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

56 files changed, 168 insertions, 56 deletions

diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/nothing_to_do.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/nothing_to_do.pass.cpp
index f77636c8475..1f764da05d6 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/nothing_to_do.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/nothing_to_do.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/T_size_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/T_size_size.pass.cpp
index f2848295baf..43752406362 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/T_size_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/T_size_size.pass.cpp
@@ -71,7 +71,7 @@ test_npos(S s, SV sv, typename S::size_type pos, S expected)
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -196,4 +196,6 @@ int main()
     s.append(sv, 0, std::string::npos);
     assert(s == "ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/initializer_list.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/initializer_list.pass.cpp
index 04483865d56..da74fb4e09c 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/initializer_list.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/initializer_list.pass.cpp
@@ -18,7 +18,7 @@
 #include "test_macros.h"
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
         std::string s("123");
@@ -31,4 +31,6 @@ int main()
         s.append({'a', 'b', 'c'});
         assert(s == "123abc");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/iterator.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/iterator.pass.cpp
index 08f554b34d4..8f280e828d9 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/iterator.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/iterator.pass.cpp
@@ -42,7 +42,7 @@ test_exceptions(S s, It first, It last)
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -219,4 +219,6 @@ int main()
     s.append(MoveIt(It(std::begin(p))), MoveIt(It(std::end(p) - 1)));
     assert(s == "ABCD");
   }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/pointer.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/pointer.pass.cpp
index dec79a67cd1..eba693d0e3d 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/pointer.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/pointer.pass.cpp
@@ -26,7 +26,7 @@ test(S s, const typename S::value_type* str, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -76,4 +76,6 @@ int main()
     s_long.append(s_long.c_str());
     assert(s_long == "Lorem ipsum dolor sit amet, consectetur/Lorem ipsum dolor sit amet, consectetur/");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/pointer_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/pointer_size.pass.cpp
index 2fb973ae983..c214ab7c2ac 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/pointer_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/pointer_size.pass.cpp
@@ -27,7 +27,7 @@ test(S s, const typename S::value_type* str, typename S::size_type n, S expected
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -85,4 +85,6 @@ int main()
     s_long.append(s_long.data(), s_long.size());
     assert(s_long == "Lorem ipsum dolor sit amet, consectetur/Lorem ipsum dolor sit amet, consectetur/");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/push_back.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/push_back.pass.cpp
index a2b9ad1e470..f1b34ad6cff 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/push_back.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/push_back.pass.cpp
@@ -31,7 +31,7 @@ test(S s, typename S::value_type c, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -56,4 +56,6 @@ int main()
     s.push_back(vl);
     s.push_back(vl);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/size_char.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/size_char.pass.cpp
index 59d0199a2bf..c4062489291 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/size_char.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/size_char.pass.cpp
@@ -26,7 +26,7 @@ test(S s, typename S::size_type n, typename S::value_type c, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -60,4 +60,6 @@ int main()
     test(S("12345678901234567890"), 10, 'a', S("12345678901234567890aaaaaaaaaa"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string.pass.cpp
index c0c625f2e22..5e551d7a2b1 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string.pass.cpp
@@ -26,7 +26,7 @@ test(S s, S str, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -85,4 +85,6 @@ int main()
     assert(s == "a");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string_size_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string_size_size.pass.cpp
index 21ddd9bb225..37985d00115 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string_size_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string_size_size.pass.cpp
@@ -71,7 +71,7 @@ test_npos(S s, S str, typename S::size_type pos, S expected)
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -133,4 +133,6 @@ int main()
     test_npos(S(), S("12345"), 5, S(""));
     test_npos(S(), S("12345"), 6, S("not happening"));
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string_view.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string_view.pass.cpp
index 301fc77b704..d0fb1cc3315 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string_view.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_append/string_view.pass.cpp
@@ -27,7 +27,7 @@ test(S s, SV sv, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -79,4 +79,6 @@ int main()
          S("1234567890123456789012345678901234567890"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/T_size_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/T_size_size.pass.cpp
index b0541712257..044b3724041 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/T_size_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/T_size_size.pass.cpp
@@ -70,7 +70,7 @@ test_npos(S s, SV sv, typename S::size_type pos, S expected)
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -191,4 +191,6 @@ int main()
     s.assign(sv, 0, std::string::npos);
     assert(s == "ABCDEFGHIJKLMNOPQRSTUVWXYZ");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/initializer_list.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/initializer_list.pass.cpp
index 72097dae630..692b84b557d 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/initializer_list.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/initializer_list.pass.cpp
@@ -18,7 +18,7 @@
 #include "test_macros.h"
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
         std::string s("123");
@@ -31,4 +31,6 @@ int main()
         s.assign({'a', 'b', 'c'});
         assert(s == "abc");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/iterator.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/iterator.pass.cpp
index 4bf805c99d6..c03b5efdfd5 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/iterator.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/iterator.pass.cpp
@@ -43,7 +43,7 @@ test_exceptions(S s, It first, It last)
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -204,4 +204,6 @@ int main()
     s.assign(p, p + 4);
     assert(s == "ABCD");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/pointer.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/pointer.pass.cpp
index 62a173a186d..325c354c56a 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/pointer.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/pointer.pass.cpp
@@ -26,7 +26,7 @@ test(S s, const typename S::value_type* str, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -74,4 +74,6 @@ int main()
     s_long.assign(s_long.c_str() + 30);
     assert(s_long == "nsectetur/");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/pointer_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/pointer_size.pass.cpp
index 442d8c00024..5d3fe262184 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/pointer_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/pointer_size.pass.cpp
@@ -27,7 +27,7 @@ test(S s, const typename S::value_type* str, typename S::size_type n, S expected
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -85,4 +85,6 @@ int main()
     s_long.assign(s_long.data() + 2, 8 );
     assert(s_long == "rem ipsu");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/rv_string.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/rv_string.pass.cpp
index 3d401c8a917..ac26f369ddb 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/rv_string.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/rv_string.pass.cpp
@@ -27,7 +27,7 @@ test(S s, S str, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -77,4 +77,6 @@ int main()
          S("12345678901234567890"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/size_char.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/size_char.pass.cpp
index 8c69b138f9f..4e5ecad2e9d 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/size_char.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/size_char.pass.cpp
@@ -26,7 +26,7 @@ test(S s, typename S::size_type n, typename S::value_type c, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -60,4 +60,6 @@ int main()
     test(S("12345678901234567890"), 10, 'a', S(10, 'a'));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string.pass.cpp
index 274703a565d..fae45c80de0 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string.pass.cpp
@@ -37,7 +37,7 @@ testAlloc(S s, S str, const typename S::allocator_type& a)
     assert(s.get_allocator() == a);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -113,4 +113,6 @@ int main()
     static_assert(noexcept(S().assign(S())), "");  // LWG#2063
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string_size_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string_size_size.pass.cpp
index 76dd273455b..8e11b150e91 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string_size_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string_size_size.pass.cpp
@@ -71,7 +71,7 @@ test_npos(S s, S str, typename S::size_type pos, S expected)
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -133,4 +133,6 @@ int main()
     test_npos(S(), S("12345"), 5, S(""));
     test_npos(S(), S("12345"), 6, S("not happening"));
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string_view.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string_view.pass.cpp
index d445ad9b793..2d1158e41de 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string_view.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_assign/string_view.pass.cpp
@@ -38,7 +38,7 @@ testAlloc(S s, SV sv, const typename S::allocator_type& a)
     assert(s.get_allocator() == a);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -101,4 +101,6 @@ int main()
     testAlloc(S(), SV("12345678901234567890"), min_allocator<char>());
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_copy/copy.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_copy/copy.pass.cpp
index 81dc3329c43..778fb70c069 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_copy/copy.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_copy/copy.pass.cpp
@@ -49,7 +49,7 @@ test(S str, typename S::value_type* s, typename S::size_type n,
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -177,4 +177,6 @@ int main()
     test(S("abcdefghijklmnopqrst"), s, 21, 0);
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/iter.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/iter.pass.cpp
index 1923c62b4d2..12b13d738cc 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/iter.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/iter.pass.cpp
@@ -28,7 +28,7 @@ test(S s, typename S::difference_type pos, S expected)
     assert(i - s.begin() == pos);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -62,4 +62,6 @@ int main()
     test(S("abcdefghijklmnopqrst"), 19, S("abcdefghijklmnopqrs"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/iter_iter.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/iter_iter.pass.cpp
index 0eba9361d8a..a5e6d1251d1 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/iter_iter.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/iter_iter.pass.cpp
@@ -29,7 +29,7 @@ test(S s, typename S::difference_type pos, typename S::difference_type n, S expe
     assert(i - s.begin() == pos);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -147,4 +147,6 @@ int main()
     test(S("abcdefghijklmnopqrst"), 20, 0, S("abcdefghijklmnopqrst"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/pop_back.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/pop_back.pass.cpp
index e6f2a4e6035..e6490abcd2e 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/pop_back.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/pop_back.pass.cpp
@@ -26,7 +26,7 @@ test(S s, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -42,4 +42,6 @@ int main()
     test(S("abcdefghijklmnopqrst"), S("abcdefghijklmnopqrs"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/size_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/size_size.pass.cpp
index a8e31c9c694..88dace52f8a 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/size_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_erase/size_size.pass.cpp
@@ -88,7 +88,7 @@ test(S s, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -298,4 +298,6 @@ int main()
     test(S("abcdefghijklmnopqrst"), S(""));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_char.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_char.pass.cpp
index d570428c054..ef6144dadb5 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_char.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_char.pass.cpp
@@ -32,7 +32,7 @@ test(S& s, typename S::const_iterator p, typename S::value_type c, S expected)
         assert(i == p);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -72,4 +72,6 @@ int main()
     test(s, s.begin()+6, 'C', S("a567ABC1432dcb"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_initializer_list.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_initializer_list.pass.cpp
index 0acc50b4549..6dd043c6db9 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_initializer_list.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_initializer_list.pass.cpp
@@ -18,7 +18,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
         std::string s("123456");
@@ -33,4 +33,6 @@ int main()
         assert(i - s.begin() == 3);
         assert(s == "123abc456");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_iter_iter.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_iter_iter.pass.cpp
index c1b16872928..6d4f1a6686e 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_iter_iter.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_iter_iter.pass.cpp
@@ -49,7 +49,7 @@ test_exceptions(S s, typename S::difference_type pos, It first, It last)
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -218,4 +218,6 @@ int main()
     s.insert(s.begin(), MoveIt(It(std::begin(p))), MoveIt(It(std::end(p) - 1)));
     assert(s == "ABCD");
   }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_size_char.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_size_char.pass.cpp
index ac29e3b3325..699b67924b1 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_size_char.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/iter_size_char.pass.cpp
@@ -28,7 +28,7 @@ test(S s, typename S::difference_type pos, typename S::size_type n,
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -166,4 +166,6 @@ int main()
     test(S("abcdefghijklmnopqrst"), 20, 20, '1', S("abcdefghijklmnopqrst11111111111111111111"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_T_size_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_T_size_size.pass.cpp
index fb8c7e63a5c..2b54b67202b 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_T_size_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_T_size_size.pass.cpp
@@ -1729,7 +1729,7 @@ void test30()
     test_npos(S("abcdefghijklmnopqrst"), 10, SV("12345"), 6, S("can't happen"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -1838,4 +1838,6 @@ int main()
     assert(s == "");
     s.clear();
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_pointer.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_pointer.pass.cpp
index ee7ef204a33..24859fa8be2 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_pointer.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_pointer.pass.cpp
@@ -47,7 +47,7 @@ test(S s, typename S::size_type pos, const typename S::value_type* str, S expect
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -233,4 +233,6 @@ int main()
     s_long.insert(0, s_long.c_str());
     assert(s_long == "Lorem ipsum dolor sit amet, consectetur/Lorem ipsum dolor sit amet, consectetur/");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_pointer_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_pointer_size.pass.cpp
index 67a03400528..3dbd93f1df5 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_pointer_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_pointer_size.pass.cpp
@@ -48,7 +48,7 @@ test(S s, typename S::size_type pos, const typename S::value_type* str,
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -714,4 +714,6 @@ int main()
     s_long.insert(0, s_long.data(), s_long.size());
     assert(s_long == "Lorem ipsum dolor sit amet, consectetur/Lorem ipsum dolor sit amet, consectetur/");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_size_char.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_size_char.pass.cpp
index e64e9c997e3..dce8b7d7edb 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_size_char.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_size_char.pass.cpp
@@ -48,7 +48,7 @@ test(S s, typename S::size_type pos, typename S::size_type n,
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -218,4 +218,6 @@ int main()
     test(S("abcdefghijklmnopqrst"), 21, 20, '1', S("can't happen"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_string.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_string.pass.cpp
index 2f74fec3f79..93bc3f6d961 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_string.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_string.pass.cpp
@@ -47,7 +47,7 @@ test(S s, typename S::size_type pos, S str, S expected)
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -226,4 +226,6 @@ int main()
     assert(s == "a");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_string_size_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_string_size_size.pass.cpp
index 23b8852b4c3..18a688a5d1f 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_string_size_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/size_string_size_size.pass.cpp
@@ -1727,7 +1727,7 @@ void test30()
     test_npos(S("abcdefghijklmnopqrst"), 10, S("12345"), 6, S("can't happen"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -1799,4 +1799,6 @@ int main()
     test30<S>();
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/string_view.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/string_view.pass.cpp
index 0596ce9849e..129389a9a7b 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/string_view.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_insert/string_view.pass.cpp
@@ -47,7 +47,7 @@ test(S s, typename S::size_type pos, SV sv, S expected)
 #endif
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -235,4 +235,6 @@ int main()
     s_long.insert(0, s_long.c_str());
     assert(s_long == "Lorem ipsum dolor sit amet, consectetur/Lorem ipsum dolor sit amet, consectetur/");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/char.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/char.pass.cpp
index 3c15f6f919e..2cc4496eb67 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/char.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/char.pass.cpp
@@ -25,7 +25,7 @@ test(S s, typename S::value_type str, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -43,4 +43,6 @@ int main()
     test(S("12345678901234567890"), 'a', S("12345678901234567890a"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/initializer_list.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/initializer_list.pass.cpp
index 7f27559f0e6..689389eb7a6 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/initializer_list.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/initializer_list.pass.cpp
@@ -17,7 +17,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
         std::string s("123");
@@ -30,4 +30,6 @@ int main()
         s += {'a', 'b', 'c'};
         assert(s == "123abc");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/pointer.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/pointer.pass.cpp
index 3a769693518..a9edf17be5b 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/pointer.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/pointer.pass.cpp
@@ -25,7 +25,7 @@ test(S s, const typename S::value_type* str, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -75,4 +75,6 @@ int main()
          S("1234567890123456789012345678901234567890"));
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/string.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/string.pass.cpp
index 53e1cacf4a1..f81d4bec0d2 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/string.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_op_plus_equal/string.pass.cpp
@@ -26,7 +26,7 @@ test(S s, S str, S expected)
     assert(s == expected);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -85,4 +85,6 @@ int main()
     assert(s == "a");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_initializer_list.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_initializer_list.pass.cpp
index 8e8a1f8ef9e..3df49f32535 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_initializer_list.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_initializer_list.pass.cpp
@@ -17,7 +17,7 @@
 
 #include "min_allocator.h"
 
-int main()
+int main(int, char**)
 {
     {
         std::string s("123def456");
@@ -30,4 +30,6 @@ int main()
         s.replace(s.cbegin() + 3, s.cbegin() + 6, {'a', 'b', 'c'});
         assert(s == "123abc456");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_iter_iter.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_iter_iter.pass.cpp
index fc6f33beafe..47a1193be73 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_iter_iter.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_iter_iter.pass.cpp
@@ -963,7 +963,7 @@ void test8()
     test(S("abcdefghijklmnopqrst"), 20, 0, str, str+20, S("abcdefghijklmnopqrst12345678901234567890"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -1036,4 +1036,6 @@ int main()
     s.replace(s.begin(), s.end(), p, p + 4);
     assert(s == "EFGH");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_pointer.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_pointer.pass.cpp
index ccbd0ff66fb..8ed1dc3df30 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_pointer.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_pointer.pass.cpp
@@ -265,7 +265,7 @@ void test2()
     test(S("abcdefghijklmnopqrst"), 20, 0, "12345678901234567890", S("abcdefghijklmnopqrst12345678901234567890"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -297,4 +297,6 @@ int main()
     s_long.replace(s_long.begin(), s_long.begin(), s_long.c_str());
     assert(s_long == "Lorem ipsum dolor sit amet, consectetur/Lorem ipsum dolor sit amet, consectetur/");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_pointer_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_pointer_size.pass.cpp
index 79ae58fce2e..39b518c9146 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_pointer_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_pointer_size.pass.cpp
@@ -943,7 +943,7 @@ void test8()
     test(S("abcdefghijklmnopqrst"), 20, 0, "12345678901234567890", 20, S("abcdefghijklmnopqrst12345678901234567890"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -987,4 +987,6 @@ int main()
     s_long.replace(s_long.begin(), s_long.begin(), s_long.data(), s_long.size());
     assert(s_long == "Lorem ipsum dolor sit amet, consectetur/Lorem ipsum dolor sit amet, consectetur/");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_size_char.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_size_char.pass.cpp
index 8a79b733fe2..e60c69f7a27 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_size_char.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_size_char.pass.cpp
@@ -265,7 +265,7 @@ void test2()
     test(S("abcdefghijklmnopqrst"), 20, 0, 20, '3', S("abcdefghijklmnopqrst33333333333333333333"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -281,4 +281,6 @@ int main()
     test2<S>();
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_string.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_string.pass.cpp
index b47d2931b9b..7008736610f 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_string.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_string.pass.cpp
@@ -264,7 +264,7 @@ void test2()
     test(S("abcdefghijklmnopqrst"), 20, 0, S("12345678901234567890"), S("abcdefghijklmnopqrst12345678901234567890"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -289,4 +289,6 @@ int main()
     assert(s == "a");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_string_view.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_string_view.pass.cpp
index 81ecca69fb3..0acf8286853 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_string_view.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/iter_iter_string_view.pass.cpp
@@ -264,7 +264,7 @@ void test2()
     test(S("abcdefghijklmnopqrst"), 20, 0, SV("12345678901234567890"), S("abcdefghijklmnopqrst12345678901234567890"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -282,4 +282,6 @@ int main()
     test2<S, SV>();
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_T_size_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_T_size_size.pass.cpp
index b320eff372c..2348747def0 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_T_size_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_T_size_size.pass.cpp
@@ -5869,7 +5869,7 @@ void test55()
     test_npos(S("abcdefghij"), 9, 2, SV("12345"), 6, S("can't happen"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -6025,4 +6025,6 @@ int main()
     s.replace(0, 4, arr, 0, std::string::npos);    // calls replace(pos1, n1, string("IJKL"), pos, npos)
     assert(s == "IJKL");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_pointer.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_pointer.pass.cpp
index 6718242e0e8..a6a6c7d9dcf 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_pointer.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_pointer.pass.cpp
@@ -363,7 +363,7 @@ void test2()
     test(S("abcdefghijklmnopqrst"), 21, 0, "12345678901234567890", S("can't happen"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -379,4 +379,6 @@ int main()
     test2<S>();
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_pointer_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_pointer_size.pass.cpp
index 53465bf680e..e3056670704 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_pointer_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_pointer_size.pass.cpp
@@ -1297,7 +1297,7 @@ void test11()
     test(S("abcdefghijklmnopqrst"), 21, 0, "12345678901234567890", 20, S("can't happen"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -1331,4 +1331,6 @@ int main()
     test11<S>();
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_size_char.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_size_char.pass.cpp
index 2e8c4527cc7..7d37e107561 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_size_char.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_size_char.pass.cpp
@@ -364,7 +364,7 @@ void test2()
     test(S("abcdefghijklmnopqrst"), 21, 0, 20, '2', S("can't happen"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -380,4 +380,6 @@ int main()
     test2<S>();
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string.pass.cpp
index 85306d59595..c0fad33a398 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string.pass.cpp
@@ -362,7 +362,7 @@ void test2()
     test(S("abcdefghijklmnopqrst"), 21, 0, S("12345678901234567890"), S("can't happen"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -387,4 +387,6 @@ int main()
     assert(s == "a");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string_size_size.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string_size_size.pass.cpp
index 7a75f03e59b..3fa32699fda 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string_size_size.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string_size_size.pass.cpp
@@ -5859,7 +5859,7 @@ void test55()
     test_npos(S("abcdefghij"), 9, 2, S("12345"), 6, S("can't happen"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -5981,4 +5981,6 @@ int main()
     test55<S>();
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string_view.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string_view.pass.cpp
index 9b35da025f9..542220aea70 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string_view.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_replace/size_size_string_view.pass.cpp
@@ -362,7 +362,7 @@ void test2()
     test(S("abcdefghijklmnopqrst"), 21, 0, SV("12345678901234567890"), S("can't happen"));
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -380,4 +380,6 @@ int main()
     test2<S, SV>();
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/strings/basic.string/string.modifiers/string_swap/swap.pass.cpp b/libcxx/test/std/strings/basic.string/string.modifiers/string_swap/swap.pass.cpp
index 79adee48764..8fdf3fea9b4 100644
--- a/libcxx/test/std/strings/basic.string/string.modifiers/string_swap/swap.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.modifiers/string_swap/swap.pass.cpp
@@ -31,7 +31,7 @@ test(S s1, S s2)
     assert(s2 == s1_);
 }
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::string S;
@@ -73,4 +73,6 @@ int main()
     test(S("abcdefghijklmnopqrst"), S("12345678901234567890"));
     }
 #endif
+
+  return 0;
 }