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rust: allow `unknown_lints` in generated bindings for Rust < 1.88

PATCH In review Miguel Ojeda 3 participants 4 messages Sep 8

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Miguel Ojeda

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#0 lore raw

PATCH 1/1 rust: allow `unknown_lints` in generated bindings for Rust < 1.88

Starting with bindgen 0.73.2 [1], #[allow(unnecessary_transmutes)] are used, even when --rust-target 1.85 is passed.

However, the lint was introduced in Rust 1.88.0. Thus building with older Rust versions warns like:

    error: unknown lint: `unnecessary_transmutes`
         --> rust/uapi/uapi_generated.rs:26294:13
          |
    26294 |     #[allow(unnecessary_transmutes)]
          |             ^^^^^^^^^^^^^^^^^^^^^^
          |
          = note: `-D unknown-lints` implied by `-D warnings`
          = help: to override `-D warnings` add `#[allow(unknown_lints)]`

Thus allow unknown_lints in the generated bindings -- only when building with older Rust versions.

I have asked upstream if this is intentional [1], i.e. if we are supposed to always allow unknown lints in case bindgen uses such attributes, or whether it is an oversight.

Cc [email protected] # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Cc Emilio Cobos Álvarez <[email protected]>
Link https://github.com/rust-lang/rust-bindgen/pull/3455 [1]
Assisted-by LLM
Signed-off-by Miguel Ojeda <[email protected]>
---
 rust/bindings/lib.rs | 1 +
 rust/uapi/lib.rs     | 1 +
 2 files changed, 2 insertions(+)
rust/bindings/lib.rs +1 -0
index ad24c920b919..9e2c9a8e7e6c 100644
@@ -27,6 +27,7 @@
 #[allow(clippy::ptr_as_ptr)]
 #[allow(clippy::ref_as_ptr)]
 #[allow(clippy::undocumented_unsafe_blocks)]
+#[cfg_attr(not(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES), allow(unknown_lints))]
 #[cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_transmutes))]
 #[cfg_attr(
     CONFIG_RUSTC_HAS_SUSPICIOUS_RUNTIME_SYMBOL_DEFINITIONS,
rust/uapi/lib.rs +1 -0
index 2df0340e63d1..c1e27192ecce 100644
@@ -24,6 +24,7 @@
     unreachable_pub,
     unsafe_op_in_unsafe_fn
 )]
+#![cfg_attr(not(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES), allow(unknown_lints))]
 #![cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_transmutes))]
 #![cfg_attr(
     CONFIG_RUSTC_HAS_SUSPICIOUS_RUNTIME_SYMBOL_DEFINITIONS,

base-commit: 2ac74c6db40adaa29c50cbb281ae9a6f63de18e1

Signature · 1 line
2.55.0
reviewer
#1 lore raw
Quoted 37 lines · Miguel Ojeda

Starting with bindgen 0.73.2 [1], #[allow(unnecessary_transmutes)] are used, even when --rust-target 1.85 is passed.

However, the lint was introduced in Rust 1.88.0. Thus building with older Rust versions warns like:

    error: unknown lint: `unnecessary_transmutes`
         --> rust/uapi/uapi_generated.rs:26294:13
          |
    26294 |     #[allow(unnecessary_transmutes)]
          |             ^^^^^^^^^^^^^^^^^^^^^^
          |
          = note: `-D unknown-lints` implied by `-D warnings`
          = help: to override `-D warnings` add `#[allow(unknown_lints)]`

Thus allow unknown_lints in the generated bindings -- only when building with older Rust versions.

I have asked upstream if this is intentional [1], i.e. if we are supposed to always allow unknown lints in case bindgen uses such attributes, or whether it is an oversight.

Cc [email protected] # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Cc Emilio Cobos Álvarez <[email protected]>
Link https://github.com/rust-lang/rust-bindgen/pull/3455 [1]
Assisted-by LLM
Signed-off-by Miguel Ojeda <[email protected]>
---
 rust/bindings/lib.rs | 1 +
 rust/uapi/lib.rs     | 1 +
 2 files changed, 2 insertions(+)
rust/bindings/lib.rs +0 -0
index ad24c920b919..9e2c9a8e7e6c 100644

rust/bindings/lib.rs line 31

Quoted 5 lines
rust/bindings/lib.rs +1 -0
@@ -27,6 +27,7 @@
 #[allow(clippy::ptr_as_ptr)]
 #[allow(clippy::ref_as_ptr)]
 #[allow(clippy::undocumented_unsafe_blocks)]
+#[cfg_attr(not(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES), allow(unknown_lints))]
 #[cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_transmutes))]

I think we can drop the cfg on the allow(unnecessary_transmutes).

Best,
Gary

Quoted 16 lines
rust/bindings/lib.rs +0 -0
 #[cfg_attr(
     CONFIG_RUSTC_HAS_SUSPICIOUS_RUNTIME_SYMBOL_DEFINITIONS,
rust/uapi/lib.rs +1 -0
index 2df0340e63d1..c1e27192ecce 100644
@@ -24,6 +24,7 @@
     unreachable_pub,
     unsafe_op_in_unsafe_fn
 )]
+#![cfg_attr(not(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES), allow(unknown_lints))]
 #![cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_transmutes))]
 #![cfg_attr(
     CONFIG_RUSTC_HAS_SUSPICIOUS_RUNTIME_SYMBOL_DEFINITIONS,

base-commit: 2ac74c6db40adaa29c50cbb281ae9a6f63de18e1

#2 lore raw
Quoted 2 lines · Gary Guo

I think we can drop the cfg on the allow(unnecessary_transmutes).

Yeah, you are right. Perhaps it could have been temporary with a quick 0.73.3, but Emilio replied already.

Cheers,
Miguel

#3 lore raw
In reply to Miguel Ojeda
Quoted 23 lines · Miguel Ojeda

Starting with bindgen 0.73.2 [1], #[allow(unnecessary_transmutes)] are used, even when --rust-target 1.85 is passed.

However, the lint was introduced in Rust 1.88.0. Thus building with older Rust versions warns like:

    error: unknown lint: `unnecessary_transmutes`
         --> rust/uapi/uapi_generated.rs:26294:13
          |
    26294 |     #[allow(unnecessary_transmutes)]
          |             ^^^^^^^^^^^^^^^^^^^^^^
          |
          = note: `-D unknown-lints` implied by `-D warnings`
          = help: to override `-D warnings` add `#[allow(unknown_lints)]`

Thus allow unknown_lints in the generated bindings -- only when building with older Rust versions.

I have asked upstream if this is intentional [1], i.e. if we are supposed to always allow unknown lints in case bindgen uses such attributes, or whether it is an oversight.

Quoted 5 lines
Cc [email protected] # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Cc Emilio Cobos Álvarez <[email protected]>
Link https://github.com/rust-lang/rust-bindgen/pull/3455 [1]
Assisted-by LLM
Signed-off-by Miguel Ojeda <[email protected]>

Applied early to rust-fixes, but tags still welcome for a day or so -- thanks!

[ Emilio said it wasn't intentional -- we will work around it for now
on the kernel side. - Miguel ]

[ Removed the cfg for allow(unnecessary_transmutes) as suggested by
Gary. - Miguel ]

Cheers,
Miguel