DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:message-id:date:from:mime-version:to:subject
	:references:in-reply-to:content-type:content-transfer-encoding;
	 q=dns; s=default; b=rF6GTWwXhZ0YKBSfro6R8NPIt3kUom5Lp6EJMvNRoPp
	4WIKHFDVirEUCWx/6kXw7Op7A2XSNG9gTpTK+DVejDT6apIs5IwIK8oNEO5XpnTi
	k8OPOuoEBtqdPGtrPJLSNVxy0jxHh8eNue9Eu5oAZJ4pqKLKyU9VrrnFGBsD4+r8
	=
Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm
Sender: cygwin-owner@cygwin.com
Mail-Followup-To: cygwin@cygwin.com
Message-ID: <542175EF.4040703@t-online.de>
Date: Tue, 23 Sep 2014 15:30:23 +0200
From: Christian Franke <Christian.Franke@t-online.de>
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:29.0) Gecko/20100101 Firefox/29.0 SeaMonkey/2.26.1
MIME-Version: 1.0
To: cygwin@cygwin.com
Subject: Re: ffs problem in windows64
References: <CAHAq8pG0xMtSLJYs_u8OW4Z1Loovpyzzyo4oLBZQPqYsWFUU6w@mail.gmail.com> <54216D72.2070307@cs.umass.edu>
In-Reply-To: <54216D72.2070307@cs.umass.edu>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit

Eliot Moss wrote:
> On 9/23/2014 8:47 AM, Paulo César Pereira de Andrade wrote:
>>    Hi,
>>
>>    I am almost done porting https://savannah.gnu.org/projects/lightning
>> to cygwin and windows64 abi. But I found a problem with the ffs 
>> function.
>>
>>    The test case is simple:
>>
>> $ cat x.c
>> extern int ffs(int);
>> int main(void) {
>> long l = 0x80000000;
>> int i = ffs((int)l);
>> return 0;
>> }
>>
>> $ gcc -O0 -g3 x.c
>>
>> $ ./a.exe
>> Segmentation fault (...)
>
> WJFFM in 32 bit cygwin.
>

It fails under 64 bit cygwin.

This segfaults if gcc -fno-builtin option is used:
   ffs(0x80000000)

These work:
   ffs(0xc0000000)
   ffs(0x40000000)

Likely a subtle problem in table based ffs() implementation in 
winsup/cygwin/syscalls.cc if only upper bit is set. The newlib version 
of ffs() works.

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