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4317. The meaning of "resource" in the Cpp17Destructible requirements is undefined

Section: 16.4.4.2 [utility.arg.requirements] Status: WP Submitter: Jiang An Opened: 2025-08-15 Last modified: 2025-11-11

Priority: Not Prioritized

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Discussion:

The meaning of "resource" in the Cpp17Destructible requirements cannot be inferred from the standard wording and it seems unlikely that the standard will determine its meaning in the future. What are considered as resources generally depends on users' intent, so the standard shouldn't determine the well-definedness of a program execution due to it. Moreover, the wording doesn't seem to consider shared ownership, which can be represented by shared_ptr.

[2025-10-14; Reflector poll]

Set status to Tentatively Ready after six votes in favour during reflector poll.

[Kona 2025-11-08; Status changed: Voting → WP.]

Proposed resolution:

This wording is relative to N5014.

1. Modify 16.4.4.2 [utility.arg.requirements], Table 35 [tab:cpp17.destructible] as indicated:

   Table 35 — Cpp17Destructible requirements [tab:cpp17.destructible]

   Expression	Post-condition
   u.~T()	All resources owned by u are reclaimed, nNo exception is propagated.
   [Note 3: Array types and non-object types are not Cpp17Destructible. — end note]