Support tests in freestanding

Summary:
Freestanding is *weird*. The standard allows it to differ in a bunch of odd
manners from regular C++, and the committee would like to improve that
situation. I'd like to make libc++ behave better with what freestanding should
be, so that it can be a tool we use in improving the standard. To do that we
need to try stuff out, both with "freestanding the language mode" and
"freestanding the library subset".

Let's start with the super basic: run the libc++ tests in freestanding, using
clang as the compiler, and see what works. The easiest hack to do this:

In utils/libcxx/test/config.py add:

  self.cxx.compile_flags += ['-ffreestanding']

Run the tests and they all fail.

Why? Because in freestanding `main` isn't special. This "not special" property
has two effects: main doesn't get mangled, and main isn't allowed to omit its
`return` statement. The first means main gets mangled and the linker can't
create a valid executable for us to test. The second means we spew out warnings
(ew) and the compiler doesn't insert the `return` we omitted, and main just
falls of the end and does whatever undefined behavior (if you're luck, ud2
leading to non-zero return code).

Let's start my work with the basics. This patch changes all libc++ tests to
declare `main` as `int main(int, char**` so it mangles consistently (enabling us
to declare another `extern "C"` main for freestanding which calls the mangled
one), and adds `return 0;` to all places where it was missing. This touches 6124
files, and I apologize.

The former was done with The Magic Of Sed.

The later was done with a (not quite correct but decent) clang tool:

  https://gist.github.com/jfbastien/793819ff360baa845483dde81170feed

This works for most tests, though I did have to adjust a few places when e.g.
the test runs with `-x c`, macros are used for main (such as for the filesystem
tests), etc.

Once this is in we can create a freestanding bot which will prevent further
regressions. After that, we can start the real work of supporting C++
freestanding fairly well in libc++.

<rdar://problem/47754795>

Reviewers: ldionne, mclow.lists, EricWF

Subscribers: christof, jkorous, dexonsmith, arphaman, miyuki, libcxx-commits

Differential Revision: https://reviews.llvm.org/D57624

llvm-svn: 353086

35 files changed, 107 insertions, 35 deletions

diff --git a/libcxx/test/std/containers/sequences/array/array.cons/deduct.fail.cpp b/libcxx/test/std/containers/sequences/array/array.cons/deduct.fail.cpp
index fb882eea071..0c0d32f69c1 100644
--- a/libcxx/test/std/containers/sequences/array/array.cons/deduct.fail.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.cons/deduct.fail.cpp
@@ -28,9 +28,11 @@
 
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
     {
     std::array arr{1,2,3L}; // expected-error {{no viable constructor or deduction guide for deduction of template arguments of 'array'}}
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.cons/deduct.pass.cpp b/libcxx/test/std/containers/sequences/array/array.cons/deduct.pass.cpp
index fead8cacfde..141aafc2a31 100644
--- a/libcxx/test/std/containers/sequences/array/array.cons/deduct.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.cons/deduct.pass.cpp
@@ -30,7 +30,7 @@
 
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
 //  Test the explicit deduction guides
     {
@@ -61,4 +61,6 @@ int main()
     assert(arr[0] == 4.0);
     assert(arr[1] == 5.0);
   }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.cons/default.pass.cpp b/libcxx/test/std/containers/sequences/array/array.cons/default.pass.cpp
index 22ed4d8320f..daa6a525210 100644
--- a/libcxx/test/std/containers/sequences/array/array.cons/default.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.cons/default.pass.cpp
@@ -21,7 +21,7 @@ struct NoDefault {
   NoDefault(int) {}
 };
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -44,4 +44,6 @@ int main()
       C c2 = {{}};
       assert(c2.size() == 0);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.cons/implicit_copy.pass.cpp b/libcxx/test/std/containers/sequences/array/array.cons/implicit_copy.pass.cpp
index 9d82c93b52c..c0e205c8322 100644
--- a/libcxx/test/std/containers/sequences/array/array.cons/implicit_copy.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.cons/implicit_copy.pass.cpp
@@ -32,7 +32,7 @@ struct NoDefault {
   NoDefault(int) {}
 };
 
-int main() {
+int main(int, char**) {
   {
     typedef double T;
     typedef std::array<T, 3> C;
@@ -89,4 +89,6 @@ int main() {
     TEST_NOT_COPY_ASSIGNABLE(C);
   }
 
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.cons/initializer_list.pass.cpp b/libcxx/test/std/containers/sequences/array/array.cons/initializer_list.pass.cpp
index 6a9da4e4fdd..e85269796fb 100644
--- a/libcxx/test/std/containers/sequences/array/array.cons/initializer_list.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.cons/initializer_list.pass.cpp
@@ -17,7 +17,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -48,4 +48,6 @@ int main()
         C c = {};
         assert(c.size() == 1);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.data/data.pass.cpp b/libcxx/test/std/containers/sequences/array/array.data/data.pass.cpp
index 36640160ee2..ce1843eb549 100644
--- a/libcxx/test/std/containers/sequences/array/array.data/data.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.data/data.pass.cpp
@@ -25,7 +25,7 @@ struct NoDefault {
 };
 
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -67,4 +67,6 @@ int main()
       T* p = c.data();
       LIBCPP_ASSERT(p != nullptr);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.data/data_const.pass.cpp b/libcxx/test/std/containers/sequences/array/array.data/data_const.pass.cpp
index 3b035e67ca9..32c05d7ef35 100644
--- a/libcxx/test/std/containers/sequences/array/array.data/data_const.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.data/data_const.pass.cpp
@@ -24,7 +24,7 @@ struct NoDefault {
   NoDefault(int) {}
 };
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -70,4 +70,6 @@ int main()
         static_assert ( *c2.data()  ==  c2[0], "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.fill/fill.fail.cpp b/libcxx/test/std/containers/sequences/array/array.fill/fill.fail.cpp
index 96641c5cb9d..9f560dab4e4 100644
--- a/libcxx/test/std/containers/sequences/array/array.fill/fill.fail.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.fill/fill.fail.cpp
@@ -17,7 +17,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main() {
+int main(int, char**) {
   {
     typedef double T;
     typedef std::array<const T, 0> C;
@@ -25,4 +25,6 @@ int main() {
     // expected-error-re@array:* {{static_assert failed {{.*}}"cannot fill zero-sized array of type 'const T'"}}
     c.fill(5.5); // expected-note {{requested here}}
   }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.fill/fill.pass.cpp b/libcxx/test/std/containers/sequences/array/array.fill/fill.pass.cpp
index d4dfe9a7119..db7363ab975 100644
--- a/libcxx/test/std/containers/sequences/array/array.fill/fill.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.fill/fill.pass.cpp
@@ -17,7 +17,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -36,4 +36,6 @@ int main()
         c.fill(5.5);
         assert(c.size() == 0);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.size/size.pass.cpp b/libcxx/test/std/containers/sequences/array/array.size/size.pass.cpp
index 038df0160dc..f837bdcf8fb 100644
--- a/libcxx/test/std/containers/sequences/array/array.size/size.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.size/size.pass.cpp
@@ -19,7 +19,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -55,4 +55,6 @@ int main()
         static_assert(c.empty(), "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.special/swap.pass.cpp b/libcxx/test/std/containers/sequences/array/array.special/swap.pass.cpp
index f4751cc7661..6c9ed957b83 100644
--- a/libcxx/test/std/containers/sequences/array/array.special/swap.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.special/swap.pass.cpp
@@ -35,7 +35,7 @@ std::false_type can_swap_imp(...);
 template <class Tp>
 struct can_swap : std::is_same<decltype(can_swap_imp<Tp>(0)), void> {};
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -81,4 +81,6 @@ int main()
         static_assert(!can_swap<C1&>::value, "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.swap/swap.fail.cpp b/libcxx/test/std/containers/sequences/array/array.swap/swap.fail.cpp
index 3e5dc815c24..90c1496156a 100644
--- a/libcxx/test/std/containers/sequences/array/array.swap/swap.fail.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.swap/swap.fail.cpp
@@ -17,7 +17,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main() {
+int main(int, char**) {
   {
     typedef double T;
     typedef std::array<const T, 0> C;
@@ -26,4 +26,6 @@ int main() {
     // expected-error-re@array:* {{static_assert failed {{.*}}"cannot swap zero-sized array of type 'const T'"}}
     c.swap(c2); // expected-note {{requested here}}
   }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.swap/swap.pass.cpp b/libcxx/test/std/containers/sequences/array/array.swap/swap.pass.cpp
index e23daa88e79..aac8a13b29a 100644
--- a/libcxx/test/std/containers/sequences/array/array.swap/swap.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.swap/swap.pass.cpp
@@ -27,7 +27,7 @@ private:
   NonSwappable& operator=(NonSwappable const&);
 };
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -89,4 +89,6 @@ int main()
 #endif
     }
 
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.tuple/get.fail.cpp b/libcxx/test/std/containers/sequences/array/array.tuple/get.fail.cpp
index 25bf53835a0..7bfe670b20d 100644
--- a/libcxx/test/std/containers/sequences/array/array.tuple/get.fail.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.tuple/get.fail.cpp
@@ -23,7 +23,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -32,4 +32,6 @@ int main()
         std::get<3>(c) = 5.5; // expected-note {{requested here}}
         // expected-error-re@array:* {{static_assert failed{{( due to requirement '3U[L]{0,2} < 3U[L]{0,2}')?}} "Index out of bounds in std::get<> (std::array)"}}
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.tuple/get.pass.cpp b/libcxx/test/std/containers/sequences/array/array.tuple/get.pass.cpp
index bbc1c071a79..9e94417ac97 100644
--- a/libcxx/test/std/containers/sequences/array/array.tuple/get.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.tuple/get.pass.cpp
@@ -30,7 +30,7 @@ struct S {
 constexpr std::array<int, 2> getArr () { return { 3, 4 }; }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -55,4 +55,6 @@ int main()
         static_assert(std::get<1>(getArr()) == 4, "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.tuple/get_const.pass.cpp b/libcxx/test/std/containers/sequences/array/array.tuple/get_const.pass.cpp
index 7b964870b37..b22a76185b6 100644
--- a/libcxx/test/std/containers/sequences/array/array.tuple/get_const.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.tuple/get_const.pass.cpp
@@ -19,7 +19,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -39,4 +39,6 @@ int main()
         static_assert(std::get<2>(c) == 3.5, "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.tuple/get_const_rv.pass.cpp b/libcxx/test/std/containers/sequences/array/array.tuple/get_const_rv.pass.cpp
index 599e919a384..ce8fc4fd365 100644
--- a/libcxx/test/std/containers/sequences/array/array.tuple/get_const_rv.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.tuple/get_const_rv.pass.cpp
@@ -24,7 +24,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
 
     {
@@ -47,4 +47,6 @@ int main()
     static_assert(std::get<2>(std::move(c)) == 3.5, "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.tuple/get_rv.pass.cpp b/libcxx/test/std/containers/sequences/array/array.tuple/get_rv.pass.cpp
index 77d4633db5e..d36fcdcc206 100644
--- a/libcxx/test/std/containers/sequences/array/array.tuple/get_rv.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.tuple/get_rv.pass.cpp
@@ -21,7 +21,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
 
     {
@@ -31,4 +31,6 @@ int main()
         T t = std::get<0>(std::move(c));
         assert(*t == 3.5);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.tuple/tuple_element.fail.cpp b/libcxx/test/std/containers/sequences/array/array.tuple/tuple_element.fail.cpp
index 35cd9864717..a4fbd3ab4c2 100644
--- a/libcxx/test/std/containers/sequences/array/array.tuple/tuple_element.fail.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.tuple/tuple_element.fail.cpp
@@ -23,7 +23,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -31,4 +31,6 @@ int main()
         std::tuple_element<3, C> foo; // expected-note {{requested here}}
         // expected-error-re@array:* {{static_assert failed{{( due to requirement '3U[L]{0,2} < 3U[L]{0,2}')?}} "Index out of bounds in std::tuple_element<> (std::array)"}}
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.tuple/tuple_element.pass.cpp b/libcxx/test/std/containers/sequences/array/array.tuple/tuple_element.pass.cpp
index 6980838ab63..fbf5210f26f 100644
--- a/libcxx/test/std/containers/sequences/array/array.tuple/tuple_element.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.tuple/tuple_element.pass.cpp
@@ -46,8 +46,10 @@ void test()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test<double>();
     test<int>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.tuple/tuple_size.pass.cpp b/libcxx/test/std/containers/sequences/array/array.tuple/tuple_size.pass.cpp
index e542f34eefb..dddcbcaff7f 100644
--- a/libcxx/test/std/containers/sequences/array/array.tuple/tuple_size.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.tuple/tuple_size.pass.cpp
@@ -33,9 +33,11 @@ void test()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test<double, 0>();
     test<double, 3>();
     test<double, 5>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/array.zero/tested_elsewhere.pass.cpp b/libcxx/test/std/containers/sequences/array/array.zero/tested_elsewhere.pass.cpp
index ba3c5405d07..966e603d134 100644
--- a/libcxx/test/std/containers/sequences/array/array.zero/tested_elsewhere.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/array.zero/tested_elsewhere.pass.cpp
@@ -12,6 +12,8 @@
 
 #include <array>
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/at.pass.cpp b/libcxx/test/std/containers/sequences/array/at.pass.cpp
index b8d1d2b804b..0240d5a8372 100644
--- a/libcxx/test/std/containers/sequences/array/at.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/at.pass.cpp
@@ -30,7 +30,7 @@ constexpr bool check_idx( size_t idx, double val )
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -116,4 +116,6 @@ int main()
         static_assert (check_idx(2, 3.5), "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/begin.pass.cpp b/libcxx/test/std/containers/sequences/array/begin.pass.cpp
index ce023aa3890..7b26d231dbd 100644
--- a/libcxx/test/std/containers/sequences/array/begin.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/begin.pass.cpp
@@ -24,7 +24,7 @@ struct NoDefault {
 };
 
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -48,4 +48,6 @@ int main()
       LIBCPP_ASSERT(ib != nullptr);
       LIBCPP_ASSERT(ie != nullptr);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/compare.fail.cpp b/libcxx/test/std/containers/sequences/array/compare.fail.cpp
index 1710fe7888b..47859ad49db 100644
--- a/libcxx/test/std/containers/sequences/array/compare.fail.cpp
+++ b/libcxx/test/std/containers/sequences/array/compare.fail.cpp
@@ -41,7 +41,7 @@ void test_compare(const Array& LHS, const Array& RHS) {
 
 template <int Dummy> struct NoCompare {};
 
-int main()
+int main(int, char**)
 {
   {
     typedef NoCompare<0> T;
@@ -67,4 +67,6 @@ int main()
     TEST_IGNORE_NODISCARD (c1 == c1);
     TEST_IGNORE_NODISCARD (c1 < c1);
   }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/compare.pass.cpp b/libcxx/test/std/containers/sequences/array/compare.pass.cpp
index 56eabbd00ab..c05dd19405b 100644
--- a/libcxx/test/std/containers/sequences/array/compare.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/compare.pass.cpp
@@ -28,7 +28,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
   {
     typedef int T;
@@ -58,4 +58,6 @@ int main()
   static_assert(testComparisons6(a2, a1, false, false), "");
   }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/contiguous.pass.cpp b/libcxx/test/std/containers/sequences/array/contiguous.pass.cpp
index ce953794a56..e0ab5b61c44 100644
--- a/libcxx/test/std/containers/sequences/array/contiguous.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/contiguous.pass.cpp
@@ -20,11 +20,13 @@ void test_contiguous ( const C &c )
         assert ( *(c.begin() + i) == *(std::addressof(*c.begin()) + i));
 }
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
         typedef std::array<T, 3> C;
         test_contiguous (C());
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/empty.fail.cpp b/libcxx/test/std/containers/sequences/array/empty.fail.cpp
index 424f715413d..3bbb3c8e1c0 100644
--- a/libcxx/test/std/containers/sequences/array/empty.fail.cpp
+++ b/libcxx/test/std/containers/sequences/array/empty.fail.cpp
@@ -20,11 +20,13 @@
 
 #include "test_macros.h"
 
-int main ()
+int main(int, char**)
 {
 
     std::array<int, 1> c;
     c.empty(); // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
     std::array<int, 0> c0;
     c0.empty(); // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/empty.pass.cpp b/libcxx/test/std/containers/sequences/array/empty.pass.cpp
index 48580694708..a17aa50c5b2 100644
--- a/libcxx/test/std/containers/sequences/array/empty.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/empty.pass.cpp
@@ -18,7 +18,7 @@
 #include "test_macros.h"
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::array<int, 2> C;
@@ -32,4 +32,6 @@ int main()
     ASSERT_NOEXCEPT(c.empty());
     assert( c.empty());
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/front_back.pass.cpp b/libcxx/test/std/containers/sequences/array/front_back.pass.cpp
index 13368683a56..1a714369ffc 100644
--- a/libcxx/test/std/containers/sequences/array/front_back.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/front_back.pass.cpp
@@ -36,7 +36,7 @@ constexpr bool check_back( double val )
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -115,4 +115,6 @@ int main()
         static_assert (check_back (3.5), "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/indexing.pass.cpp b/libcxx/test/std/containers/sequences/array/indexing.pass.cpp
index a33a597fc5e..bf55711a141 100644
--- a/libcxx/test/std/containers/sequences/array/indexing.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/indexing.pass.cpp
@@ -30,7 +30,7 @@ constexpr bool check_idx( size_t idx, double val )
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -104,4 +104,6 @@ int main()
         static_assert (check_idx(2, 3.5), "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/iterators.pass.cpp b/libcxx/test/std/containers/sequences/array/iterators.pass.cpp
index 7e4c9b75620..71fad183ff7 100644
--- a/libcxx/test/std/containers/sequences/array/iterators.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/iterators.pass.cpp
@@ -20,7 +20,7 @@
 // Disable the missing braces warning for this reason.
 #include "disable_missing_braces_warning.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::array<int, 5> C;
@@ -141,4 +141,6 @@ int main()
         static_assert ( *std::crbegin(c) == 4, "" );
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/max_size.pass.cpp b/libcxx/test/std/containers/sequences/array/max_size.pass.cpp
index 1f3ec0472ae..a0b77392ee8 100644
--- a/libcxx/test/std/containers/sequences/array/max_size.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/max_size.pass.cpp
@@ -18,7 +18,7 @@
 #include "test_macros.h"
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::array<int, 2> C;
@@ -32,4 +32,6 @@ int main()
     ASSERT_NOEXCEPT(c.max_size());
     assert(c.max_size() == 0);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/size_and_alignment.pass.cpp b/libcxx/test/std/containers/sequences/array/size_and_alignment.pass.cpp
index c57740bcaa5..f585da6ce7a 100644
--- a/libcxx/test/std/containers/sequences/array/size_and_alignment.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/size_and_alignment.pass.cpp
@@ -57,7 +57,9 @@ struct TEST_ALIGNAS(TEST_ALIGNOF(std::max_align_t) * 2) TestType2 {
   char data[1000];
 };
 
-int main() {
+//static_assert(sizeof(void*) == 4, "");
+
+int main(int, char**) {
   test_type<char>();
   test_type<int>();
   test_type<double>();
@@ -65,4 +67,6 @@ int main() {
   test_type<std::max_align_t>();
   test_type<TestType1>();
   test_type<TestType2>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/containers/sequences/array/types.pass.cpp b/libcxx/test/std/containers/sequences/array/types.pass.cpp
index e76c06e6d46..f86e008d2e8 100644
--- a/libcxx/test/std/containers/sequences/array/types.pass.cpp
+++ b/libcxx/test/std/containers/sequences/array/types.pass.cpp
@@ -47,7 +47,7 @@ void test_iterators() {
     static_assert((std::is_same<typename CItT::difference_type, typename C::difference_type>::value), "");
 }
 
-int main()
+int main(int, char**)
 {
     {
         typedef double T;
@@ -93,4 +93,6 @@ int main()
         static_assert((std::is_same<typename C::difference_type,
             typename std::iterator_traits<typename C::const_iterator>::difference_type>::value), "");
     }
+
+  return 0;
 }