Some adapt(...) methods fail for clang-11 because size_type is not a member of std::allocator

[melton1968]

In the standard library for clang-11, size_type is no longer a member of std::allocator. This is a difference from clang-10. Line 1765 of <memory> versus line 1830 of <memory> in the two libraries.

By my reading of the standard, although several members are removed for c++20, both size_type and difference_type should still be available. However, I am unsure about this interpretation.

In either case, this is causing several of the adapt template methods to fail because they rely on the expression typename A::size_type to deduce the type of a parameter.

I have been using the following patch in xadapt.hpp to work around the issue:

        template <class P>
        struct default_allocator_for_ptr
        {
            using raw_type = std::allocator<std::remove_const_t<std::remove_pointer_t<std::remove_r\
eference_t<P>>>>;
            struct enhanced_type : public raw_type {
                using raw_type::raw_type;
                using size_type = std::size_t;
                using difference_typye = std::ptrdiff_t;
            };
            using type = enhanced_type;
        };

I'd like someone with more expertise to weigh in on whether this is something that needs to be submitted as a bug to clang or if we need to develop a fix for xtensor.

[JohanMabille]

Hi,

Sorry for the late reply. For me, this is definitely a bug of clang that should be fixed.