rust: pin-init: examples, tests: add conditional compilation in order to compile under any feature combination

In the CI, all examples & tests should be run under all feature
combinations. Currently several examples & tests use `std` without
conditionally enabling it. Thus make them all compile under any feature
combination by conditionally disabling the code that uses e.g. `std`.

Link: https://github.com/Rust-for-Linux/pin-init/pull/50/commits/fdfb70efddbc711b4543c850ee38a2f5a8d17cb6
Link: https://lore.kernel.org/all/20250523125424.192843-2-lossin@kernel.org
Signed-off-by: Benno Lossin <lossin@kernel.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/rust/pin-init/examples/linked_list.rs b/rust/pin-init/examples/linked_list.rs
index 0bbc7b8d83a1..f9e117c7dfe0 100644
--- a/rust/pin-init/examples/linked_list.rs
+++ b/rust/pin-init/examples/linked_list.rs
@@ -14,8 +14,9 @@ use core::{
 
 use pin_init::*;
 
-#[expect(unused_attributes)]
+#[allow(unused_attributes)]
 mod error;
+#[allow(unused_imports)]
 use error::Error;
 
 #[pin_data(PinnedDrop)]
@@ -39,6 +40,7 @@ impl ListHead {
     }
 
     #[inline]
+    #[allow(dead_code)]
     pub fn insert_next(list: &ListHead) -> impl PinInit<Self, Infallible> + '_ {
         try_pin_init!(&this in Self {
             prev: list.next.prev().replace(unsafe { Link::new_unchecked(this)}),
@@ -112,6 +114,7 @@ impl Link {
     }
 
     #[inline]
+    #[allow(dead_code)]
     fn prev(&self) -> &Link {
         unsafe { &(*self.0.get().as_ptr()).prev }
     }
@@ -138,7 +141,12 @@ impl Link {
 }
 
 #[allow(dead_code)]
+#[cfg(not(any(feature = "std", feature = "alloc")))]
+fn main() {}
+
+#[allow(dead_code)]
 #[cfg_attr(test, test)]
+#[cfg(any(feature = "std", feature = "alloc"))]
 fn main() -> Result<(), Error> {
     let a = Box::pin_init(ListHead::new())?;
     stack_pin_init!(let b = ListHead::insert_next(&a));