nit

substrate/frame/contracts/src/benchmarking/call_builder.rs

@@ -21,6 +21,7 @@ impl<T> LeakReclaimer<T> {
 	/// reference to its content, along with the guard for later cleanup.
 	///
 	/// # Safety
+	///
 	/// The caller must ensure that the returned reference is not used after the `LeakReclaimer` is
 	/// dropped.
 	unsafe fn new(value: T) -> (&'static mut T, Self) {
@@ -75,11 +76,11 @@ where
 	/// Prepare a call to the module.
 	/// Returns a tuple containing an opaque object that will reclaim the leaked boxes and a closure
 	/// used to invoke the call.
-	///
-	/// Safety: The caller must ensure that the "Leak Guard" is dropped after the call is invoked.
-	pub unsafe fn build(self) -> (impl Drop, impl FnOnce()) {
+	pub fn build(self) -> impl FnOnce() {
 		let input = self.input.clone();
-		let (sbox, reclaim_sbox) = LeakReclaimer::new(self);
+
+		// Safety: reclaim_sbox is dropped after the closure is called.
+		let (sbox, reclaim_sbox) = unsafe { LeakReclaimer::new(self) };
 
 		let (ext, module) = Stack::bench_new_call(
 			sbox.dest.clone(),
@@ -92,10 +93,13 @@ where
 			Determinism::Enforced,
 		);
 
-		let (ext, reclaim_ext): (&mut StackExt<T>, _) = LeakReclaimer::new(ext);
+		// Safety: reclaim_ext is dropped after the closure is called.
+		let (ext, reclaim_ext): (&mut StackExt<T>, _) = unsafe { LeakReclaimer::new(ext) };
 		let (func, mut store) = module.bench_prepare_call(ext, input);
-		(Box::new((reclaim_ext, reclaim_sbox)), move || {
+		move || {
 			func.call(&mut store, &[], &mut []).unwrap();
-		})
+			drop(reclaim_ext);
+			drop(reclaim_sbox);
+		}
 	}
 }

substrate/frame/contracts/src/benchmarking/mod.rs

@@ -799,13 +799,11 @@ mod benchmarks {
 
 	#[benchmark(pov_mode = Measured)]
 	fn seal_now(r: Linear<0, API_BENCHMARK_RUNS>) {
-		let builder = CallBuilder::<T>::new(WasmModule::getter("seal0", "seal_now", r));
-		let (reclaim, invoke) = unsafe { builder.build() };
+		let invoke = CallBuilder::<T>::new(WasmModule::getter("seal0", "seal_now", r)).build();
 		#[block]
 		{
 			invoke();
 		}
-		drop(reclaim);
 	}
 
 	#[benchmark(pov_mode = Measured)]