[libc++] Work around C1XX bug which breaks poisoned hash tests.

[EricWF]

Summary

This is my attempt to work around the C1XX bug described to me by @BillyONeal.

[BillyONeal]

I mean, looks good to me, but you really don't need to go there :). (Though you might want something like this anyway if you try libc++ with MSVC++ on Windows...)

[EricWF]

In D31260#708139, @BillyONeal wrote:

(Though you might want something like this anyway if you try libc++ with MSVC++ on Windows...)

Exactly why I volunteered to do this. As libc++ and MSVC implement C++17 at different rates I suspect we'll need temporary workarounds like this more often.

[CaseyCarter]

I also have no problem with this change.

test/support/poisoned_hash_helper.hpp

53

I would merge these conditionals since they have identical extent. YMMV ;)

test/support/test.workarounds/c1xx_broken_nullptr_conversion_operator.pass.cpp

16

IIRC, including "" headers before <> headers is not conventional for the test suite.

test/support/poisoned_hash_helper.hpp

 // -*- 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.
 //
 //===----------------------------------------------------------------------===//
 #ifndef SUPPORT_POISONED_HASH_HELPER_HPP
 #define SUPPORT_POISONED_HASH_HELPER_HPP
 
 #include <type_traits>
 #include <cassert>
 
 #include "test_macros.h"
+#include "test_workarounds.h"
 
 #if TEST_STD_VER < 11
 #error this header may only be used in C++11 or newer
 #endif
 
 template <class ...Args> struct TypeList;
 
 // Test that the specified Hash meets the requirements of an enabled hash
namespace PoisonedHashDetail {
   enum EnumClass : bool {};
   struct Class {};
 }
 
 // Each header that declares the template hash provides enabled
 // specializations of hash for nullptr t and all cv-unqualified
 // arithmetic, enumeration, and pointer types.
 using LibraryHashTypes = TypeList<
+#if !defined(TEST_WORKAROUND_C1XX_BROKEN_NULLPTR_CONVERSION_OPERATOR)
 #if TEST_STD_VER > 14
       decltype(nullptr),
 #endif
+#endif
       bool,
       char,
       signed char,
       unsigned char,
       wchar_t,
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
       char16_t,
       char32_t,

test/support/test.workarounds/c1xx_broken_nullptr_conversion_operator.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     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
+
+// Verify TEST_WORKAROUND_C1XX_BROKEN_NULLPTR_CONVERSION_OPERATOR.
+
+#include "test_workarounds.h"
+
+#include <type_traits>
+
+struct ConvertsToNullptr {
+  using DestType = decltype(nullptr);
+  operator DestType() const { return nullptr; }
+};
+
+int main() {
+#if defined(TEST_WORKAROUND_C1XX_BROKEN_NULLPTR_CONVERSION_OPERATOR)
+  static_assert(!std::is_convertible<ConvertsToNullptr, decltype(nullptr)>::value, "");
+#else
+  static_assert(std::is_convertible<ConvertsToNullptr, decltype(nullptr)>::value, "");
+#endif
+}

test/support/test_macros.h

 #ifdef __is_identifier
 // '__is_identifier' returns '0' if '__x' is a reserved identifier provided by
 // the compiler and '1' otherwise.
 #define TEST_HAS_BUILTIN_IDENTIFIER(X) !__is_identifier(X)
 #else
 #define TEST_HAS_BUILTIN_IDENTIFIER(X) 0
 #endif
 
+#if defined(__clang__)
+#define TEST_COMPILER_CLANG
+# if defined(__apple_build_version__)
+#   define TEST_COMPILER_APPLE_CLANG
+# endif
+#elif defined(_MSC_VER)
+# define TEST_COMPILER_C1XX
+#elif defined(__GNUC__)
+# define TEST_COMPILER_GCC
+#endif
+
 #if defined(__apple_build_version__)
 #define TEST_APPLE_CLANG_VER (__clang_major__ * 100) + __clang_minor__
 #elif defined(__clang_major__)
 #define TEST_CLANG_VER (__clang_major__ * 100) + __clang_minor__
 #elif defined(__GNUC__)
 #define TEST_GCC_VER (__GNUC__ * 100 + __GNUC_MINOR__)
 #endif
 

test/support/test_workarounds.h

+// -*- C++ -*-
+//===---------------------------- test_macros.h ---------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SUPPORT_TEST_WORKAROUNDS_H
+#define SUPPORT_TEST_WORKAROUNDS_H
+
+#include "test_macros.h"
+
+#if defined(TEST_COMPILER_C1XX)
+# define TEST_WORKAROUND_C1XX_BROKEN_NULLPTR_CONVERSION_OPERATOR
+#endif
+
+#endif // SUPPORT_TEST_WORKAROUNDS_H