From e66cfc29e0d06fec34c06bb40d4d281f595677b1 Mon Sep 17 00:00:00 2001 From: FUJITA Tomonori Date: Sat, 1 Aug 2026 11:48:41 +0900 Subject: rust: bug: prevent dead_code warning from warn_on!'s flags constant Fix the following dead_code warning on some configurations in an atomic development branch: warning: constant `WARN_ON_FLAGS` is never used --> linux/rust/kernel/bug.rs:126:19 | 126 | const WARN_ON_FLAGS: u32 = $crate::bug::bugflag_taint($crate::bindings::TAINT_WARN); | ^^^^^^^^^^^^^ | ::: linux/rust/kernel/sync/srcu.rs:106:12 | 106 | if crate::warn_on!( | ____________- 107 | | // SAFETY: By the type invariants, `self` contains a valid and pinned `struct srcu_struct` 108 | | // and `srcu_readers_active()` only checks the active reader count. 109 | | unsafe { bindings::srcu_readers_active(ptr) } 110 | | ) { | |_________- in this macro invocation | = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default = note: this warning originates in the macro `crate::warn_on` (in Nightly builds, run with -Z macro-backtrace for more info) The warn_on! macro always defines a WARN_ON_FLAGS constant and hands it to warn_flags!. On configurations where warn_flags! does not reference its flags argument (the LOONGARCH/ARM variant, which only calls WARN_ON(), and the !CONFIG_BUG no-op variant), the constant is left unused and triggers a dead_code warning. warn_flags! is the macro that accepts (and here discards) the flags argument, so make it responsible for the argument it drops. Also rename `_COND_STR` to `COND_STR` and consume `$file` for consistency. Fixes: dff64b072708 ("rust: Add warn_on macro") Signed-off-by: FUJITA Tomonori Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260801024841.786664-1-tomo@flapping.org [ Added newlines. - Miguel ] Signed-off-by: Miguel Ojeda --- rust/kernel/bug.rs | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) (limited to 'rust') diff --git a/rust/kernel/bug.rs b/rust/kernel/bug.rs index ed943960f851..a09e6c9b314e 100644 --- a/rust/kernel/bug.rs +++ b/rust/kernel/bug.rs @@ -53,6 +53,10 @@ macro_rules! warn_flags { ($file:expr, $flags:expr) => { const FLAGS: u32 = $crate::bindings::BUGFLAG_WARNING | $flags; + if false { + _ = $file; + } + // SAFETY: // - `flags` and `size` are all compile-time constants, preventing // any invalid memory access. @@ -76,6 +80,10 @@ macro_rules! warn_flags { #[cfg(all(CONFIG_BUG, CONFIG_UML))] macro_rules! warn_flags { ($file:expr, $flags:expr) => { + if false { + _ = $file; + } + // SAFETY: It is always safe to call `warn_slowpath_fmt()` // with a valid null-terminated string. unsafe { @@ -94,6 +102,11 @@ macro_rules! warn_flags { #[cfg(all(CONFIG_BUG, any(CONFIG_LOONGARCH, CONFIG_ARM)))] macro_rules! warn_flags { ($file:expr, $flags:expr) => { + if false { + _ = $file; + _ = $flags; + } + // SAFETY: It is always safe to call `WARN_ON()`. unsafe { $crate::bindings::WARN_ON(true) } }; @@ -103,7 +116,12 @@ macro_rules! warn_flags { #[doc(hidden)] #[cfg(not(CONFIG_BUG))] macro_rules! warn_flags { - ($file:expr, $flags:expr) => {}; + ($file:expr, $flags:expr) => { + if false { + _ = $file; + _ = $flags; + } + }; } #[doc(hidden)] @@ -118,14 +136,14 @@ macro_rules! warn_on { let cond = $cond; #[cfg(CONFIG_DEBUG_BUGVERBOSE_DETAILED)] - const _COND_STR: &str = concat!("[", stringify!($cond), "] ", file!()); + const COND_STR: &str = concat!("[", stringify!($cond), "] ", file!()); #[cfg(not(CONFIG_DEBUG_BUGVERBOSE_DETAILED))] - const _COND_STR: &str = file!(); + const COND_STR: &str = file!(); if cond { const WARN_ON_FLAGS: u32 = $crate::bug::bugflag_taint($crate::bindings::TAINT_WARN); - $crate::warn_flags!(_COND_STR, WARN_ON_FLAGS); + $crate::warn_flags!(COND_STR, WARN_ON_FLAGS); } cond }}; -- cgit