`improper_ctypes_definitions` lint #72700

davidtwco · 2020-05-28T16:31:14Z

Addresses #19834, #66220, and #66373.

This PR takes another attempt at #65134 (reverted in #66378). Instead of modifying the existing improper_ctypes lint to consider extern "C" fn definitions in addition to extern "C" {} declarations, this PR adds a new lint - improper_ctypes_definitions - which only applies to extern "C" fn definitions.

In addition, the improper_ctype_definitions lint differs from improper_ctypes by considering *T and &T (where T: Sized) FFI-safe (addressing #66220).

There wasn't a clear consensus in #66220 (where the issues with #65134 were primarily discussed) on the approach to take, but there has been some discussion in Zulip. I fully expect that we'll want to iterate on this before landing.

cc @varkor + @shepmaster (from #19834) @hanna-kruppe (active in discussing #66220), @SimonSapin (#65134 caused problems for Servo, want to make sure that this PR doesn't)

rust-highfive · 2020-05-28T16:31:18Z

r? @ecstatic-morse

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SimonSapin · 2020-05-28T17:42:22Z

#65134 caused problems for Servo, want to make sure that this PR doesn't

A try build that I could install with rustup-toolchain-install-master would be good. Is the new lint warn by default? (Affected by -D warnings?)

davidtwco · 2020-05-29T08:50:50Z

#65134 caused problems for Servo, want to make sure that this PR doesn't

A try build that I could install with rustup-toolchain-install-master would be good. Is the new lint warn by default? (Affected by -D warnings?)

The lint is warn-by-default.

@bors try

bors · 2020-05-29T08:51:02Z

⌛ Trying commit 7cbdc2d58423511e6f336424955a17c891b13c03 with merge 672712eca084ef382c9505561aac6e15fbefe8ab...

bors · 2020-05-29T11:31:23Z

☀️ Try build successful - checks-azure
Build commit: 672712eca084ef382c9505561aac6e15fbefe8ab (672712eca084ef382c9505561aac6e15fbefe8ab)

SimonSapin · 2020-05-29T13:02:58Z

I am unable to test this build in Servo as the llvm-tools-preview component appears to not be available. It is now required for linking compiler plugins: #72594 (comment)

$ rustup-toolchain-install-master 672712eca084ef382c9505561aac6e15fbefe8ab -c rustc-dev -c llvm-tools-preview 
[…]
downloading <https://rust-lang-ci2.s3-us-west-1.amazonaws.com/rustc-builds/672712eca084ef382c9505561aac6e15fbefe8ab/llvm-tools-preview-nightly-x86_64-unknown-linux-gnu.tar.xz>...
error: missing component `llvm-tools-preview` on toolchain `672712eca084ef382c9505561aac6e15fbefe8ab` on channel `nightly` for target `x86_64-unknown-linux-gnu`

hanna-kruppe · 2020-05-30T09:19:22Z

I don't have the time to actually review this at the moment, but after glancing over the implementation I remembered some unstated ideas underlying my past comments advocating for separate lints. The tl;dr is that I think the approach of adding more "modes" to the existing improper_ctypes visitor is not scalable as we add more lints that are concerned with layout/ABI questions (which we should), and the code could do with an untangling anyway. This definitely doesn't have to happen in this PR, though, so I wrote down the details in a new issue #72774 before I forget again.

davidtwco · 2020-06-09T10:24:02Z

r? @varkor

varkor · 2020-06-09T13:11:47Z

Will try to review soon.

src/librustc_lint/types.rs

Aaron1011 · 2020-06-25T04:21:52Z

@bors retry

bors · 2020-06-25T04:22:07Z

⌛ Testing commit 4504648 with merge ae3f308cf38eb55957fed008aa952276ac949b3e...

bors · 2020-06-25T08:37:07Z

💥 Test timed out

@ghost

Rollup of 6 pull requests Successful merges: - rust-lang#72700 (`improper_ctypes_definitions` lint) - rust-lang#73516 (Allow dynamic linking for iOS/tvOS targets) - rust-lang#73616 (Liballoc minor hash import tweak) - rust-lang#73634 (Add UI test for issue 73592) - rust-lang#73688 (Document the self keyword) - rust-lang#73698 (Add procedure for prioritization notifications on Zulip) Failed merges: r? @ghost

rust-lang/rust#72700 caused the existing `allow(improper_ctypes)` guard to stop working, we now need `allow(improper_ctypes_definitions)` instead. We keep the old one to avoid any issues with older nightlies. Signed-off-by: Joe Richey <joerichey@google.com>

alexcrichton · 2020-07-16T14:28:24Z

Sorry for being a bit late to the punch on this, but this feels like it's still noisy in some cases where it probably shouldn't be. For example:

warning: `extern` fn uses type `std::option::Option<std::boxed::Box<error::wasmtime_error_t>>`, which is not FFI-safe

where in this case wasmtime_error_t is a #[repr(C)] structure, but the internals are intentionally not FFI-safe. We're returning an opaque pointer across the FFI boundary so we don't want to make the contents all FFI-safe. This warning also seems to be about Option and Box which are perhaps missing being allowed since I believe they have defined ABIs?

This was enabled in rust-lang/rust#72700 but it looks like it's still too noisy for it to be useful to us.

alexcrichton · 2020-07-16T15:26:33Z

FWIW this is actually a bit extra onerous because if you write #![allow(improper_ctypes_definitions)] you also have to write #![allow(unknown_lints)] since the lint doesn't exist on stable right now.

This was enabled in rust-lang/rust#72700 but it looks like it's still too noisy for it to be useful to us.

CryZe · 2020-07-16T16:07:23Z

Yeah I'm now also getting these warnings all over the place for Rust types in Boxes, which should be FFI safe (in fact that's specifically documented to be FFI safe)

davidtwco · 2020-07-16T16:10:04Z

I'll have a PR up to resolve this soon.

@alexcrichton

…ns-boxes, r=davidtwco improper_ctypes_definitions: allow `Box` Addresses rust-lang#72700 (comment). This PR stops linting against `Box` in `extern "C" fn`s for the `improper_ctypes_definitions` lint - boxes are documented to be FFI-safe. cc @alexcrichton @CryZe

@alexcrichton

…ns-boxes, r=davidtwco improper_ctypes_definitions: allow `Box` Addresses rust-lang#72700 (comment). This PR stops linting against `Box` in `extern "C" fn`s for the `improper_ctypes_definitions` lint - boxes are documented to be FFI-safe. cc @alexcrichton @CryZe

@alexcrichton

…ns-boxes, r=davidtwco improper_ctypes_definitions: allow `Box` Addresses rust-lang#72700 (comment). This PR stops linting against `Box` in `extern "C" fn`s for the `improper_ctypes_definitions` lint - boxes are documented to be FFI-safe. cc @alexcrichton @CryZe

@alexcrichton

…ns-boxes, r=davidtwco improper_ctypes_definitions: allow `Box` Addresses rust-lang#72700 (comment). This PR stops linting against `Box` in `extern "C" fn`s for the `improper_ctypes_definitions` lint - boxes are documented to be FFI-safe. cc @alexcrichton @CryZe

rust-highfive assigned ecstatic-morse May 28, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 28, 2020

davidtwco changed the title ~~improper_ctypes_declarations lint~~ improper_ctypes_definitions lint May 28, 2020

SimonSapin mentioned this pull request May 30, 2020

Fix improper_ctypes warnings in Rust Nightly servo/servo#24684

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hanna-kruppe mentioned this pull request May 30, 2020

Refactor improper_ctypes to separate "UCG questions" from linting decisions #72774

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davidtwco force-pushed the issue-66220-improper-ctypes-declarations branch from 7cbdc2d to dbc8a3a Compare June 9, 2020 10:23

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davidtwco mentioned this pull request Jun 12, 2020

Should improper_ctypes pierce through impl Trait? #60855

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lcnr reviewed Jun 20, 2020

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bors merged commit 67db7a2 into rust-lang:master Jun 25, 2020

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This was referenced Jul 2, 2020

improper_ctypes lint should check types referenced in C ABI function definitions #19834

Closed

improper_ctypes fires for &mut T, &T, *const T and *mut T (when T: Sized) #66220

Closed

josephlr mentioned this pull request Jul 8, 2020

Fix warnings on latest nightly rust-lang/compiler-builtins#364

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LeSeulArtichaut mentioned this pull request Jul 14, 2020

Nightly ICEs trying to normalize during a cast #73747

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alexcrichton added a commit to alexcrichton/wasmtime that referenced this pull request Jul 16, 2020

Allow improper_ctypes_definitions in C API

88b5cac

This was enabled in rust-lang/rust#72700 but it looks like it's still too noisy for it to be useful to us.

alexcrichton mentioned this pull request Jul 16, 2020

Allow improper_ctypes_definitions in C API bytecodealliance/wasmtime#2033

Merged

alexcrichton added a commit to alexcrichton/wasmtime that referenced this pull request Jul 16, 2020

Allow improper_ctypes_definitions in C API

298d2da

This was enabled in rust-lang/rust#72700 but it looks like it's still too noisy for it to be useful to us.

alexcrichton added a commit to alexcrichton/wasmtime that referenced this pull request Jul 16, 2020

Allow improper_ctypes_definitions in C API

9760f7a

This was enabled in rust-lang/rust#72700 but it looks like it's still too noisy for it to be useful to us.

bnjbvr pushed a commit to bytecodealliance/wasmtime that referenced this pull request Jul 16, 2020

Allow improper_ctypes_definitions in C API

41e1300

This was enabled in rust-lang/rust#72700 but it looks like it's still too noisy for it to be useful to us.

davidtwco mentioned this pull request Jul 17, 2020

improper_ctypes_definitions: allow Box #74448

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`improper_ctypes_definitions` lint #72700

`improper_ctypes_definitions` lint #72700

davidtwco commented May 28, 2020 •

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improper_ctypes_definitions lint #72700

improper_ctypes_definitions lint #72700

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`improper_ctypes_definitions` lint #72700

`improper_ctypes_definitions` lint #72700

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