Add #[must_use] to alloc functions that would leak memory #90427

jkugelman · 2021-10-31T02:11:27Z

Please do go ahead and add the ones whose only legitimate use for ignoring the return value is leaking memory. (In a separate PR please.) I think it's sufficiently error-prone to call something like alloc and ignore the result that it's legitimate to require let _ = for that.

I added realloc myself. Clippy ignored it because of its mut argument.

alloc/src/alloc.rs:123:1   alloc   unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8;

Parent issue: #89692

r? @joshtriplett

joshtriplett · 2021-10-31T08:15:38Z

@bors r+

bors · 2021-10-31T08:15:39Z

📌 Commit 42e0282 has been approved by joshtriplett

…askrgr Rollup of 8 pull requests Successful merges: - rust-lang#89446 (Add paragraph to ControlFlow docs to menion it works with the ? operator (rust-lang#88715)) - rust-lang#89677 (Stabilize `is_symlink()` for `Metadata` and `Path`) - rust-lang#89833 (Add #[must_use] to Rc::downgrade) - rust-lang#89835 (Add #[must_use] to expensive computations) - rust-lang#89839 (Add #[must_use] to mem/ptr functions) - rust-lang#89897 (Add #[must_use] to remaining core functions) - rust-lang#89951 (Stabilize `option_result_unwrap_unchecked`) - rust-lang#90427 (Add #[must_use] to alloc functions that would leak memory) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

matklad · 2021-11-30T05:51:16Z

library/alloc/src/sync.rs

@@ -804,6 +804,7 @@ impl<T: ?Sized> Arc<T> {
    /// let x_ptr = Arc::into_raw(x);
    /// assert_eq!(unsafe { &*x_ptr }, "hello");
    /// ```
+    #[must_use = "losing the pointer will leak memory"]


This one feels like it could lead to false positives. This is Arc, so you can get the data back via another instance.

not sure if it happens in practice though. I think I used that once to simulate
increment_strong_count? Not sure.

rust-highfive assigned joshtriplett Oct 31, 2021

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 31, 2021

jkugelman mentioned this pull request Oct 31, 2021

Tracking issue for adding #[must_use] annotations throughout the standard library #89692

Closed

Add #[must_use] to alloc functions that would leak memory

42e0282

jkugelman force-pushed the must-use-alloc-leak branch from b0c783b to 42e0282 Compare October 31, 2021 02:19

joshtriplett added the relnotes Marks issues that should be documented in the release notes of the next release. label Oct 31, 2021

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 Oct 31, 2021

matthiaskrgr mentioned this pull request Oct 31, 2021

Rollup of 8 pull requests #90434

Merged

bors merged commit ff6d8ec into rust-lang:master Oct 31, 2021

rustbot added this to the 1.58.0 milestone Oct 31, 2021

jkugelman deleted the must-use-alloc-leak branch October 31, 2021 14:38

matklad reviewed Nov 30, 2021

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Add #[must_use] to alloc functions that would leak memory #90427

Add #[must_use] to alloc functions that would leak memory #90427

jkugelman commented Oct 31, 2021

joshtriplett commented Oct 31, 2021

bors commented Oct 31, 2021

matklad Nov 30, 2021

Add #[must_use] to alloc functions that would leak memory #90427

Add #[must_use] to alloc functions that would leak memory #90427

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jkugelman commented Oct 31, 2021

joshtriplett commented Oct 31, 2021

bors commented Oct 31, 2021

matklad Nov 30, 2021

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