main()
+int main(int, char**)
 {
     {
         using T = int;
@@ -67,4 +67,6 @@ int main()
 
     static_assert(!(std::is_move_assignable<optional<Z1>>::value), "");
     static_assert(!(std::is_move_assignable<optional<Z2>>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/optional/optional.object/optional.object.ctor/copy.pass.cpp b/libcxx/test/libcxx/utilities/optional/optional.object/optional.object.ctor/copy.pass.cpp
@@ -35,7 +35,7 @@ struct Z
     Z& operator=(const Z&) = delete;
 };
 
-int main()
+int main(int, char**)
 {
     {
         using T = int;
@@ -55,4 +55,6 @@ int main()
     static_assert(!(std::is_trivially_copy_constructible<optional<std::string>>::value), "");
 
     static_assert(!(std::is_copy_constructible<optional<Z>>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/optional/optional.object/optional.object.ctor/move.pass.cpp b/libcxx/test/libcxx/utilities/optional/optional.object/optional.object.ctor/move.pass.cpp
@@ -36,7 +36,7 @@ struct Z
     Z& operator=(const Z&) = delete;
 };
 
-int main()
+int main(int, char**)
 {
     {
         using T = int;
@@ -56,4 +56,6 @@ int main()
     static_assert(!(std::is_trivially_move_constructible<optional<std::string>>::value), "");
 
     static_assert(!(std::is_move_constructible<optional<Z>>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/optional/optional.object/triviality.abi.pass.cpp b/libcxx/test/libcxx/utilities/optional/optional.object/triviality.abi.pass.cpp
@@ -85,7 +85,7 @@ struct TrivialCopyNonTrivialMove {
     TrivialCopyNonTrivialMove& operator=(TrivialCopyNonTrivialMove&&) { return *this; }
 };
 
-int main()
+int main(int, char**)
 {
     sink(
         ImplicitTypes::ApplyTypes<DoTestsMetafunction>{},
@@ -94,4 +94,6 @@ int main()
         NonTrivialTypes::ApplyTypes<DoTestsMetafunction>{},
         DoTestsMetafunction<TrivialMoveNonTrivialCopy, TrivialCopyNonTrivialMove>{}
     );
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/optional/version.pass.cpp b/libcxx/test/libcxx/utilities/optional/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/ratio/version.pass.cpp b/libcxx/test/libcxx/utilities/ratio/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/template.bitset/includes.pass.cpp b/libcxx/test/libcxx/utilities/template.bitset/includes.pass.cpp
@@ -26,6 +26,8 @@
 #error <iosfwd> has not been included
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/template.bitset/version.pass.cpp b/libcxx/test/libcxx/utilities/template.bitset/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/time/date.time/asctime.thread-unsafe.fail.cpp b/libcxx/test/libcxx/utilities/time/date.time/asctime.thread-unsafe.fail.cpp
@@ -10,8 +10,10 @@
 
 #include <ctime>
 
-int main() {
+int main(int, char**) {
     // asctime is not thread-safe.
     std::time_t t = 0;
     std::asctime(&t);
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/time/date.time/ctime.thread-unsafe.fail.cpp b/libcxx/test/libcxx/utilities/time/date.time/ctime.thread-unsafe.fail.cpp
@@ -10,8 +10,10 @@
 
 #include <ctime>
 
-int main() {
+int main(int, char**) {
     // ctime is not thread-safe.
     std::time_t t = 0;
     std::ctime(&t);
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/time/date.time/gmtime.thread-unsafe.fail.cpp b/libcxx/test/libcxx/utilities/time/date.time/gmtime.thread-unsafe.fail.cpp
@@ -10,8 +10,10 @@
 
 #include <ctime>
 
-int main() {
+int main(int, char**) {
     // gmtime is not thread-safe.
     std::time_t t = 0;
     std::gmtime(&t);
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/time/date.time/localtime.thread-unsafe.fail.cpp b/libcxx/test/libcxx/utilities/time/date.time/localtime.thread-unsafe.fail.cpp
@@ -10,8 +10,10 @@
 
 #include <ctime>
 
-int main() {
+int main(int, char**) {
     // localtime is not thread-safe.
     std::time_t t = 0;
     std::localtime(&t);
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/time/version.pass.cpp b/libcxx/test/libcxx/utilities/time/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/tuple/tuple.tuple/empty_member.pass.cpp b/libcxx/test/libcxx/utilities/tuple/tuple.tuple/empty_member.pass.cpp
@@ -20,7 +20,7 @@ struct A {};
 
 struct B {};
 
-int main()
+int main(int, char**)
 {
     {
         typedef std::tuple<int, A> T;
@@ -42,4 +42,6 @@ int main()
         typedef std::tuple<int, A, B> T;
         static_assert((sizeof(T) == sizeof(int)), "");
     }
+
+  return 0;
 }
diff --git a/...xx/utilities/tuple/tuple.tuple/tuple.cnstr/PR20855_tuple_ref_binding_diagnostics.fail.cpp b/...xx/utilities/tuple/tuple.tuple/tuple.cnstr/PR20855_tuple_ref_binding_diagnostics.fail.cpp
@@ -43,7 +43,7 @@ template <class ...Args>
 void F(typename CannotDeduce<std::tuple<Args...>>::type const&) {}
 
 
-int main() {
+int main(int, char**) {
 #if TEST_HAS_BUILTIN_IDENTIFIER(__reference_binds_to_temporary)
   // Test that we emit our diagnostic from the library.
   // expected-error@tuple:* 8 {{"Attempted construction of reference element binds to a temporary whose lifetime has ended"}}
@@ -81,4 +81,6 @@ int main() {
 #error force failure
 // expected-error@-1 {{force failure}}
 #endif
+
+  return 0;
 }
diff --git a/...ies/tuple/tuple.tuple/tuple.cnstr/disable_reduced_arity_initialization_extension.pass.cpp b/...ies/tuple/tuple.tuple/tuple.cnstr/disable_reduced_arity_initialization_extension.pass.cpp
@@ -77,7 +77,7 @@ void test_example_from_docs() {
   assert(std::get<2>(tup) == std::error_code{});
 }
 
-int main()
+int main(int, char**)
 {
     {
         using E = MoveOnly;
@@ -104,4 +104,6 @@ int main()
     // constructor extensions.
     test_default_constructible_extension_sfinae();
     test_example_from_docs();
+
+  return 0;
 }
diff --git a/...ties/tuple/tuple.tuple/tuple.cnstr/enable_reduced_arity_initialization_extension.pass.cpp b/...ties/tuple/tuple.tuple/tuple.cnstr/enable_reduced_arity_initialization_extension.pass.cpp
@@ -89,7 +89,7 @@ void test_example_from_docs() {
   assert(std::get<2>(tup) == std::error_code{});
 }
 
-int main()
+int main(int, char**)
 {
 
     {
@@ -113,4 +113,6 @@ int main()
     // constructor extensions.
     test_default_constructible_extension_sfinae();
     test_example_from_docs();
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/tuple/version.pass.cpp b/libcxx/test/libcxx/utilities/tuple/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/type.index/version.pass.cpp b/libcxx/test/libcxx/utilities/type.index/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/__is_inplace_index.pass.cpp b/libcxx/test/libcxx/utilities/utility/__is_inplace_index.pass.cpp
@@ -14,7 +14,7 @@
 
 struct S {};
 
-int main() {
+int main(int, char**) {
   using I = std::in_place_index_t<0>;
   static_assert( std::__is_inplace_index<I>::value, "");
   static_assert( std::__is_inplace_index<const I>::value, "");
@@ -30,4 +30,6 @@ int main() {
   static_assert(!std::__is_inplace_index<void>::value, "");
   static_assert(!std::__is_inplace_index<int>::value, "");
   static_assert(!std::__is_inplace_index<S>::value, "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/__is_inplace_type.pass.cpp b/libcxx/test/libcxx/utilities/utility/__is_inplace_type.pass.cpp
@@ -14,7 +14,7 @@
 
 struct S {};
 
-int main() {
+int main(int, char**) {
   using T = std::in_place_type_t<int>;
   static_assert( std::__is_inplace_type<T>::value, "");
   static_assert( std::__is_inplace_type<const T>::value, "");
@@ -30,4 +30,6 @@ int main() {
   static_assert(!std::__is_inplace_type<void>::value, "");
   static_assert(!std::__is_inplace_type<int>::value, "");
   static_assert(!std::__is_inplace_type<S>::value, "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/U_V.pass.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/U_V.pass.cpp
@@ -37,7 +37,7 @@ struct ImplicitNothrowT {
     int value;
 };
 
-int main() {
+int main(int, char**) {
     { // explicit noexcept test
         static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>, int, int>::value, "");
         static_assert(!std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitT>, int, int>::value, "");
@@ -50,4 +50,6 @@ int main() {
         static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitNothrowT>, int, int>::value, "");
         static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>, int, int>::value, "");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/assign_tuple_like.pass.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/assign_tuple_like.pass.cpp
@@ -27,7 +27,7 @@
 #pragma clang diagnostic ignored "-Wmissing-braces"
 #endif
 
-int main()
+int main(int, char**)
 {
     using C = TestTypes::TestType;
     {
@@ -100,4 +100,6 @@ int main()
        assert(p.first.value == 42);
        assert(p.second.value == -42);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/const_first_const_second.pass.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/const_first_const_second.pass.cpp
@@ -37,7 +37,7 @@ struct ImplicitNothrowT {
     ImplicitNothrowT(ImplicitNothrowT const&) noexcept {}
 };
 
-int main() {
+int main(int, char**) {
     { // explicit noexcept test
         static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>,
                                                      ExplicitT const&, ExplicitT const&>::value, "");
@@ -58,4 +58,6 @@ int main() {
         static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>,
                                                      ImplicitNothrowT const&, ImplicitNothrowT const&>::value, "");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/const_pair_U_V.pass.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/const_pair_U_V.pass.cpp
@@ -39,7 +39,7 @@ struct ImplicitNothrowT {
     int value;
 };
 
-int main() {
+int main(int, char**) {
     { // explicit noexcept test
         static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>,
                                                      std::pair<int, int> const&>::value, "");
@@ -60,4 +60,6 @@ int main() {
         static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>,
                                                      std::pair<int, int> const&>::value, "");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/default.pass.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/default.pass.cpp
@@ -26,10 +26,12 @@ struct NonThrowingDefault {
   NonThrowingDefault() noexcept { }
 };
 
-int main() {
+int main(int, char**) {
 
     static_assert(!std::is_nothrow_default_constructible<std::pair<ThrowingDefault, ThrowingDefault>>::value, "");
     static_assert(!std::is_nothrow_default_constructible<std::pair<NonThrowingDefault, ThrowingDefault>>::value, "");
     static_assert(!std::is_nothrow_default_constructible<std::pair<ThrowingDefault, NonThrowingDefault>>::value, "");
     static_assert( std::is_nothrow_default_constructible<std::pair<NonThrowingDefault, NonThrowingDefault>>::value, "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/non_trivial_copy_move_ABI.pass.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/non_trivial_copy_move_ABI.pass.cpp
@@ -158,7 +158,8 @@ void test_layout() {
     static_assert(offsetof(PairT, first) == 0, "");
 }
 
-int main() {
+int main(int, char**) {
     test_trivial();
     test_layout();
+    return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/pair.tuple_element.fail.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/pair.tuple_element.fail.cpp
@@ -14,11 +14,13 @@
 
 #include <utility>
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::pair<int, double> P;
     std::tuple_element<2, P>::type foo; // expected-note {{requested here}}
         // expected-error-re@utility:* {{static_assert failed{{( due to requirement '2U[L]{0,2} < 2')?}} "Index out of bounds in std::tuple_element<std::pair<T1, T2>>"}}
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/piecewise.pass.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/piecewise.pass.cpp
@@ -23,7 +23,7 @@
 #include "archetypes.hpp"
 
 
-int main() {
+int main(int, char**) {
     using NonThrowingConvert = NonThrowingTypes::ConvertingType;
     using ThrowingConvert = NonTrivialTypes::ConvertingType;
     static_assert(!std::is_nothrow_constructible<std::pair<ThrowingConvert, ThrowingConvert>,
@@ -34,4 +34,6 @@ int main() {
                                                  std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
     static_assert( std::is_nothrow_constructible<std::pair<NonThrowingConvert, NonThrowingConvert>,
                                                  std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/rv_pair_U_V.pass.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/rv_pair_U_V.pass.cpp
@@ -38,7 +38,7 @@ struct ImplicitNothrowT {
     int value;
 };
 
-int main() {
+int main(int, char**) {
     { // explicit noexcept test
         static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>,
                                                      std::pair<int, int>&&>::value, "");
@@ -59,4 +59,6 @@ int main() {
         static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>,
                                                      std::pair<int, int>&&>::value, "");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/trivial_copy_move_ABI.pass.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/trivial_copy_move_ABI.pass.cpp
@@ -153,7 +153,8 @@ void test_layout() {
     static_assert(offsetof(PairT, first) == 0, "");
 }
 
-int main() {
+int main(int, char**) {
     test_trivial();
     test_layout();
+    return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/utility/version.pass.cpp b/libcxx/test/libcxx/utilities/utility/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/...test/libcxx/utilities/variant/variant.variant/variant.helper/variant_alternative.fail.cpp b/...test/libcxx/utilities/variant/variant.variant/variant.helper/variant_alternative.fail.cpp
@@ -25,11 +25,13 @@
 #include <cassert>
 
 
-int main()
+int main(int, char**)
 {
     {
         typedef std::variant<int, double> T;
         std::variant_alternative<2, T>::type foo; // expected-note {{requested here}}
         // expected-error-re@variant:* {{static_assert failed{{( due to requirement '2U[L]{0,2} < sizeof...\(_Types\)')?}} "Index out of bounds in std::variant_alternative<>"}}
     }
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/variant/variant.variant/variant_size.pass.cpp b/libcxx/test/libcxx/utilities/variant/variant.variant/variant_size.pass.cpp
@@ -59,10 +59,12 @@ void test_index_internals() {
   static_assert(std::__variant_npos<IndexT> == IndexLim::max(), "");
 }
 
-int main() {
+int main(int, char**) {
   test_index_type<unsigned char>();
   // This won't compile due to template depth issues.
   //test_index_type<unsigned short>();
   test_index_internals<unsigned char>();
   test_index_internals<unsigned short>();
+
+  return 0;
 }
diff --git a/libcxx/test/libcxx/utilities/variant/version.pass.cpp b/libcxx/test/libcxx/utilities/variant/version.pass.cpp
@@ -14,6 +14,8 @@
 #error _LIBCPP_VERSION not defined
 #endif
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/nothing_to_do.pass.cpp b/libcxx/test/nothing_to_do.pass.cpp
@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.c.library/tested_elsewhere.pass.cpp b/libcxx/test/std/algorithms/alg.c.library/tested_elsewhere.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy.pass.cpp
@@ -46,7 +46,7 @@ test()
         assert(ia[i] == ib[i]);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<int*> >();
@@ -86,4 +86,6 @@ int main()
 // #if TEST_STD_VER > 17
 //     static_assert(test_constexpr());
 // #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_backward.pass.cpp
@@ -49,7 +49,7 @@ test()
         assert(ia[i] == ib[i]);
 }
 
-int main()
+int main(int, char**)
 {
     test<bidirectional_iterator<const int*>, bidirectional_iterator<int*> >();
     test<bidirectional_iterator<const int*>, random_access_iterator<int*> >();
@@ -66,4 +66,6 @@ int main()
 // #if TEST_STD_VER > 17
 //     static_assert(test_constexpr());
 // #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_if.pass.cpp
@@ -53,7 +53,7 @@ test()
         assert(ib[i] % 3 == 0);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<int*> >();
@@ -93,4 +93,6 @@ int main()
 // #if TEST_STD_VER > 17
 //     static_assert(test_constexpr());
 // #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.copy/copy_n.pass.cpp
@@ -49,7 +49,7 @@ test()
         assert(ia[i] == ib[i]);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<int*> >();
@@ -89,4 +89,6 @@ int main()
 // #if TEST_STD_VER > 17
 //     static_assert(test_constexpr());
 // #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill.pass.cpp
@@ -56,7 +56,7 @@ test_int()
     assert(ia[3] == 1);
 }
 
-int main()
+int main(int, char**)
 {
     test_char<forward_iterator<char*> >();
     test_char<bidirectional_iterator<char*> >();
@@ -71,4 +71,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill_n.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.fill/fill_n.pass.cpp
@@ -148,7 +148,7 @@ void test6()
 }
 
 
-int main()
+int main(int, char**)
 {
     test_char<forward_iterator<char*> >();
     test_char<bidirectional_iterator<char*> >();
@@ -170,4 +170,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate.pass.cpp
@@ -51,7 +51,7 @@ test()
     assert(ia[3] == 1);
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*> >();
     test<bidirectional_iterator<int*> >();
@@ -61,4 +61,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate_n.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.generate/generate_n.pass.cpp
@@ -74,7 +74,7 @@ test()
     test2<Iter, long double>();
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*> >();
     test<bidirectional_iterator<int*> >();
@@ -84,4 +84,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move.pass.cpp
@@ -54,7 +54,7 @@ test1()
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<int*> >();
@@ -127,4 +127,6 @@ int main()
     test1<std::unique_ptr<int>*, random_access_iterator<std::unique_ptr<int>*> >();
     test1<std::unique_ptr<int>*, std::unique_ptr<int>*>();
 #endif // TEST_STD_VER >= 11
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move_backward.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move_backward.pass.cpp
@@ -54,7 +54,7 @@ test1()
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     test<bidirectional_iterator<const int*>, bidirectional_iterator<int*> >();
     test<bidirectional_iterator<const int*>, random_access_iterator<int*> >();
@@ -81,4 +81,6 @@ int main()
     test1<std::unique_ptr<int>*, random_access_iterator<std::unique_ptr<int>*> >();
     test1<std::unique_ptr<int>*, std::unique_ptr<int>*>();
 #endif // TEST_STD_VER >= 11
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/is_partitioned.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/is_partitioned.pass.cpp
@@ -35,7 +35,7 @@ TEST_CONSTEXPR bool test_constexpr() {
 #endif
 
 
-int main() {
+int main(int, char**) {
   {
     const int ia[] = {1, 2, 3, 4, 5, 6};
     unary_counting_predicate<is_odd, int> pred((is_odd()));
@@ -94,4 +94,6 @@ int main() {
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/partition.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/partition.pass.cpp
@@ -93,9 +93,11 @@ test()
         assert(!is_odd()(*i));
 }
 
-int main()
+int main(int, char**)
 {
     test<bidirectional_iterator<int*> >();
     test<random_access_iterator<int*> >();
     test<int*>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/partition_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/partition_copy.pass.cpp
@@ -43,7 +43,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
         const int ia[] = {1, 2, 3, 4, 6, 8, 5, 7};
@@ -68,4 +68,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/partition_point.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/partition_point.pass.cpp
@@ -35,7 +35,7 @@ TEST_CONSTEXPR bool test_constexpr() {
 #endif
 
 
-int main()
+int main(int, char**)
 {
     {
         const int ia[] = {2, 4, 6, 8, 10};
@@ -89,4 +89,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/stable_partition.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.partitions/stable_partition.pass.cpp
@@ -301,7 +301,7 @@ test1()
 
 #endif  // TEST_STD_VER >= 11
 
-int main()
+int main(int, char**)
 {
     test<bidirectional_iterator<std::pair<int,int>*> >();
     test<random_access_iterator<std::pair<int,int>*> >();
@@ -310,4 +310,6 @@ int main()
 #if TEST_STD_VER >= 11
     test1<bidirectional_iterator<std::unique_ptr<int>*> >();
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.fail.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.fail.cpp
@@ -32,9 +32,11 @@ template <class PopulationIterator, class SampleIterator> void test() {
                             SampleIterator(oa), os, g);
 }
 
-int main() {
+int main(int, char**) {
   // expected-error-re@algorithm:* {{static_assert failed{{( due to requirement '.*')?}} "SampleIterator must meet the requirements of RandomAccessIterator"}}
   // expected-error@algorithm:* 2 {{does not provide a subscript operator}}
   // expected-error@algorithm:* {{invalid operands}}
   test<input_iterator<int *>, output_iterator<int *> >();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.pass.cpp
@@ -136,7 +136,7 @@ void test_small_population() {
   }
 }
 
-int main() {
+int main(int, char**) {
   test<input_iterator, int, random_access_iterator, int>();
   test<forward_iterator, int, output_iterator, int>();
   test<forward_iterator, int, random_access_iterator, int>();
@@ -156,4 +156,6 @@ int main() {
   test_small_population<input_iterator, int, random_access_iterator, int>();
   test_small_population<forward_iterator, int, output_iterator, int>();
   test_small_population<forward_iterator, int, random_access_iterator, int>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.stable.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.stable.pass.cpp
@@ -48,7 +48,9 @@ void test_stability(bool expect_stable) {
   assert(expect_stable == !unstable);
 }
 
-int main() {
+int main(int, char**) {
   test_stability<forward_iterator<int *>, output_iterator<int *> >(true);
   test_stability<input_iterator<int *>, random_access_iterator<int *> >(false);
+
+  return 0;
 }
diff --git a/...x/test/std/algorithms/alg.modifying.operations/alg.random.shuffle/random_shuffle.pass.cpp b/...x/test/std/algorithms/alg.modifying.operations/alg.random.shuffle/random_shuffle.pass.cpp
@@ -39,7 +39,7 @@ test_with_iterator()
 }
 
 
-int main()
+int main(int, char**)
 {
     int ia[]  = {1, 2, 3, 4};
     int ia1[] = {1, 4, 3, 2};
@@ -57,4 +57,5 @@ int main()
     test_with_iterator<random_access_iterator<int*> >();
     test_with_iterator<int*>();
 
+  return 0;
 }
diff --git a/...t/std/algorithms/alg.modifying.operations/alg.random.shuffle/random_shuffle_rand.pass.cpp b/...t/std/algorithms/alg.modifying.operations/alg.random.shuffle/random_shuffle_rand.pass.cpp
@@ -51,8 +51,9 @@ test_with_iterator()
 }
 
 
-int main()
+int main(int, char**)
 {
     test_with_iterator<random_access_iterator<int*> >();
     test_with_iterator<int*>();
-}
+    return 0;
+}
diff --git a/...t/std/algorithms/alg.modifying.operations/alg.random.shuffle/random_shuffle_urng.pass.cpp b/...t/std/algorithms/alg.modifying.operations/alg.random.shuffle/random_shuffle_urng.pass.cpp
@@ -18,7 +18,7 @@
 
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
     int ia[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
     int ia1[] = {2, 7, 1, 4, 3, 6, 5, 10, 9, 8};
@@ -31,4 +31,6 @@ int main()
     std::shuffle(ia, ia+sa, std::move(g));
     LIBCPP_ASSERT(std::equal(ia, ia+sa, ia2));
     assert(std::is_permutation(ia, ia+sa, ia2));
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.remove/remove.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.remove/remove.pass.cpp
@@ -73,7 +73,7 @@ test1()
 }
 #endif // TEST_STD_VER >= 11
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*> >();
     test<bidirectional_iterator<int*> >();
@@ -90,4 +90,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.remove/remove_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.remove/remove_copy.pass.cpp
@@ -50,7 +50,7 @@ test()
     assert(ib[5] == 4);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, forward_iterator<int*> >();
@@ -85,4 +85,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.remove/remove_copy_if.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.remove/remove_copy_if.pass.cpp
@@ -55,7 +55,7 @@ test()
     assert(ib[5] == 4);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, forward_iterator<int*> >();
@@ -90,4 +90,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.remove/remove_if.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.remove/remove_if.pass.cpp
@@ -88,7 +88,7 @@ test1()
 }
 #endif // TEST_STD_VER >= 11
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*> >();
     test<bidirectional_iterator<int*> >();
@@ -105,4 +105,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.replace/replace.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.replace/replace.pass.cpp
@@ -47,7 +47,7 @@ test()
     assert(ia[4] == 4);
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*> >();
     test<bidirectional_iterator<int*> >();
@@ -57,4 +57,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.replace/replace_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.replace/replace_copy.pass.cpp
@@ -54,7 +54,7 @@ test()
     assert(ib[4] == 4);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, forward_iterator<int*> >();
@@ -89,4 +89,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.replace/replace_copy_if.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.replace/replace_copy_if.pass.cpp
@@ -58,7 +58,7 @@ test()
     assert(ib[4] == 4);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, forward_iterator<int*> >();
@@ -93,4 +93,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.replace/replace_if.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.replace/replace_if.pass.cpp
@@ -50,7 +50,7 @@ test()
     assert(ia[4] == 4);
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*> >();
     test<bidirectional_iterator<int*> >();
@@ -60,4 +60,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.reverse/reverse.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.reverse/reverse.pass.cpp
@@ -51,9 +51,11 @@ test()
     assert(id[3] == 0);
 }
 
-int main()
+int main(int, char**)
 {
     test<bidirectional_iterator<int*> >();
     test<random_access_iterator<int*> >();
     test<int*>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.reverse/reverse_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.reverse/reverse_copy.pass.cpp
@@ -72,7 +72,7 @@ test()
     assert(jd[3] == 0);
 }
 
-int main()
+int main(int, char**)
 {
     test<bidirectional_iterator<const int*>, output_iterator<int*> >();
     test<bidirectional_iterator<const int*>, forward_iterator<int*> >();
@@ -95,4 +95,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.rotate/rotate.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.rotate/rotate.pass.cpp
@@ -419,7 +419,7 @@ test1()
 
 #endif  // TEST_STD_VER >= 11
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*> >();
     test<bidirectional_iterator<int*> >();
@@ -434,4 +434,6 @@ int main()
     test1<std::unique_ptr<int>*>();
 
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.rotate/rotate_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.rotate/rotate_copy.pass.cpp
@@ -128,7 +128,7 @@ test()
     assert(ib[3] == 3);
 }
 
-int main()
+int main(int, char**)
 {
     test<bidirectional_iterator<const int*>, output_iterator<int*> >();
     test<bidirectional_iterator<const int*>, forward_iterator<int*> >();
@@ -151,4 +151,6 @@ int main()
 // #if TEST_STD_VER > 17
 //    static_assert(test_constexpr());
 // #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.swap/iter_swap.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.swap/iter_swap.pass.cpp
@@ -16,11 +16,13 @@
 #include <algorithm>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     int i = 1;
     int j = 2;
     std::iter_swap(&i, &j);
     assert(i == 2);
     assert(j == 1);
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.swap/swap_ranges.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.swap/swap_ranges.pass.cpp
@@ -105,7 +105,7 @@ void test2()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*>, forward_iterator<int*> >();
     test<forward_iterator<int*>, bidirectional_iterator<int*> >();
@@ -150,4 +150,6 @@ int main()
 #endif // TEST_STD_VER >= 11
 
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/binary_transform.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/binary_transform.pass.cpp
@@ -56,7 +56,7 @@ test()
     assert(ib[4] == 1);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<const int*>, input_iterator<int*> >();
@@ -236,4 +236,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/unary_transform.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.transform/unary_transform.pass.cpp
@@ -57,7 +57,7 @@ test()
     assert(ib[4] == 5);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<int*> >();
@@ -97,4 +97,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique.pass.cpp
@@ -181,7 +181,7 @@ test1()
 }
 #endif // TEST_STD_VER >= 11
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*> >();
     test<bidirectional_iterator<int*> >();
@@ -198,4 +198,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy.pass.cpp
@@ -105,7 +105,7 @@ test()
     assert(ji[2] == 2);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, forward_iterator<int*> >();
@@ -140,4 +140,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy_pred.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_copy_pred.pass.cpp
@@ -133,7 +133,7 @@ test()
     assert(count_equal::count == si-1);
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, forward_iterator<int*> >();
@@ -168,4 +168,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_pred.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/unique_pred.pass.cpp
@@ -223,7 +223,7 @@ test1()
 }
 #endif // TEST_STD_VER >= 11
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<int*> >();
     test<bidirectional_iterator<int*> >();
@@ -240,4 +240,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/nothing_to_do.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/nothing_to_do.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.adjacent.find/adjacent_find.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.adjacent.find/adjacent_find.pass.cpp
@@ -30,7 +30,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 2, 0, 1, 2, 3};
     const unsigned sa = sizeof(ia)/sizeof(ia[0]);
@@ -47,4 +47,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.adjacent.find/adjacent_find_pred.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.adjacent.find/adjacent_find_pred.pass.cpp
@@ -34,7 +34,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 2, 0, 1, 2, 3};
     const unsigned sa = sizeof(ia)/sizeof(ia[0]);
@@ -54,4 +54,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.all_of/all_of.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.all_of/all_of.pass.cpp
@@ -36,7 +36,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
         int ia[] = {2, 4, 6, 8};
@@ -58,4 +58,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.any_of/any_of.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.any_of/any_of.pass.cpp
@@ -36,7 +36,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
         int ia[] = {2, 4, 6, 8};
@@ -66,4 +66,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.count/count.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.count/count.pass.cpp
@@ -29,7 +29,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 2, 0, 1, 2, 3};
     const unsigned sa = sizeof(ia)/sizeof(ia[0]);
@@ -43,4 +43,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.count/count_if.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.count/count_if.pass.cpp
@@ -36,7 +36,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 2, 0, 1, 2, 3};
     const unsigned sa = sizeof(ia)/sizeof(ia[0]);
@@ -53,4 +53,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/equal.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/equal.pass.cpp
@@ -44,7 +44,7 @@ TEST_CONSTEXPR bool test_constexpr() {
 #endif
 
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 3, 4, 5};
     const unsigned s = sizeof(ia)/sizeof(ia[0]);
@@ -88,4 +88,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/equal_pred.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.equal/equal_pred.pass.cpp
@@ -58,7 +58,7 @@ bool counting_equals ( const T &a, const T &b ) {
     return a == b;
 }
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 3, 4, 5};
     const unsigned s = sizeof(ia)/sizeof(ia[0]);
@@ -114,4 +114,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.find.end/find_end.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.find.end/find_end.pass.cpp
@@ -62,7 +62,7 @@ test()
     assert(std::find_end(Iter1(ia), Iter1(ia), Iter2(b), Iter2(b+1)) == Iter1(ia));
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*>, forward_iterator<const int*> >();
     test<forward_iterator<const int*>, bidirectional_iterator<const int*> >();
@@ -77,4 +77,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.find.end/find_end_pred.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.find.end/find_end_pred.pass.cpp
@@ -92,7 +92,7 @@ test()
     assert(count_equal::count <= 0);
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*>, forward_iterator<const int*> >();
     test<forward_iterator<const int*>, bidirectional_iterator<const int*> >();
@@ -107,4 +107,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.find.first.of/find_first_of.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.find.first.of/find_first_of.pass.cpp
@@ -38,7 +38,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 3, 0, 1, 2, 3};
     const unsigned sa = sizeof(ia)/sizeof(ia[0]);
@@ -69,4 +69,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.find.first.of/find_first_of_pred.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.find.first.of/find_first_of_pred.pass.cpp
@@ -40,7 +40,7 @@ constexpr bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 3, 0, 1, 2, 3};
     const unsigned sa = sizeof(ia)/sizeof(ia[0]);
@@ -75,4 +75,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.find/find.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.find/find.pass.cpp
@@ -29,7 +29,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 3, 4, 5};
     const unsigned s = sizeof(ia)/sizeof(ia[0]);
@@ -42,4 +42,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.find/find_if.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.find/find_if.pass.cpp
@@ -37,7 +37,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 3, 4, 5};
     const unsigned s = sizeof(ia)/sizeof(ia[0]);
@@ -53,4 +53,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.find/find_if_not.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.find/find_if_not.pass.cpp
@@ -37,7 +37,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 3, 4, 5};
     const unsigned s = sizeof(ia)/sizeof(ia[0]);
@@ -53,4 +53,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.foreach/for_each_n.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.foreach/for_each_n.pass.cpp
@@ -40,7 +40,7 @@ struct for_each_test
     void operator()(int& i) {++i; ++count;}
 };
 
-int main()
+int main(int, char**)
 {
     typedef input_iterator<int*> Iter;
     int ia[] = {0, 1, 2, 3, 4, 5};
@@ -76,4 +76,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.foreach/test.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.foreach/test.pass.cpp
@@ -37,7 +37,7 @@ struct for_each_test
     void operator()(int& i) {++i; ++count;}
 };
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 3, 4, 5};
     const unsigned s = sizeof(ia)/sizeof(ia[0]);
@@ -51,4 +51,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.is_permutation/is_permutation.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.is_permutation/is_permutation.pass.cpp
@@ -35,7 +35,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
         const int ia[] = {0};
@@ -618,4 +618,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.is_permutation/is_permutation_pred.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.is_permutation/is_permutation_pred.pass.cpp
@@ -55,7 +55,7 @@ struct eq {
 };
 
 
-int main()
+int main(int, char**)
 {
     {
         const int ia[] = {0};
@@ -769,4 +769,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.none_of/none_of.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.none_of/none_of.pass.cpp
@@ -36,7 +36,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
         int ia[] = {2, 4, 6, 8};
@@ -66,4 +66,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.search/search.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.search/search.pass.cpp
@@ -95,7 +95,7 @@ test()
     assert(std::search(Iter1(ij), Iter1(ij+sj), Iter2(ik), Iter2(ik+sk)) == Iter1(ij+6));
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*>, forward_iterator<const int*> >();
     test<forward_iterator<const int*>, bidirectional_iterator<const int*> >();
@@ -121,4 +121,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.search/search_n.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.search/search_n.pass.cpp
@@ -79,7 +79,7 @@ test()
     (void)std::search_n(Iter(ic), Iter(ic+sc), UserDefinedIntegral<unsigned>(0), 0);
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*> >();
     test<bidirectional_iterator<const int*> >();
@@ -88,4 +88,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.search/search_n_pred.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.search/search_n_pred.pass.cpp
@@ -158,7 +158,7 @@ test()
     count_equal::count = 0;
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*> >();
     test<bidirectional_iterator<const int*> >();
@@ -167,4 +167,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.search/search_pred.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.search/search_pred.pass.cpp
@@ -110,7 +110,7 @@ test()
     assert(count_equal::count <= sh*3);
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*>, forward_iterator<const int*> >();
     test<forward_iterator<const int*>, bidirectional_iterator<const int*> >();
@@ -125,4 +125,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/mismatch/mismatch.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/mismatch/mismatch.pass.cpp
@@ -58,7 +58,7 @@ TEST_CONSTEXPR bool test_constexpr() {
     }
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 2, 0, 1, 2, 3};
     const unsigned sa = sizeof(ia)/sizeof(ia[0]);
@@ -89,4 +89,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/mismatch/mismatch_pred.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/mismatch/mismatch_pred.pass.cpp
@@ -68,7 +68,7 @@ TEST_CONSTEXPR bool test_constexpr() {
 #define HAS_FOUR_ITERATOR_VERSION
 #endif
 
-int main()
+int main(int, char**)
 {
     int ia[] = {0, 1, 2, 2, 0, 1, 2, 3};
     const unsigned sa = sizeof(ia)/sizeof(ia[0]);
@@ -114,4 +114,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/nothing_to_do.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/nothing_to_do.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/...xx/test/std/algorithms/alg.sorting/alg.binary.search/binary.search/binary_search.pass.cpp b/...xx/test/std/algorithms/alg.sorting/alg.binary.search/binary.search/binary_search.pass.cpp
@@ -61,7 +61,7 @@ test()
     test(Iter(v.data()), Iter(v.data()+v.size()), M, false);
 }
 
-int main()
+int main(int, char**)
 {
     int d[] = {0, 2, 4, 6};
     for (int* e = d; e <= d+4; ++e)
@@ -76,4 +76,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/...st/std/algorithms/alg.sorting/alg.binary.search/binary.search/binary_search_comp.pass.cpp b/...st/std/algorithms/alg.sorting/alg.binary.search/binary.search/binary_search_comp.pass.cpp
@@ -62,7 +62,7 @@ test()
     test(Iter(v.data()), Iter(v.data()+v.size()), M, false);
 }
 
-int main()
+int main(int, char**)
 {
     int d[] = {6, 4, 2, 0};
     for (int* e = d; e <= d+4; ++e)
@@ -77,4 +77,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.binary.search/equal.range/equal_range.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.binary.search/equal.range/equal_range.pass.cpp
@@ -69,7 +69,7 @@ test()
         test(Iter(v.data()), Iter(v.data()+v.size()), x);
 }
 
-int main()
+int main(int, char**)
 {
     int d[] = {0, 1, 2, 3};
     for (int* e = d; e <= d+4; ++e)
@@ -84,4 +84,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/...x/test/std/algorithms/alg.sorting/alg.binary.search/equal.range/equal_range_comp.pass.cpp b/...x/test/std/algorithms/alg.sorting/alg.binary.search/equal.range/equal_range_comp.pass.cpp
@@ -68,7 +68,7 @@ test()
         test(Iter(v.data()), Iter(v.data()+v.size()), x);
 }
 
-int main()
+int main(int, char**)
 {
     int d[] = {3, 2, 1, 0};
     for (int* e = d; e <= d+4; ++e)
@@ -83,4 +83,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.binary.search/lower.bound/lower_bound.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.binary.search/lower.bound/lower_bound.pass.cpp
@@ -64,7 +64,7 @@ test()
         test(Iter(v.data()), Iter(v.data()+v.size()), x);
 }
 
-int main()
+int main(int, char**)
 {
     int d[] = {0, 1, 2, 3};
     for (int* e = d; e <= d+4; ++e)
@@ -79,4 +79,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/...x/test/std/algorithms/alg.sorting/alg.binary.search/lower.bound/lower_bound_comp.pass.cpp b/...x/test/std/algorithms/alg.sorting/alg.binary.search/lower.bound/lower_bound_comp.pass.cpp
@@ -64,7 +64,7 @@ test()
         test(Iter(v.data()), Iter(v.data()+v.size()), x);
 }
 
-int main()
+int main(int, char**)
 {
     int d[] = {3, 2, 1, 0};
     for (int* e = d; e <= d+4; ++e)
@@ -79,4 +79,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.binary.search/nothing_to_do.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.binary.search/nothing_to_do.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.binary.search/upper.bound/upper_bound.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.binary.search/upper.bound/upper_bound.pass.cpp
@@ -61,7 +61,7 @@ test()
         test(Iter(v.data()), Iter(v.data()+v.size()), x);
 }
 
-int main()
+int main(int, char**)
 {
     int d[] = {0, 1, 2, 3};
     for (int* e = d; e <= d+4; ++e)
@@ -76,4 +76,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/...x/test/std/algorithms/alg.sorting/alg.binary.search/upper.bound/upper_bound_comp.pass.cpp b/...x/test/std/algorithms/alg.sorting/alg.binary.search/upper.bound/upper_bound_comp.pass.cpp
@@ -64,7 +64,7 @@ test()
         test(Iter(v.data()), Iter(v.data()+v.size()), x);
 }
 
-int main()
+int main(int, char**)
 {
     int d[] = {3, 2, 1, 0};
     for (int* e = d; e <= d+4; ++e)
@@ -79,4 +79,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.clamp/clamp.comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.clamp/clamp.comp.pass.cpp
@@ -38,7 +38,7 @@ test(const T& v, const T& lo, const T& hi, C c, const T& x)
     assert(&std::clamp(v, lo, hi, c) == &x);
 }
 
-int main()
+int main(int, char**)
 {
     {
     int x = 0;
@@ -123,4 +123,6 @@ int main()
     static_assert(std::clamp(x, y, z, std::greater<T>()) == y, "" );
     static_assert(std::clamp(y, x, z, std::greater<T>()) == y, "" );
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.clamp/clamp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.clamp/clamp.pass.cpp
@@ -36,7 +36,7 @@ test(const T& a, const T& lo, const T& hi, const T& x)
     assert(&std::clamp(a, lo, hi) == &x);
 }
 
-int main()
+int main(int, char**)
 {
     {
     int x = 0;
@@ -121,4 +121,6 @@ int main()
     static_assert(std::clamp(x, y, z) == x, "" );
     static_assert(std::clamp(y, x, z) == x, "" );
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/is.heap/is_heap.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/is.heap/is_heap.pass.cpp
@@ -525,11 +525,13 @@ void test()
     assert(std::is_heap(i246, i246+7) == (std::is_heap_until(i246, i246+7) == i246+7));
 }
 
-int main()
+int main(int, char**)
 {
     test();
 
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/is.heap/is_heap_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/is.heap/is_heap_comp.pass.cpp
@@ -526,11 +526,13 @@ void test()
     assert(std::is_heap(i246, i246+7, std::greater<int>()) == (std::is_heap_until(i246, i246+7, std::greater<int>()) == i246+7));
 }
 
-int main()
+int main(int, char**)
 {
     test();
 
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/is.heap/is_heap_until.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/is.heap/is_heap_until.pass.cpp
@@ -525,11 +525,13 @@ void test()
     assert(std::is_heap_until(i246, i246+7) == i246+7);
 }
 
-int main()
+int main(int, char**)
 {
     test();
 
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/...x/test/std/algorithms/alg.sorting/alg.heap.operations/is.heap/is_heap_until_comp.pass.cpp b/...x/test/std/algorithms/alg.sorting/alg.heap.operations/is.heap/is_heap_until_comp.pass.cpp
@@ -526,11 +526,13 @@ void test()
     assert(std::is_heap_until(i246, i246+7, std::greater<int>()) == i246+6);
 }
 
-int main()
+int main(int, char**)
 {
     test();
 
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/make.heap/make_heap.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/make.heap/make_heap.pass.cpp
@@ -30,12 +30,14 @@ void test(int N)
     delete [] ia;
 }
 
-int main()
+int main(int, char**)
 {
     test(0);
     test(1);
     test(2);
     test(3);
     test(10);
     test(1000);
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/make.heap/make_heap_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/make.heap/make_heap_comp.pass.cpp
@@ -74,7 +74,7 @@ void test(int N)
     delete [] ia;
 }
 
-int main()
+int main(int, char**)
 {
     test(0);
     test(1);
@@ -97,4 +97,6 @@ int main()
     delete [] ia;
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/nothing_to_do.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/nothing_to_do.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/pop.heap/pop_heap.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/pop.heap/pop_heap.pass.cpp
@@ -35,7 +35,9 @@ void test(int N)
     delete [] ia;
 }
 
-int main()
+int main(int, char**)
 {
     test(1000);
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/pop.heap/pop_heap_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/pop.heap/pop_heap_comp.pass.cpp
@@ -47,7 +47,7 @@ void test(int N)
     delete [] ia;
 }
 
-int main()
+int main(int, char**)
 {
     test(1000);
 
@@ -67,4 +67,6 @@ int main()
     delete [] ia;
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/push.heap/push_heap.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/push.heap/push_heap.pass.cpp
@@ -34,7 +34,9 @@ void test(int N)
     delete [] ia;
 }
 
-int main()
+int main(int, char**)
 {
     test(1000);
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/push.heap/push_heap_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/push.heap/push_heap_comp.pass.cpp
@@ -45,7 +45,7 @@ void test(int N)
     delete [] ia;
 }
 
-int main()
+int main(int, char**)
 {
     test(1000);
 
@@ -64,4 +64,6 @@ int main()
     delete [] ia;
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/sort.heap/sort_heap.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/sort.heap/sort_heap.pass.cpp
@@ -31,12 +31,14 @@ void test(int N)
     delete [] ia;
 }
 
-int main()
+int main(int, char**)
 {
     test(0);
     test(1);
     test(2);
     test(3);
     test(10);
     test(1000);
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/sort.heap/sort_heap_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.heap.operations/sort.heap/sort_heap_comp.pass.cpp
@@ -42,7 +42,7 @@ void test(int N)
     delete [] ia;
 }
 
-int main()
+int main(int, char**)
 {
     test(0);
     test(1);
@@ -64,4 +64,6 @@ int main()
     delete [] ia;
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.lex.comparison/lexicographical_compare.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.lex.comparison/lexicographical_compare.pass.cpp
@@ -46,7 +46,7 @@ test()
     assert(!std::lexicographical_compare(Iter1(ib+1), Iter1(ib+3),  Iter2(ia),   Iter2(ia+sa)));
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, input_iterator<const int*> >();
     test<input_iterator<const int*>, forward_iterator<const int*> >();
@@ -81,4 +81,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/.../test/std/algorithms/alg.sorting/alg.lex.comparison/lexicographical_compare_comp.pass.cpp b/.../test/std/algorithms/alg.sorting/alg.lex.comparison/lexicographical_compare_comp.pass.cpp
@@ -51,7 +51,7 @@ test()
     assert( std::lexicographical_compare(Iter1(ib+1), Iter1(ib+3),  Iter2(ia),   Iter2(ia+sa), c));
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, input_iterator<const int*> >();
     test<input_iterator<const int*>, forward_iterator<const int*> >();
@@ -86,4 +86,6 @@ int main()
 #if TEST_STD_VER > 17
     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge.pass.cpp
@@ -96,7 +96,7 @@ test()
     test<Iter>(1000);
 }
 
-int main()
+int main(int, char**)
 {
     test<bidirectional_iterator<int*> >();
     test<random_access_iterator<int*> >();
@@ -107,4 +107,6 @@ int main()
     test<random_access_iterator<S*> >();
     test<S*>();
 #endif  // TEST_STD_VER >= 11
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.merge/inplace_merge_comp.pass.cpp
@@ -135,7 +135,7 @@ void test_PR31166 ()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test<bidirectional_iterator<int*> >();
     test<random_access_iterator<int*> >();
@@ -167,4 +167,6 @@ int main()
 #endif  // TEST_STD_VER >= 11
 
     test_PR31166();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.merge/merge.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.merge/merge.pass.cpp
@@ -89,7 +89,7 @@ test()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<const int*>, forward_iterator<int*> >();
@@ -245,4 +245,6 @@ int main()
 //  Not yet - waiting on std::copy
 //     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.merge/merge_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.merge/merge_comp.pass.cpp
@@ -100,7 +100,7 @@ test()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test<input_iterator<const int*>, input_iterator<const int*>, output_iterator<int*> >();
     test<input_iterator<const int*>, input_iterator<const int*>, forward_iterator<int*> >();
@@ -256,4 +256,6 @@ int main()
 //  Not yet - waiting on std::copy
 //     static_assert(test_constexpr());
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max.pass.cpp
@@ -24,7 +24,7 @@ test(const T& a, const T& b, const T& x)
     assert(&std::max(a, b) == &x);
 }
 
-int main()
+int main(int, char**)
 {
     {
     int x = 0;
@@ -52,4 +52,6 @@ int main()
     static_assert(std::max(y, x) == x, "" );
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_comp.pass.cpp
@@ -26,7 +26,7 @@ test(const T& a, const T& b, C c, const T& x)
     assert(&std::max(a, b, c) == &x);
 }
 
-int main()
+int main(int, char**)
 {
     {
     int x = 0;
@@ -54,4 +54,6 @@ int main()
     static_assert(std::max(y, x, std::greater<int>()) == y, "" );
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_element.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_element.pass.cpp
@@ -71,12 +71,14 @@ void constexpr_test()
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*> >();
     test<bidirectional_iterator<const int*> >();
     test<random_access_iterator<const int*> >();
     test<const int*>();
 
     constexpr_test ();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_element_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_element_comp.pass.cpp
@@ -91,7 +91,7 @@ void constexpr_test()
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*> >();
     test<bidirectional_iterator<const int*> >();
@@ -100,4 +100,6 @@ int main()
     test_eq();
 
     constexpr_test();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_init_list.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_init_list.pass.cpp
@@ -19,7 +19,7 @@
 
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
     int i = std::max({2, 3, 1});
     assert(i == 3);
@@ -40,4 +40,6 @@ int main()
     static_assert(std::max({3, 2, 1}) == 3, "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_init_list_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/max_init_list_comp.pass.cpp
@@ -20,7 +20,7 @@
 
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
     int i = std::max({2, 3, 1}, std::greater<int>());
     assert(i == 1);
@@ -41,4 +41,6 @@ int main()
     static_assert(std::max({3, 2, 1}, std::greater<int>()) == 1, "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min.pass.cpp
@@ -24,7 +24,7 @@ test(const T& a, const T& b, const T& x)
     assert(&std::min(a, b) == &x);
 }
 
-int main()
+int main(int, char**)
 {
     {
     int x = 0;
@@ -52,4 +52,6 @@ int main()
     static_assert(std::min(y, x) == y, "" );
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_comp.pass.cpp
@@ -26,7 +26,7 @@ test(const T& a, const T& b, C c, const T& x)
     assert(&std::min(a, b, c) == &x);
 }
 
-int main()
+int main(int, char**)
 {
     {
     int x = 0;
@@ -54,4 +54,6 @@ int main()
     static_assert(std::min(y, x, std::greater<int>()) == x, "" );
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_element.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_element.pass.cpp
@@ -71,12 +71,14 @@ void constexpr_test()
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*> >();
     test<bidirectional_iterator<const int*> >();
     test<random_access_iterator<const int*> >();
     test<const int*>();
 
     constexpr_test();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_element_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_element_comp.pass.cpp
@@ -91,7 +91,7 @@ void constexpr_test()
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     test<forward_iterator<const int*> >();
     test<bidirectional_iterator<const int*> >();
@@ -100,4 +100,6 @@ int main()
     test_eq();
 
     constexpr_test();
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_init_list.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_init_list.pass.cpp
@@ -19,7 +19,7 @@
 
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
     int i = std::min({2, 3, 1});
     assert(i == 1);
@@ -40,4 +40,6 @@ int main()
     static_assert(std::min({3, 2, 1}) == 1, "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_init_list_comp.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/min_init_list_comp.pass.cpp
@@ -20,7 +20,7 @@
 
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
     int i = std::min({2, 3, 1}, std::greater<int>());
     assert(i == 3);
@@ -41,4 +41,6 @@ int main()
     static_assert(std::min({3, 2, 1}, std::greater<int>()) == 3, "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/algorithms/alg.sorting/alg.min.max/minmax.pass.cpp b/libcxx/test/std/algorithms/alg.sorting/alg.min.max/minmax.pass.cpp
@@ -26,7 +26,7 @@ test(const T& a, const T& b, const T& x, const T& y)
     assert(&p.second == &y);
 }
 
-int main()
+int main(int, char**)
 {
     {
     int x = 0;
@@ -60,4 +60,6 @@ int main()
     static_assert(p2.second == x, "");
     }
 #endif
+
+  return 0;
 }