Index: lib/Tooling/CommonOptionsParser.cpp
===================================================================
--- lib/Tooling/CommonOptionsParser.cpp
+++ lib/Tooling/CommonOptionsParser.cpp
@@ -25,6 +25,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/StringSaver.h"
 #include "clang/Tooling/ArgumentsAdjusters.h"
 #include "clang/Tooling/CommonOptionsParser.h"
 #include "clang/Tooling/Tooling.h"
@@ -116,6 +117,14 @@
 
   cl::HideUnrelatedOptions(Category);
 
+  // Expand response files before loading compilation database from command line.
+  SmallVector<const char *, 20> NewArgv(argv, argv + argc);
+  BumpPtrAllocator A;
+  StringSaver Saver(A);
+  cl::ExpandResponseFiles(Saver, cl::TokenizeGNUCommandLine, NewArgv);
+  argv = &NewArgv[0];
+  argc = static_cast<int>(NewArgv.size());
+
   std::string ErrorMessage;
   Compilations =
       FixedCompilationDatabase::loadFromCommandLine(argc, argv, ErrorMessage);
Index: unittests/Tooling/CMakeLists.txt
===================================================================
--- unittests/Tooling/CMakeLists.txt
+++ unittests/Tooling/CMakeLists.txt
@@ -14,6 +14,7 @@
   CastExprTest.cpp
   CommentHandlerTest.cpp
   CompilationDatabaseTest.cpp
+  CommonOptionsParserTest.cpp
   DiagnosticsYamlTest.cpp
   FixItTest.cpp
   LookupTest.cpp
Index: unittests/Tooling/CommonOptionsParserTest.cpp
===================================================================
--- /dev/null
+++ unittests/Tooling/CommonOptionsParserTest.cpp
@@ -0,0 +1,72 @@
+//===- unittests/Tooling/CommonOptionsParserTest.cpp -------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Tooling/CommonOptionsParser.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+#include "gtest/gtest.h"
+
+#include <fstream>
+
+namespace clang {
+namespace tooling {
+
+class CommonOptionsParserTest : public testing::Test {
+public:
+  SmallString<128> TestDir;
+  SmallString<128> ResponseFileName;
+
+  CommonOptionsParserTest() {
+    std::error_code EC = llvm::sys::fs::createUniqueDirectory("unittest", TestDir);
+    EXPECT_TRUE(!EC);
+    llvm::sys::path::append(ResponseFileName, TestDir, "resp");
+  }
+
+  void setResponseFileContent(const std::string &Content) {
+    std::ofstream File(ResponseFileName.c_str());
+    EXPECT_TRUE(File.is_open());
+    File << Content;
+    File.close();
+  }
+
+  ~CommonOptionsParserTest() override {
+    llvm::sys::fs::remove(ResponseFileName);
+    llvm::sys::fs::remove(TestDir);
+  }
+};
+
+TEST_F(CommonOptionsParserTest, ExpandResponseFilesBeforeLoadingCompilationDatabase) {
+  setResponseFileContent("-- -a=true -b");
+  SmallString<128> ResponseFileRef;
+  ResponseFileRef.append(1, '@');
+  ResponseFileRef.append(ResponseFileName.c_str());
+  int Argc = 3;
+  const char *Argv[] = { "1", "2", ResponseFileRef.c_str() };
+  llvm::cl::OptionCategory Category("options");
+  llvm::cl::opt<bool> option1("a", llvm::cl::desc(""), llvm::cl::init(false),
+                              llvm::cl::cat(Category));
+  llvm::cl::opt<bool> option2("b", llvm::cl::desc(""), llvm::cl::init(false),
+                              llvm::cl::cat(Category));
+  CommonOptionsParser Parser(Argc, Argv, Category);
+  CompilationDatabase &Database = Parser.getCompilations();
+  std::vector<CompileCommand> ActualCC = Database.getCompileCommands("source");
+  ASSERT_EQ(1u, ActualCC.size());
+  std::vector<std::string> ExpectedCmd;
+  ExpectedCmd.push_back("clang-tool");
+  ExpectedCmd.push_back("-a=true");
+  ExpectedCmd.push_back("-b");
+  ExpectedCmd.push_back("source");
+
+  ASSERT_EQ(ExpectedCmd, ActualCC[0].CommandLine);
+}
+	
+} // end namespace tooling
+} // end namespace clang