use modern type trait implementations when available

[rsmith]

Summary

Teach libcxx to stop using various deprecated __has_* type traits, in favor of the ("modern", C++11 era) __is_* type traits.

This is mostly just a simplification, but fixes at least one bug: _Atomic T should be considered trivially-destructible, but is not considered to be POD by Clang, and __has_trivial_destructor is specified in the GCC documentation as returning false for non-POD non-class types.

[EricWF]

LGTM minus nits.

include/type_traits

3742

We don't support anything before GCC 4.9, so you can replace the GCC guard with || defined(_LIBCPP_COMPILER_GCC)

3763–3764

We should use variadics in C++03 when Clang is the compiler. I would write this check as #if !defined(_LIBCPP_CXX03_LANG) || defined(__clang__)

3766

At this point I believe #elif !defined(_LIBCPP_CXX03_LANG) should work.

test/std/utilities/meta/meta.unary/meta.unary.prop/is_trivially_destructible.pass.cpp

119

You can use TEST_HAS_BUILTIN_IDENTIFIER defined by test_macros.h (https://github.com/llvm-mirror/libcxx/blob/master/test/support/test_macros.h#L58)

[rsmith]

include/type_traits

3742

Nice. I'll do this more broadly as a separate patch, if that's OK with you. There's lots of support for older GCCs scattered around in this file and elsewhere.

3763–3764

Would it make more sense to change the definition of _LIBCPP_HAS_NO_VARIADICS to do that globally? This same pattern is used in various places in libc++, both in existing code in <type_traits>, in <future> (for packaged_task / async), and in <memory> (for traits and allocator::construct). In every case we're guarding use of variadics to define a template that is specified as being variadic.

3766

I'll do that as part of the GCC4.9 change.

[EricWF]

This patch is OK to land as-is.

Doing the cleanup separately makes sense.

include/type_traits

3742

That sounds good to me.

I'm happy to take over the cleanup if you want.

3763–3764

I'm trying to replace _LIBCPP_HAS_NO_VARIADICS with _LIBCPP_CXX03_LANG. Almost all usages of _LIBCPP_HAS_NO_VARIADICS guard more C++11 features than just variadic templates (like rvalue references) -- so simply changing the definition of _LIBCPP_HAS_NO_VARIADICS may be subtly wrong.

I'll work on cleaning the macro up.

[rsmith]

include/type_traits

3742

https://reviews.llvm.org/D61107 for that :)

[ldionne]

I think this broke the C++03 bots: http://green.lab.llvm.org/green/view/Libcxx/job/libc++%20and%20libc++abi%20trunk/CI_ARCH=64,CI_EXCEPTIONS=ON,CI_STD=c++03/103/consoleFull

[rsmith]

In D48292#1478617, @ldionne wrote:

I think this broke the C++03 bots: http://green.lab.llvm.org/green/view/Libcxx/job/libc++%20and%20libc++abi%20trunk/CI_ARCH=64,CI_EXCEPTIONS=ON,CI_STD=c++03/103/consoleFull

Thanks, should be fixed in r359229.

[thakis]

This test is broken with Xcode 9:

-- Testing: 53613 tests, 8 threads --
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90
FAIL: libc++ :: std/utilities/meta/meta.unary/meta.unary.prop/is_trivially_destructible.pass.cpp (50845 of 53613)
******************** TEST 'libc++ :: std/utilities/meta/meta.unary/meta.unary.prop/is_trivially_destructible.pass.cpp' FAILED ********************
Command: ['/Applications/Xcode9.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++', '-o', '/b/rr/tmp7bTZVi/w/src/third_party/llvm-bootstrap/projects/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/Output/is_trivially_destructible.pass.cpp.o', '-x', 'c++', '/b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_trivially_destructible.pass.cpp', '-c', '-D_LIBCPP_DISABLE_AVAILABILITY', '-v', '-arch', 'x86_64', '-mmacosx-version-min=10.12', '-ftemplate-depth=270', '-Werror=thread-safety', '-std=c++1z', '-include', '/b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/support/nasty_macros.hpp', '-nostdinc++', '-I/b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/include', '-I/b/rr/tmp7bTZVi/w/src/third_party/llvm-bootstrap/projects/libcxx/include/c++build', '-isysroot', '/Applications/Xcode9.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk', '-I/b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/support', '-DLIBCXX_FILESYSTEM_STATIC_TEST_ROOT="/b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/std/input.output/filesystems/Inputs/static_test_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT="/b/rr/tmp7bTZVi/w/src/third_party/llvm-bootstrap/projects/libcxx/test/filesystem/Output/dynamic_env"', '-DLIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER="/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python /b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/support/filesystem_dynamic_test_helper.py"', '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER', '-Wall', '-Wextra', '-Werror', '-Wuser-defined-warnings', '-Wshadow', '-Wno-unused-command-line-argument', '-Wno-attributes', '-Wno-pessimizing-move', '-Wno-c++11-extensions', '-Wno-user-defined-literals', '-Wsign-compare', '-Wunused-variable', '-Wunused-parameter', '-Wunreachable-code', '-c']
Exit Code: 1
Standard Error:
--
Apple LLVM version 9.0.0 (clang-900.0.37)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
InstalledDir: /Applications/Xcode9.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
 "/Applications/Xcode9.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang" -cc1 -triple x86_64-apple-macosx10.12.0 -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -discard-value-names -main-file-name is_trivially_destructible.pass.cpp -mrelocation-model pic -pic-level 2 -mthread-model posix -mdisable-fp-elim -fno-strict-return -masm-verbose -munwind-tables -target-cpu penryn -target-linker-version 302.3 -v -dwarf-column-info -debugger-tuning=lldb -coverage-notes-file /b/rr/tmp7bTZVi/w/src/third_party/llvm-bootstrap/projects/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/Output/is_trivially_destructible.pass.cpp.gcno -nostdinc++ -resource-dir /Applications/Xcode9.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/9.0.0 -include /b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/support/nasty_macros.hpp -isysroot /Applications/Xcode9.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -D _LIBCPP_DISABLE_AVAILABILITY -I /b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/include -I /b/rr/tmp7bTZVi/w/src/third_party/llvm-bootstrap/projects/libcxx/include/c++build -I /b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/support -D "LIBCXX_FILESYSTEM_STATIC_TEST_ROOT=\"/b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/std/input.output/filesystems/Inputs/static_test_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_ROOT=\"/b/rr/tmp7bTZVi/w/src/third_party/llvm-bootstrap/projects/libcxx/test/filesystem/Output/dynamic_env\"" -D "LIBCXX_FILESYSTEM_DYNAMIC_TEST_HELPER=\"/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python /b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/support/filesystem_dynamic_test_helper.py\"" -D _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -stdlib=libc++ -Werror=thread-safety -Wall -Wextra -Werror -Wuser-defined-warnings -Wshadow -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move -Wno-c++11-extensions -Wno-user-defined-literals -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code -std=c++1z -fdeprecated-macro -fdebug-compilation-dir /b/rr/tmp7bTZVi/w/src/third_party/llvm-bootstrap/projects/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop -ftemplate-depth 270 -ferror-limit 19 -fmessage-length 0 -stack-protector 1 -fblocks -fobjc-runtime=macosx-10.12.0 -fencode-extended-block-signature -fcxx-exceptions -fexceptions -fmax-type-align=16 -fdiagnostics-show-option -o /b/rr/tmp7bTZVi/w/src/third_party/llvm-bootstrap/projects/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/Output/is_trivially_destructible.pass.cpp.o -x c++ /b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_trivially_destructible.pass.cpp
clang -cc1 version 9.0.0 (clang-900.0.37) default target x86_64-apple-darwin16.7.0
ignoring nonexistent directory "/Applications/Xcode9.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/usr/local/include"
ignoring nonexistent directory "/Applications/Xcode9.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
 /b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/include
 /b/rr/tmp7bTZVi/w/src/third_party/llvm-bootstrap/projects/libcxx/include/c++build
 /b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/support
 /Applications/Xcode9.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/9.0.0/include
 /Applications/Xcode9.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include
 /Applications/Xcode9.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/usr/include
 /Applications/Xcode9.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk/System/Library/Frameworks (framework directory)
End of search list.
/b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_trivially_destructible.pass.cpp:24:5: error: static_assert failed ""
    static_assert( std::is_trivially_destructible<T>::value, "");
    ^              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/b/rr/tmp7bTZVi/w/src/third_party/llvm/projects/libcxx/test/std/utilities/meta/meta.unary/meta.unary.prop/is_trivially_destructible.pass.cpp:120:5: note: in instantiation of function template specialization 'test_is_trivially_destructible<_Atomic(int)>' requested here
    test_is_trivially_destructible<_Atomic int>();
    ^

Does this just need an // XFAIL: apple-clang-9 or is this unexpected?

[ldionne]

In D48292#1490060, @thakis wrote:

This test is broken with Xcode 9:

[...]

Does this just need an // XFAIL: apple-clang-9 or is this unexpected?

This seems to have been fixed in LLVM Clang trunk since the 8 release, and AppleClang 9 just doesn't have that fix. So I think it's reasonable to XFAIL it.

Clang 8: https://wandbox.org/permlink/nung9OHLrvObZGjq
Clang 9 (trunk): https://wandbox.org/permlink/y8e3UUx6CDf8x7im

[thakis]

Done in r359907, thanks!

include/type_traits

 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
 template <class _Tp>
 _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_move_assignable_v
     = is_trivially_move_assignable<_Tp>::value;
 #endif
 
 // is_trivially_destructible
 
-#if __has_feature(has_trivial_destructor) || (_GNUC_VER >= 403)
+#if __has_keyword(__is_trivially_destructible)
+
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible
+    : public integral_constant<bool, __is_trivially_destructible(_Tp)> {};
+
+#elif __has_feature(has_trivial_destructor) || (_GNUC_VER >= 403)
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible
     : public integral_constant<bool, is_destructible<_Tp>::value && __has_trivial_destructor(_Tp)> {};
 
 #else
 
 template <class _Tp> struct __libcpp_trivial_destructor
     : public integral_constant<bool, is_scalar<_Tp>::value ||
                                      is_reference<_Tp>::value> {};
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible
     : public __libcpp_trivial_destructor<typename remove_all_extents<_Tp>::type> {};
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible<_Tp[]>
     : public false_type {};
 
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
 template <class _Tp>
 _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_destructible_v
     = is_trivially_destructible<_Tp>::value;
 #endif
 
 // is_nothrow_constructible
 
-#if 0
-template <class _Tp, class... _Args>
-struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
-    : public integral_constant<bool, __is_nothrow_constructible(_Tp(_Args...))>
-{
-};
+#ifndef _LIBCPP_HAS_NO_VARIADICS
 
-#else
+#if __has_keyword(__is_nothrow_constructible)
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+template <class _Tp, class... _Args>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
+    : public integral_constant<bool, __is_nothrow_constructible(_Tp, _Args...)> {};
 
-#if __has_feature(cxx_noexcept) || (_GNUC_VER >= 407 && __cplusplus >= 201103L)
+#elif __has_feature(cxx_noexcept) || (_GNUC_VER >= 407 && __cplusplus >= 201103L)
 
 template <bool, bool, class _Tp, class... _Args> struct __libcpp_is_nothrow_constructible;
 
 template <class _Tp, class... _Args>
 struct __libcpp_is_nothrow_constructible</*is constructible*/true, /*is reference*/false, _Tp, _Args...>
     : public integral_constant<bool, noexcept(_Tp(declval<_Args>()...))>
 {
 };

 };
 
 template <class _Tp, size_t _Ns>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp[_Ns]>
     : __libcpp_is_nothrow_constructible<is_constructible<_Tp>::value, is_reference<_Tp>::value, _Tp>
 {
 };
 
-#else  // __has_feature(cxx_noexcept)
+#else  // __has_keyword(__is_nothrow_constructible) || __has_feature(cxx_noexcept)
 
 template <class _Tp, class... _Args>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
     : false_type
 {
 };
 
 template <class _Tp>

 #endif
 {
 };
 
 #endif  // __has_feature(cxx_noexcept)
 
 #else  // _LIBCPP_HAS_NO_VARIADICS
 
+#if __has_keyword(__is_nothrow_constructible)
+
+template <class _Tp, class _A0 = __is_construct::__nat,
+                     class _A1 = __is_construct::__nat>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
+    : public integral_constant<bool, __is_nothrow_constructible(_Tp, _A0, _A1)> {};
+
+template <class _Tp, class _A0>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _A0>
+    : public integral_constant<bool, __is_nothrow_constructible(_Tp, _A0)> {};
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp>
+    : public integral_constant<bool, __is_nothrow_constructible(_Tp)> {};
+
+#else  // __has_keyword(__is_nothrow_constructible)
+
 template <class _Tp, class _A0 = __is_construct::__nat,
                      class _A1 = __is_construct::__nat>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
     : false_type
 {
 };
 
 template <class _Tp>

 #if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
 #else
     : integral_constant<bool, is_scalar<_Tp>::value>
 #endif
 {
 };
 
+#endif  // __has_keyword(__is_nothrow_constructible)
 #endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // __has_feature(is_nothrow_constructible)
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
 template <class _Tp, class ..._Args>
 _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_constructible_v
     = is_nothrow_constructible<_Tp, _Args...>::value;
 #endif
 
 // is_nothrow_default_constructible

 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
 template <class _Tp>
 _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_move_constructible_v
     = is_nothrow_move_constructible<_Tp>::value;
 #endif
 
 // is_nothrow_assignable
 
-#if __has_feature(cxx_noexcept) || (_GNUC_VER >= 407 && __cplusplus >= 201103L)
+#if __has_keyword(__is_nothrow_assignable)
+
+template <class _Tp, class _Arg>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable
+    : public integral_constant<bool, __is_nothrow_assignable(_Tp, _Arg)> {};
+
+#elif __has_feature(cxx_noexcept) || (_GNUC_VER >= 407 && __cplusplus >= 201103L)
 
 template <bool, class _Tp, class _Arg> struct __libcpp_is_nothrow_assignable;
 
 template <class _Tp, class _Arg>
 struct __libcpp_is_nothrow_assignable<false, _Tp, _Arg>
     : public false_type
 {
 };
 
 template <class _Tp, class _Arg>
 struct __libcpp_is_nothrow_assignable<true, _Tp, _Arg>
     : public integral_constant<bool, noexcept(_VSTD::declval<_Tp>() = _VSTD::declval<_Arg>()) >
 {
 };
 
 template <class _Tp, class _Arg>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable
     : public __libcpp_is_nothrow_assignable<is_assignable<_Tp, _Arg>::value, _Tp, _Arg>
 {
 };
 
-#else  // __has_feature(cxx_noexcept)
+#else  // __has_keyword(__is_nothrow_assignable) || __has_feature(cxx_noexcept)
 
 template <class _Tp, class _Arg>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable
     : public false_type {};
 
 template <class _Tp>
 struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable<_Tp&, _Tp>
 #if __has_feature(has_nothrow_assign) || (_GNUC_VER >= 403)

test/std/utilities/meta/meta.unary/meta.unary.prop/is_trivially_destructible.pass.cpp

#if TEST_STD_VER >= 11
     test_is_not_trivially_destructible<ProtectedDestructor>();
     test_is_not_trivially_destructible<PrivateDestructor>();
     test_is_not_trivially_destructible<VirtualProtectedDestructor>();
     test_is_not_trivially_destructible<VirtualPrivateDestructor>();
     test_is_not_trivially_destructible<PureProtectedDestructor>();
     test_is_not_trivially_destructible<PurePrivateDestructor>();
 #endif
 
+#if TEST_HAS_BUILTIN_IDENTIFIER(_Atomic)
+    test_is_trivially_destructible<_Atomic int>();
+    test_is_trivially_destructible<_Atomic float>();
+    test_is_trivially_destructible<_Atomic int*>();
+#endif
+
   return 0;
 }