From a36698a7b685d16d03a2978e918d1d1b49a0ae0b Mon Sep 17 00:00:00 2001
From: Marcus Comstedt <marcus@mc.pp.se>
Date: Sat, 23 May 2020 15:02:15 +0200
Subject: [PATCH] Thread.Queue: Fix broken fallback implementation of
 try_read()

---
 lib/modules/Thread.pmod | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/modules/Thread.pmod b/lib/modules/Thread.pmod
index 03cbae4102..82bc27fd64 100644
--- a/lib/modules/Thread.pmod
+++ b/lib/modules/Thread.pmod
@@ -1125,6 +1125,7 @@ optional class Queue
 
   mixed try_read()
   {
+    if (w_ptr == r_ptr) return UNDEFINED;
     mixed tmp=buffer[r_ptr];
     buffer[r_ptr++] = 0;	// Throw away any references.
     return tmp;
-- 
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