Implement no_std support using hashbrown and lock_api
#9
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juntyr
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no_std support using hashbrown and lock_api
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Just to note, I don't have much spare time to spend on OSS atm (final semester at $gradschool!), so I'll probably not get to this soon; it's a significant chunk of API/impl to digest. Feel free to yoink what you need in the meantime; the project is intended to be trivial enough that it could be vendored without issue. |
| // Safety: | ||
| // - unlock_shared may only be called if a shared lock is held | ||
| // in the current context | ||
| // - thus an old guard for that shared lock must exist | ||
| let old_guard = std::ptr::read(&new_guard); |
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I'm very unconvinced that this is guaranteed to work as intended. I agree that it does work without UB for the current std distribution, but this isn't guaranteed to be the case forever, e.g. if RwLockReadGuard owns some allocation in the future rather than just borrowing the RwLock.
I'd be more comfortable if lock_api provided a raw version of the std lock for use with lock_api. That they don't optionally provide such suggests that they agree with me that this isn't sound.
| [features] | ||
| raw = ["hashbrown", "hashbrown/raw"] | ||
| default = ["std"] | ||
| std = [] | ||
| raw = ["hashbrown/raw"] | ||
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| [dependencies] | ||
| parking_lot = { version = "0.12.1", optional = true, default-features = false } | ||
| hashbrown = { version = "0.13.2", optional = true, default-features = false } | ||
| hashbrown = { version = "0.13.2", default-features = false } | ||
| lock_api = { version = "0.4.9" } |
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You can make this not API-breaking by adding dummy features for the no-longer-optional crates which don't do anything.
(I haven't inspected the rest of the touched API surface.)
Follow-up to #6
This second attempt is a shot at a very different design that attempts to keep the feature matrix as slim and non-annoying as possible. It is breaking since it makes
hashbrownnon-optional and removes theparking_lotfeature (since theInterneris now always parameterised by alock_api::RawRwLock, soparking_lotcan be supported by any user).To get
stdsupport working as-is, theInterneruses type defaults for the hash builder and rwlock with thestdfeature. For this, I've implemented a non-trivial private wrapper aroundstd::sync::Rwlock.If this PR would be the direction to go, I'd still need to write a nice change log entry to document the breaking change. If not, it can hopefully still serve as inspiration for how to implement
no_stdsupport.