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, 15 insertions, 11 deletions

diff --git a/rust/pin-init/examples/big_struct_in_place.rs b/rust/pin-init/examples/big_struct_in_place.rs
index 30d44a334ffd..b0ee793a0a0c 100644
--- a/rust/pin-init/examples/big_struct_in_place.rs
+++ b/rust/pin-init/examples/big_struct_in_place.rs
@@ -4,6 +4,7 @@ use pin_init::*;
 
 // Struct with size over 1GiB
 #[derive(Debug)]
+#[allow(dead_code)]
 pub struct BigStruct {
     buf: [u8; 1024 * 1024 * 1024],
     a: u64,
@@ -25,15 +26,18 @@ impl ManagedBuf {
 }
 
 fn main() {
-    // we want to initialize the struct in-place, otherwise we would get a stackoverflow
-    let buf: Box<BigStruct> = Box::init(init!(BigStruct {
-        buf <- zeroed(),
-        a: 7,
-        b: 186,
-        c: 7789,
-        d: 34,
-        managed_buf <- ManagedBuf::new(),
-    }))
-    .unwrap();
-    println!("{}", core::mem::size_of_val(&*buf));
+    #[cfg(any(feature = "std", feature = "alloc"))]
+    {
+        // we want to initialize the struct in-place, otherwise we would get a stackoverflow
+        let buf: Box<BigStruct> = Box::init(init!(BigStruct {
+            buf <- zeroed(),
+            a: 7,
+            b: 186,
+            c: 7789,
+            d: 34,
+            managed_buf <- ManagedBuf::new(),
+        }))
+        .unwrap();
+        println!("{}", core::mem::size_of_val(&*buf));
+    }
 }