Date: Tue, 13 Jun 2006 02:30:25 GMT From: Kris Kennaway <kris@obsecurity.org> To: freebsd-amd64@FreeBSD.org Subject: Re: amd64/98893: cc error at -O2 on amd64/6-STABLE compiling port ucspi-tcp Message-ID: <200606130230.k5D2UPw0074455@freefall.freebsd.org>
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The following reply was made to PR amd64/98893; it has been noted by GNATS.
From: Kris Kennaway <kris@obsecurity.org>
To: Andrew Reilly <andrew-freebsd@areilly.bpc-users.org>
Cc: FreeBSD-gnats-submit@FreeBSD.org
Subject: Re: amd64/98893: cc error at -O2 on amd64/6-STABLE compiling port ucspi-tcp
Date: Mon, 12 Jun 2006 22:27:03 -0400
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On Tue, Jun 13, 2006 at 02:01:22AM -0000, Andrew Reilly wrote:
>=20
> >Number: 98893
> >Category: amd64
> >Synopsis: cc error at -O2 on amd64/6-STABLE compiling port ucspi-t=
cp
> >Confidential: no
> >Severity: serious
> >Priority: medium
> >Responsible: freebsd-amd64
> >State: open
> >Quarter: =20
> >Keywords: =20
> >Date-Required:
> >Class: sw-bug
> >Submitter-Id: current-users
> >Arrival-Date: Tue Jun 13 02:10:18 GMT 2006
> >Closed-Date:
> >Last-Modified:
> >Originator: Andrew Reilly
> >Release: FreeBSD 6.1-STABLE amd64
> >Organization:
> >Environment:
> System: FreeBSD duncan.reilly.home 6.1-STABLE FreeBSD 6.1-STABLE #4: Mon =
Jun 12 13:57:57 EST 2006 root@:/usr/obj/usr/src/sys/DUNCAN amd64
>=20
> machine is an AMD64-X2-4200+
> /etc/make.conf exists but does not set or change CFLAGS
>=20
> >Description:
> tcpserver, from the port sysutils/ucspi-tcp, built as
> normal, fails with the error message:=20
> "tcpserver: fatal: temporarily unable to figure out IP
> address for 0.0.0.0: file does not exist"
> Debugging shows that this is the result of the following
> line in dns_rcrw.c always returning -1:
> if (gethostname(host,sizeof host) =3D=3D -1) return -1;
> Now, ENOFILE ("file does not exist") is not a valid
> errno return from gethostname, and separate testing
> shows that gethostname() runs just fine. Indeed, this
> piece of kdump output shows that it was called, and
> returned 0, as expected:
> 13441 tcpserver CALL open(0x4086fe,0x4,0x40)
> 13441 tcpserver NAMI "/etc/resolv.conf"
> 13441 tcpserver RET open -1 errno 2 No such file or directory
> 13441 tcpserver CALL __sysctl(0x7fffffffe3b8,0x2,0x7fffffffe3d0,0x7ffff=
fffe3b0,0,0)
> 13441 tcpserver RET __sysctl 0
> 13441 tcpserver CALL write(0x2,0x50b960,0x5f)
> 13441 tcpserver GIO fd 2 wrote 95 bytes
> "tcpserver: fatal: temporarily unable to figure out IP address for=
0.0.\
> 0.0: file does not exist
> "
> 13441 tcpserver RET write 95/0x5f
> 13441 tcpserver CALL exit(0x6f)
> (gethostname is that __sysctl. errno is no-doubt still
> set to ENOFILE from the failed open of /etc/resolv.conf.)
> So: the only conclusion is that the compiler flubbed the
> comparison of the return value against -1, and returned
> (-1) anyway. Unfortunately, the code produced by cc (gcc3.4.4)
> at -O2 bears so little resemblance to the source that I
> can't follow it, to point this out explicitly (and
> neither can objdump -S...)
> The code works fine if the gethostname call is made
> without checking the return value (it can't reasonably
> fail, anyway).
> It also works fine if the default -O2 is overridden with
> -O, which is what I'm recommending here.
> It also works fine with default CFLAGS (-O2
> -fno-strict-aliasing -pipe) with CC=3Dgcc41, built from ports.
>=20
> >How-To-Repeat:
> cd /usr/ports/sysutils/ucspi-tcp
> sudo make
> cd work/ucspi-tcp-0.88
> ./tcpserver 0 2525 /bin/cat
>=20
> >Fix:
>=20
> Well, this is a work-around for this particular case.
> I'm surprised that this could be the only program that
> has trouble at -O2, given the zillions of lines of code
> in the system and ports that seems to be running OK. So
> I doubt my diagnosis of a compiler bug, but I can't
> think of an alternative. The code itself looks
> perfectly fine.
So I'm confused, is it using -O2 or -O2 -fno-strict-aliasing (the
default). If the former, it's probably an aliasing bug in the source,
which is why the default is not plain -O2.
Kris
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