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diff --git a/clang-r353983e/include/llvm/Support/LockFileManager.h b/clang-r353983e/include/llvm/Support/LockFileManager.h
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+//===--- LockFileManager.h - File-level locking utility ---------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_SUPPORT_LOCKFILEMANAGER_H
+#define LLVM_SUPPORT_LOCKFILEMANAGER_H
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/SmallString.h"
+#include <system_error>
+#include <utility> // for std::pair
+
+namespace llvm {
+class StringRef;
+
+/// Class that manages the creation of a lock file to aid
+/// implicit coordination between different processes.
+///
+/// The implicit coordination works by creating a ".lock" file alongside
+/// the file that we're coordinating for, using the atomicity of the file
+/// system to ensure that only a single process can create that ".lock" file.
+/// When the lock file is removed, the owning process has finished the
+/// operation.
+class LockFileManager {
+public:
+  /// Describes the state of a lock file.
+  enum LockFileState {
+    /// The lock file has been created and is owned by this instance
+    /// of the object.
+    LFS_Owned,
+    /// The lock file already exists and is owned by some other
+    /// instance.
+    LFS_Shared,
+    /// An error occurred while trying to create or find the lock
+    /// file.
+    LFS_Error
+  };
+
+  /// Describes the result of waiting for the owner to release the lock.
+  enum WaitForUnlockResult {
+    /// The lock was released successfully.
+    Res_Success,
+    /// Owner died while holding the lock.
+    Res_OwnerDied,
+    /// Reached timeout while waiting for the owner to release the lock.
+    Res_Timeout
+  };
+
+private:
+  SmallString<128> FileName;
+  SmallString<128> LockFileName;
+  SmallString<128> UniqueLockFileName;
+
+  Optional<std::pair<std::string, int> > Owner;
+  std::error_code ErrorCode;
+  std::string ErrorDiagMsg;
+
+  LockFileManager(const LockFileManager &) = delete;
+  LockFileManager &operator=(const LockFileManager &) = delete;
+
+  static Optional<std::pair<std::string, int> >
+  readLockFile(StringRef LockFileName);
+
+  static bool processStillExecuting(StringRef Hostname, int PID);
+
+public:
+
+  LockFileManager(StringRef FileName);
+  ~LockFileManager();
+
+  /// Determine the state of the lock file.
+  LockFileState getState() const;
+
+  operator LockFileState() const { return getState(); }
+
+  /// For a shared lock, wait until the owner releases the lock.
+  WaitForUnlockResult waitForUnlock();
+
+  /// Remove the lock file.  This may delete a different lock file than
+  /// the one previously read if there is a race.
+  std::error_code unsafeRemoveLockFile();
+
+  /// Get error message, or "" if there is no error.
+  std::string getErrorMessage() const;
+
+  /// Set error and error message
+  void setError(const std::error_code &EC, StringRef ErrorMsg = "") {
+    ErrorCode = EC;
+    ErrorDiagMsg = ErrorMsg.str();
+  }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_SUPPORT_LOCKFILEMANAGER_H