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unpredictable_function_pointer_comparisons doesn't lint against Option<fn()> #134527

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kornelski opened this issue Dec 19, 2024 · 1 comment · May be fixed by #134536
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unpredictable_function_pointer_comparisons doesn't lint against Option<fn()> #134527

kornelski opened this issue Dec 19, 2024 · 1 comment · May be fixed by #134536
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@Urgau
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A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. C-bug Category: This is a bug.

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@kornelski
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In C FFI it's very common to use Option<fn()> for callbacks, but the lint #118833 doesn't fire when Options of function pointers are compared:

unsafe extern "C" fn func() {}

type FnPtr = unsafe extern "C" fn();

fn main() {
    assert_eq!(Some::<FnPtr>(func), Some(func as unsafe extern "C" fn()));
}

This pattern is used in: https://github.com/ImageOptim/mozjpeg-rust/blob/cff5aad77c726c11f460baefc348c7279d0ee647/src/readsrc.rs#L136
@kornelski kornelski added the C-bug Category: This is a bug. label Dec 19, 2024
@rustbot rustbot added the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Dec 19, 2024
@Urgau Urgau mentioned this issue Dec 19, 2024
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Urgau commented Dec 19, 2024

Looks reasonable to me. Opened #134536

@Urgau Urgau self-assigned this Dec 19, 2024
@Urgau Urgau added A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. and removed needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. labels Dec 19, 2024
@Urgau Urgau mentioned this issue Dec 20, 2024
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matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Dec 21, 2024
@matthiaskrgr
Rollup merge of rust-lang#134586 - Urgau:fn-ptr-lint-option, r=compil…
b7ac8d7 
…er-errors

Also lint on option of function pointer comparisons

This PR is the first part of rust-lang#134536, ie. the linting on `Option<{fn ptr}>` in the `unpredictable_function_pointer_comparisons` lint, which isn't part of the lang nomination that the second part is going trough, and so should be able to be approved independently.

Related to rust-lang#134527
r? `@compiler-errors`
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Dec 21, 2024
@rust-timer
Unrolled build for rust-lang#134586
b2f8864 
Rollup merge of rust-lang#134586 - Urgau:fn-ptr-lint-option, r=compiler-errors

Also lint on option of function pointer comparisons

This PR is the first part of rust-lang#134536, ie. the linting on `Option<{fn ptr}>` in the `unpredictable_function_pointer_comparisons` lint, which isn't part of the lang nomination that the second part is going trough, and so should be able to be approved independently.

Related to rust-lang#134527
r? `@compiler-errors`
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A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. C-bug Category: This is a bug.
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Lint on fn pointers comparisons in external macros Urgau/rust
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@kornelski @Urgau @rustbot