From fcee83810a5bcf774d3e13cf9e65ccf3b29e3319 Mon Sep 17 00:00:00 2001
From: Jake Senne <26696846+w1wwwwww@users.noreply.github.com>
Date: Tue, 3 Jan 2023 15:16:45 -0600
Subject: [PATCH] Only close file if already open

Ensures that the tablebase file is only closed if already open.

Fixes #4268
Closes https://github.com/official-stockfish/Stockfish/pull/4321

No functional change
---
 AUTHORS                | 1 +
 src/syzygy/tbprobe.cpp | 9 +++------
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/AUTHORS b/AUTHORS
index 70b500ea..998399b9 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -92,6 +92,7 @@ Ivan Ivec (IIvec)
 Jacques B. (Timshel)
 Jan Ondruš (hxim)
 Jared Kish (Kurtbusch, kurt22i)
+Jake Senne (w1wwwwww)
 Jarrod Torriero (DU-jdto)
 Jean Gauthier (OuaisBla)
 Jean-Francois Romang (jromang)
diff --git a/src/syzygy/tbprobe.cpp b/src/syzygy/tbprobe.cpp
index b7ba3240..cc5e2852 100644
--- a/src/syzygy/tbprobe.cpp
+++ b/src/syzygy/tbprobe.cpp
@@ -199,13 +199,10 @@ public:
         }
     }
 
-    // Memory map the file and check it. File should be already open and will be
-    // closed after mapping.
+    // Memory map the file and check it.
     uint8_t* map(void** baseAddress, uint64_t* mapping, TBType type) {
-
-        assert(is_open());
-
-        close(); // Need to re-open to get native file descriptor
+        if (is_open())
+            close(); // Need to re-open to get native file descriptor
 
 #ifndef _WIN32
         struct stat statbuf;
-- 
2.39.2