大家好 大家好,,因工作需求要多緒程式的實作,,看了版上大家的討論 可以用Critical_Section  or Mutex來達到需求.. 於是我試改了了"lu"版主的的程式來看這兩者有何差異 觀看結果我會得到說Critical Section並無真正達到保護的作用(我很困惑).. 這讓我蠻困惑的..,,請問這應該怎麼解釋 程式  

 
//---------------------------------------------------------------------------
__fastcall TMyThread::TMyThread (HANDLE ttHandle,unsigned int *ttNum,bool AddFlag)
        : TThread(true)
{
FAddFlag = AddFlag;
Num = ttNum;
FormHandle = ttHandle;
OperationMutex = CreateMutex (NULL,false,"Test Program MyThread Version 1");
InitializeCriticalSection(&cs);
//InitializeCriticalSection(&cs[1]);
}
//---------------------------------------------------------------------------    void __fastcall TMyThread::Execute()
{
int c;
//    EnterCriticalSection(&cs);
for (c=0;c<50;c  )
  {
//    WaitForSingleObject (OperationMutex,INFINITE);//¸ÕµÛ­×§ï¬Ý¬Ýµ²ªG
//    EnterCriticalSection(&cs);
    if (FAddFlag)
     {
           EnterCriticalSection(&cs);
           *Num = *Num   1;
           LeaveCriticalSection(&cs);
      }
    else
      {
           EnterCriticalSection(&cs);
          *Num = *Num - 1;
           LeaveCriticalSection(&cs);
      }
    Sleep (10);      //¸ÕµÛ­×§ï¬Ý¬Ýµ²ªG
//    LeaveCriticalSection(&cs);
//    ReleaseMutex (OperationMutex); //¸ÕµÛ­×§ï¬Ý¬Ýµ²ªG
    PostMessage  (FormHandle,WM_USER   100 , 0,FAddFlag);
  }
//    LeaveCriticalSection(&cs);
}
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------    void __fastcall TForm1::Button1Click(TObject *Sender)
{
Num = 0;
Memo1->Clear ();
MyThread1->Resume ();
MyThread2->Resume ();
}
//---------------------------------------------------------------------------    void __fastcall TForm1::FormCreate(TObject *Sender)
{
MyThread1 = new TMyThread (this->Handle,&Num,true); //add
MyThread2 = new TMyThread (this->Handle,&Num,false);//minus
}
//---------------------------------------------------------------------------    void __fastcall TForm1::FormClose(TObject *Sender, TCloseAction &Action)
{
MyThread1->WaitFor ();
delete MyThread1;    MyThread2->WaitFor ();
delete MyThread2;
}
//---------------------------------------------------------------------------    void __fastcall TForm1::ShowNumber(TMessage Msg)
{
String ss = "Number:"   (String)Num   ", "   (String)Msg.LParam  ;
Memo1->Lines->Add (ss);
}
//---------------------------------------------------------------------------

結果如下: 用Mutex的結果 Number:1, 1 Number:0, 0 Number:1, 1 Number:1, 0 Number:1, 1 Number:0, 0 Number:1, 1 Number:0, 0 Number:1, 1 Number:0, 0 Number:1, 1 Number:0, 0 Number:0, 1 Number:0, 0 用CriticalSection的結果 Number:0, 0 Number:0, 1 Number:0, 1 Number:0, 0 Number:0, 0 Number:4294967295, 1 Number:0, 0 Number:0, 1 Number:0, 1 Number:0, 0 Number:0, 0 //-------- 因為出現紅色的那些訊息,,讓我感到困惑 //-------------------- Begin with the end in mind. 發表人 - Fm 於 2005/03/20 13:29:57

cs 變數是由兩個 threads share 的嗎？

作minus的绪连续执行了两次, 使Num成为负值, 即-1.    -1的二进制表示为0xFFFFFFFF, 也就是你看到的 4294967295.    改动一下Num的初始值, 就可以看到CriticalSection还是有效的.     

void __fastcall TForm1::Button1Click(TObject *Sender)
{
  Num = 1000;
  Memo1->Clear ();
  MyThread1->Resume ();
  MyThread2->Resume ();
}

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