diff --git a/src/sync.h b/src/sync.h
index 584aad206..546b9fa39 100644
--- a/src/sync.h
+++ b/src/sync.h
@@ -1,364 +1,365 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Copyright (c) 2009-2016 The Bitcoin Core developers
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #ifndef BITCOIN_SYNC_H
 #define BITCOIN_SYNC_H
 
 #include <threadsafety.h>
 #include <util/macros.h>
 
 #include <condition_variable>
 #include <mutex>
+#include <string>
 #include <thread>
 
 /////////////////////////////////////////////////
 //                                             //
 // THE SIMPLE DEFINITION, EXCLUDING DEBUG CODE //
 //                                             //
 /////////////////////////////////////////////////
 
 /*
 RecursiveMutex mutex;
     std::recursive_mutex mutex;
 
 LOCK(mutex);
     std::unique_lock<std::recursive_mutex> criticalblock(mutex);
 
 LOCK2(mutex1, mutex2);
     std::unique_lock<std::recursive_mutex> criticalblock1(mutex1);
     std::unique_lock<std::recursive_mutex> criticalblock2(mutex2);
 
 TRY_LOCK(mutex, name);
     std::unique_lock<std::recursive_mutex> name(mutex, std::try_to_lock_t);
 
 ENTER_CRITICAL_SECTION(mutex); // no RAII
     mutex.lock();
 
 LEAVE_CRITICAL_SECTION(mutex); // no RAII
     mutex.unlock();
  */
 
 ///////////////////////////////
 //                           //
 // THE ACTUAL IMPLEMENTATION //
 //                           //
 ///////////////////////////////
 
 #ifdef DEBUG_LOCKORDER
 void EnterCritical(const char *pszName, const char *pszFile, int nLine,
                    void *cs, bool fTry = false);
 void LeaveCritical();
 void CheckLastCritical(void *cs, std::string &lockname, const char *guardname,
                        const char *file, int line);
 std::string LocksHeld();
 template <typename MutexType>
 void AssertLockHeldInternal(const char *pszName, const char *pszFile, int nLine,
                             MutexType *cs) ASSERT_EXCLUSIVE_LOCK(cs);
 void AssertLockNotHeldInternal(const char *pszName, const char *pszFile,
                                int nLine, void *cs);
 void DeleteLock(void *cs);
 
 /**
  * Call abort() if a potential lock order deadlock bug is detected, instead of
  * just logging information and throwing a logic_error. Defaults to true, and
  * set to false in DEBUG_LOCKORDER unit tests.
  */
 extern bool g_debug_lockorder_abort;
 #else
 static inline void EnterCritical(const char *pszName, const char *pszFile,
                                  int nLine, void *cs, bool fTry = false) {}
 static inline void LeaveCritical() {}
 static inline void CheckLastCritical(void *cs, std::string &lockname,
                                      const char *guardname, const char *file,
                                      int line) {}
 template <typename MutexType>
 static inline void AssertLockHeldInternal(const char *pszName,
                                           const char *pszFile, int nLine,
                                           MutexType *cs)
     ASSERT_EXCLUSIVE_LOCK(cs) {}
 static inline void AssertLockNotHeldInternal(const char *pszName,
                                              const char *pszFile, int nLine,
                                              void *cs) {}
 static inline void DeleteLock(void *cs) {}
 #endif
 #define AssertLockHeld(cs) AssertLockHeldInternal(#cs, __FILE__, __LINE__, &cs)
 #define AssertLockNotHeld(cs)                                                  \
     AssertLockNotHeldInternal(#cs, __FILE__, __LINE__, &cs)
 
 /**
  * Template mixin that adds -Wthread-safety locking annotations and lock order
  * checking to a subset of the mutex API.
  */
 template <typename PARENT> class LOCKABLE AnnotatedMixin : public PARENT {
 public:
     ~AnnotatedMixin() { DeleteLock((void *)this); }
 
     void lock() EXCLUSIVE_LOCK_FUNCTION() { PARENT::lock(); }
 
     void unlock() UNLOCK_FUNCTION() { PARENT::unlock(); }
 
     bool try_lock() EXCLUSIVE_TRYLOCK_FUNCTION(true) {
         return PARENT::try_lock();
     }
 
     using UniqueLock = std::unique_lock<PARENT>;
 };
 
 /**
  * Wrapped mutex: supports recursive locking, but no waiting
  * TODO: We should move away from using the recursive lock by default.
  */
 using RecursiveMutex = AnnotatedMixin<std::recursive_mutex>;
 
 /** Wrapped mutex: supports waiting but not recursive locking */
 typedef AnnotatedMixin<std::mutex> Mutex;
 
 #ifdef DEBUG_LOCKCONTENTION
 void PrintLockContention(const char *pszName, const char *pszFile, int nLine);
 #endif
 
 /** Wrapper around std::unique_lock style lock for Mutex. */
 template <typename Mutex, typename Base = typename Mutex::UniqueLock>
 class SCOPED_LOCKABLE UniqueLock : public Base {
 private:
     void Enter(const char *pszName, const char *pszFile, int nLine) {
         EnterCritical(pszName, pszFile, nLine, (void *)(Base::mutex()));
 #ifdef DEBUG_LOCKCONTENTION
         if (!Base::try_lock()) {
             PrintLockContention(pszName, pszFile, nLine);
 #endif
             Base::lock();
 #ifdef DEBUG_LOCKCONTENTION
         }
 #endif
     }
 
     bool TryEnter(const char *pszName, const char *pszFile, int nLine) {
         EnterCritical(pszName, pszFile, nLine, (void *)(Base::mutex()), true);
         Base::try_lock();
         if (!Base::owns_lock()) {
             LeaveCritical();
         }
         return Base::owns_lock();
     }
 
 public:
     UniqueLock(Mutex &mutexIn, const char *pszName, const char *pszFile,
                int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(mutexIn)
         : Base(mutexIn, std::defer_lock) {
         if (fTry) {
             TryEnter(pszName, pszFile, nLine);
         } else {
             Enter(pszName, pszFile, nLine);
         }
     }
 
     UniqueLock(Mutex *pmutexIn, const char *pszName, const char *pszFile,
                int nLine, bool fTry = false) EXCLUSIVE_LOCK_FUNCTION(pmutexIn) {
         if (!pmutexIn) {
             return;
         }
 
         *static_cast<Base *>(this) = Base(*pmutexIn, std::defer_lock);
         if (fTry) {
             TryEnter(pszName, pszFile, nLine);
         } else {
             Enter(pszName, pszFile, nLine);
         }
     }
 
     ~UniqueLock() UNLOCK_FUNCTION() {
         if (Base::owns_lock()) {
             LeaveCritical();
         }
     }
 
     operator bool() { return Base::owns_lock(); }
 
 protected:
     // needed for reverse_lock
     UniqueLock() {}
 
 public:
     /**
      * An RAII-style reverse lock. Unlocks on construction and locks on
      * destruction.
      */
     class reverse_lock {
     public:
         explicit reverse_lock(UniqueLock &_lock, const char *_guardname,
                               const char *_file, int _line)
             : lock(_lock), file(_file), line(_line) {
             CheckLastCritical((void *)lock.mutex(), lockname, _guardname, _file,
                               _line);
             lock.unlock();
             LeaveCritical();
             lock.swap(templock);
         }
 
         ~reverse_lock() {
             templock.swap(lock);
             EnterCritical(lockname.c_str(), file.c_str(), line,
                           (void *)lock.mutex());
             lock.lock();
         }
 
     private:
         reverse_lock(reverse_lock const &);
         reverse_lock &operator=(reverse_lock const &);
 
         UniqueLock &lock;
         UniqueLock templock;
         std::string lockname;
         const std::string file;
         const int line;
     };
     friend class reverse_lock;
 };
 
 #define REVERSE_LOCK(g)                                                        \
     typename std::decay<decltype(g)>::type::reverse_lock PASTE2(               \
         revlock, __COUNTER__)(g, #g, __FILE__, __LINE__)
 
 template <typename MutexArg>
 using DebugLock = UniqueLock<typename std::remove_reference<
     typename std::remove_pointer<MutexArg>::type>::type>;
 
 #define LOCK(cs)                                                               \
     DebugLock<decltype(cs)> PASTE2(criticalblock,                              \
                                    __COUNTER__)(cs, #cs, __FILE__, __LINE__)
 #define LOCK2(cs1, cs2)                                                        \
     DebugLock<decltype(cs1)> criticalblock1(cs1, #cs1, __FILE__, __LINE__);    \
     DebugLock<decltype(cs2)> criticalblock2(cs2, #cs2, __FILE__, __LINE__);
 #define TRY_LOCK(cs, name)                                                     \
     DebugLock<decltype(cs)> name(cs, #cs, __FILE__, __LINE__, true)
 #define WAIT_LOCK(cs, name)                                                    \
     DebugLock<decltype(cs)> name(cs, #cs, __FILE__, __LINE__)
 
 #define ENTER_CRITICAL_SECTION(cs)                                             \
     {                                                                          \
         EnterCritical(#cs, __FILE__, __LINE__, (void *)(&cs));                 \
         (cs).lock();                                                           \
     }
 
 #define LEAVE_CRITICAL_SECTION(cs)                                             \
     {                                                                          \
         (cs).unlock();                                                         \
         LeaveCritical();                                                       \
     }
 
 //! Run code while locking a mutex.
 //!
 //! Examples:
 //!
 //!   WITH_LOCK(cs, shared_val = shared_val + 1);
 //!
 //!   int val = WITH_LOCK(cs, return shared_val);
 //!
 #define WITH_LOCK(cs, code)                                                    \
     [&] {                                                                      \
         LOCK(cs);                                                              \
         code;                                                                  \
     }()
 
 class CSemaphore {
 private:
     std::condition_variable condition;
     std::mutex mutex;
     int value;
 
 public:
     explicit CSemaphore(int init) : value(init) {}
 
     void wait() {
         std::unique_lock<std::mutex> lock(mutex);
         condition.wait(lock, [&]() { return value >= 1; });
         value--;
     }
 
     bool try_wait() {
         std::lock_guard<std::mutex> lock(mutex);
         if (value < 1) {
             return false;
         }
         value--;
         return true;
     }
 
     void post() {
         {
             std::lock_guard<std::mutex> lock(mutex);
             value++;
         }
         condition.notify_one();
     }
 };
 
 /** RAII-style semaphore lock */
 class CSemaphoreGrant {
 private:
     CSemaphore *sem;
     bool fHaveGrant;
 
 public:
     void Acquire() {
         if (fHaveGrant) {
             return;
         }
         sem->wait();
         fHaveGrant = true;
     }
 
     void Release() {
         if (!fHaveGrant) {
             return;
         }
         sem->post();
         fHaveGrant = false;
     }
 
     bool TryAcquire() {
         if (!fHaveGrant && sem->try_wait()) {
             fHaveGrant = true;
         }
         return fHaveGrant;
     }
 
     void MoveTo(CSemaphoreGrant &grant) {
         grant.Release();
         grant.sem = sem;
         grant.fHaveGrant = fHaveGrant;
         fHaveGrant = false;
     }
 
     CSemaphoreGrant() : sem(nullptr), fHaveGrant(false) {}
 
     explicit CSemaphoreGrant(CSemaphore &sema, bool fTry = false)
         : sem(&sema), fHaveGrant(false) {
         if (fTry) {
             TryAcquire();
         } else {
             Acquire();
         }
     }
 
     ~CSemaphoreGrant() { Release(); }
 
     operator bool() const { return fHaveGrant; }
 };
 
 // Utility class for indicating to compiler thread analysis that a mutex is
 // locked (when it couldn't be determined otherwise).
 struct SCOPED_LOCKABLE LockAssertion {
     template <typename Mutex>
     explicit LockAssertion(Mutex &mutex) EXCLUSIVE_LOCK_FUNCTION(mutex) {
 #ifdef DEBUG_LOCKORDER
         AssertLockHeld(mutex);
 #endif
     }
     ~LockAssertion() UNLOCK_FUNCTION() {}
 };
 
 #endif // BITCOIN_SYNC_H