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Date: Mon, 8 Mar 2021 15:01:34 +0100
To: cygwin@cygwin.com
Subject: Re: segfault on 32bit cygwin snapshot
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From: Corinna Vinschen via Cygwin <cygwin@cygwin.com>
Reply-To: cygwin@cygwin.com
Cc: Corinna Vinschen <corinna-cygwin@cygwin.com>
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On Mar  8 03:07, Mark Geisert wrote:
> Following up to myself...
> 
> Mark Geisert wrote:
> > Hi Corinna,
> > 
> > On Fri, 5 Mar 2021, Corinna Vinschen wrote:
> > > On Mar  5 01:11, Mark Geisert wrote:
> > > > Marco Atzeri via Cygwin wrote:
> > > > > On 04.03.2021 21:17, Marco Atzeri wrote:
> > > > > > On 04.03.2021 16:17, Ken Brown via Cygwin wrote:
> > > > > > > On 3/4/2021 6:50 AM, Takashi Yano via Cygwin wrote:
> > > > > > > > On Thu, 4 Mar 2021 12:11:11 +0100
> > > > > > > > marco atzeri wrote:
> > > > > > > > > I have no problem to patch Python to solve the issue,
> > > > > > > > > but I have not seen evidence of the dlsym mechanism .
> > > > > > > > > But of course I an NOT and expert in this field.
> > > > > > > > > 
> > > > > > > > > If someone looking to the code can give me some hints,
> > > > > > > > > I will appreciate
> > > > > > > > 
> > > > > > > > I am also not sure where the dlsym() is used in python.
> > > > > > > > At least, os.uname() works in python 3.8.7 and 2.7.18 in my
> > > > > > > > environment even without that snippet. It seems that os.uname()
> > > > > > > > does not use dlsym(). Do I overlook something?
> > > > > > > 
> > > > > > > This all started because Mark reported a problem building python 3.8.3:
> > > > > > > 
> > > > > > >    https://cygwin.com/pipermail/cygwin-apps/2020-December/040765.html
> > > > > > > https://cygwin.com/pipermail/cygwin-developers/2020-December/012019.html
> > > > > > > 
> > > > > > > It's strange that Marco never bumped into the problem.
> > > > > > > 
> > > > > > > Ken
> > > > > > 
> > > > > > I never built python using cygwin snapshots as Mark was trying to do,
> > > > > > all my builds were using 3.1.7.
> > > > > > 
> > > > > > Let me set a separate enviroment for building on latest snapshot
> > > > > 
> > > > > I can not replicate with latest snapshot
> > > > > 
> > > > > $ uname -svr
> > > > > CYGWIN_NT-10.0-WOW 3.2.0s(0.340/5/3) 2021-03-01 15:42
> > > > > 
> > > > > nor in 64bit when building 3.8.8
> > > > > 
> > > > > For what I see the DLL is always using a proper import
> > > > > from cygwin1.dll
> > > > > 
> > > > > $ objdump -x libpython3.8.dll |grep uname
> > > > >          2b9de0   2170  uname
> > > > >          2b9de8   2171  uname_x
> > > > > 
> > > > > the only thing not standard on my build system is a case sensitive
> > > > > filesystem and mount
> > > > 
> > > > I had concerns that I had somehow corrupted my build environment, and it was
> > > > Marco's successes that convinced me to reinstall 3.1.7 to recover a
> > > > known-good environment.  Then seeing Marco go ahead and release the
> > > > different Python releases (yay!) I didn't investigate any further.
> > > > 
> > > > I'm now trying to locate the os.uname usage of dlopen/dlsym again just for
> > > > the record but am having some difficulty.  I'll reply again when I've got
> > > > it.
> > > 
> > > Guys,
> > > 
> > > if it turns out that we fixed a problem that doesn't actually is a
> > > real-world problem, I'm wondering if we shouldn't just revert the Cygwin
> > > patch we're talking about here (commit 532b91d24e9496) and be done with
> > > it.
> > > 
> > > Special casing dynamic loading of uname just to support some experimental
> > > bordercase doesn't make much sense.  In that case I'm all for "don't do
> > > that"!
> > 
> > That may well be the appropriate endpoint, but please let me dig a
> > little further into the recent Python versions.  The fact that they had
> > an explicit dlopen/dlsym to get at uname(), but now they don't, troubles
> > me. I want to be sure us Cygwin folk aren't in an inadvertent "arms
> > race" with the Python devs over the uname API change.  Dunno why this
> > didn't occur 15+ years ago, but here we are.
> > 
> > I think it was in Python's Modules/posixmodule.c.  They're certainly
> > using uname() directly in their most recent builds.  But I believe that
> > wasn't always the case, even just a few months ago.  Let me dig for a
> > day or two.
> 
> Not to put too fine a point on it, but I now believe I hit the issue I
> reported due to my own corrupted build environment.  Marco and Ken have both
> built recent Python packages on Cygwin 3.1.7 and proto-3.2.0 respectively,
> Ken having reverted the commit you're talking about (not sure about Marco).
> Both had success.
> 
> I believe reverting that commit 532b91d24e9496 is the correct action to take.

Did so this morning.


Thanks,
Corinna
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