C++ 靜態變數初始化（static pthread_mutex_t 初始化）

c++類中定義的static變數 需要在 類外初始化，且前面沒有static。例如：

M.h:

#include <pthread.h>

class MonitorPThread
{
    public:
        static pthread_mutex_t mut; 
        
        MonitorPThread();
     ~MonitorPThread();
      

   private:
      ........    
           

};

M.cpp:

#include <iostream>
#include <unistd.h>
#include "MonitorPThread.h"
#include "string.h"

using namespace std;

//init mutex
pthread_mutex_t MonitorPThread::mut = PTHREAD_MUTEX_INITIALIZER;

MonitorPThread::MonitorPThread()
{
    
}

MonitorPThread::~MonitorPThread()
{

}