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@giltho giltho commented Aug 12, 2025

I believe the current doc of dangling is slightly off as it indicates:
Note that the pointer value may potentially represent a valid pointer to a T

The returned pointer has no provenance, so it may not be a valid pointer (except in the case of ZSTs, but I don't think this is what the documentation is trying to warn about).

See: https://rust-lang.zulipchat.com/#narrow/channel/136281-t-opsem/topic/Dangling.20pointers.3A.20definition

The value returned by dangling may never be used to dereference a value that isn't a ZST, even if address equality is detected with that of a valid pointer.
This is a minor fix, but this doc still got me confused for a second

Signed-off-by: Sacha Ayoun <[email protected]>
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rustbot commented Aug 12, 2025

r? @scottmcm

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@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Aug 12, 2025
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Man I wish github had a better diff for stuff like this, but I agree that talking about the address here is probably better.

@bors r+ rollup

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bors commented Aug 13, 2025

📌 Commit 427be23 has been approved by scottmcm

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 13, 2025
bors added a commit that referenced this pull request Aug 13, 2025
Rollup of 11 pull requests

Successful merges:

 - #143467 (Add ASCII-related methods from `u8` and `MIN`/`MAX` to `core::ascii::Char`)
 - #144519 (Constify `SystemTime` methods)
 - #144642 (editorconfig: don't trim trailing whitespace in tests)
 - #144870 (Stabilize `path_file_prefix` feature)
 - #145269 (Deprecate RUST_TEST_* env variables)
 - #145274 (Remove unused `#[must_use]`)
 - #145289 (chore(ci): upgrade checkout to v5)
 - #145303 (Docs: Link to payload_as_str() from payload().)
 - #145308 (Adjust documentation of `dangling`)
 - #145320 (Allow cross-compiling the Cranelift dist component)
 - #145325 (Add `cast_init` and `cast_uninit` methods for pointers)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit b60d5b3 into rust-lang:master Aug 13, 2025
10 checks passed
@rustbot rustbot added this to the 1.91.0 milestone Aug 13, 2025
rust-timer added a commit that referenced this pull request Aug 13, 2025
Rollup merge of #145308 - giltho:dangling-doc, r=scottmcm

Adjust documentation of `dangling`

I believe the current doc of `dangling` is slightly off as it indicates:
`Note that the pointer value may potentially represent a valid pointer to a T`

The returned pointer has no provenance, so it may not be a valid pointer (except in the case of ZSTs, but I don't think this is what the documentation is trying to warn about).

See: https://rust-lang.zulipchat.com/#narrow/channel/136281-t-opsem/topic/Dangling.20pointers.3A.20definition

The value returned by dangling may never be used to dereference a value that isn't a ZST, even if address equality is detected with that of a valid pointer.
This is a minor fix, but this doc still got me confused for a second
github-actions bot pushed a commit to model-checking/verify-rust-std that referenced this pull request Aug 18, 2025
Adjust documentation of `dangling`

I believe the current doc of `dangling` is slightly off as it indicates:
`Note that the pointer value may potentially represent a valid pointer to a T`

The returned pointer has no provenance, so it may not be a valid pointer (except in the case of ZSTs, but I don't think this is what the documentation is trying to warn about).

See: https://rust-lang.zulipchat.com/#narrow/channel/136281-t-opsem/topic/Dangling.20pointers.3A.20definition

The value returned by dangling may never be used to dereference a value that isn't a ZST, even if address equality is detected with that of a valid pointer.
This is a minor fix, but this doc still got me confused for a second
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