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

18 files changed, 54 insertions, 18 deletions

diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.basic/iterator.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.basic/iterator.pass.cpp
index e922a4bfa46..b5929ca8c10 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.basic/iterator.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.basic/iterator.pass.cpp
@@ -72,10 +72,12 @@ test5()
     static_assert((std::is_same<typename It::iterator_category, std::input_iterator_tag>::value), "");
 }
 
-int main()
+int main(int, char**)
 {
     test2<A>();
     test3<A>();
     test4<A>();
     test5<A>();
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/advance.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/advance.pass.cpp
index 6382d06c74b..45408056370 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/advance.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/advance.pass.cpp
@@ -42,7 +42,7 @@ constepxr_test(It i, typename std::iterator_traits<It>::difference_type n, It x)
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
     const char* s = "1234567890";
@@ -68,4 +68,6 @@ int main()
     static_assert( constepxr_test(s+5, -5, s), "" );
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/distance.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/distance.pass.cpp
index 86fcfbc5853..bd1b02a484d 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/distance.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/distance.pass.cpp
@@ -37,7 +37,7 @@ constexpr_test(It first, It last, typename std::iterator_traits<It>::difference_
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
     const char* s = "1234567890";
@@ -57,4 +57,6 @@ int main()
     static_assert( constexpr_test(s, s+10, 10), "");
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.pass.cpp
index ad99aed99b5..87f79fbd32b 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/next.pass.cpp
@@ -51,7 +51,7 @@ constexpr_test(It i, It x)
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
     const char* s = "1234567890";
@@ -83,4 +83,6 @@ int main()
     static_assert( constexpr_test(s, s+1), "" );
     }
 #endif
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/prev.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/prev.pass.cpp
index b7d99391723..2ee0444ce14 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.operations/prev.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.operations/prev.pass.cpp
@@ -49,7 +49,7 @@ constexpr_test(It i, It x)
 }
 #endif
 
-int main()
+int main(int, char**)
 {
     {
     const char* s = "1234567890";
@@ -74,4 +74,6 @@ int main()
     }
 #endif
 
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/const_pointer.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/const_pointer.pass.cpp
index 246aeb5e8bb..5abf59bf3de 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/const_pointer.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/const_pointer.pass.cpp
@@ -23,7 +23,7 @@
 
 struct A {};
 
-int main()
+int main(int, char**)
 {
     typedef std::iterator_traits<const A*> It;
     static_assert((std::is_same<It::difference_type, std::ptrdiff_t>::value), "");
@@ -31,4 +31,6 @@ int main()
     static_assert((std::is_same<It::pointer, const A*>::value), "");
     static_assert((std::is_same<It::reference, const A&>::value), "");
     static_assert((std::is_same<It::iterator_category, std::random_access_iterator_tag>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/const_volatile_pointer.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/const_volatile_pointer.pass.cpp
index 774609e1cc1..358abb619b1 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/const_volatile_pointer.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/const_volatile_pointer.pass.cpp
@@ -16,7 +16,7 @@
 
 struct A {};
 
-int main()
+int main(int, char**)
 {
     typedef std::iterator_traits<const volatile A*> It;
     static_assert((std::is_same<It::difference_type, std::ptrdiff_t>::value), "");
@@ -24,4 +24,6 @@ int main()
     static_assert((std::is_same<It::pointer, const volatile A*>::value), "");
     static_assert((std::is_same<It::reference, const volatile A&>::value), "");
     static_assert((std::is_same<It::iterator_category, std::random_access_iterator_tag>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/empty.fail.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/empty.fail.cpp
index 5c5c07d442d..728909e693c 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/empty.fail.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/empty.fail.cpp
@@ -63,7 +63,7 @@ struct NotAnIteratorNoCategory
 //     typedef std::forward_iterator_tag iterator_category;
 };
 
-int main()
+int main(int, char**)
 {
     {
     typedef std::iterator_traits<NotAnIteratorEmpty> T;
@@ -118,4 +118,6 @@ int main()
     typedef T::reference         RT; // expected-error-re {{no type named 'reference' in 'std::{{.+}}::iterator_traits<{{.+}}>}}
     typedef T::iterator_category CT; // expected-error-re {{no type named 'iterator_category' in 'std::{{.+}}::iterator_traits<{{.+}}>}}
     }
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/empty.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/empty.pass.cpp
index 81dca5186ec..35fc877f206 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/empty.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/empty.pass.cpp
@@ -30,8 +30,10 @@ public:
     static const bool value = sizeof(test<T>(0)) == 1;
 };
 
-int main()
+int main(int, char**)
 {
     typedef std::iterator_traits<not_an_iterator> It;
     static_assert(!(has_value_type<It>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/iterator.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/iterator.pass.cpp
index 1c8d11eb151..1e4d87c757c 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/iterator.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/iterator.pass.cpp
@@ -32,7 +32,7 @@ struct test_iterator
     typedef std::forward_iterator_tag iterator_category;
 };
 
-int main()
+int main(int, char**)
 {
     typedef std::iterator_traits<test_iterator> It;
     static_assert((std::is_same<It::difference_type, int>::value), "");
@@ -40,4 +40,6 @@ int main()
     static_assert((std::is_same<It::pointer, A*>::value), "");
     static_assert((std::is_same<It::reference, A&>::value), "");
     static_assert((std::is_same<It::iterator_category, std::forward_iterator_tag>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/pointer.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/pointer.pass.cpp
index 3be21c49a3b..6016f6d4088 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/pointer.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/pointer.pass.cpp
@@ -23,7 +23,7 @@
 
 struct A {};
 
-int main()
+int main(int, char**)
 {
     typedef std::iterator_traits<A*> It;
     static_assert((std::is_same<It::difference_type, std::ptrdiff_t>::value), "");
@@ -31,4 +31,6 @@ int main()
     static_assert((std::is_same<It::pointer, A*>::value), "");
     static_assert((std::is_same<It::reference, A&>::value), "");
     static_assert((std::is_same<It::iterator_category, std::random_access_iterator_tag>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/volatile_pointer.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/volatile_pointer.pass.cpp
index ebcc30075af..035360645dc 100644
--- a/libcxx/test/std/iterators/iterator.primitives/iterator.traits/volatile_pointer.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/iterator.traits/volatile_pointer.pass.cpp
@@ -16,7 +16,7 @@
 
 struct A {};
 
-int main()
+int main(int, char**)
 {
     typedef std::iterator_traits<volatile A*> It;
     static_assert((std::is_same<It::difference_type, std::ptrdiff_t>::value), "");
@@ -24,4 +24,6 @@ int main()
     static_assert((std::is_same<It::pointer, volatile A*>::value), "");
     static_assert((std::is_same<It::reference, volatile A&>::value), "");
     static_assert((std::is_same<It::iterator_category, std::random_access_iterator_tag>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/nothing_to_do.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/nothing_to_do.pass.cpp
index f77636c8475..1f764da05d6 100644
--- a/libcxx/test/std/iterators/iterator.primitives/nothing_to_do.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/nothing_to_do.pass.cpp
@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-int main()
+int main(int, char**)
 {
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/bidirectional_iterator_tag.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/bidirectional_iterator_tag.pass.cpp
index 6d7f64b9a1e..8380fb6b4e2 100644
--- a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/bidirectional_iterator_tag.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/bidirectional_iterator_tag.pass.cpp
@@ -13,7 +13,7 @@
 #include <iterator>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     std::bidirectional_iterator_tag tag;
     ((void)tag); // Prevent unused warning
@@ -21,4 +21,6 @@ int main()
                                    std::bidirectional_iterator_tag>::value), "");
     static_assert((!std::is_base_of<std::output_iterator_tag,
                                     std::bidirectional_iterator_tag>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/forward_iterator_tag.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/forward_iterator_tag.pass.cpp
index 753f25c667b..0afdc3eca0a 100644
--- a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/forward_iterator_tag.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/forward_iterator_tag.pass.cpp
@@ -13,7 +13,7 @@
 #include <iterator>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     std::forward_iterator_tag tag;
     ((void)tag); // Prevent unused warning
@@ -21,4 +21,6 @@ int main()
                                    std::forward_iterator_tag>::value), "");
     static_assert((!std::is_base_of<std::output_iterator_tag,
                                     std::forward_iterator_tag>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/input_iterator_tag.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/input_iterator_tag.pass.cpp
index ac517dd6785..26de37448d1 100644
--- a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/input_iterator_tag.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/input_iterator_tag.pass.cpp
@@ -13,10 +13,12 @@
 #include <iterator>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     std::input_iterator_tag tag;
     ((void)tag); // Prevent unused warning
     static_assert((!std::is_base_of<std::output_iterator_tag,
                                     std::input_iterator_tag>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/output_iterator_tag.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/output_iterator_tag.pass.cpp
index 1635850cf59..657e6f8ea18 100644
--- a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/output_iterator_tag.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/output_iterator_tag.pass.cpp
@@ -13,10 +13,12 @@
 #include <iterator>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     std::output_iterator_tag tag;
     ((void)tag); // Prevent unused warning
     static_assert((!std::is_base_of<std::input_iterator_tag,
                                     std::output_iterator_tag>::value), "");
+
+  return 0;
 }
diff --git a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/random_access_iterator_tag.pass.cpp b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/random_access_iterator_tag.pass.cpp
index da2de468176..5448a671573 100644
--- a/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/random_access_iterator_tag.pass.cpp
+++ b/libcxx/test/std/iterators/iterator.primitives/std.iterator.tags/random_access_iterator_tag.pass.cpp
@@ -13,7 +13,7 @@
 #include <iterator>
 #include <type_traits>
 
-int main()
+int main(int, char**)
 {
     std::random_access_iterator_tag tag;
     ((void)tag); // Prevent unused warning
@@ -21,4 +21,6 @@ int main()
                                    std::random_access_iterator_tag>::value), "");
     static_assert((!std::is_base_of<std::output_iterator_tag,
                                     std::random_access_iterator_tag>::value), "");
+
+  return 0;
 }