From fc6400a1ef599ae3eb04512e5deffc547f9e95ef Mon Sep 17 00:00:00 2001
From: Christopher Kohlhoff <chris@kohlhoff.com>
Date: Mon, 2 Nov 2020 12:47:56 +1100
Subject: [PATCH] Restore null pointer check for better performance.

---
 include/boost/asio/detail/thread_info_base.hpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/boost/asio/detail/thread_info_base.hpp b/include/boost/asio/detail/thread_info_base.hpp
index a05320ab..35c03cbb 100644
--- a/include/boost/asio/detail/thread_info_base.hpp
+++ b/include/boost/asio/detail/thread_info_base.hpp
@@ -66,7 +66,13 @@ public:
   ~thread_info_base()
   {
     for (int i = 0; i < max_mem_index; ++i)
-      ::operator delete(reusable_memory_[i]);
+    {
+      // The following test for non-null pointers is technically redundant, but
+      // it is significantly faster when using a tight io_context::poll() loop
+      // in latency sensitive applications.
+      if (reusable_memory_[i])
+        ::operator delete(reusable_memory_[i]);
+    }
   }
 
   static void* allocate(thread_info_base* this_thread, std::size_t size)