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### 3498. Inconsistent `noexcept`-specifiers for `basic_syncbuf`

Section: 31.11.2.1 [syncstream.syncbuf.overview], 31.11.2.3 [syncstream.syncbuf.assign] Status: WP Submitter: Jonathan Wakely Opened: 2020-11-10 Last modified: 2021-10-14

Priority: 3

View all other issues in [syncstream.syncbuf.overview].

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Discussion:

The synopsis in 31.11.2.1 [syncstream.syncbuf.overview] shows the move assignment operator and `swap` member as potentially throwing. The detailed descriptions in 31.11.2.3 [syncstream.syncbuf.assign] are `noexcept`.

Daniel:

This mismatch is already present in the originally accepted paper P0053R7, so this is nothing that could be resolved editorially.

[2020-11-21; Reflector prioritization]

Set priority to 3 during reflector discussions.

[2021-05-22 Tim adds PR]

The move assignment is specified to call `emit()` which can throw, and there's nothing in the wording providing for catching/ignoring the exception, so it can't be `noexcept`. The `swap` needs to call `basic_streambuf::swap`, which isn't `noexcept`, so it shouldn't be `noexcept` either.

[2021-06-23; Reflector poll]

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

[2021-10-14 Approved at October 2021 virtual plenary. Status changed: Voting → WP.]

Proposed resolution:

This wording is relative to N4885.

1. Modify 31.11.2.3 [syncstream.syncbuf.assign] as indicated:

   >     basic_syncbuf& operator=(basic_syncbuf&& rhs) noexcept;

   > > -1- Effects: […]

   > > -2- Postconditions: […]

   > > -3- Returns: […]

   > > -4- Remarks: […]

   >     void swap(basic_syncbuf& other) noexcept;

   > > -5- Preconditions: […]

   > > -6- Effects: […]