From d4bc8db614068a0aee9ceaf4dadd41667d843fff Mon Sep 17 00:00:00 2001
From: Noah <33094578+coolreader18@users.noreply.github.com>
Date: Wed, 14 Oct 2020 21:59:34 -0500
Subject: [PATCH 1/2] Get rid of the hack for epoch::unprotected

---
 crossbeam-epoch/src/guard.rs | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/crossbeam-epoch/src/guard.rs b/crossbeam-epoch/src/guard.rs
index c6a0ba377..64eaed4c9 100644
--- a/crossbeam-epoch/src/guard.rs
+++ b/crossbeam-epoch/src/guard.rs
@@ -502,12 +502,10 @@ impl fmt::Debug for Guard {
 /// [`defer`]: Guard::defer
 #[inline]
 pub unsafe fn unprotected() -> &'static Guard {
-    // HACK(stjepang): An unprotected guard is just a `Guard` with its field `local` set to null.
-    // Since this function returns a `'static` reference to a `Guard`, we must return a reference
-    // to a global guard. However, it's not possible to create a `static` `Guard` because it does
-    // not implement `Sync`. To get around the problem, we create a static `usize` initialized to
-    // zero and then transmute it into a `Guard`. This is safe because `usize` and `Guard`
-    // (consisting of a single pointer) have the same representation in memory.
-    static UNPROTECTED: usize = 0;
-    &*(&UNPROTECTED as *const _ as *const Guard)
+    // An unprotected guard is just a `Guard` with its field `local` set to null.
+    // The static needs to be a `static mut` because `Guard` isn't `Sync`
+    static mut UNPROTECTED: Guard = Guard {
+        local: std::ptr::null(),
+    };
+    &UNPROTECTED
 }

From a248d3175308d48e901259779ae848d83e064a1c Mon Sep 17 00:00:00 2001
From: Noah <33094578+coolreader18@users.noreply.github.com>
Date: Thu, 15 Oct 2020 12:40:08 -0500
Subject: [PATCH 2/2] Use a newtype to store the unprotected guard

---
 crossbeam-epoch/src/guard.rs | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/crossbeam-epoch/src/guard.rs b/crossbeam-epoch/src/guard.rs
index 64eaed4c9..6db3750b0 100644
--- a/crossbeam-epoch/src/guard.rs
+++ b/crossbeam-epoch/src/guard.rs
@@ -503,9 +503,12 @@ impl fmt::Debug for Guard {
 #[inline]
 pub unsafe fn unprotected() -> &'static Guard {
     // An unprotected guard is just a `Guard` with its field `local` set to null.
-    // The static needs to be a `static mut` because `Guard` isn't `Sync`
-    static mut UNPROTECTED: Guard = Guard {
-        local: std::ptr::null(),
-    };
-    &UNPROTECTED
+    // We make a newtype over `Guard` because `Guard` isn't `Sync`, so can't be directly stored in
+    // a `static`
+    struct GuardWrapper(Guard);
+    unsafe impl Sync for GuardWrapper {}
+    static UNPROTECTED: GuardWrapper = GuardWrapper(Guard {
+        local: core::ptr::null(),
+    });
+    &UNPROTECTED.0
 }