Add a new lint that warns for pointers to stack memory #134218

1c3t3a · 2024-12-12T16:32:52Z

This adds a new lint with level Warn to check for code like:

fn foo() -> *const i32 {
  let x = 42;
  &x
}

and produce a warning like:

error: returning a pointer to stack memory associated with a local variable
  --> <source>:12:5
   |
 LL|  &x
   |  ^^

This fixes #134215.

rustbot · 2024-12-12T16:33:03Z

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1c3t3a · 2024-12-12T16:34:24Z

I am aware that this may warn on existing code. I wonder what is a good strategy here? Should it be an Allow lint first and then be migrated to Warn as part of an edition? Or even stay Allow forever?

compiler-errors · 2024-12-12T16:49:32Z

Is there a reason why this was implemented as a rust lint rather than a clippy suspicious lint or something?

I guess let's find the fallout of this lint

@bors try

Add a new lint that warns for pointers to stack memory This adds a new lint with level `Warn` to check for code like: ```rust fn foo() -> *const i32 { let x = 42; &x } ``` and produce a warning like: ```text error: returning a pointer to stack memory associated with a local variable --> <source>:12:5 | LL| &x | ^^ ``` This fixes rust-lang#134215.

bors · 2024-12-12T16:50:47Z

⌛ Trying commit 40eb5d7 with merge 6db1a6a7ebb2ad243051f3ff949f987dd70cde2b...

1c3t3a · 2024-12-12T16:52:25Z

Is there a reason why this was implemented as a rust lint rather than a clippy suspicious lint or something?

This was completely my judgment, I am happy to change this if requested. My reasoning was that this is a pretty fundamental lint, since the code it lints should probably never exist? And looking at the list of rustc lints I thought it might be a good fit.

compiler/rustc_lint/src/builtin.rs

This adds a new lint with level `Warn` to check for code like: ```rust fn foo() -> *const i32 { let x = 42; &x } ``` and produce a warning like: ```text error: returning a pointer to stack memory associated with a local variable --> <source>:12:5 | LL| &x | ^^ ```

1c3t3a · 2024-12-12T17:18:26Z

The job x86_64-gnu-llvm-18 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

Oops - I don't fully understand that error. The failure looks like in the .stderr file, but it still has unexpected errors that it doesn't match on... This even happens when passing --bless.

compiler-errors · 2024-12-12T19:55:46Z

@craterbot check

craterbot · 2024-12-12T19:55:49Z

🚨 Error: missing start toolchain

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compiler-errors · 2024-12-12T19:56:50Z

@craterbot run mode=check-only start=master#8e37e151835d96d6a7415e93e6876561485a3354 end=try#6db1a6a7ebb2ad243051f3ff949f987dd70cde2b

craterbot · 2024-12-12T19:57:13Z

👌 Experiment pr-134218 created and queued.
🔍 You can check out the queue and this experiment's details.

ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

jyn514 · 2024-12-13T02:33:31Z

The job x86_64-gnu-llvm-18 failed! Check out the build log: (web) (plain)
Click to see the possible cause of the failure (guessed by this bot)

Oops - I don't fully understand that error. The failure looks like in the .stderr file, but it still has unexpected errors that it doesn't match on... This even happens when passing --bless.

bless will generate a .stderr file for you, but it will not update the original .rs file. compiletest is complaining because it expects each warning to be annotated with //~ WARN. see https://rustc-dev-guide.rust-lang.org/tests/ui.html#error-annotations

rustbot · 2024-12-13T15:49:15Z

The Miri subtree was changed

cc @rust-lang/miri

rustbot assigned compiler-errors Dec 12, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Dec 12, 2024