From 4ea16835ba66f2240d050ffcaee44cee6c97cab9 Mon Sep 17 00:00:00 2001
From: Dimitry Andric <dim@FreeBSD.org>
Date: Mon, 26 Jun 2017 20:33:45 +0000
Subject: Vendor import of lld trunk r306325:
 https://llvm.org/svn/llvm-project/lld/trunk@306325

---
 COFF/Strings.cpp | 5 +++++
 1 file changed, 5 insertions(+)

(limited to 'COFF/Strings.cpp')

diff --git a/COFF/Strings.cpp b/COFF/Strings.cpp
index d0558413f673..84f9b9a55a32 100644
--- a/COFF/Strings.cpp
+++ b/COFF/Strings.cpp
@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "Strings.h"
+#include <mutex>
 
 #if defined(_MSC_VER)
 #include <Windows.h>
@@ -21,6 +22,10 @@ using namespace llvm;
 
 Optional<std::string> coff::demangle(StringRef S) {
 #if defined(_MSC_VER)
+  // UnDecorateSymbolName is not thread-safe, so we need a mutex.
+  static std::mutex Mu;
+  std::lock_guard<std::mutex> Lock(Mu);
+
   char Buf[4096];
   if (S.startswith("?"))
     if (size_t Len = UnDecorateSymbolName(S.str().c_str(), Buf, sizeof(Buf), 0))
-- 
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