From 269bd24da9e9b713f3bca0782e460c00369548ae Mon Sep 17 00:00:00 2001
From: fakeshadow <24548779@qq.com>
Date: Wed, 14 Apr 2021 20:29:50 +0800
Subject: [PATCH] Make double set_available false debug assert panic

---
 actix-server/src/accept.rs | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/actix-server/src/accept.rs b/actix-server/src/accept.rs
index 571777b5..147cbf23 100644
--- a/actix-server/src/accept.rs
+++ b/actix-server/src/accept.rs
@@ -119,7 +119,11 @@ impl Availability {
         if avail {
             self.0[offset] |= 1 << idx as u128;
         } else {
-            self.0[offset] ^= 1 << idx as u128;
+            let shift = 1 << idx as u128;
+
+            debug_assert_ne!(self.0[offset] & shift, 0);
+
+            self.0[offset] ^= shift;
         }
     }
 
@@ -519,6 +523,8 @@ mod test {
         aval.set_available(idx, true);
         assert!(aval.available());
 
+        aval.set_available(idx, true);
+
         aval.set_available(idx, false);
         assert!(!aval.available());
     }
@@ -559,6 +565,13 @@ mod test {
         single(&mut aval, 512);
     }
 
+    #[test]
+    #[should_panic]
+    fn double_set_unavailable() {
+        let mut aval = Availability::default();
+        aval.set_available(233, false);
+    }
+
     #[test]
     fn pin_point() {
         let mut aval = Availability::default();