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clarify Arc::clone overflow check comment #98364

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Jun 24, 2022
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RalfJung
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I had to read this twice to realize that this is explaining that the code is technically unsound, so move that into a dedicated paragraph and make the wording a bit more explicit.

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Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

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@rustbot rustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Jun 22, 2022
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r? @Mark-Simulacrum

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@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 22, 2022
// any realistic program.
//
// This check is not 100% water-proof: we error when the refcount grows beyond `isize::MAX`
// on the assumption that there aren't ~2 billion threads incrementing the reference count
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Maybe worth noting where the 2 billion comes from? On a 16-bit platform for example this is much more of a problem (not that we support those today, I think?).

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So no test that triggers this logic on 64 bit pointer systems ? :)
This logic Is more a bout detecting corrupted memory.
Could this functionality be configurable ?. So can get smaller code size, and 1 less branch.

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r=me with or without nit fixed

@Mark-Simulacrum Mark-Simulacrum 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 Jun 22, 2022
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I did some more rewording to avoid the issue you pointed out; please take another look.

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@bors r+ rollup

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bors commented Jun 22, 2022

📌 Commit 46b2454 has been approved by Mark-Simulacrum

@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 Jun 22, 2022
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Jun 23, 2022
clarify Arc::clone overflow check comment

I had to read this twice to realize that this is explaining that the code is technically unsound, so move that into a dedicated paragraph and make the wording a bit more explicit.
compiler-errors added a commit to compiler-errors/rust that referenced this pull request Jun 23, 2022
clarify Arc::clone overflow check comment

I had to read this twice to realize that this is explaining that the code is technically unsound, so move that into a dedicated paragraph and make the wording a bit more explicit.
bors added a commit to rust-lang-ci/rust that referenced this pull request Jun 24, 2022
…piler-errors

Rollup of 16 pull requests

Successful merges:

 - rust-lang#96173 (Fix documentation for  `with_capacity` and `reserve` families of methods)
 - rust-lang#98184 (Give name if anonymous region appears in impl signature)
 - rust-lang#98259 (Greatly improve error reporting for futures and generators in `note_obligation_cause_code`)
 - rust-lang#98269 (Provide a `PathSegment.res` in more cases)
 - rust-lang#98283 (Point at private fields in struct literal)
 - rust-lang#98305 (prohibit_generics: don't alloc error string if no error emitted)
 - rust-lang#98310 (rustdoc: optimize loading of source sidebar)
 - rust-lang#98353 (Migrate two diagnostics from the `rustc_builtin_macros` crate)
 - rust-lang#98355 (Update no_default_libraries handling for emscripten target)
 - rust-lang#98364 (clarify Arc::clone overflow check comment)
 - rust-lang#98365 (Address review comments from rust-lang#98259)
 - rust-lang#98388 (implement `iter_projections` function on `PlaceRef`)
 - rust-lang#98390 (Fixes handling of keywords in rustdoc json output)
 - rust-lang#98409 (triagebot.toml: Allow applying nominated labels)
 - rust-lang#98410 (Update books)
 - rust-lang#98422 (Update browser-ui-test version to 0.9.6)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit e749ba2 into rust-lang:master Jun 24, 2022
@rustbot rustbot added this to the 1.63.0 milestone Jun 24, 2022
@RalfJung RalfJung deleted the arc-clone branch June 25, 2022 12:51
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6 participants