From: Bennet Bleßmann <bb-github@t-online.de>
Date: Sat, 3 Aug 2024 17:36:05 +0000 (+0200)
Subject: prevent accidental double free by checking tag before drop
X-Git-Tag: v0.10.0~125^2
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=9e8d8aa19e4a2512042e8d1221ec9a0438c22e16;p=scryer-prolog.git

prevent accidental double free by checking tag before drop
---

diff --git a/src/arena.rs b/src/arena.rs
index a3449d44..6acb279b 100644
--- a/src/arena.rs
+++ b/src/arena.rs
@@ -305,8 +305,10 @@ impl<T: ?Sized + ArenaAllocated> TypedArenaPtr<T> {
 
 impl<P, T: ?Sized + ArenaAllocated<Payload = ManuallyDrop<P>>> TypedArenaPtr<T> {
     pub fn drop_payload(&mut self) {
-        self.set_tag(ArenaHeaderTag::Dropped);
-        unsafe { ManuallyDrop::drop(&mut *self.as_ptr()) }
+        if self.get_tag() != ArenaHeaderTag::Dropped {
+            self.set_tag(ArenaHeaderTag::Dropped);
+            unsafe { ManuallyDrop::drop(&mut *self.as_ptr()) }
+        }
     }
 }