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Subject: Re: Segfault in _Unwind_* code called from pthread_exit
To: Tijl Coosemans <tijl@FreeBSD.org>
Cc: Konstantin Belousov <kostikbel@gmail.com>, freebsd-current@FreeBSD.org,
 gerald@FreeBSD.org
References: <20170823163707.096f93ab@kalimero.tijl.coosemans.org>
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 <20171029182351.502f53cf@kalimero.tijl.coosemans.org>
 <20171029191358.GU2566@kib.kiev.ua>
 <9a724da4-70f1-4330-9a77-619739008a14@fgznet.ch>
 <20171030153207.15a42a1e@kalimero.tijl.coosemans.org>
From: Andreas Tobler <andreast-list@fgznet.ch>
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Date: Mon, 30 Oct 2017 22:54:05 +0100
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On 30.10.17 15:32, Tijl Coosemans wrote:
> On Sun, 29 Oct 2017 20:40:46 +0100 Andreas Tobler <andreast-list@fgznet.ch> wrote:
>> Attached what I have for libgcc. It can be applied to gcc5-8, should
>> give no issues. The mentioned tc from this thread and mine,
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82635 do pass.
>>
>> What do you think?
> 
> Like I said before the return address can be anything.  It could for
> instance point to some instruction in a random function and then the
> stack unwinder will think thread_start was called from that function.
> There's no check you can add to libgcc to distinguish that from a
> normal valid return address.
> 
Maybe not, and most probably I do not understand what is happening. But 
with my modification I survive the test case.

If no objections from your or Konstantin's side come up I will commit it 
to the gcc repo. It will not 'fix' the issue, but it will improve the 
gcc behavior.

Andreas