Re: Mutex troubles?

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#4373

From: Nate Lockwood
Date: Fri, 24 Feb 2006 21:03

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  Bruce Salzman wrote:


> You *should* get the handle to the existing mutex. You have to call 
> GetLastError() after CreateMutex() to see if it returns 
> ERROR_ALREADY_EXISTS.

Thanks, I got that thought after I posted and changed my code to that 
below.  The first instance is detected but the message doesn't get through.

Nate

HANDLE CheckForInstance(const UINT WM_MYMSG)
{
   SetLastError(0) ;
   char * m_Name = "USDA.FS.FireScience.GooleEarthTool";
   HANDLE m_Handle = CreateMutex(NULL, false, m_Name);
   if(m_Handle != NULL)
     if(GetLastError() != ERROR_ALREADY_EXISTS)
       return m_Handle;      // this is the first instance

   PostMessage(HWND_BROADCAST, WM_MYMSG, NULL, NULL);
   return NULL;     //  NULL handle
}

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