X-Recipient:	archive-cygwin AT delorie DOT com
DomainKey-Signature:	a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:subject:to:references:from:message-id:date
	:mime-version:in-reply-to:content-type
	:content-transfer-encoding; q=dns; s=default; b=GoJ+ybdDxycaQnG0
	fIaj1MOe5/TRwcdYkADA28P2yr+NH9GtgBG/LKqIpfRqzPrjn0zfQTWN/iuWJv9v
	9yjuq+Xw5kF2I9HTKMuQfRl7cROBwANEyeyi8aEE+/dOz4xKGqrLQ1HdGGvhm4kG
	VvH4gCPpmF5L+H5/d9E+ARoxrbY=
DKIM-Signature:	v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:subject:to:references:from:message-id:date
	:mime-version:in-reply-to:content-type
	:content-transfer-encoding; s=default; bh=GDhzkXltLGIBqGpMAO1RSc
	UCIWE=; b=d1Ux2UbgPInWZ2u+ogltKyQlbiAt7VwTOtOhrqHFh632brWGvnTl3w
	Aw7JTkJS2kA+1WvcSuTiPqwzTvtR8YePOw11oa0Ve7ydvfEjILOJ593rxR+NVyjP
	BlrNDAMx+DrlQWS5abFq6Qqqr9VKBt1pfS1zeWqX3kDjCJe/dUMcw=
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com
Authentication-Results:	sourceware.org; auth=none
X-Virus-Found:	No
X-Spam-SWARE-Status:	No, score=1.7 required=5.0 tests=AWL,BAYES_50,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_NONE,RCVD_IN_SORBS_SPAM,RP_MATCHES_RCVD autolearn=no version=3.3.2 spammy=examined, upgrading, jony, JonY
X-HELO:	mailout04.t-online.de
Subject:	Re: gcc-6.3.0-1 regression: libstdc++6 DLL breaks exception handling
To:	cygwin AT cygwin DOT com
References:	<6a80a46a-8de9-5d28-f7ef-897a53159603 AT t-online DOT de> <dcea951e-96f2-b592-4804-1c58abf84a83 AT gmail DOT com>
From:	Christian Franke <Christian DOT Franke AT t-online DOT de>
Message-ID:	<a4c62a64-5570-e39c-a8b5-d659fdbfbc6d@t-online.de>
Date:	Tue, 7 Feb 2017 16:26:37 +0100
User-Agent:	Mozilla/5.0 (Windows NT 10.0; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0 SeaMonkey/2.47
MIME-Version:	1.0
In-Reply-To:	<dcea951e-96f2-b592-4804-1c58abf84a83@gmail.com>
X-IsSubscribed:	yes

JonY wrote:
> On 01/26/2017 10:30 AM, Christian Franke wrote:
>> After upgrading to gcc test version 6.3.0-1, C++ exception handling is
>> broken if DLL version of new libstdc++6 is used.
>>
> Noted, I'll consider the test version broken for now.
>
>

Meantime I examined the testcase with gdb: The DLL exports a bogus 
address for the symbol "_ZTIi" ('typeinfo for int'). This results in 
this more simple testcase:

#include <typeinfo>
int main() {
   const std::type_info & ti = typeid(int); // &_ZTIi from DLL
   const char * p = ti.name(); // segfaults because &_ZTIi is bogus.
}


And indeed, the export table of the DLL looks 'interesting'. The offsets 
of various exported symbols are apparently all 93980000:

$ objdump -p cygstdc++-6.dll

     [5142] +base[5143] c6760 Export RVA
     [5143] +base[5144] c6768 Export RVA
     [5144] +base[5145] 93980000 Export RVA
...
     [5151] +base[5152] 93980000 Export RVA
     [5152] +base[5153] 93980000 Export RVA
     [5153] +base[5154] 93980000 Export RVA
     [5154] +base[5155] 93980000 Export RVA
...
     [5167] +base[5168] 93980000 Export RVA
     [5168] +base[5169] c6780 Export RVA
...
[Ordinal/Name Pointer] Table
...
     [5143] _ZTISt9type_info
     [5144] _ZTIa
...
     [5151] _ZTIh
     [5152] _ZTIi
     [5153] _ZTIj
     [5154] _ZTIl
...
     [5167] _ZTSDs
     [5168] _ZTSN10__cxxabiv115__forced_unwindE

$  objdump -p cygstdc++-6.dll | grep -cw 93980000
759


Hmm... bug in the (bin)utils used to build the DLL?

Possibly related:
https://cygwin.com/ml/cygwin/2017-01/msg00375.html

Christian


--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

- Raw text -