Add a private call '__libcpp_is_constant_evaluated' which 'works' for old language versions and w/o any compiler support. 'Working', in this case, means that it returns false in those cases.

llvm-svn: 364873

1 files changed, 34 insertions, 0 deletions

diff --git a/libcxx/test/libcxx/type_traits/is_constant_evaluated.pass.cpp b/libcxx/test/libcxx/type_traits/is_constant_evaluated.pass.cpp
new file mode 100644
index 00000000000..157d913ccfe
--- /dev/null
+++ b/libcxx/test/libcxx/type_traits/is_constant_evaluated.pass.cpp
@@ -0,0 +1,34 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+
+// <type_traits>
+
+// __libcpp_is_constant_evaluated()
+
+// returns false when there's no constant evaluation support from the compiler.
+//  as well as when called not in a constexpr context
+
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main (int, char**) {
+    ASSERT_SAME_TYPE(decltype(std::__libcpp_is_constant_evaluated()), bool);
+    ASSERT_NOEXCEPT(std::__libcpp_is_constant_evaluated());
+
+#if !defined(_LIBCPP_HAS_NO_BUILTIN_IS_CONSTANT_EVALUATED) && !defined(_LIBCPP_CXX03_LANG)
+    static_assert(std::__libcpp_is_constant_evaluated(), "");
+#endif
+
+    bool p = std::__libcpp_is_constant_evaluated();
+    assert(!p);
+
+    return 0;
+    }