From 4a19ef938c3670afb8cc278d3d31a803b19addab Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Tue, 26 Nov 2019 09:29:39 +0100
Subject: [PATCH] explain why __rust_start_panic does not take a Box

---
 src/libstd/panicking.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/libstd/panicking.rs b/src/libstd/panicking.rs
index 8f9a4c05b5702..e0d980fc306b5 100644
--- a/src/libstd/panicking.rs
+++ b/src/libstd/panicking.rs
@@ -47,6 +47,8 @@ extern {
                                 vtable_ptr: *mut usize) -> u32;
 
     /// `payload` is actually a `*mut &mut dyn BoxMeUp` but that would cause FFI warnings.
+    /// It cannot be `Box<dyn BoxMeUp>` because the other end of this call does not depend
+    /// on liballoc, and thus cannot use `Box`.
     #[unwind(allowed)]
     fn __rust_start_panic(payload: usize) -> u32;
 }