Implement p0137r1 - std::launder. Reviewed as https://reviews.llvm.org/D40144

llvm-svn: 318864

3 files changed, 96 insertions, 0 deletions

diff --git a/libcxx/test/std/language.support/support.dynamic/ptr.launder/launder.nodiscard.fail.cpp b/libcxx/test/std/language.support/support.dynamic/ptr.launder/launder.nodiscard.fail.cpp
new file mode 100644
index 00000000000..1c75e561d7c
--- /dev/null
+++ b/libcxx/test/std/language.support/support.dynamic/ptr.launder/launder.nodiscard.fail.cpp
@@ -0,0 +1,27 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <new>
+
+// template <class T> constexpr T* launder(T* p) noexcept;
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// UNSUPPORTED: clang-3.3, clang-3.4, clang-3.5, clang-3.6, clang-3.7, clang-3.8
+
+#include <new>
+#include <cassert>
+
+#include "test_macros.h"
+
+int main ()
+{
+    int *p = nullptr;
+    std::launder(p);  // expected-error {{ignoring return value of function declared with 'nodiscard' attribute}}
+}
diff --git a/libcxx/test/std/language.support/support.dynamic/ptr.launder/launder.pass.cpp b/libcxx/test/std/language.support/support.dynamic/ptr.launder/launder.pass.cpp
new file mode 100644
index 00000000000..1aa462957c8
--- /dev/null
+++ b/libcxx/test/std/language.support/support.dynamic/ptr.launder/launder.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.
+//
+//===----------------------------------------------------------------------===//
+
+// <new>
+
+// template <class T> constexpr T* launder(T* p) noexcept;
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+#include <new>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr int gi = 5;
+constexpr float gf = 8.f;
+
+int main() {
+	static_assert(std::launder(&gi) == &gi, "" );
+	static_assert(std::launder(&gf) == &gf, "" );
+
+  	const int *i = &gi;
+  	const float *f = &gf;
+    static_assert(std::is_same<decltype(i), decltype(std::launder(i))>::value, "");
+    static_assert(std::is_same<decltype(f), decltype(std::launder(f))>::value, "");
+
+	assert(std::launder(i) == i);
+	assert(std::launder(f) == f);
+}
diff --git a/libcxx/test/std/language.support/support.dynamic/ptr.launder/launder.types.fail.cpp b/libcxx/test/std/language.support/support.dynamic/ptr.launder/launder.types.fail.cpp
new file mode 100644
index 00000000000..71f5e4588b8
--- /dev/null
+++ b/libcxx/test/std/language.support/support.dynamic/ptr.launder/launder.types.fail.cpp
@@ -0,0 +1,34 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <new>
+
+// template <class T> constexpr T* launder(T* p) noexcept;
+// The program is ill-formed if T is a function type or cv void.
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14
+
+#include <new>
+#include <cassert>
+
+#include "test_macros.h"
+
+void foo() {}
+
+int main ()
+{
+    void *p = nullptr;
+    (void) std::launder((               void *) nullptr);
+    (void) std::launder((const          void *) nullptr);
+    (void) std::launder((      volatile void *) nullptr);
+    (void) std::launder((const volatile void *) nullptr);  // expected-error-re@new:* 4 {{static_assert failed{{.*}} "can't launder cv-void"}}
+
+    (void) std::launder(foo);                              // expected-error-re@new:* 1 {{static_assert failed{{.*}} "can't launder functions"}}
+}