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patterns: reject raw pointers that are not just integers #116930

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merged 5 commits into from
Nov 8, 2023

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@RalfJung RalfJung commented Oct 19, 2023

Matching against 0 as *const i32 is fine, matching against &42 as *const i32 is not.

This extends the existing check against function pointers and wide pointers: we now uniformly reject all these pointer types during valtree construction, and then later lint because of that. See here for some more explanation and context.

Also fixes #116929.

Cc @oli-obk @lcnr

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r? @davidtwco

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@rustbot 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 Oct 19, 2023
pub POINTER_STRUCTURAL_MATCH,
Allow,
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I didn't realize this lint is still allow-by-default oO. Seems high time we make it warn-by-default?

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The 2nd commit makes this forbid-by-default so we can crater it.
@bors try

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bors commented Oct 19, 2023

⌛ Trying commit 0787e62 with merge ebb1189...

bors added a commit to rust-lang-ci/rust that referenced this pull request Oct 19, 2023
patterns: reject raw pointers that are not just integers

Matching against `0 as *const i32` is fine, matching against `&42 as *const i32` is not.

Cc `@oli-obk` `@lcnr`
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Due to #116929 this lint still has a big gap, it'll only find bad raw pointers "at the root".

I wonder if with this change to valtree construction, we can make it so that some lint always fires when a const is used as a pattern and valtree construction fails? I do think those cases should all become hard errors eventually...

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bors commented Oct 19, 2023

☀️ Try build successful - checks-actions
Build commit: ebb1189 (ebb118907fa893a392c699ddf120848fa0a8d6c2)

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Let's see how much fallout we're getting from this weak form of the lint.
@craterbot check

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👌 Experiment pr-116930 created and queued.
🤖 Automatically detected try build ebb1189
🔍 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

@craterbot craterbot added S-waiting-on-crater Status: Waiting on a crater run to be completed. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 19, 2023
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Some changes might have occurred in exhaustiveness checking

cc @Nadrieril

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Lol, the doctest for StructuralEq uses a function pointer as a bad example.^^

@@ -247,6 +247,7 @@ marker_impls! {
///
/// const CFN: Wrap<fn(&())> = Wrap(higher_order);
///
/// #[allow(pointer_structural_match)]
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FWIW these entire trait docs are outdated; that's tracked in #115881.

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🚧 Experiment pr-116930 is now running

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

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🎉 Experiment pr-116930 is completed!
📊 876 regressed and 3 fixed (379825 total)
📰 Open the full report.

⚠️ If you notice any spurious failure please add them to the blacklist!
ℹ️ Crater is a tool to run experiments across parts of the Rust ecosystem. Learn more

@craterbot craterbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-crater Status: Waiting on a crater run to be completed. labels Oct 22, 2023
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@craterbot craterbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 22, 2023
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Those seem to be 3 legit regressions:

  • this matched on a fn ptr (so already triggered the lint before this PR, but the lint was allow-by-default)
  • same here
  • and same here

In particular, none of them is matching on a raw pointer that was not derived from an integer. So IMO we should land this PR to make sure people don't start doing that.

@RalfJung RalfJung added the I-lang-nominated Nominated for discussion during a lang team meeting. label Oct 30, 2023
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RalfJung commented Oct 30, 2023

@rust-lang/lang this PR does three things:

  • it fixes our old lint that detects match on function pointers and wide pointers to also catch cases where those pointers are hidden inside other types
  • it makes that lint warn-by-default (but doesn't yet make it show up in dependencies)
  • it makes the lint also trigger when encountering a raw pointer that was not constructed via int as *const/mut T, but e.g. via &something as *const T -- those allocations don't have guarantees on their ptr equality just like function pointers and vtables, so we should reject them for the same reason.

We haven't reached a proper conclusion in the recent "match on const" meeting, but the general direction seems to have been towards "it should still work like a pattern" (and not like sugar for ==), and this PR is a crucial step towards ensuring that they do indeed behave like a pattern, with structural properties and all that. Even if the goal is just to future-proof against both options (as has been the strategy so far), we want this warning.

Crater found only 3 cases where the warning triggers, in the entire ecosystem. All of them would already warn on stable if they enabled the lint; the new cases covered by this PR were not detected at all by crater.

@RalfJung RalfJung added the S-waiting-on-team Status: Awaiting decision from the relevant subteam (see the T-<team> label). label Oct 30, 2023
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Implementation changes look good to me, r=me after decisions from t-lang.

);
}
_ => {}
if !have_valtree {
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nit: could be part of the condition on the previous line

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nikomatsakis commented Nov 8, 2023

I'm in favor of this. (I also have thoughts on the semantics of matching on constants -- tl;dr I think I'm ready to accept "match is not an extensible mechanism" and hence will not act the same as == so we can stop talking about it -- but those are best discussed elsewhere, I assume)

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T-lang meeting consensus: let's do this, no FCP needed.

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RalfJung commented Nov 8, 2023

@bors r=davidtwco

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bors commented Nov 8, 2023

📌 Commit 3058865 has been approved by davidtwco

It is now in the queue for this repository.

@bors 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. S-waiting-on-team Status: Awaiting decision from the relevant subteam (see the T-<team> label). labels Nov 8, 2023
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bors commented Nov 8, 2023

⌛ Testing commit 3058865 with merge fdaaaf9...

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bors commented Nov 8, 2023

☀️ Test successful - checks-actions
Approved by: davidtwco
Pushing fdaaaf9 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Nov 8, 2023
@bors bors merged commit fdaaaf9 into rust-lang:master Nov 8, 2023
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@rustbot rustbot added this to the 1.75.0 milestone Nov 8, 2023
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Finished benchmarking commit (fdaaaf9): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
0.6% [0.4%, 1.4%] 5
Regressions ❌
(secondary)
3.6% [3.6%, 3.6%] 1
Improvements ✅
(primary)
-0.7% [-1.1%, -0.5%] 7
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) -0.1% [-1.1%, 1.4%] 12

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

mean range count
Regressions ❌
(primary)
0.4% [0.4%, 0.5%] 2
Regressions ❌
(secondary)
- - 0
Improvements ✅
(primary)
-0.4% [-0.4%, -0.4%] 1
Improvements ✅
(secondary)
- - 0
All ❌✅ (primary) 0.1% [-0.4%, 0.5%] 3

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 662.394s -> 663.159s (0.12%)
Artifact size: 308.74 MiB -> 308.75 MiB (0.00%)

@RalfJung RalfJung deleted the raw-ptr-match branch November 11, 2023 09:58
github-actions bot pushed a commit to rust-lang/miri that referenced this pull request Nov 15, 2023
patterns: reject raw pointers that are not just integers

Matching against `0 as *const i32` is fine, matching against `&42 as *const i32` is not.

This extends the existing check against function pointers and wide pointers: we now uniformly reject all these pointer types during valtree construction, and then later lint because of that. See [here](rust-lang/rust#116930 (comment)) for some more explanation and context.

Also fixes rust-lang/rust#116929.

Cc `@oli-obk` `@lcnr`
lnicola pushed a commit to lnicola/rust-analyzer that referenced this pull request Apr 7, 2024
patterns: reject raw pointers that are not just integers

Matching against `0 as *const i32` is fine, matching against `&42 as *const i32` is not.

This extends the existing check against function pointers and wide pointers: we now uniformly reject all these pointer types during valtree construction, and then later lint because of that. See [here](rust-lang/rust#116930 (comment)) for some more explanation and context.

Also fixes rust-lang/rust#116929.

Cc `@oli-obk` `@lcnr`
RalfJung pushed a commit to RalfJung/rust-analyzer that referenced this pull request Apr 27, 2024
patterns: reject raw pointers that are not just integers

Matching against `0 as *const i32` is fine, matching against `&42 as *const i32` is not.

This extends the existing check against function pointers and wide pointers: we now uniformly reject all these pointer types during valtree construction, and then later lint because of that. See [here](rust-lang/rust#116930 (comment)) for some more explanation and context.

Also fixes rust-lang/rust#116929.

Cc `@oli-obk` `@lcnr`
celinval added a commit to celinval/rust-dev that referenced this pull request Jun 4, 2024
Update Rust toolchain from nightly-2023-11-08 to nightly-2023-11-09
without any other source changes.
This is an automatically generated pull request. If any of the CI checks
fail, manual intervention is required. In such a case, review the
changes at https://github.com/rust-lang/rust from
rust-lang@7adc89b
up to
rust-lang@fdaaaf9.
The log for this commit range is:
rust-lang@fdaaaf9f92 Auto merge of
rust-lang#116930 - RalfJung:raw-ptr-match, r=davidtwco
rust-lang@30588657b7 avoid unnecessary
nested conditionals
rust-lang@90fdc1fc27 Auto merge of
rust-lang#117716 - GuillaumeGomez:rollup-83gnhll, r=GuillaumeGomez
rust-lang@9d3c80248b Rollup merge of
rust-lang#117713 - GuillaumeGomez:document-hidden-json, r=notriddle
rust-lang@d8c52b378d Rollup merge of
rust-lang#117702 - davidtwco:target-tier-refactors, r=petrochenkov
rust-lang@5d00a5d936 Rollup merge of
rust-lang#117679 - aDotInTheVoid:yes-core, r=GuillaumeGomez
rust-lang@c828371179 Rollup merge of
rust-lang#117282 - clubby789:recover-wrong-function-header, r=TaKO8Ki
rust-lang@e05e4f38b5 Rollup merge of
rust-lang#117263 - onur-ozkan:change-id-fix, r=saethlin
rust-lang@341efb1017 Auto merge of
rust-lang#117560 - lqd:issue-117146, r=matthewjasper
rust-lang@33edea60f0 Add test for
reexported hidden item with `--document-hidden-items`
rust-lang@28acba3c61 Auto merge of
rust-lang#115460 - zachs18:borrowedcursor_write_no_panic, r=dtolnay
rust-lang@755629fe59 Auto merge of
rust-lang#117706 - matthiaskrgr:rollup-lscx7dg, r=matthiaskrgr
rust-lang@e0cb1cc296 bootstrap: add more
detail on change-id comments
rust-lang@e878100386 bootstrap: improve
`fn check_version`
rust-lang@ae4d18b2da handle the case when
the change-id isn't found
rust-lang@7e4ffa98b5 Rollup merge of
rust-lang#117700 - Zalathar:rename-run-coverage, r=onur-ozkan
rust-lang@55306535dd Rollup merge of
rust-lang#117698 - nnethercote:space_between-2, r=petrochenkov
rust-lang@b1b5a8ea9d Rollup merge of
rust-lang#117667 - Alexendoo:doc-clippy-config, r=albertlarsan68
rust-lang@adf4981969 Rollup merge of
rust-lang#117663 - klensy:bump-deps, r=davidtwco
rust-lang@8198864377 Rollup merge of
rust-lang#117650 - saethlin:inline-me-please, r=davidtwco
rust-lang@ba7ec56639 Rollup merge of
rust-lang#117531 - fmease:rustdoc-effects-properly-elide-x-crate-host-args,
r=GuillaumeGomez
rust-lang@b74a84c0bc Rollup merge of
rust-lang#114316 - ecnelises:aix_doc, r=workingjubilee
rust-lang@fab1054e17 Auto merge of
rust-lang#117542 - compiler-errors:only-normalize-predicate, r=lcnr
rust-lang@750c2ecd15 Auto merge of
rust-lang#116881 - LuuuXXX:issue-110087, r=onur-ozkan
rust-lang@b9b7982f72 Add AIX
platform-support doc
rust-lang@ef7ebaa788 rustc_target: move
file for uniformity
rust-lang@1af256fe8a targets: move target
specs to spec/targets
rust-lang@76aa83e3e1 target: move base
specs to spec/base
rust-lang@a573880373 coverage: Rename the
`run-coverage` test mode to `coverage-run`
rust-lang@7cc997d373 Auto merge of
rust-lang#117699 - weihanglo:update-cargo, r=weihanglo
rust-lang@0670466e2c Update cargo
rust-lang@438b9a6e82 More tests for token
stream pretty-printing with adjacent punctuation.
rust-lang@783d4b8b26 Clarify
`space_between`.
rust-lang@91cfcb0219 Auto merge of
rust-lang#117484 - Zalathar:tests, r=cjgillot
rust-lang@97c9d8f405 Only use
normalize_param_env when normalizing predicate in check_item_bounds
rust-lang@1b8dee19e8 Fix issue rust-lang#110087
rust-lang@0d5ec963bb Auto merge of
rust-lang#117692 - matthiaskrgr:rollup-umaf5pr, r=matthiaskrgr
rust-lang@f72e974e3f Rollup merge of
rust-lang#117655 - compiler-errors:method-tweaks, r=estebank
rust-lang@7552dd19ad Rollup merge of
rust-lang#117625 - nnethercote:clippy-perf, r=cuviper
rust-lang@3c6307240c Rollup merge of
rust-lang#116399 - WaffleLapkin:erase_small_things, r=cjgillot
rust-lang@b724d9c90e Rollup merge of
rust-lang#113925 - clubby789:const-ctor-repeat, r=estebank
rust-lang@fcdd99edca Add
-Zcross-crate-inline-threshold=yes
rust-lang@e8cf29b584 rustdoc: minor
changes suggested by clippy perf lints.
rust-lang@ff0b4b6091 Auto merge of
rust-lang#117672 - lqd:ci-gcc-lld, r=Kobzol
rust-lang@1b3733e5a4 rustc: minor changes
suggested by clippy perf lints.
rust-lang@eca9a1533f Add an explanation
for `transmute_unchecked`
rust-lang@1d1fe9a205 add note to remember
to update a url when bumping to gcc 10.1.0
rust-lang@434b69a1d6 tests/rustdoc-json:
Rewrite tests no not use `#![no_core]`.
rust-lang@0875f456f1 tests/rustdoc-json:
Remove more needless uses of `#![no_core]`.
rust-lang@f784fa7bd9 tests/rustdoc-json:
Remove some needless uses of `#![no_core]`.
rust-lang@d73eaaac5f ci: bump gcc on dist
x64 linux builder to 9.5
rust-lang@f2fd8ad788 Document
clippy_config in nightly-rustc docs
rust-lang@eed89185bb bump some deps
rust-lang@0add056dee Rework
print_disambiguation_help
rust-lang@88a37acb26 Yeet
MethodCallComponents
rust-lang@4e6f438d2a coverage: Register
`test::Coverage` as the test suite for `tests/coverage`
rust-lang@49127c64d6 coverage: Migrate
`tests/coverage-map` into `tests/coverage`
rust-lang@e9d04c5e24 coverage: Migrate
`tests/run-coverage` into `tests/coverage`
rust-lang@aea7c27eae coverage: Set up a
macro for declaring unified coverage test suites
rust-lang@3509aed632 coverage: Add
`./x.py test coverage`, an alias for `coverage-map` and `run-coverage`
rust-lang@e585a99230 coverage: Give each
coverage test mode a separate output directory
rust-lang@211d4cee8e coverage: Copy all
remaining run-coverage tests into coverage-map
rust-lang@4b76b97bc8 coverage: Copy all
remaining coverage-map tests into run-coverage
rust-lang@f5df56b26b coverage: Flatten
`coverage-map/status-quo/` into its parent directory
rust-lang@8eef39f082 coverage: Remove
`tests/coverage-map/if.rs`
rust-lang@7f8a6de72c coverage: Use
`-Copt-level=2` by default in run-coverage tests
rust-lang@1dcdf83927 rustdoc: properly
elide cross-crate host effect args
rust-lang@2dff90dc23 add test for issue
117146
rust-lang@de7a8305ae traverse region
graph instead of SCCs to compute polonius loan scopes
rust-lang@03b24f2756 remove some dead
code
rust-lang@70a8e157ab make
pointer_structural_match warn-by-default
rust-lang@af6c7e0ca1 also lint against fn
ptr and raw ptr nested inside the const
rust-lang@bec88ad4aa patterns: reject raw
pointers that are not just integers
rust-lang@be0b42fabe Recover from
incorrectly ordered/duplicated function keywords
rust-lang@b3d50255d9 Use consisntent
style of `size_of` in query type erasure
rust-lang@61361bb212 Use
`transmute_unchecked` and make the types explicit in query type erasure
rust-lang@11a64a1834 don't panic in
BorrowedCursor::write
rust-lang@86b112204a Improve diagnostic
for const ctors in array repeat expressions

Co-authored-by: celinval <celinval@users.noreply.github.com>
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We're not warning against fn ptr and wide raw ptr nested inside ADTs
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