From 3a0cdc05a5b8ccdefad8e8a402403f50f491ed29 Mon Sep 17 00:00:00 2001
From: David Chisnall <David.Chisnall@microsoft.com>
Date: Mon, 8 Jul 2019 19:24:56 +0100
Subject: [PATCH] Fix on macOS.

Fixes an issue where the global placeholder allocator was being
released.
---
 src/mem/threadalloc.h | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/mem/threadalloc.h b/src/mem/threadalloc.h
index ede455d..4ac6708 100644
--- a/src/mem/threadalloc.h
+++ b/src/mem/threadalloc.h
@@ -125,7 +125,11 @@ namespace snmalloc
      */
     ~ThreadAllocThreadDestructor()
     {
-      current_alloc_pool()->release(alloc);
+      if (alloc != &GlobalPlaceHolder)
+      {
+        current_alloc_pool()->release(alloc);
+        alloc = &GlobalPlaceHolder;
+      }
     }
 
   public:
@@ -172,8 +176,11 @@ namespace snmalloc
       *pp = nullptr;
       // Actually destroy the allocator and reset TLS
       Alloc*& alloc = ThreadAllocExplicitTLSCleanup::get();
-      current_alloc_pool()->release(alloc);
-      alloc = &GlobalPlaceHolder;
+      if (alloc != &GlobalPlaceHolder)
+      {
+        current_alloc_pool()->release(alloc);
+        alloc = &GlobalPlaceHolder;
+      }
     }
 
 #  ifdef _WIN32
@@ -314,6 +321,7 @@ namespace snmalloc
       return local_alloc;
     }
     local_alloc = current_alloc_pool()->acquire();
+    assert(local_alloc != &GlobalPlaceHolder);
     ThreadAlloc::register_cleanup();
     return local_alloc;
   }