From 3708afb1b6002a54e3d7403c692ba6357d43898e Mon Sep 17 00:00:00 2001
From: Georg Bauer <gb@rfc1437.de>
Date: Sat, 25 Jul 2026 13:04:09 +0200
Subject: [PATCH] Document Metal executor drop order

---
 src/engine/metal.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/engine/metal.rs b/src/engine/metal.rs
index 992a4bd..8c6f34d 100644
--- a/src/engine/metal.rs
+++ b/src/engine/metal.rs
@@ -558,6 +558,11 @@ impl Session {
     }
 }
 
+// SAFETY: declaration order is required because Rust drops fields in order.
+// `session` must release every Buffer before `_context` calls ds4_gpu_cleanup(),
+// and `_context` must drop before `model` unmaps memory wrapped without copying
+// by native/metal/ds4_metal.m:10329. This intentionally differs from
+// ../ds4/ds4.c:56287-56288; do not reorder these fields to match it.
 pub(super) struct Executor {
     weights: Weights,
     session: Session,