Replace boost::call_once with std::call_once

Cherry-picked from: 57dae3f

src/util.cpp

@@ -166,20 +166,20 @@ instance_of_cinit;
  * the mutex).
  */
 
-static boost::once_flag debugPrintInitFlag = BOOST_ONCE_INIT;
+static std::once_flag debugPrintInitFlag;
 
 /**
- * We use boost::call_once() to make sure mutexDebugLog and
+ * We use std::call_once() to make sure mutexDebugLog and
  * vMsgsBeforeOpenLog are initialized in a thread-safe manner.
  *
  * NOTE: fileout, mutexDebugLog and sometimes vMsgsBeforeOpenLog
  * are leaked on exit. This is ugly, but will be cleaned up by
  * the OS/libc. When the shutdown sequence is fully audited and
  * tested, explicit destruction of these objects can be implemented.
  */
-static FILE* fileout = NULL;
-static boost::mutex* mutexDebugLog = NULL;
-static list<string> *vMsgsBeforeOpenLog;
+static FILE* fileout = nullptr;
+static std::mutex* mutexDebugLog = nullptr;
+static std::list<std::string>* vMsgsBeforeOpenLog;
 
 static int FileWriteStr(const std::string &str, FILE *fp)
 {
@@ -188,15 +188,15 @@ static int FileWriteStr(const std::string &str, FILE *fp)
 
 static void DebugPrintInit()
 {
-    assert(mutexDebugLog == NULL);
-    mutexDebugLog = new boost::mutex();
-    vMsgsBeforeOpenLog = new list<string>;
+    assert(mutexDebugLog == nullptr);
+    mutexDebugLog = new std::mutex();
+    vMsgsBeforeOpenLog = new std::list<std::string>;
 }
 
 void OpenDebugLog()
 {
-    boost::call_once(&DebugPrintInit, debugPrintInitFlag);
-    boost::mutex::scoped_lock scoped_lock(*mutexDebugLog);
+    std::call_once(debugPrintInitFlag, &DebugPrintInit);
+    std::lock_guard<std::mutex> scoped_lock(*mutexDebugLog);
 
     assert(fileout == NULL);
     assert(vMsgsBeforeOpenLog);
@@ -291,8 +291,8 @@ int LogPrintStr(const std::string &str)
     }
     else if (fPrintToDebugLog)
     {
-        boost::call_once(&DebugPrintInit, debugPrintInitFlag);
-        boost::mutex::scoped_lock scoped_lock(*mutexDebugLog);
+        std::call_once(debugPrintInitFlag, &DebugPrintInit);
+        std::lock_guard<std::mutex> scoped_lock(*mutexDebugLog);
 
         // buffer if we haven't opened the log yet
         if (fileout == NULL) {