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sync: add track_caller to public APIs #4808

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merged 1 commit into from Jul 6, 2022

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hds
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@hds hds commented Jul 5, 2022

Motivation

When a user of tokio calls a function that panics when misused (e.g. calling
Mutex::blocking_lock() from within a tokio runtime) then the user currently
sees the line number of the panic call inside tokio. It would be more informative
for the user to see the place where they called the panicking function.

It is still possible for the user to see the full stack trace by setting the
environment variable RUST_BACKLOG=1, so no useful information is
hidden.

This change is the 7th in a series towards closing #4413 (starting with #4772),
this change is for the sync functions in the main tokio crate.

Solution

Functions that may panic can be annotated with #[track_caller] so that
in the event of a panic, the function where the user called the
panicking function is shown instead of the file and line within Tokio
source.

This change adds #[track_caller] to all the public APIs in the sync
module of the tokio crate where the documentation describes how the
function may panic due to incorrect context or inputs.

In cases where #[track_caller] does not work, it has been left out.
For example, it currently does not work on async functions, blocks, or
closures. So any call stack that passes through one of these before
reaching the actual panic is not able to show the calling site outside
of tokio as the panic location.

The following functions have call stacks that pass through closures:

  • sync::watch::Sender::send_modify
  • sync::watch::Sender::send_if_modified

Additionally, in the above functions it is a panic inside the supplied
closure which causes the function to panic, and so showing the location
of the panic itself is desirable.

The following functions are async:

  • sync::mpsc::bounded::Sender::send_timeout

Tests are included to cover each potentially panicking function.

Refs: #4413

Functions that may panic can be annotated with `#[track_caller]` so that
in the event of a panic, the function where the user called the
panicking function is shown instead of the file and line within Tokio
source.

This change adds `#[track_caller]` to all the public APIs in the sync
module of the tokio crate where the documentation describes how the
function may panic due to incorrect context or inputs.

In cases where `#[track_caller]` does not work, it has been left out.
For example, it currently does not work on async functions, blocks, or
closures. So any call stack that passes through one of these before
reaching the actual panic is not able to show the calling site outside
of tokio as the panic location.

The following functions have call stacks that pass through closures:
* `sync::watch::Sender::send_modify`
* `sync::watch::Sender::send_if_modified`

Additionally, in the above functions it is a panic inside the supplied
closure which causes the function to panic, and so showing the location
of the panic itself is desirable.

The following functions are async:
* `sync::mpsc::bounded::Sender::send_timeout`

Tests are included to cover each potentially panicking function.

Refs: tokio-rs#4413
@github-actions github-actions bot added the R-loom Run loom tests on this PR label Jul 5, 2022
@Noah-Kennedy
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wait what, double approve lol

@Darksonn Darksonn added A-tokio Area: The main tokio crate M-sync Module: tokio/sync labels Jul 6, 2022
@Darksonn Darksonn merged commit 4daeea8 into tokio-rs:master Jul 6, 2022
crapStone pushed a commit to Calciumdibromid/CaBr2 that referenced this pull request Jul 18, 2022
This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [tokio](https://tokio.rs) ([source](https://github.com/tokio-rs/tokio)) | dependencies | minor | `1.19.2` -> `1.20.0` |
| [tokio](https://tokio.rs) ([source](https://github.com/tokio-rs/tokio)) | dev-dependencies | minor | `1.19.2` -> `1.20.0` |

---

### Release Notes

<details>
<summary>tokio-rs/tokio</summary>

### [`v1.20.0`](https://github.com/tokio-rs/tokio/releases/tag/tokio-1.20.0)

[Compare Source](tokio-rs/tokio@tokio-1.19.2...tokio-1.20.0)

##### 1.20.0 (July 12, 2022)

##### Added

-   tokio: add track_caller to public APIs ([#&#8203;4772], [#&#8203;4791], [#&#8203;4793], [#&#8203;4806], [#&#8203;4808])
-   sync: Add `has_changed` method to `watch::Ref` ([#&#8203;4758])

##### Changed

-   time: remove `src/time/driver/wheel/stack.rs` ([#&#8203;4766])
-   rt: clean up arguments passed to basic scheduler ([#&#8203;4767])
-   net: be more specific about winapi features ([#&#8203;4764])
-   tokio: use const initialized thread locals where possible ([#&#8203;4677])
-   task: various small improvements to LocalKey ([#&#8203;4795])

##### Fixed

##### Documented

-   fs: warn about performance pitfall ([#&#8203;4762])
-   chore: fix spelling ([#&#8203;4769])
-   sync: document spurious failures in oneshot ([#&#8203;4777])
-   sync: add warning for watch in non-Send futures ([#&#8203;4741])
-   chore: fix typo ([#&#8203;4798])

##### Unstable

-   joinset: rename `join_one` to `join_next` ([#&#8203;4755])
-   rt: unhandled panic config for current thread rt ([#&#8203;4770])

[#&#8203;4677]: tokio-rs/tokio#4677

[#&#8203;4741]: tokio-rs/tokio#4741

[#&#8203;4755]: tokio-rs/tokio#4755

[#&#8203;4758]: tokio-rs/tokio#4758

[#&#8203;4762]: tokio-rs/tokio#4762

[#&#8203;4764]: tokio-rs/tokio#4764

[#&#8203;4766]: tokio-rs/tokio#4766

[#&#8203;4767]: tokio-rs/tokio#4767

[#&#8203;4769]: tokio-rs/tokio#4769

[#&#8203;4770]: tokio-rs/tokio#4770

[#&#8203;4772]: tokio-rs/tokio#4772

[#&#8203;4777]: tokio-rs/tokio#4777

[#&#8203;4791]: tokio-rs/tokio#4791

[#&#8203;4793]: tokio-rs/tokio#4793

[#&#8203;4795]: tokio-rs/tokio#4795

[#&#8203;4798]: tokio-rs/tokio#4798

[#&#8203;4806]: tokio-rs/tokio#4806

[#&#8203;4808]: tokio-rs/tokio#4808

</details>

---

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---

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---

This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzMi4xMTEuMSIsInVwZGF0ZWRJblZlciI6IjMyLjExMS4xIn0=-->

Co-authored-by: cabr2-bot <cabr2.help@gmail.com>
Reviewed-on: https://codeberg.org/Calciumdibromid/CaBr2/pulls/1458
Reviewed-by: crapStone <crapstone@noreply.codeberg.org>
Co-authored-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org>
Co-committed-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org>
@hds hds deleted the track-caller-sync branch July 21, 2022 12:46
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