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

46 files changed, 54 insertions, 46 deletions

diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/algorithm.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/algorithm.version.pass.cpp
index 57234ad4362..5458e919429 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/algorithm.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/algorithm.version.pass.cpp
@@ -188,4 +188,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/any.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/any.version.pass.cpp
index 9bbaca7aa15..f5255c0e26a 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/any.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/any.version.pass.cpp
@@ -52,4 +52,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/array.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/array.version.pass.cpp
index 85bda432290..d590f98042d 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/array.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/array.version.pass.cpp
@@ -101,4 +101,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/atomic.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/atomic.version.pass.cpp
index 3fb2c7ed147..d8f6f548cd2 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/atomic.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/atomic.version.pass.cpp
@@ -118,4 +118,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/bit.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/bit.version.pass.cpp
index 6c26e06a0b0..3e42d06fbe8 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/bit.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/bit.version.pass.cpp
@@ -55,4 +55,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/charconv.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/charconv.pass.cpp
index 045dcb8ac38..2afe2e26ba5 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/charconv.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/charconv.pass.cpp
@@ -17,7 +17,7 @@
 #include <cassert>
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
 //  ensure that the macros that are supposed to be defined in <utility> are defined.
 
@@ -28,4 +28,6 @@ int main()
 # error "__cpp_lib_fooby has an invalid value"
 #endif
 */
+
+  return 0;
 }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/chrono.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/chrono.version.pass.cpp
index 9e434c5c253..88da2dcca6d 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/chrono.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/chrono.version.pass.cpp
@@ -78,4 +78,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/cmath.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/cmath.version.pass.cpp
index bcc2053585a..d81218e66ab 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/cmath.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/cmath.version.pass.cpp
@@ -87,4 +87,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/compare.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/compare.version.pass.cpp
index 2864c9f4eb0..7f1836fba00 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/compare.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/compare.version.pass.cpp
@@ -55,4 +55,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/complex.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/complex.version.pass.cpp
index c6a9b16481f..bcff0bbe185 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/complex.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/complex.version.pass.cpp
@@ -55,4 +55,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/concepts.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/concepts.version.pass.cpp
index 9d9b9bca3fe..16febf8d3e2 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/concepts.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/concepts.version.pass.cpp
@@ -19,7 +19,7 @@
 #include <cassert>
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
 //  ensure that the macros that are supposed to be defined in <concepts> are defined.
 
@@ -30,4 +30,6 @@ int main()
 # error "__cpp_lib_fooby has an invalid value"
 #endif
 */
+
+  return 0;
 }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/cstddef.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/cstddef.version.pass.cpp
index 82a0932d0dc..b18ea07ea0c 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/cstddef.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/cstddef.version.pass.cpp
@@ -52,4 +52,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/deque.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/deque.version.pass.cpp
index 53a1b33450b..9d07dcdd246 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/deque.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/deque.version.pass.cpp
@@ -95,4 +95,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/exception.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/exception.version.pass.cpp
index c27bdc6b063..1ecebb48f0f 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/exception.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/exception.version.pass.cpp
@@ -52,4 +52,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/execution.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/execution.version.pass.cpp
index 476a31ef93f..b05f41bb173 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/execution.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/execution.version.pass.cpp
@@ -19,7 +19,7 @@
 #include <cassert>
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
 //  ensure that the macros that are supposed to be defined in <execution> are defined.
 
@@ -30,4 +30,6 @@ int main()
 # error "__cpp_lib_fooby has an invalid value"
 #endif
 */
+
+  return 0;
 }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/filesystem.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/filesystem.version.pass.cpp
index 6638cdee90c..d1c09fc7ee4 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/filesystem.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/filesystem.version.pass.cpp
@@ -78,4 +78,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/forward_list.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/forward_list.version.pass.cpp
index 102cd29ea56..7ecad6d3e34 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/forward_list.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/forward_list.version.pass.cpp
@@ -144,4 +144,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/functional.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/functional.version.pass.cpp
index e1146423119..a29a1d708a3 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/functional.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/functional.version.pass.cpp
@@ -241,4 +241,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/iomanip.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/iomanip.version.pass.cpp
index bd2ea2417a2..23378e0e2e3 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/iomanip.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/iomanip.version.pass.cpp
@@ -55,4 +55,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/istream.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/istream.version.pass.cpp
index 9194ff85528..3d8fb7a4cf9 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/istream.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/istream.version.pass.cpp
@@ -55,4 +55,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/iterator.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/iterator.version.pass.cpp
index b1ad28206f7..9c1719b53cf 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/iterator.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/iterator.version.pass.cpp
@@ -179,4 +179,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/limits.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/limits.version.pass.cpp
index bb2005e327c..2d2f243e704 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/limits.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/limits.version.pass.cpp
@@ -55,4 +55,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/list.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/list.version.pass.cpp
index c1159cf73a1..b736d1f9a21 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/list.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/list.version.pass.cpp
@@ -144,4 +144,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/locale.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/locale.version.pass.cpp
index c5a5b543650..eeea5390afd 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/locale.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/locale.version.pass.cpp
@@ -55,4 +55,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/map.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/map.version.pass.cpp
index c1ecad72321..a41dd1b8e98 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/map.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/map.version.pass.cpp
@@ -167,4 +167,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.pass.cpp
index 55e595fa9a8..6c845d71feb 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/memory.version.pass.cpp
@@ -243,4 +243,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/memory_resource.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/memory_resource.version.pass.cpp
index cb182adc16a..d712a8bca8d 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/memory_resource.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/memory_resource.version.pass.cpp
@@ -19,7 +19,7 @@
 #include <cassert>
 #include "test_macros.h"
 
-int main()
+int main(int, char**)
 {
 //  ensure that the macros that are supposed to be defined in <memory_resource> are defined.
 
@@ -30,4 +30,6 @@ int main()
 # error "__cpp_lib_fooby has an invalid value"
 #endif
 */
+
+  return 0;
 }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/mutex.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/mutex.version.pass.cpp
index 4986a1f192d..9dae806b812 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/mutex.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/mutex.version.pass.cpp
@@ -52,4 +52,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/new.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/new.version.pass.cpp
index 95a717dfbd2..5f012cd55f6 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/new.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/new.version.pass.cpp
@@ -101,4 +101,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/numeric.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/numeric.version.pass.cpp
index f44cbc2c75c..eb5eb557b7b 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/numeric.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/numeric.version.pass.cpp
@@ -87,4 +87,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/optional.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/optional.version.pass.cpp
index 59e698d769d..d88fbb0fee8 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/optional.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/optional.version.pass.cpp
@@ -52,4 +52,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/ostream.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/ostream.version.pass.cpp
index 17be75c2e72..d3ba25867d0 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/ostream.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/ostream.version.pass.cpp
@@ -55,4 +55,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/regex.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/regex.version.pass.cpp
index 412e29c6c54..66becadbbfb 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/regex.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/regex.version.pass.cpp
@@ -52,4 +52,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/scoped_allocator.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/scoped_allocator.version.pass.cpp
index d111f263c13..2ea98256e1b 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/scoped_allocator.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/scoped_allocator.version.pass.cpp
@@ -52,4 +52,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/set.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/set.version.pass.cpp
index c886850ceba..80cf9c0af3c 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/set.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/set.version.pass.cpp
@@ -144,4 +144,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/shared_mutex.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/shared_mutex.version.pass.cpp
index 12c58480bdf..7c92dfc085c 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/shared_mutex.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/shared_mutex.version.pass.cpp
@@ -110,4 +110,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/string.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/string.version.pass.cpp
index 0f1c37b90e4..bdd517da0de 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/string.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/string.version.pass.cpp
@@ -170,4 +170,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/string_view.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/string_view.version.pass.cpp
index adad6b084e3..816083e0d7f 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/string_view.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/string_view.version.pass.cpp
@@ -104,4 +104,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/tuple.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/tuple.version.pass.cpp
index e2d9865324e..5c1e6580c57 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/tuple.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/tuple.version.pass.cpp
@@ -153,4 +153,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/type_traits.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/type_traits.version.pass.cpp
index 59994b77956..7e8b3de35f4 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/type_traits.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/type_traits.version.pass.cpp
@@ -393,4 +393,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/unordered_map.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/unordered_map.version.pass.cpp
index f6f4e6cecc2..07eb1a9bc35 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/unordered_map.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/unordered_map.version.pass.cpp
@@ -167,4 +167,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/unordered_set.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/unordered_set.version.pass.cpp
index 07a3c302adc..845318a79a5 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/unordered_set.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/unordered_set.version.pass.cpp
@@ -144,4 +144,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/utility.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/utility.version.pass.cpp
index 6b051d289d4..1fd38627a71 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/utility.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/utility.version.pass.cpp
@@ -191,4 +191,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/variant.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/variant.version.pass.cpp
index 23a15a67060..7a17307460d 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/variant.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/variant.version.pass.cpp
@@ -52,4 +52,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/vector.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/vector.version.pass.cpp
index c22921e775d..3ea2a0cf00b 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/vector.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/vector.version.pass.cpp
@@ -118,4 +118,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }
diff --git a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp
index aa409e1547a..b85d42d00ca 100644
--- a/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp
+++ b/libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp
@@ -2174,4 +2174,4 @@
 
 #endif // TEST_STD_VER > 17
 
-int main() {}
+int main(int, char**) { return 0; }