chore: backport "fix deprecation and clippy warnings" #1208
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This branch fixes two known warnings.
The first fixed warning was in `tracing-core/src/callsite.rs`, where
clippy suggested using `std::ptr::eq` to compare addresses instead of
casting `&T` to a `*const T`, which `&T` coerces to _anyways_. Below is
the warning:
```
error: use `std::ptr::eq` when comparing raw pointers
--> tracing-core/src/callsite.rs:238:9
|
238 | self.0 as *const _ as *const () == other.0 as *const _ as *const ()
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(self.0 as *const _, other.0 as *const _)`
|
= note: `-D clippy::ptr-eq` implied by `-D warnings`
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_eq
```
The second fixed warning is a bit more complex. As of Rust 1.50,
[`AtomicUsize::compare_and_swap`][1] has been deprecated in favor of
[`AtomicUsize::compare_exchange`][2] and
[`AtomicUsize::compare_exchange_weak`][3]. I've moved
`tracing_core::dispatch::set_global_default` to use
`AtomicUsize::compare_exchange` as `AtomicUsize::compare_exchange_weak`
is designed for atomic loads in loops. Here are a few notes on the
differences between `AtomicUsize::compare_and_swap` and
`AtomicUsize::compare_exchange`:
- `AtomicUsize::compare_exchange` returns a result, where the
`Result::Ok(_)` branch contains the prior value. This is equivalent
to the now-deprecated [`AtomicUsize::compare_and_swap`][1] returning
the `current` parameter upon a successful compare-and-swap operation,
but success is now established through a `Result`, not an equality
operation.
- `AtomicUsize::compare_exchange` accepts an `Ordering` for the failure
case of a compare-and-swap. The [migration guide suggests][4] using
`Ordering::SeqCst` for both the success and failure cases and I saw
no reason to depart from its guidance.
After this branch is approved, I'll backport these fixes to the `v0.1.0` branch.
[1]: https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicUsize.html#method.compare_and_swap
[2]: https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicUsize.html#method.compare_exchange
[3]: https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicUsize.html#method.compare_exchange_weak
[4]: https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicUsize.html#migrating-to-compare_exchange-and-compare_exchange_weak
This was referenced Jan 26, 2021
kaffarell
pushed a commit
to kaffarell/tracing
that referenced
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May 22, 2024
…1208) This branch fixes two known warnings. The first fixed warning was in `tracing-core/src/callsite.rs`, where clippy suggested using `std::ptr::eq` to compare addresses instead of casting `&T` to a `*const T`, which `&T` coerces to _anyways_. Below is the warning: ``` error: use `std::ptr::eq` when comparing raw pointers --> tracing-core/src/callsite.rs:238:9 | 238 | self.0 as *const _ as *const () == other.0 as *const _ as *const () | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(self.0 as *const _, other.0 as *const _)` | = note: `-D clippy::ptr-eq` implied by `-D warnings` = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_eq ``` The second fixed warning is a bit more complex. As of Rust 1.50, [`AtomicUsize::compare_and_swap`][1] has been deprecated in favor of [`AtomicUsize::compare_exchange`][2] and [`AtomicUsize::compare_exchange_weak`][3]. I've moved `tracing_core::dispatch::set_global_default` to use `AtomicUsize::compare_exchange` as `AtomicUsize::compare_exchange_weak` is designed for atomic loads in loops. Here are a few notes on the differences between `AtomicUsize::compare_and_swap` and `AtomicUsize::compare_exchange`: - `AtomicUsize::compare_exchange` returns a result, where the `Result::Ok(_)` branch contains the prior value. This is equivalent to the now-deprecated [`AtomicUsize::compare_and_swap`][1] returning the `current` parameter upon a successful compare-and-swap operation, but success is now established through a `Result`, not an equality operation. - `AtomicUsize::compare_exchange` accepts an `Ordering` for the failure case of a compare-and-swap. The [migration guide suggests][4] using `Ordering::SeqCst` for both the success and failure cases and I saw no reason to depart from its guidance. After this branch is approved, I'll backport these fixes to the `v0.1.0` branch. [1]: https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicUsize.html#method.compare_and_swap [2]: https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicUsize.html#method.compare_exchange [3]: https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicUsize.html#method.compare_exchange_weak [4]: https://doc.rust-lang.org/nightly/std/sync/atomic/struct.AtomicUsize.html#migrating-to-compare_exchange-and-compare_exchange_weak
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Backports #1195 to v0.1.x; unblocks #1205 and #1207.