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rust: clean Rust 1.88.0's unnecessary_transmutes lint

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Starting with Rust 1.88.0 (expected 2025-06-26) [1][2], `rustc` may
introduce a new lint that catches unnecessary transmutes, e.g.:

     error: unnecessary transmute
         --> rust/uapi/uapi_generated.rs:23242:18
          |
    23242 |         unsafe { ::core::mem::transmute(self._bitfield_1.get(0usize, 1u8) as u8) }
          |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace this with: `(self._bitfield_1.get(0usize, 1u8) as u8 == 1)`
          |
          = note: `-D unnecessary-transmutes` implied by `-D warnings`
          = help: to override `-D warnings` add `#[allow(unnecessary_transmutes)]`

There are a lot of them (at least 300), but luckily they are all in
`bindgen`-generated code.

Thus clean all up by allowing it there.

Since unknown lints trigger a lint itself in older compilers, do it
conditionally so that we can keep the `unknown_lints` lint enabled.

Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Link: https://github.com/rust-lang/rust/pull/136083 [1]
Link: https://github.com/rust-lang/rust/issues/136067 [2]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250502140237.1659624-4-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Miguel Ojeda 2025-05-02 16:02:35 +02:00
parent a39f308709
commit 7129ea6e24
3 changed files with 5 additions and 0 deletions
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3
init/Kconfig
View file

@ -140,6 +140,9 @@ config LD_CAN_USE_KEEP_IN_OVERLAY
config RUSTC_HAS_COERCE_POINTEE
def_bool RUSTC_VERSION >= 108400
config RUSTC_HAS_UNNECESSARY_TRANSMUTES
def_bool RUSTC_VERSION >= 108800
config PAHOLE_VERSION
int
default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))

1
rust/bindings/lib.rs
View file

@ -26,6 +26,7 @@
#[allow(dead_code)]
#[allow(clippy::undocumented_unsafe_blocks)]
#[cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_transmutes))]
mod bindings_raw {
// Manual definition for blocklisted types.
type __kernel_size_t = usize;

1
rust/uapi/lib.rs
View file

@ -24,6 +24,7 @@
unreachable_pub,
unsafe_op_in_unsafe_fn
)]
#![cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_transmutes))]
// Manual definition of blocklisted types.
type __kernel_size_t = usize;