Re: How do I ensure only one version of my executable is running

From:

"Tom Serface" <tom.nospam@camaswood.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 8 Mar 2007 13:47:33 -0800

Message-ID:

<A14FD963-ED55-4B82-87B6-7B7178FAD5C3@microsoft.com>

HI David,

That's an interesting approach. I suppose you could also store information
about the original instance and pop it up or pass command line arguments to
it as well. I've never tried to do it this way, but I'll give this approach
a try. Thanks...

Tom

"David Ching" <dc@remove-this.dcsoft.com> wrote in message
news:67%Hh.1291$yW.568@newssvr11.news.prodigy.net...

Another reliable way is to put a simple BOOL global variable in a shared
data segment (yes, data segments can be shared for .exe's although they
are mostly used in DLL's).

#pragma data_seg(".sdata")
   BOOL g_bAppRunning = FALSE;
#pragma data_seg()

// This comment makes the above data segment shareable
// It replaces having to add a linker option to the project
#pragma comment(linker, "/SECTION:.sdata,rws")

Then:

CMyApp::InitInstance()
{
   if ( g_bAppRunning )
       return FALSE; // another instance is running

   g_bAppRunning = TRUE; // record app is running

   ...
}

This works great and is lighter weight than a mutex. The only negative
I've heard is that if you have 2 copies of the .exe (say one in RELEASE
and another in DEBUG), then the global variable is not shared between
these disparate copies of the .exe, so it is possible to launch both the
release and debug versions simultaneously. However, this doesn't happen
in deployed solutions.

-- David (MVP)