Implement LWG 3145: file_clock breaks ABI for C++17 implementations.

This patch adds std::chrono::file_clock, but without breaking the
existing ABI for std::filesystem.

7 files changed, 171 insertions, 32 deletions

diff --git a/libcxx/include/chrono b/libcxx/include/chrono
index e99e3c74c74..a5bb9afa8b2 100644
--- a/libcxx/include/chrono
+++ b/libcxx/include/chrono
@@ -808,6 +808,9 @@ constexpr chrono::year                                  operator ""y(unsigned lo
 _LIBCPP_PUSH_MACROS
 #include <__undef_macros>
 
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+struct _FilesystemClock;
+_LIBCPP_END_NAMESPACE_FILESYSTEM
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
@@ -1581,9 +1584,13 @@ typedef system_clock high_resolution_clock;
 #endif
 
 #if _LIBCPP_STD_VER > 17
+// [time.clock.file], type file_clock
+using file_clock = _VSTD_FS::_FilesystemClock;
 
-struct _LIBCPP_TYPE_VIS last_spec { explicit last_spec() = default; };
+template<class _Duration>
+using file_time = time_point<file_clock, _Duration>;
 
+struct _LIBCPP_TYPE_VIS last_spec { explicit last_spec() = default; };
 
 class _LIBCPP_TYPE_VIS day {
 private:
@@ -2689,6 +2696,40 @@ namespace chrono { // hoist the literals into namespace std::chrono
 
 _LIBCPP_END_NAMESPACE_STD
 
+#ifndef _LIBCPP_CXX03_LANG
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+struct _FilesystemClock {
+#if !defined(_LIBCPP_HAS_NO_INT128)
+  typedef __int128_t rep;
+  typedef nano period;
+#else
+  typedef long long rep;
+  typedef nano period;
+#endif
+
+  typedef chrono::duration<rep, period> duration;
+  typedef chrono::time_point<_FilesystemClock> time_point;
+
+  static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = false;
+
+  _LIBCPP_FUNC_VIS static time_point now() noexcept;
+
+  _LIBCPP_INLINE_VISIBILITY
+  static time_t to_time_t(const time_point& __t) noexcept {
+      typedef chrono::duration<rep> __secs;
+      return time_t(
+          chrono::duration_cast<__secs>(__t.time_since_epoch()).count());
+  }
+
+  _LIBCPP_INLINE_VISIBILITY
+  static time_point from_time_t(time_t __t) noexcept {
+      typedef chrono::duration<rep> __secs;
+      return time_point(__secs(__t));
+  }
+};
+_LIBCPP_END_NAMESPACE_FILESYSTEM
+#endif // !_LIBCPP_CXX03_LANG
+
 _LIBCPP_POP_MACROS
 
 #endif  // _LIBCPP_CHRONO
diff --git a/libcxx/include/filesystem b/libcxx/include/filesystem
index 339bb252fce..06a0eb33c4e 100644
--- a/libcxx/include/filesystem
+++ b/libcxx/include/filesystem
@@ -259,36 +259,6 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 
-struct _FilesystemClock {
-#if !defined(_LIBCPP_HAS_NO_INT128)
-  typedef __int128_t rep;
-  typedef nano period;
-#else
-  typedef long long rep;
-  typedef nano period;
-#endif
-
-  typedef chrono::duration<rep, period> duration;
-  typedef chrono::time_point<_FilesystemClock> time_point;
-
-  static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = false;
-
-  _LIBCPP_FUNC_VIS static time_point now() noexcept;
-
-  _LIBCPP_INLINE_VISIBILITY
-  static time_t to_time_t(const time_point& __t) noexcept {
-    typedef chrono::duration<rep> __secs;
-    return time_t(
-        chrono::duration_cast<__secs>(__t.time_since_epoch()).count());
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  static time_point from_time_t(time_t __t) noexcept {
-    typedef chrono::duration<rep> __secs;
-    return time_point(__secs(__t));
-  }
-};
-
 typedef chrono::time_point<_FilesystemClock> file_time_type;
 
 struct _LIBCPP_TYPE_VIS space_info {
diff --git a/libcxx/test/std/utilities/time/time.clock/time.clock.file/consistency.pass.cpp b/libcxx/test/std/utilities/time/time.clock/time.clock.file/consistency.pass.cpp
new file mode 100644
index 00000000000..275faa6288d
--- /dev/null
+++ b/libcxx/test/std/utilities/time/time.clock/time.clock.file/consistency.pass.cpp
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+//
+// TODO: Remove this when filesystem gets integrated into the dylib
+// REQUIRES: c++filesystem
+
+// <chrono>
+
+// file_clock
+
+// check clock invariants
+
+#include <chrono>
+
+template <class T>
+void test(const T &) {}
+
+int main()
+{
+    typedef std::chrono::system_clock C;
+    static_assert((std::is_same<C::rep, C::duration::rep>::value), "");
+    static_assert((std::is_same<C::period, C::duration::period>::value), "");
+    static_assert((std::is_same<C::duration, C::time_point::duration>::value), "");
+    static_assert((std::is_same<C::time_point::clock, C>::value), "");
+    static_assert((C::is_steady || !C::is_steady), "");
+    test(std::chrono::system_clock::is_steady);
+}
diff --git a/libcxx/test/std/utilities/time/time.clock/time.clock.file/file_time.pass.cpp b/libcxx/test/std/utilities/time/time.clock/time.clock.file/file_time.pass.cpp
new file mode 100644
index 00000000000..955e3ebe9d5
--- /dev/null
+++ b/libcxx/test/std/utilities/time/time.clock/time.clock.file/file_time.pass.cpp
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// file_time
+
+#include <chrono>
+
+#include "test_macros.h"
+
+template <class Dur>
+void test() {
+  ASSERT_SAME_TYPE(std::chrono::file_time<Dur>, std::chrono::time_point<std::chrono::file_clock, Dur>);
+}
+
+int main() {
+  test<std::chrono::nanoseconds>();
+  test<std::chrono::minutes>();
+  test<std::chrono::hours>();
+}
\ No newline at end of file
diff --git a/libcxx/test/std/utilities/time/time.clock/time.clock.file/now.pass.cpp b/libcxx/test/std/utilities/time/time.clock/time.clock.file/now.pass.cpp
new file mode 100644
index 00000000000..69dfa918093
--- /dev/null
+++ b/libcxx/test/std/utilities/time/time.clock/time.clock.file/now.pass.cpp
@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// TODO: Remove this when filesystem gets integrated into the dylib
+// REQUIRES: c++filesystem
+
+// <chrono>
+
+// file_clock
+
+// static time_point now() noexcept;
+
+#include <chrono>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main()
+{
+    typedef std::chrono::file_clock C;
+    ASSERT_NOEXCEPT(C::now());
+
+    C::time_point t1 = C::now();
+    assert(t1.time_since_epoch().count() != 0);
+    assert(C::time_point::min() < t1);
+    assert(C::time_point::max() > t1);
+}
diff --git a/libcxx/test/std/utilities/time/time.clock/time.clock.file/rep_signed.pass.cpp b/libcxx/test/std/utilities/time/time.clock/time.clock.file/rep_signed.pass.cpp
new file mode 100644
index 00000000000..c0fa0b5beda
--- /dev/null
+++ b/libcxx/test/std/utilities/time/time.clock/time.clock.file/rep_signed.pass.cpp
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// TODO: Remove this when filesystem gets integrated into the dylib
+// REQUIRES: c++filesystem
+
+// <chrono>
+
+// file_clock
+
+// rep should be signed
+
+#include <chrono>
+#include <cassert>
+
+int main()
+{
+    static_assert(std::is_signed<std::chrono::file_clock::rep>::value, "");
+    assert(std::chrono::file_clock::duration::min() <
+           std::chrono::file_clock::duration::zero());
+}
diff --git a/libcxx/www/cxx2a_status.html b/libcxx/www/cxx2a_status.html
index 25e6cdfe4e4..88aa56e38a8 100644
--- a/libcxx/www/cxx2a_status.html
+++ b/libcxx/www/cxx2a_status.html
@@ -282,7 +282,7 @@
 	<tr><td><a href="https://wg21.link/LWG3132">3132</a></td><td>Library needs to ban macros named <tt>expects</tt> or <tt>ensures</tt></td><td>San Diego</td><td><i>Nothing to do</i></td></tr>
 	<tr><td><a href="https://wg21.link/LWG3134">3134</a></td><td>[fund.ts.v3] LFTSv3 contains extraneous [meta] variable templates that should have been deleted by P09961</td><td>San Diego</td><td>Resolved by P1210R0</td></tr>
 	<tr><td><a href="https://wg21.link/LWG3137">3137</a></td><td>Header for <tt>__cpp_lib_to_chars</tt></td><td>San Diego</td><td><i>We've already made the update; but we don't support all the test macros. When we do, this will be closed</i></td></tr>
-	<tr><td><a href="https://wg21.link/LWG3145">3145</a></td><td><tt>file_clock</tt> breaks ABI for C++17 implementations</td><td>San Diego</td><td></td></tr>
+	<tr><td><a href="https://wg21.link/LWG3145">3145</a></td><td><tt>file_clock</tt> breaks ABI for C++17 implementations</td><td>San Diego</td><td>Complete</td></tr>
 	<tr><td><a href="https://wg21.link/LWG3147">3147</a></td><td>Definitions of "likely" and "unlikely" are likely to cause problems</td><td>San Diego</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG3148">3148</a></td><td><tt>&lt;concepts&gt;</tt> should be freestanding</td><td>San Diego</td><td></td></tr>
 	<tr><td><a href="https://wg21.link/LWG3153">3153</a></td><td><tt>Common</tt> and <tt>common_type</tt> have too little in common</td><td>San Diego</td><td></td></tr>