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Eliminate mut reference UB in Drop impl for Rc<T> #76530

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Merged
merged 4 commits into from
Sep 12, 2020

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carbotaniuman
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@carbotaniuman carbotaniuman commented Sep 9, 2020

This changes self.ptr.as_mut() with get_mut_unchecked which
does not use an intermediate reference. Arc already handled this
case properly.

Fixes #76509

This changes `self.ptr.as_mut()` with `get_mut_unchecked` which
does not use an intermediate reference.  Arc<T> already handled this
case properly.
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r? @sfackler

(rust_highfive has picked a reviewer for you, use r? to override)

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 9, 2020
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carbotaniuman commented Sep 9, 2020

Hmm still fails Miri - it looks like I need to change a lot more code.

This avoids overlapping a reference covering the data field,
which may be changed due in concurrent conditions. This fully
fixed the UB mainfested with `new_cyclic`.
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r? @RalfJung

@rust-highfive rust-highfive assigned RalfJung and unassigned sfackler Sep 11, 2020
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Thanks a lot, this is great. :) I just have some minor nits.

@RalfJung RalfJung added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 11, 2020
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Looking good, thanks again. :)
@bors r+ rollup

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bors commented Sep 11, 2020

📌 Commit b729368 has been approved by RalfJung

@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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 11, 2020
bors added a commit to rust-lang-ci/rust that referenced this pull request Sep 12, 2020
Rollup of 7 pull requests

Successful merges:

 - rust-lang#76114 (Add saturating methods for `Duration`)
 - rust-lang#76297 (rustdoc: fix min_const_generics with ty::Param)
 - rust-lang#76484 (Add MaybeUninit::assume_init_drop.)
 - rust-lang#76530 (Eliminate mut reference UB in Drop impl for Rc<T>)
 - rust-lang#76583 (Update `std::os` module documentation.)
 - rust-lang#76599 (Finish off revisions for const generics UI tests.)
 - rust-lang#76615 (Add missing examples on binary core traits)

Failed merges:

r? `@ghost`
@bors bors merged commit a49451c into rust-lang:master Sep 12, 2020
@rustbot rustbot added this to the 1.48.0 milestone Sep 12, 2020
@carbotaniuman carbotaniuman deleted the fix-rc branch April 20, 2022 15:24
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"test_rc_cyclic_with_one_ref" fails in Miri
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