Comment on Rc abort-guard strategy without naming unrelated fn#140483
Merged
bors merged 2 commits intorust-lang:masterfrom May 7, 2025
Merged
Comment on Rc abort-guard strategy without naming unrelated fn#140483bors merged 2 commits intorust-lang:masterfrom
Rc abort-guard strategy without naming unrelated fn#140483bors merged 2 commits intorust-lang:masterfrom
Conversation
`wrapped_add` is used, not `checked_add`
Collaborator
|
rustbot has assigned @workingjubilee. Use |
rustbot
added
S-waiting-on-review
library/alloc/src/rc.rs
Outdated
| } | ||
|
|
||
| // NOTE: We checked_add here to deal with mem::forget safely. In particular | ||
| // NOTE: We wrapping_add here to deal with mem::forget safely. In particular |
Member
There was a problem hiding this comment.
This is confusing in a different way: the wrapping_add does not offer the protection anymore, the strong == 0 conditional does.
Member
There was a problem hiding this comment.
at the very least, it should mention clearly what actually implements the guard that handles the mem::forget, if it's going to mention any code.
Contributor
Author
There was a problem hiding this comment.
I see what you mean. The fact that it's wrapping_add rather than checked_add previously is merely a detail for the sake of code generation, and that's addressed in a more local comment. In that case, I think this comment is more about the higher level issue of a potential soundness hole and isn't enhanced by mentioning the particular implementation details. How about this?
// NOTE: If you mem::forget Rcs (or Weaks), drop is skipped and the ref-count
// is not decremented, meaning the ref-count can overflow, and then you can
// free the allocation while outstanding Rcs (or Weaks) exist, which would be
// unsound. We abort because this is such a degenerate scenario that we don't
// care about what happens -- no real program should ever experience this.
Member
There was a problem hiding this comment.
Yeah, something like that seems good to me.
Member
|
I think this requires more than a one-word change to make something that makes sense. At least in the current mistaken form it's obviously " @rustbot author |
rustbot
added
S-waiting-on-author
Collaborator
|
Reminder, once the PR becomes ready for a review, use |
Update comment per review feedback
Contributor
Author
|
@rustbot ready |
rustbot
added
S-waiting-on-review
workingjubilee
changed the title
Rc abort-guard strategy without naming unrelated fn
Member
|
Thanks! @bors r+ rollup |
Collaborator
bors
added
S-waiting-on-bors
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
May 7, 2025
Rollup of 9 pull requests Successful merges: - rust-lang#134273 (de-stabilize bench attribute) - rust-lang#139534 (Added support for `apxf` target feature) - rust-lang#140419 (Move `in_external_macro` to `SyntaxContext`) - rust-lang#140483 (Comment on `Rc` abort-guard strategy without naming unrelated fn) - rust-lang#140607 (support duplicate entries in the opaque_type_storage) - rust-lang#140656 (collect all Fuchsia bindings into the `fuchsia` module) - rust-lang#140668 (Implement `VecDeque::truncate_front()`) - rust-lang#140709 (rustdoc: remove unportable markdown lint and old parser) - rust-lang#140713 (Structurally resolve in `check_ref_cast` in new solver) r? `@ghost` `@rustbot` modify labels: rollup
rust-timer
added a commit
to rust-lang-ci/rust
that referenced
this pull request
May 7, 2025
Rollup merge of rust-lang#140483 - baumanj:patch-1, r=workingjubilee Comment on `Rc` abort-guard strategy without naming unrelated fn `wrapped_add` is used, not `checked_add`, so avoid mentioning specific fn calls that may vary slightly based on "whatever produces the best code" and focus on things that will remain constant into the future.
github-actions bot
pushed a commit
to carolynzech/rust
that referenced
this pull request
May 16, 2025
Comment on `Rc` abort-guard strategy without naming unrelated fn `wrapped_add` is used, not `checked_add`, so avoid mentioning specific fn calls that may vary slightly based on "whatever produces the best code" and focus on things that will remain constant into the future.
github-actions bot
pushed a commit
to carolynzech/rust
that referenced
this pull request
May 16, 2025
Rollup of 9 pull requests Successful merges: - rust-lang#134273 (de-stabilize bench attribute) - rust-lang#139534 (Added support for `apxf` target feature) - rust-lang#140419 (Move `in_external_macro` to `SyntaxContext`) - rust-lang#140483 (Comment on `Rc` abort-guard strategy without naming unrelated fn) - rust-lang#140607 (support duplicate entries in the opaque_type_storage) - rust-lang#140656 (collect all Fuchsia bindings into the `fuchsia` module) - rust-lang#140668 (Implement `VecDeque::truncate_front()`) - rust-lang#140709 (rustdoc: remove unportable markdown lint and old parser) - rust-lang#140713 (Structurally resolve in `check_ref_cast` in new solver) r? `@ghost` `@rustbot` modify labels: rollup
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
wrapped_addis used, notchecked_add, so avoid mentioning specific fn calls that may vary slightly based on "whatever produces the best code" and focus on things that will remain constant into the future.