Alignment unit tests fail to compile on macOS

[improbablejan]

The new super-aligned types tests fail to compile on macOS at current HEAD (3fe2249). They appear to be fine on iOS.

Compiler used:

$ clang --version
Apple LLVM version 10.0.1 (clang-1001.0.46.4)
Target: x86_64-apple-darwin18.7.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Full error:

In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<int, moodycamel::MallocTrackingTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<int, moodycamel::MallocTrackingTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<int, moodycamel::MallocTrackingTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:366:46: note: in instantiation of template class 'moodycamel::ConcurrentQueue<int, moodycamel::MallocTrackingTraits>' requested here
                ConcurrentQueue<int, MallocTrackingTraits> q;
                                                           ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<16, 32> >::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<16, 32> >::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<16, 32> >::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:539:41: note: in instantiation of template class 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<16, 32> >' requested here
                        ConcurrentQueue<int, TestTraits<16>> q;
                                                             ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<2, 32> >::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<2, 32> >::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<2, 32> >::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:623:34: note: in instantiation of template class 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<2, 32> >' requested here
                        ConcurrentQueue<int, Traits2> q(2);
                                                      ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<4, 32> >::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<4, 32> >::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<4, 32> >::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:640:34: note: in instantiation of template class 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<4, 32> >' requested here
                        ConcurrentQueue<int, Traits4> q(2);
                                                      ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<8192, 32> >::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<8192, 32> >::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<8192, 32> >::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:1421:37: note: in instantiation of template class 'moodycamel::ConcurrentQueue<int, moodycamel::TestTraits<8192, 32> >' requested here
                        ConcurrentQueue<int, HugeBlocks> q(8192 * 2);           // 2 blocks
                                                         ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::TestTraits<4, 32> >::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::TestTraits<4, 32> >::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::TestTraits<4, 32> >::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:1583:33: note: in instantiation of template class 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::TestTraits<4, 32> >' requested here
                        ConcurrentQueue<Foo, Traits> q(4);              // One block
                                                     ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::TestTraits<4, 2> >::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::TestTraits<4, 2> >::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::TestTraits<4, 2> >::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:1720:33: note: in instantiation of template class 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::TestTraits<4, 2> >' requested here
                        ConcurrentQueue<Foo, Traits> q(8);              // 2 blocks, matches initial index size
                                                     ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<int, moodycamel::SmallIndexTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<int, moodycamel::SmallIndexTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<int, moodycamel::SmallIndexTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:2253:43: note: in instantiation of template class 'moodycamel::ConcurrentQueue<int, moodycamel::SmallIndexTraits>' requested here
                        ConcurrentQueue<int, SmallIndexTraits> q(16);
                                                               ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<int, moodycamel::ExtraSmallIndexTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<int, moodycamel::ExtraSmallIndexTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<int, moodycamel::ExtraSmallIndexTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:2288:48: note: in instantiation of template class 'moodycamel::ConcurrentQueue<int, moodycamel::ExtraSmallIndexTraits>' requested here
                        ConcurrentQueue<int, ExtraSmallIndexTraits> q(1);
                                                                    ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<int, moodycamel::ConcurrentQueueTests::SizeLimitTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<int, moodycamel::ConcurrentQueueTests::SizeLimitTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<int, moodycamel::ConcurrentQueueTests::SizeLimitTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:2326:42: note: in instantiation of template class 'moodycamel::ConcurrentQueue<int, moodycamel::ConcurrentQueueTests::SizeLimitTraits>' requested here
                        ConcurrentQueue<int, SizeLimitTraits> q;
                                                              ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<moodycamel::ThrowingMovable, moodycamel::TestTraits<4, 2> >::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<moodycamel::ThrowingMovable, moodycamel::TestTraits<4, 2> >::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<moodycamel::ThrowingMovable, moodycamel::TestTraits<4, 2> >::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:2443:45: note: in instantiation of template class 'moodycamel::ConcurrentQueue<moodycamel::ThrowingMovable, moodycamel::TestTraits<4, 2> >' requested here
                        ConcurrentQueue<ThrowingMovable, Traits> q;
                                                                 ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<Elem, moodycamel::LargeTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<Elem, moodycamel::LargeTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<Elem, moodycamel::LargeTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:4884:38: note: in instantiation of template class 'moodycamel::ConcurrentQueue<Elem, moodycamel::LargeTraits>' requested here
                ConcurrentQueue<Elem, LargeTraits> q(10000, 0, 48);
                                                   ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<moodycamel::Copyable, moodycamel::ConcurrentQueueDefaultTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<moodycamel::Copyable, moodycamel::ConcurrentQueueDefaultTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<moodycamel::Copyable, moodycamel::ConcurrentQueueDefaultTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:3192:38: note: in instantiation of template class 'moodycamel::ConcurrentQueue<moodycamel::Copyable, moodycamel::ConcurrentQueueDefaultTraits>' requested here
                        ConcurrentQueue<Copyable, Traits> q;
                                                          ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:335:17: note: in instantiation of function template specialization 'moodycamel::ConcurrentQueueTests::full_api<moodycamel::ConcurrentQueueDefaultTraits>' requested here
                REGISTER_TEST(full_api<ConcurrentQueueDefaultTraits>);
                              ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<moodycamel::Moveable, moodycamel::ConcurrentQueueDefaultTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<moodycamel::Moveable, moodycamel::ConcurrentQueueDefaultTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<moodycamel::Moveable, moodycamel::ConcurrentQueueDefaultTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:3204:38: note: in instantiation of template class 'moodycamel::ConcurrentQueue<moodycamel::Moveable, moodycamel::ConcurrentQueueDefaultTraits>' requested here
                        ConcurrentQueue<Moveable, Traits> q;
                                                          ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:335:17: note: in instantiation of function template specialization 'moodycamel::ConcurrentQueueTests::full_api<moodycamel::ConcurrentQueueDefaultTraits>' requested here
                REGISTER_TEST(full_api<ConcurrentQueueDefaultTraits>);
                              ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::ConcurrentQueueDefaultTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::ConcurrentQueueDefaultTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::ConcurrentQueueDefaultTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:3614:33: note: in instantiation of template class 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::ConcurrentQueueDefaultTraits>' requested here
                        ConcurrentQueue<Foo, Traits> q;
                                                     ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:335:17: note: in instantiation of function template specialization 'moodycamel::ConcurrentQueueTests::full_api<moodycamel::ConcurrentQueueDefaultTraits>' requested here
                REGISTER_TEST(full_api<ConcurrentQueueDefaultTraits>);
                              ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<moodycamel::Copyable, moodycamel::SmallIndexTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<moodycamel::Copyable, moodycamel::SmallIndexTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<moodycamel::Copyable, moodycamel::SmallIndexTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:3192:38: note: in instantiation of template class 'moodycamel::ConcurrentQueue<moodycamel::Copyable, moodycamel::SmallIndexTraits>' requested here
                        ConcurrentQueue<Copyable, Traits> q;
                                                          ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:336:17: note: in instantiation of function template specialization 'moodycamel::ConcurrentQueueTests::full_api<moodycamel::SmallIndexTraits>' requested here
                REGISTER_TEST(full_api<SmallIndexTraits>);
                              ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<moodycamel::Moveable, moodycamel::SmallIndexTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<moodycamel::Moveable, moodycamel::SmallIndexTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<moodycamel::Moveable, moodycamel::SmallIndexTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:3204:38: note: in instantiation of template class 'moodycamel::ConcurrentQueue<moodycamel::Moveable, moodycamel::SmallIndexTraits>' requested here
                        ConcurrentQueue<Moveable, Traits> q;
                                                          ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:336:17: note: in instantiation of function template specialization 'moodycamel::ConcurrentQueueTests::full_api<moodycamel::SmallIndexTraits>' requested here
                REGISTER_TEST(full_api<SmallIndexTraits>);
                              ^
In file included from external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:31:
external/moodycamel_concurrent_queue/concurrentqueue.h:1488:9: error: requested alignment is less than minimum alignment of 8 for type 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::SmallIndexTraits>::Block'
        struct MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) Block
               ^
external/moodycamel_concurrent_queue/concurrentqueue.h:223:39: note: expanded from macro 'MOODYCAMEL_ALIGNAS'
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
                                      ^
/Applications/Xcode-10.3.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1641:40: note: in instantiation of member class 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::SmallIndexTraits>::Block' requested here
    : public integral_constant<size_t, __alignof__(_Tp)> {};
                                       ^
external/moodycamel_concurrent_queue/concurrentqueue.h:1618:21: note: in instantiation of template class 'std::__1::alignment_of<moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::SmallIndexTraits>::Block>' requested here
        static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
                           ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:3614:33: note: in instantiation of template class 'moodycamel::ConcurrentQueue<moodycamel::Foo, moodycamel::SmallIndexTraits>' requested here
                        ConcurrentQueue<Foo, Traits> q;
                                                     ^
external/moodycamel_concurrent_queue/tests/unittests/unittests.cpp:336:17: note: in instantiation of function template specialization 'moodycamel::ConcurrentQueueTests::full_api<moodycamel::SmallIndexTraits>' requested here
                REGISTER_TEST(full_api<SmallIndexTraits>);
                              ^
18 errors generated.

[improbablejan]

I believe the issue is that the alignment of some members of Block such as std::atomic<Block*> is 8 on a 64b platform, while alignment of T can be smaller, and clang results in a static error if we explicitly under-align a type.

Is there a reason the struct is explicitly aligned instead of changing the storage to be aligned storage? If we changed the elements storage from char elements[sizeof(T) * BLOCK_SIZE]; to something like typename std::aligned_storage<sizeof(T) * BLOCK_SIZE, MOODYCAMEL_ALIGNOF(T)>::type elements;, we would not need to specify an explicit alignment for Block anymore. That seems simplest to me, but maybe std::aligned_storage is not used for some reason?

[cameron314]

Yup, bug, sorry. Will fix today.
I think your suggestion of aligning the char type is good

[improbablejan]

Cool, I will make a PR.