Lint against invalid POSIX symbol definitions by Urgau · Pull Request #158522 · rust-lang/rust

Urgau · 2026-06-28T12:08:20Z

This PR extends the invalid_runtime_symbol_definitions and suspicious_runtime_symbol_definitions lints to lint againts the following POSIX symbols:

I/O: open, read, write, close
Alloc: malloc, realloc, free
Program: exit

This is meant to address the multiple reports of users tripping over std symbols:

Those symbols are defined in std, so as long as the std crate is imported (and we are on a UNIX-like target) we lint on those symbols.

Follow up to #155521

rustbot · 2026-06-28T12:08:25Z

r? @chenyukang

rustbot has assigned @chenyukang.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

Owners of files modified in this PR: compiler
compiler expanded to 73 candidates
Random selection from 18 candidates

rustbot · 2026-06-28T14:57:20Z

miri is developed in its own repository. If possible, consider making this change to rust-lang/miri instead.

cc @rust-lang/miri

traviscross · 2026-07-01T15:23:19Z

Makes sense to me. Included in this FCP is preapproval for extending this to all extern functions referenced by the standard library when linked, such that defining a function of the same name in your program with a mismatched signature would cause problems.

@rfcbot fcp merge lang

rust-rfcbot · 2026-07-01T15:23:22Z

@traviscross has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

cc @rust-lang/lang-advisors: FCP proposed for lang, please feel free to register concerns.
See this document for info about what commands tagged team members can give me.

joshtriplett · 2026-07-01T15:23:32Z

@rfcbot reviewed

joshtriplett · 2026-07-01T15:24:36Z

Tagging relnotes as a reminder to extend the release notes on this lint to list the additional symbols.

rust-rfcbot · 2026-07-01T15:24:41Z

🔔 This is now entering its final comment period, as per the review above. 🔔

chenyukang · 2026-07-08T10:12:29Z

    ExpectedSymbol { symbol: "bcmp", lang: LanguageItems::bcmp_fn },
    ExpectedSymbol { symbol: "strlen", lang: LanguageItems::strlen_fn },
+    // POSIX symbols
+    ExpectedSymbol { symbol: "open", lang: LanguageItems::open_fn },


A definition of open64 with the wrong signature would still bypass the lint?

View changes since the review

Yes, only symbols defined in this list are checked, but given that T-lang wants to lint on all the functions used by core/std #158522 (comment) it makes sense to add open64 (and any other libc function) in a follow-up PR.

rustbot · 2026-07-10T21:34:43Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

rust-rfcbot · 2026-07-11T15:29:35Z

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

chenyukang · 2026-07-15T10:10:43Z

@bors r=chenyukang

rust-bors · 2026-07-15T10:10:45Z

📌 Commit 676a82f has been approved by chenyukang

It is now in the queue for this repository.

Rollup of 5 pull requests Successful merges: - #156712 (Pointer authentication config and user facing options) - #158522 (Lint against invalid POSIX symbol definitions) - #159229 (ast_lowering: Reject invalid direct_const_arg owners) - #159270 (Only force backtraces when a panic occurs in bootstrap) - #159308 (Reorganize `tests/ui/issues` [24/N])

Rollup merge of #158522 - Urgau:runtime-symbols-posix, r=chenyukang Lint against invalid POSIX symbol definitions This PR extends the `invalid_runtime_symbol_definitions` and `suspicious_runtime_symbol_definitions` lints to lint againts the following POSIX symbols: - I/O: `open`, `read`, `write`, `close` - Alloc: `malloc`, `realloc`, `free` - Program: `exit` This is meant to address the multiple reports of users tripping over `std` symbols: - [Why does `#[no_mangle] fn open() {}` make `cargo t` hang?](https://users.rust-lang.org/t/why-does-no-mangle-fn-open-make-cargo-t-hang/103423) - [Pointer becomes misaligned in test with `no_mangle`](https://users.rust-lang.org/t/pointer-becomes-misaligned-in-test-with-no-mangle/126580) Those symbols are defined in `std`, so as long as the `std` crate is imported (and we are on a UNIX-like target) we lint on those symbols. Follow up to #155521

Rollup of 5 pull requests Successful merges: - rust-lang/rust#156712 (Pointer authentication config and user facing options) - rust-lang/rust#158522 (Lint against invalid POSIX symbol definitions) - rust-lang/rust#159229 (ast_lowering: Reject invalid direct_const_arg owners) - rust-lang/rust#159270 (Only force backtraces when a panic occurs in bootstrap) - rust-lang/rust#159308 (Reorganize `tests/ui/issues` [24/N])

Replace weak only lang items with a custom attribute When I added the `invalid_runtime_symbol_definitions` and `suspicious_runtime_symbol_definitions` lints in #155521 I added the concept of "weak only" lang item. It's a `LangItem` that has no implementation, this is useful because the `core` symbols where not directly called, they were inserted by the compiler. This mechanism work well, but T-lang [approved](#158522 (comment)) the extension to "all extern functions referenced by the standard library", which makes the lang item approach impractical as we needs to update 5 files just to declare them. I'm not sure we can ask library contributor to do the dance for each `extern "C"` functions. But the most problematic thing is that many extern functions in `std` come from `libc` not `std`, and adding lang items there is just no feasible I think. Instead this PR proposed that we introduce a proper mechanism for them by adding a attribute `#[rustc_canonical_symbol = "..."]`, which is encoded and decoded in `rmeta` like lang items and diagnostics items. This simplifies the declaration as we only need to put the attribute to be effective `#[rustc_canonical_symbol = "open"]`. It also opens up many possibilities (none implemented here) like putting them on `use` statements (so we don't need to modify `libc`) or having the attribute be placed on a module. The table may also be useful on it's own if we want someday to do it for all crates, not just the standard library. Follow up to #155521 and #158522

rustbot assigned chenyukang Jun 28, 2026

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. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 28, 2026

Urgau changed the title ~~Lint lint against invalid POSIX symbol definitions~~ Lint against invalid POSIX symbol definitions Jun 28, 2026

Urgau added the I-lang-nominated Nominated for discussion during a lang team meeting. label Jun 28, 2026

Urgau force-pushed the runtime-symbols-posix branch from 315bb46 to 070c3d9 Compare June 28, 2026 12:41

This comment has been minimized.

Sign in to view

joshtriplett added the relnotes Marks issues that should be documented in the release notes of the next release. label Jul 1, 2026

rustbot mentioned this pull request Jul 1, 2026

Tracking issue for release notes of #158522: Lint against invalid POSIX symbol definitions #158662

Open

traviscross removed I-lang-nominated Nominated for discussion during a lang team meeting. P-lang-drag-1 Lang team prioritization drag level 1. https://rust-lang.zulipchat.com/#narrow/channel/410516-t-lang labels Jul 1, 2026

rust-rfcbot added the final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. label Jul 1, 2026

rust-rfcbot removed the proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. label Jul 1, 2026

ogoffart reviewed Jul 2, 2026

View reviewed changes

Comment thread tests/ui/lint/runtime-symbols-no-std.rs Outdated

chenyukang reviewed Jul 8, 2026

View reviewed changes

This comment was marked as resolved.

Sign in to view

Urgau force-pushed the runtime-symbols-posix branch from 02eca56 to 3155f8f Compare July 10, 2026 21:34

This comment was marked as resolved.

Sign in to view

Urgau added 3 commits July 11, 2026 10:38

Lint against invalid POSIX function definitions

cddad24

Fix UI tests for invalid POSIX function definitions

86db662

Fix Miri fail tests by allowing the lints

676a82f

Urgau force-pushed the runtime-symbols-posix branch from 3155f8f to 676a82f Compare July 11, 2026 09:31

rust-bors Bot 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 Jul 15, 2026

jhpratt mentioned this pull request Jul 15, 2026

Rollup of 5 pull requests #159325

Merged

rust-bors Bot merged commit 8365df9 into rust-lang:main Jul 15, 2026
13 checks passed

rustbot added this to the 1.99.0 milestone Jul 15, 2026

traviscross added the waived-reference-pr This language change does not need a Reference PR. label Jul 15, 2026

Urgau mentioned this pull request Jul 15, 2026

Replace weak only lang items with a custom attribute #159344

Open

ehuss mentioned this pull request Jul 16, 2026

Fix failing test due to invalid_runtime_symbol_definitions rust-lang/edition-guide#386

Merged

Uh oh!

Uh oh!

Conversation

Urgau commented Jun 28, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

rustbot commented Jun 28, 2026

Uh oh!

This comment has been minimized.

rustbot commented Jun 28, 2026

Uh oh!

traviscross commented Jul 1, 2026

Uh oh!

rust-rfcbot commented Jul 1, 2026 • edited by scottmcm Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

joshtriplett commented Jul 1, 2026

Uh oh!

joshtriplett commented Jul 1, 2026

Uh oh!

rust-rfcbot commented Jul 1, 2026

Uh oh!

Uh oh!

chenyukang Jul 8, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Urgau Jul 8, 2026

Choose a reason for hiding this comment

Uh oh!

This comment was marked as resolved.

rustbot commented Jul 10, 2026

Uh oh!

This comment was marked as resolved.

rust-rfcbot commented Jul 11, 2026

Uh oh!

chenyukang commented Jul 15, 2026

Uh oh!

rust-bors Bot commented Jul 15, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

8 participants

Urgau commented Jun 28, 2026 •

edited

Loading

rust-rfcbot commented Jul 1, 2026 •

edited by scottmcm

Loading

chenyukang Jul 8, 2026 •

edited by rustbot

Loading