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

39 files changed, 117 insertions, 39 deletions

diff --git a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/member_swap.pass.cpp b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/member_swap.pass.cpp
index cb4644aad43..d0a5863ed84 100644
--- a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/member_swap.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/member_swap.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::istringstream ss0(" 123 456");
@@ -52,4 +52,6 @@ int main()
         ss0 >> i;
         assert(i == 321);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/move.pass.cpp b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/move.pass.cpp
index b906db8d5bf..5677959438f 100644
--- a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/move.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/move.pass.cpp
@@ -18,7 +18,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::istringstream ss0(" 123 456");
@@ -82,4 +82,6 @@ int main()
         s1 >> s;
         assert(s == L"Dddddddddddddddddd");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/nonmember_swap.pass.cpp b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/nonmember_swap.pass.cpp
index 09b6e4b3996..b8b00310dbe 100644
--- a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/nonmember_swap.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.assign/nonmember_swap.pass.cpp
@@ -19,7 +19,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::istringstream ss0(" 123 456");
@@ -55,4 +55,6 @@ int main()
         ss0 >> i;
         assert(i == 321);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/default.pass.cpp b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/default.pass.cpp
index 327c4ca124d..414c2269581 100644
--- a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/default.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/default.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::istringstream ss;
@@ -42,4 +42,6 @@ int main()
         assert(ss.good());
         assert(ss.str() == L"");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/move.pass.cpp b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/move.pass.cpp
index c5b144b0920..27eb5a745c8 100644
--- a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/move.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/move.pass.cpp
@@ -18,7 +18,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::istringstream ss0(" 123 456");
@@ -44,4 +44,6 @@ int main()
         ss >> i;
         assert(i == 456);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/string.pass.cpp b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/string.pass.cpp
index cf3c7d89130..04733d6042f 100644
--- a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/string.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.cons/string.pass.cpp
@@ -17,7 +17,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::istringstream ss(" 123 456");
@@ -63,4 +63,6 @@ int main()
         ss >> i;
         assert(i == 456);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.members/str.pass.cpp b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.members/str.pass.cpp
index 9b706a535ac..4c010e2b434 100644
--- a/libcxx/test/std/input.output/string.streams/istringstream/istringstream.members/str.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/istringstream/istringstream.members/str.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::istringstream ss(" 123 456");
@@ -52,4 +52,6 @@ int main()
         ss >> i;
         assert(i == 789);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/istringstream/types.pass.cpp b/libcxx/test/std/input.output/string.streams/istringstream/types.pass.cpp
index 0f256cbbdd4..97319644229 100644
--- a/libcxx/test/std/input.output/string.streams/istringstream/types.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/istringstream/types.pass.cpp
@@ -23,7 +23,7 @@
 #include <sstream>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     static_assert((std::is_base_of<std::basic_istream<char>, std::basic_istringstream<char> >::value), "");
     static_assert((std::is_same<std::basic_istringstream<char>::char_type, char>::value), "");
@@ -32,4 +32,6 @@ int main()
     static_assert((std::is_same<std::basic_istringstream<char>::pos_type, std::char_traits<char>::pos_type>::value), "");
     static_assert((std::is_same<std::basic_istringstream<char>::off_type, std::char_traits<char>::off_type>::value), "");
     static_assert((std::is_same<std::basic_istringstream<char>::allocator_type, std::allocator<char> >::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/member_swap.pass.cpp b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/member_swap.pass.cpp
index af5622ee2c9..01cc58ae6ae 100644
--- a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/member_swap.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/member_swap.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::ostringstream ss0(" 123 456");
@@ -44,4 +44,6 @@ int main()
         ss0 << i << ' ' << 567;
         assert(ss0.str() == L"234 567");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/move.pass.cpp b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/move.pass.cpp
index f44b0fba41a..bad3c7316d2 100644
--- a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/move.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/move.pass.cpp
@@ -18,7 +18,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::ostringstream ss0(" 123 456");
@@ -42,4 +42,6 @@ int main()
         ss << i << ' ' << 567;
         assert(ss.str() == L"234 5676");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/nonmember_swap.pass.cpp b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/nonmember_swap.pass.cpp
index 0793fd295cf..d251e6e085f 100644
--- a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/nonmember_swap.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.assign/nonmember_swap.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::ostringstream ss0(" 123 456");
@@ -44,4 +44,6 @@ int main()
         ss0 << i << ' ' << 567;
         assert(ss0.str() == L"234 567");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/default.pass.cpp b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/default.pass.cpp
index 79e0f614c5a..f772a904007 100644
--- a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/default.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/default.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::ostringstream ss;
@@ -42,4 +42,6 @@ int main()
         assert(ss.good());
         assert(ss.str() == L"");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/move.pass.cpp b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/move.pass.cpp
index 569310174b8..3b562bafd52 100644
--- a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/move.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/move.pass.cpp
@@ -18,7 +18,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::ostringstream ss0(" 123 456");
@@ -40,4 +40,6 @@ int main()
         ss << i << ' ' << 567;
         assert(ss.str() == L"234 5676");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/string.pass.cpp b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/string.pass.cpp
index 8d64dd5e5f1..98782dce1f6 100644
--- a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/string.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.cons/string.pass.cpp
@@ -17,7 +17,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::ostringstream ss(" 123 456");
@@ -55,4 +55,6 @@ int main()
         ss << i << ' ' << 567;
         assert(ss.str() == L"234 5676");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.members/str.pass.cpp b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.members/str.pass.cpp
index d74acf3a588..56a85159cca 100644
--- a/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.members/str.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/ostringstream/ostringstream.members/str.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::ostringstream ss(" 123 456");
@@ -48,4 +48,6 @@ int main()
         ss << L"abc";
         assert(ss.str() == L"abc9");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/ostringstream/types.pass.cpp b/libcxx/test/std/input.output/string.streams/ostringstream/types.pass.cpp
index 15e7dc61faf..0da5f98d46f 100644
--- a/libcxx/test/std/input.output/string.streams/ostringstream/types.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/ostringstream/types.pass.cpp
@@ -23,7 +23,7 @@
 #include <sstream>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     static_assert((std::is_base_of<std::basic_ostream<char>, std::basic_ostringstream<char> >::value), "");
     static_assert((std::is_same<std::basic_ostringstream<char>::char_type, char>::value), "");
@@ -32,4 +32,6 @@ int main()
     static_assert((std::is_same<std::basic_ostringstream<char>::pos_type, std::char_traits<char>::pos_type>::value), "");
     static_assert((std::is_same<std::basic_ostringstream<char>::off_type, std::char_traits<char>::off_type>::value), "");
     static_assert((std::is_same<std::basic_ostringstream<char>::allocator_type, std::allocator<char> >::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/member_swap.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/member_swap.pass.cpp
index b5dce8fb914..6977d3189cf 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/member_swap.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/member_swap.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf buf1("testing");
@@ -60,4 +60,6 @@ int main()
         assert(buf.str() == L"testing");
         assert(buf1.str() == L"");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/move.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/move.pass.cpp
index 2a469ebb79a..653edc0d19c 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/move.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/move.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf buf1("testing");
@@ -54,4 +54,6 @@ int main()
         buf = move(buf1);
         assert(buf.str() == L"testing");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/nonmember_swap.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/nonmember_swap.pass.cpp
index 5a57f902af3..38562fc3220 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/nonmember_swap.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.assign/nonmember_swap.pass.cpp
@@ -18,7 +18,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf buf1("testing");
@@ -62,4 +62,6 @@ int main()
         assert(buf.str() == L"testing");
         assert(buf1.str() == L"");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
index 2121a7a842e..836509f2fdd 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/default.pass.cpp
@@ -31,7 +31,7 @@ struct testbuf
     }
 };
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf buf;
@@ -49,4 +49,6 @@ int main()
         testbuf<wchar_t> buf;
         buf.check();
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/move.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/move.pass.cpp
index 70eff738492..a3cccd39c87 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/move.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/move.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf buf1("testing");
@@ -48,4 +48,6 @@ int main()
         std::wstringbuf buf(move(buf1));
         assert(buf.str() == L"testing");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/string.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/string.pass.cpp
index 607d314255b..de211c80ea1 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/string.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.cons/string.pass.cpp
@@ -17,7 +17,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf buf("testing");
@@ -43,4 +43,6 @@ int main()
         std::wstringbuf buf(L"testing", std::ios_base::out);
         assert(buf.str() == L"testing");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.members/str.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.members/str.pass.cpp
index baf406b696c..78b572454a5 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.members/str.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.members/str.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf buf("testing");
@@ -30,4 +30,6 @@ int main()
         buf.str(L"another test");
         assert(buf.str() == L"another test");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/overflow.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/overflow.pass.cpp
index 0f833070525..c9fdd0abcc9 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/overflow.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/overflow.pass.cpp
@@ -34,7 +34,7 @@ struct testbuf
     void pbump(int n) {base::pbump(n);}
 };
 
-int main()
+int main(int, char**)
 {
     {  // sanity check
     testbuf<char> tb("");
@@ -97,4 +97,6 @@ int main()
         assert(sb.sputc('2') == '2');
         assert(sb.str() == "abc12");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/pbackfail.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/pbackfail.pass.cpp
index dfbe2084b9d..458e393c8ec 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/pbackfail.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/pbackfail.pass.cpp
@@ -32,7 +32,7 @@ struct testbuf
     void pbump(int n) {base::pbump(n);}
 };
 
-int main()
+int main(int, char**)
 {
     {  // sanity check
     testbuf<char> tb("");
@@ -92,4 +92,6 @@ int main()
         assert(sb.pbackfail(std::char_traits<wchar_t>::eof()) == std::char_traits<wchar_t>::eof());
         assert(sb.str() == L"133");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/seekoff.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/seekoff.pass.cpp
index dbe117eaa17..1bee5c216a5 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/seekoff.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/seekoff.pass.cpp
@@ -17,7 +17,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf sb(std::ios_base::in);
@@ -163,4 +163,6 @@ int main()
         assert(sb.sputc(L'c') == L'c');
         assert(sb.str() == L"0123456c89");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/seekpos.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/seekpos.pass.cpp
index 7d687e070c1..fde91e74ba0 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/seekpos.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/seekpos.pass.cpp
@@ -17,7 +17,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf sb("0123456789", std::ios_base::in);
@@ -73,4 +73,6 @@ int main()
         assert(sb.sputc(L'3') == L'3');
         assert(sb.str() == L"0123456789");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/setbuf.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/setbuf.pass.cpp
index 99bc75e6c8a..f833debe39d 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/setbuf.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/setbuf.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringbuf sb("0123456789");
@@ -28,4 +28,6 @@ int main()
         assert(sb.pubsetbuf(0, 0) == &sb);
         assert(sb.str() == L"0123456789");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/underflow.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/underflow.pass.cpp
index c3244985749..23b77d229ca 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/underflow.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/stringbuf.virtuals/underflow.pass.cpp
@@ -28,7 +28,7 @@ struct testbuf
     void pbump(int n) {base::pbump(n);}
 };
 
-int main()
+int main(int, char**)
 {
     {
         testbuf<char> sb("123");
@@ -66,4 +66,6 @@ int main()
         assert(sb.underflow() == L'4');
         assert(sb.underflow() == L'4');
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringbuf/types.pass.cpp b/libcxx/test/std/input.output/string.streams/stringbuf/types.pass.cpp
index 29d651fc5e5..c27db853599 100644
--- a/libcxx/test/std/input.output/string.streams/stringbuf/types.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringbuf/types.pass.cpp
@@ -23,7 +23,7 @@
 #include <sstream>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     static_assert((std::is_base_of<std::basic_streambuf<char>, std::basic_stringbuf<char> >::value), "");
     static_assert((std::is_same<std::basic_stringbuf<char>::char_type, char>::value), "");
@@ -32,4 +32,6 @@ int main()
     static_assert((std::is_same<std::basic_stringbuf<char>::pos_type, std::char_traits<char>::pos_type>::value), "");
     static_assert((std::is_same<std::basic_stringbuf<char>::off_type, std::char_traits<char>::off_type>::value), "");
     static_assert((std::is_same<std::basic_stringbuf<char>::allocator_type, std::allocator<char> >::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringstream.cons/default.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream.cons/default.pass.cpp
index 571c3dc658e..11cf288fcc9 100644
--- a/libcxx/test/std/input.output/string.streams/stringstream.cons/default.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream.cons/default.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringstream ss;
@@ -42,4 +42,6 @@ int main()
         assert(ss.good());
         assert(ss.str() == L"");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringstream.cons/move.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream.cons/move.pass.cpp
index 671aee55397..2a73ad9c215 100644
--- a/libcxx/test/std/input.output/string.streams/stringstream.cons/move.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream.cons/move.pass.cpp
@@ -18,7 +18,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringstream ss0(" 123 456 ");
@@ -48,4 +48,6 @@ int main()
         ss << i << ' ' << 123;
         assert(ss.str() == L"456 1236 ");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringstream.cons/move2.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream.cons/move2.pass.cpp
index 4527cae33f6..044e62824ca 100644
--- a/libcxx/test/std/input.output/string.streams/stringstream.cons/move2.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream.cons/move2.pass.cpp
@@ -21,7 +21,7 @@
 #include <cassert>
 #include <cstddef>
 
-int main()
+int main(int, char**)
 {
     std::vector<std::istringstream> vecis;
     vecis.push_back(std::istringstream());
@@ -34,4 +34,6 @@ int main()
         vecis[n].seekg(0, std::ios_base::beg);
         assert(vecis[n].str().size() == 31);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringstream.cons/string.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream.cons/string.pass.cpp
index 7bc383f9a4a..29c81b3be62 100644
--- a/libcxx/test/std/input.output/string.streams/stringstream.cons/string.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream.cons/string.pass.cpp
@@ -27,7 +27,7 @@ struct NoDefaultAllocator : std::allocator<T>
 };
 
 
-int main()
+int main(int, char**)
 {
     {
         std::stringstream ss(" 123 456 ");
@@ -64,4 +64,6 @@ int main()
     //  This test is not required by the standard, but *where else* could it get the allocator?
         assert(sb.str().get_allocator() == s.get_allocator());
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/member_swap.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/member_swap.pass.cpp
index 07d3a1dea9d..2e0f4471a1c 100644
--- a/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/member_swap.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/member_swap.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringstream ss0(" 123 456 ");
@@ -52,4 +52,6 @@ int main()
         ss0 << i << ' ' << 123;
         assert(ss0.str() == L"456 123");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/move.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/move.pass.cpp
index 0332924a69f..c3088679ed6 100644
--- a/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/move.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/move.pass.cpp
@@ -18,7 +18,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringstream ss0(" 123 456 ");
@@ -50,4 +50,6 @@ int main()
         ss << i << ' ' << 123;
         assert(ss.str() == L"456 1236 ");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/nonmember_swap.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/nonmember_swap.pass.cpp
index 3225b273e68..06a95dcb394 100644
--- a/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/nonmember_swap.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream.cons/stringstream.assign/nonmember_swap.pass.cpp
@@ -19,7 +19,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringstream ss0(" 123 456 ");
@@ -55,4 +55,6 @@ int main()
         ss0 << i << ' ' << 123;
         assert(ss0.str() == L"456 123");
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringstream.members/str.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream.members/str.pass.cpp
index 392a1680e5c..1dc655193b8 100644
--- a/libcxx/test/std/input.output/string.streams/stringstream.members/str.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream.members/str.pass.cpp
@@ -16,7 +16,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         std::stringstream ss(" 123 456 ");
@@ -63,4 +63,6 @@ int main()
         ss.write("\xd1", 1);
         assert(ss.str().length() == 1);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/input.output/string.streams/stringstream/types.pass.cpp b/libcxx/test/std/input.output/string.streams/stringstream/types.pass.cpp
index e05048a2df1..580ccb9a4e6 100644
--- a/libcxx/test/std/input.output/string.streams/stringstream/types.pass.cpp
+++ b/libcxx/test/std/input.output/string.streams/stringstream/types.pass.cpp
@@ -23,7 +23,7 @@
 #include <sstream>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     static_assert((std::is_base_of<std::basic_iostream<char>, std::basic_stringstream<char> >::value), "");
     static_assert((std::is_same<std::basic_stringstream<char>::char_type, char>::value), "");
@@ -32,4 +32,6 @@ int main()
     static_assert((std::is_same<std::basic_stringstream<char>::pos_type, std::char_traits<char>::pos_type>::value), "");
     static_assert((std::is_same<std::basic_stringstream<char>::off_type, std::char_traits<char>::off_type>::value), "");
     static_assert((std::is_same<std::basic_stringstream<char>::allocator_type, std::allocator<char> >::value), "");
+
+  return 0;
 }