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

38 files changed, 114 insertions, 38 deletions

diff --git a/libcxx/test/std/numerics/rand/rand.eng/nothing_to_do.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/nothing_to_do.pass.cpp
index f77636c8475..1f764da05d6 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/nothing_to_do.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/nothing_to_do.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/assign.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/assign.pass.cpp
index 313f4278d79..cfaad1a33a5 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/assign.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/assign.pass.cpp
@@ -48,10 +48,12 @@ test()
     test1<T, M-1, M-1, M>();
 }
 
-int main()
+int main(int, char**)
 {
     test<unsigned short>();
     test<unsigned int>();
     test<unsigned long>();
     test<unsigned long long>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/copy.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/copy.pass.cpp
index c49d361787a..35585423442 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/copy.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/copy.pass.cpp
@@ -48,10 +48,12 @@ test()
     test1<T, M-1, M-1, M>();
 }
 
-int main()
+int main(int, char**)
 {
     test<unsigned short>();
     test<unsigned int>();
     test<unsigned long>();
     test<unsigned long long>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/ctor_result_type.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/ctor_result_type.pass.cpp
index 97d2ef2d290..4f2da2f612a 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/ctor_result_type.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/ctor_result_type.pass.cpp
@@ -129,7 +129,7 @@ test4()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test1<unsigned short>();
     test1<unsigned int>();
@@ -150,4 +150,6 @@ int main()
     test4<unsigned int>();
     test4<unsigned long>();
     test4<unsigned long long>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/ctor_sseq.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/ctor_sseq.pass.cpp
index a489bcd18da..7e82f6395f9 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/ctor_sseq.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/ctor_sseq.pass.cpp
@@ -16,7 +16,7 @@
 #include <random>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         unsigned a[] = {3, 5, 7};
@@ -25,4 +25,6 @@ int main()
         std::linear_congruential_engine<unsigned, 5, 7, 11> e2(4);
         assert(e1 == e2);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/default.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/default.pass.cpp
index 67846b06dd2..372d98a656c 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/default.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/default.pass.cpp
@@ -46,10 +46,12 @@ test()
     test1<T, M-1, M-1, M>();
 }
 
-int main()
+int main(int, char**)
 {
     test<unsigned short>();
     test<unsigned int>();
     test<unsigned long>();
     test<unsigned long long>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/discard.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/discard.pass.cpp
index 4848a3d76f6..dcbb3e0656b 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/discard.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/discard.pass.cpp
@@ -56,7 +56,7 @@ other()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     rand0<unsigned int>();
     rand0<unsigned long>();
@@ -69,4 +69,6 @@ int main()
     other<unsigned int>();
     other<unsigned long>();
     other<unsigned long long>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/eval.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/eval.pass.cpp
index ec217f306f0..3ee4d9113ac 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/eval.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/eval.pass.cpp
@@ -70,7 +70,7 @@ Haldir()
     assert(e() == 217250280);
 }
 
-int main()
+int main(int, char**)
 {
     randu<unsigned int>();
     randu<unsigned long>();
@@ -83,4 +83,6 @@ int main()
     Haldir<unsigned int>();
     Haldir<unsigned long>();
     Haldir<unsigned long long>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/io.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/io.pass.cpp
index 04159baa5d7..b12de7b0190 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/io.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/io.pass.cpp
@@ -27,7 +27,7 @@
 #include <sstream>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         typedef std::linear_congruential_engine<unsigned, 48271, 0, 2147483647> E;
@@ -40,4 +40,6 @@ int main()
         is >> e2;
         assert(e1 == e2);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/result_type.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/result_type.pass.cpp
index 569e76050b3..e0bb2e02cc1 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/result_type.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/result_type.pass.cpp
@@ -27,10 +27,12 @@ test()
         T>::value), "");
 }
 
-int main()
+int main(int, char**)
 {
     test<unsigned short>();
     test<unsigned int>();
     test<unsigned long>();
     test<unsigned long long>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/seed_result_type.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/seed_result_type.pass.cpp
index da944061bff..3103bf7efb5 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/seed_result_type.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/seed_result_type.pass.cpp
@@ -30,10 +30,12 @@ test1()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test1<unsigned short>();
     test1<unsigned int>();
     test1<unsigned long>();
     test1<unsigned long long>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/seed_sseq.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/seed_sseq.pass.cpp
index c3aec15f6d5..e7725bd0b58 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/seed_sseq.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/seed_sseq.pass.cpp
@@ -16,7 +16,7 @@
 #include <random>
 #include <cassert>
 
-int main()
+int main(int, char**)
 {
     {
         unsigned a[] = {3, 5, 7};
@@ -35,4 +35,6 @@ int main()
         E e2(sseq);
         assert(e1 == e2);
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/values.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/values.pass.cpp
index b649b24bb4c..a8c86bad306 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/values.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.lcong/values.pass.cpp
@@ -85,10 +85,12 @@ test()
     test1<T, M-1, M-1, M>();
 }
 
-int main()
+int main(int, char**)
 {
     test<unsigned short>();
     test<unsigned int>();
     test<unsigned long>();
     test<unsigned long long>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/assign.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/assign.pass.cpp
index 3ac6d303296..3e1002b061e 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/assign.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/assign.pass.cpp
@@ -50,8 +50,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/copy.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/copy.pass.cpp
index eb0486aa784..b1273f1bbc3 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/copy.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/copy.pass.cpp
@@ -48,8 +48,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_result_type.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_result_type.pass.cpp
index ae89e6e79e7..4eca3baad32 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_result_type.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_result_type.pass.cpp
@@ -237,8 +237,10 @@ test2()
     assert(os.str() == a);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_sseq.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_sseq.pass.cpp
index d695441cd68..b46029a2923 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_sseq.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_sseq.pass.cpp
@@ -301,8 +301,10 @@ test2()
     assert(os.str() == a);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_sseq_all_zero.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_sseq_all_zero.pass.cpp
index 9f298ea4995..a2489cf6366 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_sseq_all_zero.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/ctor_sseq_all_zero.pass.cpp
@@ -71,10 +71,12 @@ void test(void) {
   assert(e() == X0);
 }
 
-int main() {
+int main(int, char**) {
   // Test for k == 1: word_size <= 32.
   test<unsigned short, 3u>();
 
   // Test for k == 2: (32 < word_size <= 64).
   test<unsigned long long, 33u>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/default.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/default.pass.cpp
index 2d91db790da..35364f312a9 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/default.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/default.pass.cpp
@@ -37,8 +37,10 @@ test2()
     assert(e1() == 14514284786278117030ull);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/discard.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/discard.pass.cpp
index 58d59975def..750afb1e8a1 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/discard.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/discard.pass.cpp
@@ -47,8 +47,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/eval.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/eval.pass.cpp
index 9d44192f3f3..03e87dad8c4 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/eval.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/eval.pass.cpp
@@ -37,8 +37,10 @@ test2()
     assert(e() == 13109570281517897720ull);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/io.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/io.pass.cpp
index 8f7c699ee65..cbc764e8dd6 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/io.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/io.pass.cpp
@@ -61,8 +61,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/result_type.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/result_type.pass.cpp
index ce0506043c9..7987d65748e 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/result_type.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/result_type.pass.cpp
@@ -36,8 +36,10 @@ test2()
         std::uint_fast64_t>::value), "");
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/seed_result_type.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/seed_result_type.pass.cpp
index ef529ffcf6b..ff7d07374cb 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/seed_result_type.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/seed_result_type.pass.cpp
@@ -44,8 +44,10 @@ test2()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/seed_sseq.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/seed_sseq.pass.cpp
index 3d05ce779cf..8ad2ec289f6 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/seed_sseq.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/seed_sseq.pass.cpp
@@ -42,8 +42,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/values.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/values.pass.cpp
index 62ac9f516a8..1af1d85b25f 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/values.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.mers/values.pass.cpp
@@ -126,8 +126,10 @@ test2()
     where(E::default_seed);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/assign.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/assign.pass.cpp
index c05831165f8..e6cce1b2da7 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/assign.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/assign.pass.cpp
@@ -48,8 +48,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/copy.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/copy.pass.cpp
index 70a2b5b2cf7..c39f39858e4 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/copy.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/copy.pass.cpp
@@ -46,8 +46,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/ctor_result_type.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/ctor_result_type.pass.cpp
index 3045b06c92f..5a178e82e6f 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/ctor_result_type.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/ctor_result_type.pass.cpp
@@ -43,8 +43,10 @@ test2()
     assert(os.str() == a);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/ctor_sseq.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/ctor_sseq.pass.cpp
index 361a0fc25dd..0ed496e71af 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/ctor_sseq.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/ctor_sseq.pass.cpp
@@ -47,8 +47,10 @@ test2()
     assert(os.str() == a);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/default.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/default.pass.cpp
index 13dede1aa94..dbc4c5b4cb8 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/default.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/default.pass.cpp
@@ -34,8 +34,10 @@ test2()
     assert(e1() == 23459059301164ull);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/discard.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/discard.pass.cpp
index f4824cd9a1c..4d039289bff 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/discard.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/discard.pass.cpp
@@ -44,8 +44,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/eval.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/eval.pass.cpp
index 818d66c441e..d8d03c09ee5 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/eval.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/eval.pass.cpp
@@ -34,8 +34,10 @@ test2()
     assert(e() == 276846226770426ull);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/io.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/io.pass.cpp
index 88d0910d2e7..d3eeda3be4a 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/io.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/io.pass.cpp
@@ -55,8 +55,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/result_type.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/result_type.pass.cpp
index cc0fa903adc..5312bb1ff3a 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/result_type.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/result_type.pass.cpp
@@ -34,8 +34,10 @@ test2()
         std::uint_fast64_t>::value), "");
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/seed_result_type.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/seed_result_type.pass.cpp
index 201ec38d1e5..637841a679b 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/seed_result_type.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/seed_result_type.pass.cpp
@@ -42,8 +42,10 @@ test2()
     }
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/seed_sseq.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/seed_sseq.pass.cpp
index 2a178388ce0..85199c0ef3b 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/seed_sseq.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/seed_sseq.pass.cpp
@@ -40,8 +40,10 @@ test2()
     assert(e1 == e2);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }
diff --git a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/values.pass.cpp b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/values.pass.cpp
index 758a5957f12..a877eff1383 100644
--- a/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/values.pass.cpp
+++ b/libcxx/test/std/numerics/rand/rand.eng/rand.eng.sub/values.pass.cpp
@@ -74,8 +74,10 @@ test2()
     where(E::default_seed);
 }
 
-int main()
+int main(int, char**)
 {
     test1();
     test2();
+
+  return 0;
 }