has the same semantics as the corresponding macro in
the C standard library header <stddef.h>, but
accepts a restricted set of type
arguments in this document.
Use of the offsetof macro with a type
other than a standard-layout class ([class.prop])
It is recommended that implementations choose types for ptrdiff_t and size_t
whose integer conversion ranks are no greater than that of
signedlongint unless a larger size is necessary to contain all the possible values.
max_align_t is a trivial standard-layout type whose alignment requirement
is at least as great as that of every scalar type, and whose alignment
requirement is supported in every context ([basic.align]).