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core: compare callsite::Identifier data pointers only (#749 )

## Motivation

Clippy [now warns us][1] that comparing trait object pointers with
`ptr::eq` is bad, because vtable addresses are not guaranteed to be
unique due to the compiler merging vtables, and vtables for the same
trait impl may have different addresses in different compilation units.

In practice, I don't believe this actually effects `tracing-core`'s use
case for this comparison. Because callsites must be static, the data
component of the trait object wide pointer will always be unique, even
if the compiler merges the vtables for all the identical generated
`Callsite` impls (which it may very well do!).

## Solution

Although this is probably not an issue in practice, I still thought it
was good to fix the clippy warning, and to be more explicit that it's
the data pointer comparison that's load-bearing here. I've updated the
`PartialEq` impl for `callsite::Identifier` to cast to `*const ()` to
extract the data address from the wide pointer.

[1]: https://rust-lang.github.io/rust-clippy/master/index.html#vtable_address_comparisons

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

2020-06-12 10:21:42 -07:00

src

core: compare callsite::Identifier data pointers only (#749 )

2020-06-12 10:21:42 -07:00

tests

core: Add set_default method to set default dispatcher (#388 )

2019-10-18 11:56:33 -07:00

Cargo.toml

chore: clean up old CI stuff (#670 )

2020-04-07 10:52:01 -07:00

CHANGELOG.md

core: prepare to release 0.1.10 (#598 )

2020-02-24 11:31:59 -08:00

LICENSE

meta: rename everything to tracing (#99 )

2019-06-26 11:31:07 -07:00

README.md

core: prepare to release 0.1.10 (#598 )

2020-02-24 11:31:59 -08:00

README.md

tracing-core

Core primitives for application-level tracing.

Documentation | Chat

Overview

tracing is a framework for instrumenting Rust programs to collect structured, event-based diagnostic information. This crate defines the core primitives of tracing.

The crate provides:

span::Id identifies a span within the execution of a program.
Event represents a single event within a trace.
Subscriber, the trait implemented to collect trace data.
Metadata and Callsite provide information describing spans and events.
Field, FieldSet, Value, and ValueSet represent the structured data attached to spans and events.
Dispatch allows spans and events to be dispatched to Subscribers.

In addition, it defines the global callsite registry and per-thread current dispatcher which other components of the tracing system rely on.

Usage

Application authors will typically not use this crate directly. Instead, they will use the tracing crate, which provides a much more fully-featured API. However, this crate's API will change very infrequently, so it may be used when dependencies must be very stable.

Subscriber implementations may depend on tracing-core rather than tracing, as the additional APIs provided by tracing are primarily useful for instrumenting libraries and applications, and are generally not necessary for Subscriber implementations.

Crate Feature Flags

The following crate feature flags are available:

std: Depend on the Rust standard library (enabled by default).

no_std users may disable this feature with default-features = false:
```
[dependencies]
tracing-core = { version = "0.1.10", default-features = false }
```
Compiler support: requires rustc 1.39+

Note:tracing-core's no_std support requires liballoc.

License

This project is licensed under the MIT license.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Tokio by you, shall be licensed as MIT, without any additional terms or conditions.