From 8bd5f7d0af5743330f85601fab759eb08d3ad797 Mon Sep 17 00:00:00 2001
From: Deukhoofd <Deukhoofd@gmail.com>
Date: Tue, 22 Jan 2019 16:53:22 +0100
Subject: [PATCH] Lock evaluation scope when not created to prevent threading
 issues

---
 Upsilon/StandardLibraries/StaticScope.cs | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/Upsilon/StandardLibraries/StaticScope.cs b/Upsilon/StandardLibraries/StaticScope.cs
index d38f7c2..1e7706e 100644
--- a/Upsilon/StandardLibraries/StaticScope.cs
+++ b/Upsilon/StandardLibraries/StaticScope.cs
@@ -27,11 +27,13 @@ namespace Upsilon.StandardLibraries
             {
                 if (_staticScope != null)
                     return _staticScope;
-
-                var (evaluationScope, boundScope) = CreateStandardLibrary();
-                _staticScope                      = evaluationScope;
-                _staticBoundScope                 = boundScope;
-                return _staticScope;
+                lock (Scope)
+                {
+                    var (evaluationScope, boundScope) = CreateStandardLibrary();
+                    _staticScope                      = evaluationScope;
+                    _staticBoundScope                 = boundScope;
+                    return _staticScope;
+                }
             }
         }