🚀 go-pugleaf

"Jarkko Halme" <jjhalme@kotiposti.net> wrote:

>I am trying to prevent several instances of my program running. I am using C++ Builder v5 and OS is XP. My main looks like below:
>
>-----------------------------------------
>WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int)
>{
>  HANDLE mutex;
>
>  try
>  {
>    const char mutexname[]="program";
>    mutex=OpenMutex(0,false,mutexname);
>
>    //If mutex does not exist = program is not running
>    if (mutex==NULL)
>    {
>      mutex=CreateMutex(NULL, true,mutexname);
>    }
>    //mutex exists = program is aleady running
>    else
>    {
>      ShowMessage("Program is already running");
>      return 0;
>    }
>
>    Application->Initialize();
>    Application->Title = "program";
>    Application->CreateForm(__classid(TForm1), &Form1);
>    Application->Run();
>  }
>  catch (Exception &exception)
>  {
>     Application->ShowException(&exception);
>  }
>  ReleaseMutex(mutex);
>  return 0;
>}
>--------------------------------------------------

I use the CreateMutex to attempt to create one. If it already exists,
then some other program has already created it.

This is the relevant part of the class - the d'tor merely cleans up:

  bool
  SingleInstanceMutex::Acquire()
  {
    SetLastError(0) ;
    m_Handle = CreateMutex(NULL, false, m_Name) ;
    return (GetLastError() != ERROR_ALREADY_EXISTS) ;
  }

I don't actually bother calling OpenMutex.

Alan Bellingham
-- 
ACCU Conference 2005 - 20-23 April, Randolph Hotel, Oxford, UK