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Date: Thu, 08 Oct 2009 12:18:35 -0400
From: Charles Wilson <cygwin AT cwilson DOT fastmail DOT fm>
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To: cygwin AT cygwin DOT com
Subject: Re: Thread related crash
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Christopher Faylor wrote:
> On Thu, Oct 08, 2009 at 07:18:49AM -0400, Charles Wilson wrote:
>> is it possible that cygwin
>> is overzealously inserting the _cygtls::call2() function into the return
>> frame stack?  Does cygwin manipulate the TIB, even for threads created
>> by direct calls to CreateThread?
> 
> Uh, yeah.  If you are not using Cygwin methods to start threads then it
> is entirely likely that there will be problems, just like if you use
> non-Cygwin methods to do I/O.

I see.

>> Any suggestions? (Other than an STC. I'll put one together after I get
>> some sleep).

OK, I've got a *really* simple test case -- more of a sanity check,
really -- below.

>> This is coming up because any tcl app that I've built -- including
>> insight -- always dies on exit, as tcl is shutting down its various
>> utility threads.
> 
> So why isn't this a problem with the current version of insight then?

I believe it /is/ a problem, at least on cygwin-1.7.  I've tried to
restore my system to "normal", and I see a different behavior on
cygwin-1.5 and cygwin-1.7 with the test below.

[1.5] $ /usr/bin/wish84.exe /usr/share/tk8.4/demos/hello
Hello, world

works fine.  You should see a small window pop up. When you click the
button, "Hello, sorld" is printed to the console and the small window
disappears. The application exits with no problem.

[1.7] $ /usr/bin/wish84.exe /usr/share/tk8.4/demos/hello
Hello, world
Segmentation fault (core dumped)

Again, you should see a small window pop up. When you click the button,
"Hello, sorld" is printed to the console and the small window
disappears. But then, the application segfaults.

Similarly, for insight.exe:

[1.5] $ insight.exe
<then choose File->Exit>

and the application exits without error.  But on 1.7:

[1.7] $ insight.exe
<then choose File->Exit>
Segmentation fault (core dumped)

Can anybody verify this behavior for me, to make sure I haven't somehow
left dregs of my X-based tcl/tk packages lying around on my system?

--
Chuck




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