Issue 3518: Exception requirements on char trait operations unclear

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3518. Exception requirements on char trait operations unclear

Section: 27.2.2 [char.traits.require] Status: C++23 Submitter: Zoe Carver Opened: 2021-02-01 Last modified: 2023-11-22

Priority: Not Prioritized

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Discussion:

27.2.2 [char.traits.require] p1 says:

X denotes a traits class defining types and functions for the character container type C […] Operations on X shall not throw exceptions.

It should be clarified what "operations on X" means. For example, in this patch, there was some confusion around the exact meaning of "operations on X". If it refers to the expressions specified in [tab:char.traits.req] or if it refers to all member functions of X, this should be worded in some clearer way.

[2021-03-12; Reflector poll]

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

[2021-06-07 Approved at June 2021 virtual plenary. Status changed: Voting → WP.]

Proposed resolution:

This wording is relative to N4878.

Modify 27.2.2 [char.traits.require] as indicated:

-1- In Table [tab:char.traits.req], X denotes a traits class defining types and functions for the character container type C; […] ~~Operations on X shall not throw exceptions~~No expression which is part of the character traits requirements specified in this subclause 27.2.2 [char.traits.require] shall exit via an exception.