Add std::is_constant_evaluated.

Clang recently added __builtin_is_constant_evaluated() and GCC 9.0
has it as well.

This patch adds support for it in libc++.

llvm-svn: 359119

1 files changed, 29 insertions, 0 deletions

diff --git a/libcxx/test/std/utilities/meta/meta.const.eval/is_constant_evaluated.fail.cpp b/libcxx/test/std/utilities/meta/meta.const.eval/is_constant_evaluated.fail.cpp
new file mode 100644
index 00000000000..c139233b8da
--- /dev/null
+++ b/libcxx/test/std/utilities/meta/meta.const.eval/is_constant_evaluated.fail.cpp
@@ -0,0 +1,29 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <type_traits>
+
+
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main(int, char**)
+{
+#ifndef __cpp_lib_is_constant_evaluated
+  // expected-error@+1 {{no member named 'is_constant_evaluated' in namespace 'std'}}
+  bool b = std::is_constant_evaluated();
+#else
+  // expected-error@+1 {{static_assert failed}}
+  static_assert(!std::is_constant_evaluated(), "");
+#endif
+  return 0;
+}