commit 139d396572ec4ba6e8cc5c02f5c8d5d1139be4b7 upstream.
In the C side, disabling diagnostics locally, i.e. within the source code, is rare (at least in the kernel). Sometimes warnings are manipulated via the flags at the translation unit level, but that is about it.
In Rust, it is easier to change locally the "level" of lints (e.g. allowing them locally). In turn, this means it is easier to globally enable more lints that may trigger a few false positives here and there that need to be allowed locally, but that generally can spot issues or bugs.
Thus document this.
Reviewed-by: Trevor Gross tmgross@umich.edu Reviewed-by: Alice Ryhl aliceryhl@google.com Tested-by: Gary Guo gary@garyguo.net Reviewed-by: Gary Guo gary@garyguo.net Link: https://lore.kernel.org/r/20240904204347.168520-17-ojeda@kernel.org Signed-off-by: Miguel Ojeda ojeda@kernel.org --- Documentation/rust/coding-guidelines.rst | 38 ++++++++++++++++++++++++ 1 file changed, 38 insertions(+)
diff --git a/Documentation/rust/coding-guidelines.rst b/Documentation/rust/coding-guidelines.rst index 329b070a1d47..6db0420f0cea 100644 --- a/Documentation/rust/coding-guidelines.rst +++ b/Documentation/rust/coding-guidelines.rst @@ -227,3 +227,41 @@ The equivalent in Rust may look like (ignoring documentation): That is, the equivalent of ``GPIO_LINE_DIRECTION_IN`` would be referred to as ``gpio::LineDirection::In``. In particular, it should not be named ``gpio::gpio_line_direction::GPIO_LINE_DIRECTION_IN``. + + +Lints +----- + +In Rust, it is possible to ``allow`` particular warnings (diagnostics, lints) +locally, making the compiler ignore instances of a given warning within a given +function, module, block, etc. + +It is similar to ``#pragma GCC diagnostic push`` + ``ignored`` + ``pop`` in C +[#]_: + +.. code-block:: c + + #pragma GCC diagnostic push + #pragma GCC diagnostic ignored "-Wunused-function" + static void f(void) {} + #pragma GCC diagnostic pop + +.. [#] In this particular case, the kernel's ``__{always,maybe}_unused`` + attributes (C23's ``[[maybe_unused]]``) may be used; however, the example + is meant to reflect the equivalent lint in Rust discussed afterwards. + +But way less verbose: + +.. code-block:: rust + + #[allow(dead_code)] + fn f() {} + +By that virtue, it makes it possible to comfortably enable more diagnostics by +default (i.e. outside ``W=`` levels). In particular, those that may have some +false positives but that are otherwise quite useful to keep enabled to catch +potential mistakes. + +For more information about diagnostics in Rust, please see: + + https://doc.rust-lang.org/stable/reference/attributes/diagnostics.html