Make `#[repr(Rust)]` incompatible with other (non-modifier) representation hints like `C` and `simd` #116829

fmease · 2023-10-17T01:18:05Z

Read more about this change here: #116829 (comment).

Fixes [after backport] #116825.

rustbot · 2023-10-17T01:18:14Z

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compiler-errors · 2023-10-17T01:22:23Z

compiler/rustc_passes/src/errors.rs

 #[derive(LintDiagnostic)]
 #[diag(passes_repr_conflicting, code = "E0566")]
-pub struct ReprConflicting;
+pub struct ReprConflictingLint;


If you're interested in a follow-up, it's probably time to bump this lint up to a hard-error 😸

compiler-errors · 2023-10-17T01:22:57Z

I think this is pretty obviously an error, but since T-lang's triage meeting is tomorrow, I guess it doesn't hurt to wait until then. r=me after, though.

compiler/rustc_passes/src/check_attr.rs

WaffleLapkin · 2023-10-18T14:42:42Z

Consensus from the lang team triage meeting (minutes):

We should allow repr(Rust, aligned(N))
We should allow repr(Rust, packed)
We should ban all other repr(Rust, other) combinations, including, but not necesseraly limited to:
- C
- transparent
- i* and u* (u8, i8, u16, ...)
- simd

WaffleLapkin · 2023-10-18T14:44:35Z

Personally I think we can allow Rust, u*/i*, but since we didn't come to a consensus on this in the meeting, let's pospone this desicion to later.

This PR can probably be merged as-is, but someone needs to create a follow-up with banning all other combinations.

fmease · 2023-10-18T14:50:31Z

Imma update this PR instead of creating another one, otherwise we'd need to backport 2 PRs.

fmease · 2023-10-18T15:33:14Z

We already have positive behavior tests for #[repr(Rust, align(N))] and #[repr(Rust, packed)] in tests/ui/abi/explicit_repr_rust.rs.

fmease · 2023-10-18T16:32:37Z

compiler/rustc_passes/src/check_attr.rs

            self.tcx.sess.emit_err(errors::TransparentIncompatible {
                hint_spans,
                target: target.to_string(),
            });
        }
+        if is_explicit_rust && (int_reprs > 0 || is_c || is_simd) {


I could also turn the bools into a bitfield and check if the difference between the set bitflags and {Rust, align, packed} is empty to address “but not necessarily limited to” part of

We should ban all other repr(Rust, other) combinations, including, but not necesseraly limited to

I think refactoring this function would be a lot of good, as the current code seems to be error-prone and confusing. But obv this refactoring can come as a follow-up, which does not need a backport. (cc me if you'll do it please)

One of the things that would be nice is to default to disallowing, so that no changes can accidentally allow new combinations.

compiler-errors · 2023-10-18T17:15:21Z

@bors r+

bors · 2023-10-18T17:15:24Z

📌 Commit d0b99e3 has been approved by compiler-errors

It is now in the queue for this repository.

Rollup of 7 pull requests Successful merges: - rust-lang#116663 (Don't ICE when encountering unresolved regions in `fully_resolve`) - rust-lang#116761 (Fix podman detection in CI scripts) - rust-lang#116795 (Add `#[track_caller]` to `Option::unwrap_or_else`) - rust-lang#116829 (Make `#[repr(Rust)]` incompatible with other (non-modifier) representation hints like `C` and `simd`) - rust-lang#116883 (Change my name in mailmap) - rust-lang#116908 (Tweak wording of type errors involving type params) - rust-lang#116912 (Some renaming nits for `rustc_type_ir`) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#116829 - fmease:rust-aint-c, r=compiler-errors Make `#[repr(Rust)]` incompatible with other (non-modifier) representation hints like `C` and `simd` Read more about this change here: rust-lang#116829 (comment). Fixes [after backport] rust-lang#116825.

apiraino · 2023-10-19T14:14:22Z

Beta backport accepted as per compiler team on Zulip

@rustbot label +beta-accepted

[beta] backports and stage0 bump - Bump stage0 to released stable compiler - Hide host effect params from docs rust-lang#116670 - Fix a performance regression in obligation deduplication. rust-lang#116826 - Make `#[repr(Rust)]` and `#[repr(C)]` incompatible with one another rust-lang#116829 - Update to LLVM 17.0.3 rust-lang#116840 - Disable effects in libcore again rust-lang#116856 - revert rust-lang#114586 rust-lang#116879 r? cuviper

rustbot assigned b-naber Oct 17, 2023

fmease added the beta-nominated Nominated for backporting to the compiler in the beta channel. label Oct 17, 2023

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 17, 2023

compiler-errors reviewed Oct 17, 2023

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compiler-errors assigned compiler-errors and unassigned b-naber Oct 17, 2023

fmease added T-lang Relevant to the language team, which will review and decide on the PR/issue. I-lang-nominated The issue / PR has been nominated for discussion during a lang team meeting. labels Oct 17, 2023

fmease force-pushed the rust-aint-c branch 2 times, most recently from cf1fba5 to cae6344 Compare October 17, 2023 11:34

fmease commented Oct 17, 2023

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fmease added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 18, 2023

Make #[repr(Rust)] and #[repr(C)] incompatible with one another

d0b99e3

fmease force-pushed the rust-aint-c branch from cae6344 to d0b99e3 Compare October 18, 2023 15:26

fmease changed the title ~~Make #[repr(Rust)] and #[repr(C)] incompatible with one another~~ Make #[repr(Rust)] incompatible with other (non-modifier) representations like C and simd Oct 18, 2023

fmease changed the title ~~Make #[repr(Rust)] incompatible with other (non-modifier) representations like C and simd~~ Make #[repr(Rust)] incompatible with other (non-modifier) representation hints like C and simd Oct 18, 2023

fmease commented Oct 18, 2023

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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 18, 2023

fmease mentioned this pull request Oct 19, 2023

Rollup of 7 pull requests #116923

Merged

bors merged commit 2eb6e5f into rust-lang:master Oct 19, 2023
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rustbot added this to the 1.75.0 milestone Oct 19, 2023

fmease deleted the rust-aint-c branch October 19, 2023 12:02

rustbot added the beta-accepted Accepted for backporting to the compiler in the beta channel. label Oct 19, 2023

cuviper mentioned this pull request Oct 21, 2023

[beta] backports and stage0 bump #117005

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cuviper modified the milestones: 1.75.0, 1.74.0 Oct 21, 2023

cuviper removed the beta-nominated Nominated for backporting to the compiler in the beta channel. label Oct 21, 2023

fmease mentioned this pull request Oct 21, 2023

The seemingly contradictory #[repr(Rust, C)] is allowed #116825

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Automated pull from upstream master ferrocene/ferrocene#74

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Make `#[repr(Rust)]` incompatible with other (non-modifier) representation hints like `C` and `simd` #116829

Make `#[repr(Rust)]` incompatible with other (non-modifier) representation hints like `C` and `simd` #116829

fmease commented Oct 17, 2023 •

edited

rustbot commented Oct 17, 2023

compiler-errors Oct 17, 2023

compiler-errors commented Oct 17, 2023

WaffleLapkin commented Oct 18, 2023 •

edited

WaffleLapkin commented Oct 18, 2023 •

edited

fmease commented Oct 18, 2023

fmease commented Oct 18, 2023

fmease Oct 18, 2023

WaffleLapkin Oct 18, 2023

WaffleLapkin Oct 18, 2023

compiler-errors commented Oct 18, 2023

bors commented Oct 18, 2023

apiraino commented Oct 19, 2023

Make #[repr(Rust)] incompatible with other (non-modifier) representation hints like C and simd #116829

Make #[repr(Rust)] incompatible with other (non-modifier) representation hints like C and simd #116829

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fmease commented Oct 17, 2023 • edited

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apiraino commented Oct 19, 2023

Make `#[repr(Rust)]` incompatible with other (non-modifier) representation hints like `C` and `simd` #116829

Make `#[repr(Rust)]` incompatible with other (non-modifier) representation hints like `C` and `simd` #116829

fmease commented Oct 17, 2023 •

edited

WaffleLapkin commented Oct 18, 2023 •

edited

WaffleLapkin commented Oct 18, 2023 •

edited