From 5de2272174587bc8ce10a59fc20570890d0f9721 Mon Sep 17 00:00:00 2001
From: "David L. Jones" <dlj@google.com>
Date: Fri, 15 Jun 2018 06:08:54 +0000
Subject: [Format] Do not use a global static value for EOF within
 ScopedMacroState.

ScopedMacroState injects its own EOF token under certain conditions, and the
returned token may be modified in several different locations. If multiple
reformat operations are started in different threads, then they will both see
the same fake EOF token, and may both try to modify it. This is a data race.

This bug was caught with tsan.

Reviewers: klimek

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D47759

llvm-svn: 334801
---
 clang/lib/Format/UnwrappedLineParser.cpp | 16 ++++------------
 1 file changed, 4 insertions(+), 12 deletions(-)

(limited to 'clang/lib/Format/UnwrappedLineParser.cpp')

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index b257b2b74dd..e1fa72e84bd 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -83,6 +83,8 @@ public:
       : Line(Line), TokenSource(TokenSource), ResetToken(ResetToken),
         PreviousLineLevel(Line.Level), PreviousTokenSource(TokenSource),
         Token(nullptr), PreviousToken(nullptr) {
+    FakeEOF.Tok.startToken();
+    FakeEOF.Tok.setKind(tok::eof);
     TokenSource = this;
     Line.Level = 0;
     Line.InPPDirective = true;
@@ -102,7 +104,7 @@ public:
     PreviousToken = Token;
     Token = PreviousTokenSource->getNextToken();
     if (eof())
-      return getFakeEOF();
+      return &FakeEOF;
     return Token;
   }
 
@@ -121,17 +123,7 @@ private:
                                  /*MinColumnToken=*/PreviousToken);
   }
 
-  FormatToken *getFakeEOF() {
-    static bool EOFInitialized = false;
-    static FormatToken FormatTok;
-    if (!EOFInitialized) {
-      FormatTok.Tok.startToken();
-      FormatTok.Tok.setKind(tok::eof);
-      EOFInitialized = true;
-    }
-    return &FormatTok;
-  }
-
+  FormatToken FakeEOF;
   UnwrappedLine &Line;
   FormatTokenSource *&TokenSource;
   FormatToken *&ResetToken;
-- 
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