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Date: Sat, 21 Jul 2001 14:26:35 -0700 (PDT)
From: Mo DeJong <mdejong AT cygnus DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Linking to cygwin1.dll and msvcrt.dll ?
In-Reply-To: <Pine.HPP.3.96.1010720120335.16500P-100000@hp2.xraylith.wisc.edu>
Message-ID: <Pine.SOL.3.91.1010721141254.14945C-100000@cse.cygnus.com>
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On Fri, 20 Jul 2001, Mumit Khan wrote:

...

> > My question is, is this same memory leak problem going
> > to show up when using Cygwin's CreateThread() and
> > C library APIs?
> 
> I believe the memory leak is only applicable if you're using MSVCRT
> runtime, but that's not the case with Cygwin. The *ex functions close
> the various handles and TLS' that are created per thread if I remember 
> correctly.

The way I understood it, calling CreateThread() would not create the
TLS block and a later call to a C api function might allocate
the TLS block for you. Later on, you would call ExitThread() the
the TLS block that was allocated would not be deallocated and
the memory would leak.

> > Even if this is not going to be a problem, should
> > Cygwin provide the _beginthread, _beginthreadex,
> > _endthread, and _endthreadex methods to ease
> > porting existing apps that have already dealt
> > with this issue?
> 
> It's tempting, but IMO Cygwin should stay away from creeping feature'ism
> such as this. Most of the threaded applications I see tend to use Win32
> API directly, and Cygwin of course supports that just fine. Of course, we
> can always have msvcrt helper/port library that can facilitate ports.

If the app uses only the Win32 API then I don't think this problem
shows up. It only applies when a thread created with CreateThread()
calls C APIs. I don't even know if this is a problem in Cygwin
since as far as I know Cygwin does not implement C function is
the same way as msvcrt.dll.

I am not in a position to judge "creeping feature'ism". It is
just that these 4 *ex methods are documented and are even
suggested in the Microsoft documentation. If this memory
leak is not a problem in Cygwin, then these functions
should be really easy to implement since they would just
call the Win32 APIs.

cheers
Mo

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