#246 [Coding Guideline]: Do not access memory using a pointer with an incorrect provenance by manhatsu · Pull Request #264 · rustfoundation/safety-critical-rust-coding-guidelines

manhatsu · 2025-12-08T04:16:34Z

Closes #246.

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rcseacord · 2025-12-08T13:49:24Z

@manhatsu This is going to continue to be a rule about provenance so it should definitely have provenance in the title, otherwise I won't be able to find it.

For now I suggest the title be "Do not access memory using a pointer with incorrect provenance"

Updated guidelines on pointer comparisons and memory access to clarify the importance of provenance and the implications of comparing pointers from different allocations.

manhatsu · 2025-12-08T14:30:58Z

@rcseacord It was my lack of understanding. I changed the title as you suggested.

added new noncompliant / compliant solution

inkreasing · 2025-12-09T19:23:48Z

src/coding-guidelines/types-and-traits.rst

+    Do not access memory using a pointer with an incorrect provenance.
+    Pointers, including values of reference type, have two components.
+    The pointer’s address identifies the memory location where the pointer is currently pointing.
+    The pointer’s provenance determines where and when the pointer is allowed to access memory.


The provenance also determines if the pointer is allowed to mutate the memory. See also the std docs for this: https://doc.rust-lang.org/std/ptr/index.html#provenance

This should maybe also be taken into account below when discussing when a memory access is UB.

inkreasing · 2025-12-09T19:26:19Z

src/coding-guidelines/types-and-traits.rst

+    - Outcomes of pointer arithmetic across allocation boundaries
+
+    This rule ignores any metadata that may come with wide pointers;
+    it only pertains to thin pointers and the data part of a wide pointer.


Suggested change

it only pertains to thin pointers and the data part of a wide pointer.

it only pertains to thin pointers and the address part of a wide pointer.

The additional data of a wide pointer is often called metadata (See the unstable function for reading it: https://doc.rust-lang.org/std/ptr/fn.metadata.html or the previous sentence). So calling the address "data" is confusing.

Do you want to link to unstable docs? If yes it may be better to link to https://doc.rust-lang.org/std/ptr/trait.Pointee.html#pointer-metadata as here the current kinds of metadata are explained?

@inkreasing OK, i added this link. do you see any other problems with this or does it look ready to merge?

resolved (again)

@rcseacord Oh sorry i am not in any position to decide wether this is ready to be merged. This was basically a drive-by review. Will make that clear from the beginning next time.

no problem, i was just looking for your opinion.

link to unstable docs as here the current kinds of metadata are explained.

github-actions · 2026-02-10T17:20:07Z

👋 Hey @iglesias! You've been assigned to review this coding guideline PR.

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Guideline title is clear and follows conventions
Amplification section expands on the title appropriately
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Non-compliant example(s) clearly show the problem
Compliant example(s) clearly show the solution
Code examples compile (check the CI results)
FLS paragraph ID is correct

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felix91gr · 2026-02-10T17:41:12Z

@iglesias one sec, we messed up and the thing has assigned you as reviewer to 4 PRs (it should only be able to assign you to 1)

felix91gr · 2026-02-10T23:06:12Z

@iglesias okay, this one is the right one (according to the bot's queue). Sorry about the multiple pings! :)

plaindocs · 2026-02-18T15:22:47Z

Hey @iglesias would you like to claim this review, or let someone else grab it

github-actions · 2026-02-25T09:25:09Z

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iglesias · 2026-02-26T04:57:46Z

@guidelines-bot /claim

github-actions · 2026-02-26T04:58:04Z

✅ @iglesias has claimed this review.

@iglesias is designated as reviewer by queue rotation, but GitHub could not add them to PR Reviewers automatically (API 422). A triage+ approver may still be required before merge queue.

src/coding-guidelines/types-and-traits.rst

iglesias · 2026-02-26T05:59:00Z

Hey @felix91gr @plaindocs sorry the delay :-)

Co-authored-by: Fernando José <fernando.iglesiasg@gmail.com>

github-actions · 2026-03-17T18:13:38Z

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iglesias · 2026-03-18T01:00:50Z

@guidelines-bot

iglesias · 2026-03-18T01:03:11Z

@guidelines-bot /commands

iglesias · 2026-03-18T01:08:46Z

Hey @felix91gr @plaindocs
I approved the review 3 weeks ago, but still just got the review reminder 6 hours ago. Is there anything missing to approve it?
Thank you for any help :-)

iglesias

LGTM

felix91gr · 2026-03-18T11:02:02Z

GAH we have to solve those conflicts, that's the issue. Damn, I forgot. I tried to do it on the web ui a couple times, but github wouldn't have it (something something large diff). And later I forgot to do it locally (I'm not even sure I know how to do that in a way github would accept).

@iglesias your review is perfect as far as I can tell. Lemme see if we can get this solved with @plaindocs before the bot pings you again 🙇🏻

plaindocs · 2026-03-18T12:13:06Z

@felix91gr know anything about the two errors shown?

felix91gr · 2026-03-18T19:31:50Z

@plaindocs I'm checking... one sec

felix91gr · 2026-03-18T19:33:57Z

Ah. Okay, I see what's up. Hmm. I'll be back in a bit. The code examples need some help. This didn't trigger before because there were some merge conflicts that stopped CI jobs from running.

github-actions · 2026-04-01T12:12:04Z

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github-actions · 2026-04-01T13:29:45Z

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github-actions · 2026-04-01T14:29:59Z

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github-actions · 2026-04-01T15:25:56Z

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plaindocs · 2026-04-01T15:32:38Z

@PLeVasseur could you check the naggy review bot please

github-actions · 2026-04-01T16:17:14Z

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PLeVasseur · 2026-04-01T16:30:05Z

Sorry for the nagging; working on it

iglesias · 2026-04-01T23:32:34Z

Thank you 🙇

doc: prohibit comparing raw pointers with different allocation origins

bd24df5

manhatsu changed the title ~~doc: prohibit comparing raw pointers with different allocation origins~~ #246 [Coding Guideline]: Prohibit comparing raw pointers with different allocation origins Dec 8, 2025

Revise pointer comparison guidelines for clarity

510903f

Updated guidelines on pointer comparisons and memory access to clarify the importance of provenance and the implications of comparing pointers from different allocations.

manhatsu changed the title ~~#246 [Coding Guideline]: Prohibit comparing raw pointers with different allocation origins~~ #246 [Coding Guideline]: Do not access memory using a pointer with an incorrect provenance Dec 8, 2025

Update types-and-traits.rst

2276188

added new noncompliant / compliant solution

inkreasing reviewed Dec 9, 2025

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rcseacord added 3 commits December 11, 2025 14:05

Update types-and-traits.rst

67d8c04

Merge branch 'main' into feat/pointer-comparison-rule

af20e81

Update types-and-traits.rst

a016d71

link to unstable docs as here the current kinds of metadata are explained.

felix91gr added the coding guideline An issue related to a suggestion for a coding guideline label Feb 10, 2026

github-project-automation bot added this to [Safety Critical Rust Consortium Coding Guidelines] Work Items Feb 10, 2026

PLeVasseur mentioned this pull request Feb 10, 2026

fix(reviewer-bot): mutation-intent routing and git-ref CAS state lock #405

Merged

felix91gr added the chapter: unsafety label Feb 24, 2026

iglesias approved these changes Feb 26, 2026

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src/coding-guidelines/types-and-traits.rst Outdated Show resolved Hide resolved

Update src/coding-guidelines/types-and-traits.rst

53cfab8

Co-authored-by: Fernando José <fernando.iglesiasg@gmail.com>

iglesias approved these changes Mar 18, 2026

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Merge branch 'main' into feat/pointer-comparison-rule

7d8864f

plaindocs approved these changes Mar 18, 2026

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github-actions bot added the status: awaiting reviewer response Reviewer-bot is waiting on reviewer freshness or current-head review label Mar 26, 2026

	it only pertains to thin pointers and the data part of a wide pointer.
	it only pertains to thin pointers and the address part of a wide pointer.

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