From 917dafc73a9eb257b9b5c2d357c4abd8bb1c3a8e Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Fri, 10 Dec 2021 13:12:26 +0530
Subject: [PATCH] Add separate impl of unwrap_failed to avoid constructing
 trait objects

---
 library/core/src/result.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/library/core/src/result.rs b/library/core/src/result.rs
index e6b8c8ec3385a..ab067d57d082a 100644
--- a/library/core/src/result.rs
+++ b/library/core/src/result.rs
@@ -1653,6 +1653,7 @@ impl<T> Result<T, T> {
 }
 
 // This is a separate function to reduce the code size of the methods
+#[cfg(not(feature = "panic_immediate_abort"))]
 #[inline(never)]
 #[cold]
 #[track_caller]
@@ -1660,6 +1661,18 @@ fn unwrap_failed(msg: &str, error: &dyn fmt::Debug) -> ! {
     panic!("{}: {:?}", msg, error)
 }
 
+// This is a separate function to avoid constructing a `dyn Debug`
+// that gets immediately thrown away, since vtables don't get cleaned up
+// by dead code elimination if a trait object is constructed even if it goes
+// unused
+#[cfg(feature = "panic_immediate_abort")]
+#[inline]
+#[cold]
+#[track_caller]
+fn unwrap_failed<T>(_msg: &str, _error: &T) -> ! {
+    panic!()
+}
+
 /////////////////////////////////////////////////////////////////////////////
 // Trait implementations
 /////////////////////////////////////////////////////////////////////////////