fix(allocator): remove unsound impl Sync for Allocator#13033
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CodSpeed Instrumentation Performance ReportMerging #13033 will not alter performanceComparing Summary
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You need to fix breaking changes in rolldown. |
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I know! 😢 So far I've only fixed the ones in Oxc... |
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Pull Request Overview
This PR removes unsafe Send and Sync implementations for the Allocator type to fix thread safety issues. The Allocator is not thread-safe and allowing concurrent access could cause data corruption or out-of-bounds writes.
- Removes unsafe
impl Send for Allocatorandimpl Sync for Allocator - Improves memory safety by preventing unsound concurrent access to the allocator
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camc314
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Aug 19, 2025
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`Allocator` should not be `Sync`. `Allocator` is not thread-safe and allocating into it in multiple threads can cause data corruption or, in worst case, writing out of bounds. Remove the unsound `impl Sync for Allocator`. This PR also removes `impl Send for Allocator`, but that doesn't change anything. `bumpalo::Bump` is already `Send`, so `Allocator` is automatically `Send` too. It doesn't need an explicit `Send` impl.
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…3042) Previous PRs removed unsound `Sync` impl for `Allocator` (#13033) and `Send` impl for `Vec` (#13041). Previously `ScopingCell` was `Send` and `Sync` (and therefore `Scoping` was too). The recent PRs mean that `ScopingCell` lost those traits too. This PR implements both traits again for `ScopingCell` by restricting its API slightly, so now it is `Send` and `Sync` again, but this time in a manner which maintains soundness. The comments in the code outline the logic of why I believe it to be sound. Rolldown relies on `ScopingCell` being `Send` and `Sync`. After this PR, this stack does not require any changes in Rolldown. I've checked that `cargo ck` in Rolldown passes when using the version of Oxc from this branch.
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…ocationStats` (#13043) `AllocationStats` (introduced in #12555 and #12937) previously had to contain `AtomicUsize`s because `Allocator` was `Sync`. #13033 removed the `Sync` impl for `Allocator`, so now there's no need for synchronization in `AllocationStats`, and these fields can be `Cell<usize>` instead.
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Allocatorshould not beSync.Allocatoris not thread-safe and allocating into it in multiple threads can cause data corruption or, in worst case, writing out of bounds.Remove the unsound
impl Sync for Allocator.This PR also removes
impl Send for Allocator, but that doesn't change anything.bumpalo::Bumpis alreadySend, soAllocatoris automaticallySendtoo. It doesn't need an explicitSendimpl.