Use volatile access instead of `#[used]` for `on_tls_callback` The first commit adds a volatile load of `p_thread_callback` when registering a dtor so that the compiler knows if the callback is used or not. I don't believe the added volatile instruction is otherwise significant in the context. In my testing using the volatile load allowed the compiler to correctly reason about whether `on_tls_callback` is used or not, allowing it to be omitted entirely in some cases. Admittedly it usually is used due to `Thread` but that can be avoided (e.g. in DLLs or with custom entry points that avoid the offending APIs). Ideally this would be something the compiler could help a bit more with so we didn't have to use tricks like `#[used]` or volatile. But alas. I also used this as an opportunity to clean up the `unused` lints which I don't think serve a purpose any more. The second commit removes the volatile load of `_tls_used` with `#cfg[target_thread_local]` because `#[thread_local]` already implies it. And if it ever didn't then `#[thread_local]` would be broken when there aren't any dtors. |
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The Rust Programming Language
This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.
Note: this README is for users rather than contributors. If you wish to contribute to the compiler, you should read CONTRIBUTING.md instead.
Table of Contents
Quick Start
Read "Installation" from The Book.
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See CONTRIBUTING.md.
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See LICENSE-APACHE, LICENSE-MIT, and COPYRIGHT for details.
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