slotmap
miri
slotmap | miri | |
---|---|---|
14 | 122 | |
1,039 | 3,973 | |
- | 2.7% | |
3.4 | 10.0 | |
2 months ago | 2 days ago | |
Rust | Rust | |
zlib License | Apache License 2.0 |
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slotmap
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Tree Borrows - A new aliasing model for Rust
It looks like .get_disjoint_mut() from slotmap failed under stacked borrows, but seems to pass under tree borrows
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Indexing vs Smart Pointers
I think slotmap is meant to solve this exact issue. Basically when you insert into a collection you get an Id:Version tuple as key. When you reuse a slot, next time the key will be Id:Version+1 and when you try to access the removed value by using Id:Version, it will return None. You can think about it as delayed invalidation.
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Hey Rustaceans! Got a question? Ask here (5/2023)!
Dunno about existing implementations, but it looks like it's a feature they'd accept: https://github.com/orlp/slotmap/issues/73
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Unsafe is a bad practice?
It's actually quite easy.
- Rust is more portable than C for pngquant/libimagequant
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Hey Rustaceans! Got an easy question? Ask here (50/2021)!
You can use either slot map or slab to side step rust borrow checker. Example https://github.com/orlp/slotmap/blob/master/examples/rand_meld_heap.rs
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Rust data structures with circular references
I don't know, only have some theories.
1. The name isn't particularly catchy or descriptive. It is the correct name for the data structure, but not too many people know the data structure.
2. People don't even know what they're missing. It's not a very Google-able problem to begin with. Slotmap provides an interesting solution to (circular) ownership and safe allocator / weak pointer design problems, but people don't recognize that they're having them or that slotmap could help.
As an example of this, the doubly linked list example (https://github.com/orlp/slotmap/blob/master/examples/doubly_...) can safely remove nodes from the linked list given their handle, in O(1), even from the middle, completely safely and correctly, even in the presence of double deletions or ABA memory re-use. You can't replicate this with just pointers, without introducing heavy refcounting solutions.
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Is it possible to write anything using 100% safe Rust?
Nope, it's perfectly safe: https://github.com/orlp/slotmap/blob/master/examples/doubly_linked_list.rs.
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Syncing HashMap values amongst User
I think keeping the relationship between child and parent elements in the node graph might be better accommodating better via a psuedo-ECS system, see https://www.reddit.com/r/rust/comments/cnjhup/idiomatic_way_to_reference_parent_struct/. The https://github.com/orlp/slotmap crate looks promising. I think I'm just going to ditch the global shared HashMap in favor of something that can better accommodate child/parent relations.
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Beginner question: does it become easier to write datastructures with complex ownership semantics?
I think the slotmap crate is similar to what you're trying to write: https://github.com/orlp/slotmap
miri
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Rust: Box Is a Unique Type
>While we are many missing language features away from this being the case, the noalias case is also magic descended upon box itself, with no user code ever having access to it.
I'm not sure why the author thinks there's magic behind Box. Box is not a special case of `noalias`. Run this snippet with miri and you'll see the same issue: https://play.rust-lang.org/?version=stable&mode=debug&editio...
`Box` _does_ have an expectation that its inner pointer is not aliased to another Box (even if used for readonly operations). See: https://github.com/rust-lang/miri/issues/1800#issuecomment-8...)
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Bytecode VMs in Surprising Places
Miri [0] is an interpreter for the mid-level intermediate representation (MIR) generated by the Rust compiler. MIR is input for more processing steps of the compiler. However miri also runs MIR directly. This means miri is a VM. Of course it's not a bytecode VM, because MIR is not a bytecode AFAIK. I still think that miri is a interesting example.
And why does miri exist?
It is a lot slower. However it can check for some undefined behavior.
[0]: https://github.com/rust-lang/miri
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RFC: Rust Has Provenance
Provenance is a dynamic property of pointer values. The actual underlying rules that a program must follow, even when using raw pointers and `unsafe`, are written in terms of provenance. Miri (https://github.com/rust-lang/miri) represents provenance as an actual value stored alongside each pointer's address, so it can check for violations of these rules.
Lifetimes are a static approximation of provenance. They are erased after being validated by the borrow checker, and do not exist in Miri or have any impact on what transformations the optimizer may perform. In other words, the provenance rules allow a superset of what the borrow checker allows.
- Mir: Strongly typed IR to implement fast and lightweight interpreters and JITs
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Running rustc in a browser
There has been discussion of doing this with MIRI, which would be easier than all of rustc.
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Piecemeal dropping of struct members causes UB? (Miri)
This issue has been fixed: https://github.com/rust-lang/miri/issues/2964
- Erroneous UB Error with Miri?
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I've incidentally created one of the fastest bounded MPSC queue
Actually, I've done more advanced tests with MIRI (see https://github.com/rust-lang/miri/issues/2920 for example) which allowed me to fix some issues. I've also made the code compatible with loom, but I didn't found the time yet to write and execute loom tests. That's on the TODO-list, and I need to track it with an issue too.
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Interested in "secure programming languages", both theory and practice but mostly practice, where do I start?
He is one of the big brains behind Miri, which is a interpreter that runs on the MIR (compiler representation between human code and asm/machine code) and detects undefined behavior. Super useful tool for language safety, pretty interesting on its own.
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Formal verification for unsafe code?
I would also run your tests in Miri (https://github.com/rust-lang/miri) to try to cover more bases.
What are some alternatives?
rust-typed-arena - The arena, a fast but limited type of allocator
cons-list - Singly-linked list implementation in Rust
slab - Slab allocator for Rust
sanitizers - AddressSanitizer, ThreadSanitizer, MemorySanitizer
multi_mut - Methods on HashMap and BTreeMap for safely getting multiple mutable references to the contained values.
rust - Empowering everyone to build reliable and efficient software.
rust - Rust for the xtensa architecture. Built in targets for the ESP32 and ESP8266
Rust-Full-Stack - Rust projects here are easy to use. There are blog posts for them also.
stdx - The missing batteries of Rust
rfcs - RFCs for changes to Rust
nomicon - The Dark Arts of Advanced and Unsafe Rust Programming