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4538. member_offset::total_bits should be noexcept

Section: 21.4.11 [meta.reflection.layout] Status: New Submitter: Hewill Kang Opened: 2026-03-10 Last modified: 2026-04-13

Priority: 3

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Discussion:

This member simply returns the result of integer calculations, which can be noexcept.

[2026-04-13; Reflector poll.]

Set priority to 3 after reflector poll.

"The calculation can overflow ptrdiff_t which would be undefined, so there's an implicit narrow contract."

Proposed resolution:

This wording is relative to N5032.

1. Modify 21.4.11 [meta.reflection.layout] as indicated:

   struct member_offset {
     ptrdiff_t bytes;
     ptrdiff_t bits;
     constexpr ptrdiff_t total_bits() const noexcept;
     auto operator<=>(const member_offset&) const = default;
   };
   

   constexpr ptrdiff_t member_offset::total_bits() const noexcept;
   

   -1- Returns: bytes * CHAR_BIT + bits.