Document the behavior of pointer to smaller int casts
Nobody has claimed this yet.
Assessment
- Difficulty
- 5/5
- Estimated time
- Over a week
- Newbie friendliness
- 35/100
- Issue type
- Documentation
- Clarity
- Mostly clear
- Activity status
- Stale
- Tech stack
- rust
- Domain
- documentation
Research direction
Start with the linked Rust Playground snippet and investigate the behavior of casting a pointer directly to an integer that cannot hold it. Follow the proposed discussion in rust-lang/rust before editing the Reference. Done means the behavior is explicitly documented, including whether an intermediate cast or warning is expected.
Written by the indexing model from the issue text.
Description
let x = 42;
let z = &x as *const _ as u8;
As @rkruppe pointed out, this snippet casts a pointer to an int in which the pointer does not fit. AFAICT, the behavior of this operation is not guaranteed anywhere - I suppose it does a truncation. We should document what it does.
cc @Centril @RalfJung
I personally would probably prefer if it was at least a warning that suggests people to write as X as u8 instead, where X is a type in which the pointer precisely fits, e.g., usize and/or u{target_pointer_width} (e.g. u64) - if that is what that cast actually happens to mean, but this is an issue that should be better discussed in rust-lang/rust, once we know what that cast means.
- Dominant language
- Rust
- Stars
- 1.6k
- Forks
- 607
- Avg merge
- 1d 1h
- Merged PRs (30d)
- 12
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
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- Open a pull request that references the issue number.
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