nvcc and use of [[no_unique_address]]

[youyu3]

In config.hpp there are these checks for using [[no_unique_address]] or using an emulation of it.

#if !defined(_MDSPAN_USE_ATTRIBUTE_NO_UNIQUE_ADDRESS)
#  if ((__has_cpp_attribute(no_unique_address) >= 201803L) && \
       (!defined(__NVCC__) || MDSPAN_HAS_CXX_20) && \
       (!defined(_MDSPAN_COMPILER_MSVC) || MDSPAN_HAS_CXX_20))
#    define _MDSPAN_USE_ATTRIBUTE_NO_UNIQUE_ADDRESS 1
#    define _MDSPAN_NO_UNIQUE_ADDRESS [[no_unique_address]]
#  else
#    define _MDSPAN_NO_UNIQUE_ADDRESS
#  endif
#endif

Using of [[no_unique_address]] is disabled if it's compiled by nvcc. Is this just because this was not supported by nvcc at some point?

Current nvcc does support it now (as long as the host compiler supports it).

[crtrott]

There were also issues with working slightly different on host and device, and that leading to mismatched sizes.