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

10 files changed, 30 insertions, 10 deletions

diff --git a/libcxx/test/support/nothing_to_do.pass.cpp b/libcxx/test/support/nothing_to_do.pass.cpp
index 1b231332408..f54d71c86da 100644
--- a/libcxx/test/support/nothing_to_do.pass.cpp
+++ b/libcxx/test/support/nothing_to_do.pass.cpp
@@ -7,7 +7,9 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
 
diff --git a/libcxx/test/support/test.support/test_convertible_header.pass.cpp b/libcxx/test/support/test.support/test_convertible_header.pass.cpp
index 0158dfe62ce..f2923d50cd4 100644
--- a/libcxx/test/support/test.support/test_convertible_header.pass.cpp
+++ b/libcxx/test/support/test.support/test_convertible_header.pass.cpp
@@ -62,6 +62,8 @@ struct ExplicitArgs {
 };
 static_assert(!test_convertible<ExplicitArgs, int, int, int>(), "Must not be convertible");
 
-int main() {
+int main(int, char**) {
     // Nothing to do
+
+  return 0;
 }
diff --git a/libcxx/test/support/test.support/test_demangle.pass.cpp b/libcxx/test/support/test.support/test_demangle.pass.cpp
index 5c62ecbb118..2f1b16be9bb 100644
--- a/libcxx/test/support/test.support/test_demangle.pass.cpp
+++ b/libcxx/test/support/test.support/test_demangle.pass.cpp
@@ -14,7 +14,7 @@ struct MyType {};
 
 template <class T, class U> struct ArgumentListID {};
 
-int main() {
+int main(int, char**) {
   struct {
     const char* raw;
     const char* expect;
@@ -34,4 +34,6 @@ int main() {
     assert(demangle(raw) == expect);
 #endif
   }
+
+  return 0;
 }
diff --git a/libcxx/test/support/test.support/test_macros_header_exceptions.fail.cpp b/libcxx/test/support/test.support/test_macros_header_exceptions.fail.cpp
index 66a01c9673b..b120aabc02f 100644
--- a/libcxx/test/support/test.support/test_macros_header_exceptions.fail.cpp
+++ b/libcxx/test/support/test.support/test_macros_header_exceptions.fail.cpp
@@ -12,7 +12,7 @@
 
 #include "test_macros.h"
 
-int main() {
+int main(int, char**) {
 #if defined(TEST_HAS_NO_EXCEPTIONS)
     try { ((void)0); } catch (...) {} // expected-error {{exceptions disabled}}
 #else
@@ -20,4 +20,6 @@ int main() {
 #error exceptions enabled
 // expected-error@-1 {{exceptions enabled}}
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/support/test.support/test_macros_header_exceptions.pass.cpp b/libcxx/test/support/test.support/test_macros_header_exceptions.pass.cpp
index 274cad82e33..ccdf257dceb 100644
--- a/libcxx/test/support/test.support/test_macros_header_exceptions.pass.cpp
+++ b/libcxx/test/support/test.support/test_macros_header_exceptions.pass.cpp
@@ -18,6 +18,8 @@
 #error macro defined unexpectedly
 #endif
 
-int main() {
+int main(int, char**) {
     try { ((void)0); } catch (...) {}
+
+  return 0;
 }
diff --git a/libcxx/test/support/test.support/test_macros_header_rtti.fail.cpp b/libcxx/test/support/test.support/test_macros_header_rtti.fail.cpp
index 4096ce43f10..b2f3177af80 100644
--- a/libcxx/test/support/test.support/test_macros_header_rtti.fail.cpp
+++ b/libcxx/test/support/test.support/test_macros_header_rtti.fail.cpp
@@ -15,7 +15,7 @@
 struct A { virtual ~A() {} };
 struct B : A {};
 
-int main() {
+int main(int, char**) {
 #if defined(TEST_HAS_NO_RTTI)
     A* ptr = new B;
     (void)dynamic_cast<B*>(ptr); // expected-error{{cannot use dynamic_cast}}
@@ -25,4 +25,6 @@ int main() {
 #error RTTI enabled
 // expected-error@-1{{RTTI enabled}}
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/support/test.support/test_macros_header_rtti.pass.cpp b/libcxx/test/support/test.support/test_macros_header_rtti.pass.cpp
index 9461579939f..e38545f9b9c 100644
--- a/libcxx/test/support/test.support/test_macros_header_rtti.pass.cpp
+++ b/libcxx/test/support/test.support/test_macros_header_rtti.pass.cpp
@@ -21,8 +21,10 @@
 struct A { virtual ~A() {} };
 struct B : A {};
 
-int main() {
+int main(int, char**) {
     A* ptr = new B;
     (void)dynamic_cast<B*>(ptr);
     delete ptr;
+
+  return 0;
 }
diff --git a/libcxx/test/support/test.support/test_poisoned_hash_helper.pass.cpp b/libcxx/test/support/test.support/test_poisoned_hash_helper.pass.cpp
index f94f96368ee..692854b3d26 100644
--- a/libcxx/test/support/test.support/test_poisoned_hash_helper.pass.cpp
+++ b/libcxx/test/support/test.support/test_poisoned_hash_helper.pass.cpp
@@ -24,6 +24,8 @@ template <class T> struct has_complete_hash {
   enum { value = is_complete<std::hash<T> >() };
 };
 
-int main() {
+int main(int, char**) {
   static_assert(LibraryHashTypes::assertTrait<has_complete_hash, false>(), "");
+
+  return 0;
 }
diff --git a/libcxx/test/support/test.workarounds/c1xx_broken_is_trivially_copyable.pass.cpp b/libcxx/test/support/test.workarounds/c1xx_broken_is_trivially_copyable.pass.cpp
index 40e50c14e22..1b2fd1462e2 100644
--- a/libcxx/test/support/test.workarounds/c1xx_broken_is_trivially_copyable.pass.cpp
+++ b/libcxx/test/support/test.workarounds/c1xx_broken_is_trivially_copyable.pass.cpp
@@ -25,10 +25,12 @@ struct S {
   S& operator=(S&&) = delete;
 };
 
-int main() {
+int main(int, char**) {
 #if defined(TEST_WORKAROUND_C1XX_BROKEN_IS_TRIVIALLY_COPYABLE)
   static_assert(!std::is_trivially_copyable<S>::value, "");
 #else
   static_assert(std::is_trivially_copyable<S>::value, "");
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/support/test.workarounds/c1xx_broken_za_ctor_check.pass.cpp b/libcxx/test/support/test.workarounds/c1xx_broken_za_ctor_check.pass.cpp
index 27f1fb640de..688a0f798c3 100644
--- a/libcxx/test/support/test.workarounds/c1xx_broken_za_ctor_check.pass.cpp
+++ b/libcxx/test/support/test.workarounds/c1xx_broken_za_ctor_check.pass.cpp
@@ -31,10 +31,12 @@ template<class T = int>
 auto test(int) -> decltype(PushFront(std::declval<T>()), std::true_type{});
 auto test(long) -> std::false_type;
 
-int main() {
+int main(int, char**) {
 #if defined(TEST_WORKAROUND_C1XX_BROKEN_ZA_CTOR_CHECK)
     static_assert(!decltype(test(0))::value, "");
 #else
     static_assert(decltype(test(0))::value, "");
 #endif
+
+  return 0;
 }