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2979. aligned_union should require complete object types

Section: 21.3.8.7 [meta.trans.other] Status: C++20 Submitter: Tim Song Opened: 2017-06-14 Last modified: 2021-02-25

Priority: 0

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Discussion:

aligned_union's description doesn't, but should, require the types provided to be complete object types.

[2017-07 Toronto Monday issue prioritization]

Priority 0; move to Ready

Proposed resolution:

This wording is relative to N4659.

  1. In 21.3.8.7 [meta.trans.other], edit Table 50 "Other transformations" as indicated:

    Table 50 — Other transformations
    Template Comments
    […]
    template <size_t Len, class... Types>
    struct aligned_union;         		The member typedef type shall be a POD type suitable for use as uninitialized storage for any object whose type is listed in Types; its size shall be at least Len. The static member alignment_value shall be an integral constant of type size_t whose value is the strictest alignment of all types listed in Types.
    Requires: At least one type is provided. Each type in the parameter pack Types shall be a complete object type.
    […]