3225. zoned_time converting constructor shall not be noexcept

Section: 30.11.7.2 [time.zone.zonedtime.ctor] Status: C++20 Submitter: Tomasz Kamiński Opened: 2019-06-20 Last modified: 2021-02-25

Priority: 0

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Discussion:

The zoned_time constructor from zoned_time<Duration2, TimeZonePtr> (preserving same time zone, different precision of representation) is currently marked noexcept. Given that the exposition-only member tp_ of type sys_time<duration> has essentially type time_point<system_clock, Duration>, this is incompatible with the invoked time_point constructor, which is not marked as noexcept.

[2019-07 Issue Prioritization]

Status to Tentatively Ready after five positive votes on the reflector.

Proposed resolution:

This wording is relative to N4820.

1. Modify 30.11.7.1 [time.zone.zonedtime.overview], class template zoned_time synopsis, as indicated:

   template<class Duration2>
     zoned_time(const zoned_time<Duration2, TimeZonePtr>& zt) noexcept;
   

2. Modify 30.11.7.2 [time.zone.zonedtime.ctor] as indicated:

   template<class Duration2>
     zoned_time(const zoned_time<Duration2, TimeZonePtr>& y) noexcept;
   

   -9- Requires: Does not participate in overload resolution unless sys_time<Duration2> is implicitly convertible to sys_time<Duration>.

   -10- Effects: Constructs a zoned_time by initializing zone_ with y.zone_ and tp_ with y.tp_.