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### 3570. `basic_osyncstream::emit` should be an unformatted output function

Section: 29.11.3.3 [syncstream.osyncstream.members] Status: WP Submitter: Tim Song Opened: 2021-06-19 Last modified: 2021-10-14

Priority: Not Prioritized

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Discussion:

`basic_osyncstream::emit` seems rather similar to `basic_ostream::flush` — both are "flushing" operations that forward to member functions of the `streambuf` and set `badbit` if those functions fail. But the former isn't currently specified as an unformatted output function, so it a) doesn't construct or check a `sentry` and b) doesn't set `badbit` if `emit` exits via an exception. At least the latter appears to be clearly desirable — a `streambuf` operation that throws ordinarily results in `badbit` being set.

The reference implementation in P0053R7 constructs a `sentry` and only calls `emit` on the `streambuf` if the `sentry` converts to `true`, so this seems to be an accidental omission in the wording.

[2021-06-23; Reflector poll]

Set status to Tentatively Ready after five 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 29.11.3.3 [syncstream.osyncstream.members] as indicated:

   >     void emit();

   > > -1- Effects: Behaves as an unformatted output function (29.7.5.4 [ostream.unformatted]). After constructing a `sentry` object, c Calls `sb.emit()`. If that call returns `false`, calls `setstate(ios_base::badbit)`.