From 0ede7f281ee2521edae5ebf2ea3ff0ff2efad901 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Wed, 23 Nov 2016 18:34:28 +0000
Subject: [PATCH] Make log(), error() and fatal() thread-safe.

llvm-svn: 287794
---
 lld/ELF/Error.cpp | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/lld/ELF/Error.cpp b/lld/ELF/Error.cpp
index 2c2dead6d8de..3afaedbd9f93 100644
--- a/lld/ELF/Error.cpp
+++ b/lld/ELF/Error.cpp
@@ -14,6 +14,7 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/raw_ostream.h"
+#include <mutex>
 
 #if !defined(_MSC_VER) && !defined(__MINGW32__)
 #include <unistd.h>
@@ -28,19 +29,28 @@ uint64_t elf::ErrorCount;
 raw_ostream *elf::ErrorOS;
 StringRef elf::Argv0;
 
+// The functions defined in this file can be called from multiple threads,
+// but outs() or errs() are not thread-safe. We protect them using a mutex.
+static std::mutex Mu;
+
 void elf::log(const Twine &Msg) {
+  std::lock_guard<std::mutex> Lock(Mu);
   if (Config->Verbose)
     outs() << Argv0 << ": " << Msg << "\n";
 }
 
 void elf::warn(const Twine &Msg) {
-  if (Config->FatalWarnings)
+  if (Config->FatalWarnings) {
     error(Msg);
-  else
-    *ErrorOS << Argv0 << ": warning: " << Msg << "\n";
+    return;
+  }
+  std::lock_guard<std::mutex> Lock(Mu);
+  *ErrorOS << Argv0 << ": warning: " << Msg << "\n";
 }
 
 void elf::error(const Twine &Msg) {
+  std::lock_guard<std::mutex> Lock(Mu);
+
   if (Config->ErrorLimit == 0 || ErrorCount < Config->ErrorLimit) {
     *ErrorOS << Argv0 << ": error: " << Msg << "\n";
   } else if (ErrorCount == Config->ErrorLimit) {
@@ -69,6 +79,7 @@ void elf::exitLld(int Val) {
 }
 
 void elf::fatal(const Twine &Msg) {
+  std::lock_guard<std::mutex> Lock(Mu);
   *ErrorOS << Argv0 << ": error: " << Msg << "\n";
   exitLld(1);
 }