DMARC-Filter: OpenDMARC Filter v1.4.2 delorie.com 61RILGgR1725499
Authentication-Results: delorie.com; dmarc=pass (p=none dis=none) header.from=cygwin.com
Authentication-Results: delorie.com; spf=pass smtp.mailfrom=cygwin.com
DKIM-Filter: OpenDKIM Filter v2.11.0 delorie.com 61RILGgR1725499
Authentication-Results: delorie.com;
	dkim=pass (1024-bit key, unprotected) header.d=cygwin.com header.i=@cygwin.com header.a=rsa-sha256 header.s=default header.b=FjWIBhhR
X-Recipient: archive-cygwin AT delorie DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org D672E4B9DB5F
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1772216475;
	bh=CZHBrTW3+H088/QJrcfUHVGvC9hZSm/w5/UEeb9N0rY=;
	h=Date:To:Cc:In-Reply-To:References:Subject:List-Id:
	 List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe:
	 From:Reply-To:From;
	b=FjWIBhhRcCv7LclK1CLQQHz4DDD+tDMOwb4kB7Vcfh18I+pUco4uKbhIE5Ck0X7S0
	 +Zm7W2w7TMrWmNVGll8gFnEMWKoUklVVIapw72mI7C00u6ZBErbPAU5D05Gg3T/4F8
	 LIeiRONscF8bYc894gRowyhxfz4tHaFzvgUUBfNs=
X-Original-To: cygwin AT cygwin DOT com
Delivered-To: cygwin AT cygwin DOT com
DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org C5EA74BA2E14
ARC-Filter: OpenARC Filter v1.0.0 sourceware.org C5EA74BA2E14
ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1772216426; cv=none;
 b=IWoWisevBTSbR3gu9dgJn9KM22wiGDWGXDLLfZcaPjGB5WC8oHiCc5uaz6zVU6O3kAJVD96tkhRu/Qw3mLH7xr1J7Obw+NtJK8JUwb1ErZgxVD4/OZOHiirTwh8ozTCs1pdvLlx5Nt8smKzgKXa4/Qsc6cWk03A/qR46ogqglAo=
ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key;
 t=1772216426; c=relaxed/simple;
 bh=LwFjh/qfAHpe3ZwKdz0uU0/Zr9gBlT3Dddupvq/BCtw=;
 h=DKIM-Signature:Date:From:To:Message-ID:Subject:MIME-Version;
 b=U1lJx3xxa7U/54M3gdHcsKJ8u2biaO4UYOpsoOoA5gQfv17mtSd0LXRdgqUxPgtClES0YXaJk6zo/Zyjk+oLrLU73IvyC+lVF8HOJaV5YZkh9/JSC2k92fQZfh3IfAyeGN6o8+4e+0Qo4AwcSxkHu7x1TSq94JjFjTNdJ2DnHes=
ARC-Authentication-Results: i=1; server2.sourceware.org
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C5EA74BA2E14
Date: Fri, 27 Feb 2026 10:20:19 -0800 (PST)
To: Eliot Moss <moss AT cs DOT umass DOT edu>,
        Dimitry Andric <dimitry AT unified-streaming DOT com>
Cc: KENNON J CONRAD via Cygwin <cygwin AT cygwin DOT com>
Message-ID: <1990836634.1545853.1772216419837@connect.xfinity.com>
In-Reply-To: <3e0de899-a7dd-8fea-7743-10e6b05cc6b6@cs.umass.edu>
References: <547312365 DOT 1464244 DOT 1771958282029 AT connect DOT xfinity DOT com>
 <aZ7PrbisVR1R4A7v AT dimstar DOT local DOT net>
 <1670201592 DOT 1489273 DOT 1772043520008 AT connect DOT xfinity DOT com>
 <e91d8b5b-2690-4271-aa74-e6226440e33d AT SystematicSW DOT ab DOT ca>
 <1044918836 DOT 1507810 DOT 1772086967212 AT connect DOT xfinity DOT com>
 <1579472684 DOT 1508349 DOT 1772092747339 AT connect DOT xfinity DOT com>
 <aaABFf5iEowV1l7I AT xps13>
 <1148572549 DOT 1808180 DOT 1772097444036 AT mail DOT yahoo DOT com>
 <1901597260 DOT 1508573 DOT 1772100378936 AT connect DOT xfinity DOT com>
 <0C965DD0-856E-41FF-B5A4-15E472292A32 AT unified-streaming DOT com>
 <483908609 DOT 1508714 DOT 1772103775739 AT connect DOT xfinity DOT com>
 <2346fd41-2500-0db6-5849-6788174b5a1d AT cs DOT umass DOT edu>
 <1462848037 DOT 1521935 DOT 1772136952077 AT connect DOT xfinity DOT com>
 <399745a1-429a-ebb4-0f67-c32f6282caa6 AT cs DOT umass DOT edu>
 <1093316506 DOT 1533154 DOT 1772157883568 AT connect DOT xfinity DOT com>
 <3e0de899-a7dd-8fea-7743-10e6b05cc6b6 AT cs DOT umass DOT edu>
Subject: Re: Memmove causing program crashes, giving SIGTRAP in GDB(?)
MIME-Version: 1.0
X-Priority: 3
Importance: Normal
X-Mailer: Open-Xchange Mailer v7.10.6-Rev83
X-Originating-IP: ::ffff:50.47.202.14
X-Originating-Port: 44804
X-Originating-Client: open-xchange-appsuite
X-CMAE-Envelope: MS4xfPoWZU7uWahaVxb7pL81mGx8K3cbm1ZBVgPN73f5iIgR55JTqtE6SYOjPudqE6Ba7hS/SWyws3l8ut7ScuvQvu85pY15wv1wjkmVqf+ywbRaZeuBsUo7
 BUTmV9zz/2sj5HUf+RnWoZEVzh4F/jGKN+0FUrXhT/BCatXpmbTVTpT1zYMVQ4AurjYQpt7R0Yw2Y3ty+UkVuj2dtbcSNygBllH8DGboEJUQg8WXAZj86qhO
 8M8vEWkrX/CXrtb9MNY4QnQ+RB6SPj5WKetzF+2V6dxm2XUNr7V98EPpwIFspWb4
X-BeenThere: cygwin AT cygwin DOT com
X-Mailman-Version: 2.1.30
Precedence: list
List-Id: General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe: <https://cygwin.com/mailman/options/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive: <https://cygwin.com/pipermail/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe: <https://cygwin.com/mailman/listinfo/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From: KENNON J CONRAD via Cygwin <cygwin AT cygwin DOT com>
Reply-To: KENNON J CONRAD <kennonconrad AT comcast DOT net>
Content-Type: text/plain; charset="utf-8"
Errors-To: cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com
Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>
Content-Transfer-Encoding: 8bit
X-MIME-Autoconverted: from base64 to 8bit by delorie.com id 61RILGgR1725499

Hello,

   I updated the BIOS to the newest version and ran the code again.  The memmove got SIG_TRAP again.  This time the code was freeing up uint16_t array element 1525 and eliminating array element 1676 by moving elements 1525 - 1675 to elements 1526 - 1676.
RSI contains the address of element 1601, indicating the rep movsq did only 9 iterations before the SIG_TRAP happened.  The ZF shows a value of 0.  So it seems like this is perhaps an OS problem with ZF handling of interrupts.  At this point, it is easiest for me to avoid memmove for backward moves with source/destination overlap because of this problem.  I don't know how many computers are impacted by this problem but I do know it's causing crashes on my test computer and that's enough reason to avoid it.

-Kennon

> On 02/26/2026 7:06 PM PST Eliot Moss <moss AT cs DOT umass DOT edu> wrote:
> 
>  
> On 2/26/2026 9:04 PM, KENNON J CONRAD wrote:
> > Perhaps something like this?  Maybe I need to try a BIOS update?
> 
> Yes, something *like* these flaws.  The thing is to find out if your specific
> processor has a flaw that needs an update, etc.
> 
> > Intel Haswell (and related architectures) processors may experience stability issues, including machine check errors (MCEs), due to a microcode bug related to REP MOVS (specifically REP MOVSB or REP MOVSQ) handling. These issues often cause system crashes or lockups, leading to microcode, BIOS/UEFI updates to resolve them.
> > Debian Wiki
> >   +4
> > Issue: A high-rate of interrupts or specific memory operations can cause REP MOVS instructions to trigger Machine Check Errors (MCE) or internal errors (IERR) on older processors.
> > Affected Processors: The bug primarily impacts older Intel processors, including Haswell and Broadwell architectures.
> > Fix/Mitigation: The primary solution is to apply the latest motherboard BIOS/UEFI update, which contains the corrected microcode update (often labelled 20180108 or later).
> > Background: This is linked to Intel’s efforts to fix security vulnerabilities (like Spectre), where early patches for Haswell/Broadwell caused unexpected instability, requiring further refinements.
> > Debian Wiki
> >   +4
> > 
> > -Kennon
> 
> EM

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