From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:52032) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RNVcQ-0002Ps-Pf for qemu-devel@nongnu.org; Mon, 07 Nov 2011 15:16:35 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RNVcP-0000Dt-Q9 for qemu-devel@nongnu.org; Mon, 07 Nov 2011 15:16:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:2248) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RNVcP-0000Df-JB for qemu-devel@nongnu.org; Mon, 07 Nov 2011 15:16:33 -0500 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id pA7KGVTw021773 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 7 Nov 2011 15:16:31 -0500 Message-ID: <4EB83C9D.3090004@redhat.com> Date: Mon, 07 Nov 2011 22:16:29 +0200 From: Ronen Hod MIME-Version: 1.0 References: <20111106160022.GF3225@redhat.com> In-Reply-To: <20111106160022.GF3225@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] qemu_timedate_diff() shouldn't modify its argument. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: qemu-devel@nongnu.org On 11/06/2011 06:00 PM, Gleb Natapov wrote: > The caller of qemu_timedate_diff() does not expect that tm it passes to > the function will be modified, but mktime() is destructive and modifies > its argument. Pass a copy of tm to it and set tm_isdst so that mktime() > will not rely on it since its value may be outdated. I believe that the original issue was not related to outdated data at the moment of the daylight saving time transition. using tmp.tm_isdst = -1 sounds good, but why use a copy of tm? The only significant field that will change in the tm is the tm_isdst itself that will be set to 0/1 (correctly). Acked-by: Ronen Hod > Signed-off-by: Gleb Natapov > diff --git a/vl.c b/vl.c > index 624da0f..641629b 100644 > --- a/vl.c > +++ b/vl.c > @@ -460,8 +460,11 @@ int qemu_timedate_diff(struct tm *tm) > if (rtc_date_offset == -1) > if (rtc_utc) > seconds = mktimegm(tm); > - else > - seconds = mktime(tm); > + else { > + struct tm tmp = *tm; > + tmp.tm_isdst = -1; /* use timezone to figure it out */ > + seconds = mktime(&tmp); > + } > else > seconds = mktimegm(tm) + rtc_date_offset; > > -- > Gleb. >