Date: Tue, 11 Oct 2011 14:52:17 -0400 From: Arnaud Lacombe <lacombar@gmail.com> To: Larry Rosenman <ler@lerctr.org> Cc: =?ISO-8859-1?Q?Ren=E9_Ladan?= <rene@freebsd.org>, freebsd-current@freebsd.org, Dimitry Andric <dim@freebsd.org> Subject: Re: System headers with clang? Message-ID: <CACqU3MVETLMRuYuVpZ0aehdr7rX4KqZGFG17pKdFeSut7jOCCw@mail.gmail.com> In-Reply-To: <4E948D59.5020006@lerctr.org> References: <alpine.BSF.2.00.1110091229550.43656@lrosenman.dyndns.org> <4E942FF1.9000805@FreeBSD.org> <CACqU3MV9vP%2BVUR%2B2Qpzc4mCS1w3R17yvMGNPT%2BxnsGUiYr8VFQ@mail.gmail.com> <4E948D59.5020006@lerctr.org>
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Hi, On Tue, Oct 11, 2011 at 2:39 PM, Larry Rosenman <ler@lerctr.org> wrote: > On 10/11/2011 1:36 PM, Arnaud Lacombe wrote: >> >> Hi, >> >> On Tue, Oct 11, 2011 at 8:00 AM, Dimitry Andric<dim@freebsd.org> =A0wrot= e: >>> >>> On 2011-10-09 19:32, Larry Rosenman wrote: >>>> >>>> I had gotten a PR about sysutils/lsof not compiling with clang. =A0I h= ad >>>> Vic Abell check it out, and the problem is NOT with lsof per se, but >>>> with the system headers. >>>> >>>> Is there a project afoot to update the system headers to make them cla= ng >>>> compilable? >>> >>> The problem isn't that clang can't compile the system headers, but >>> normally these don't get included from userspace. =A0And they certainly >>> won't work as expected when you define _KERNEL in userspace, as the lso= f >>> port foolishly does. =A0It probably can't be avoided in such a tool, >>> though. >>> >> #ifdef _KERNEL/#endif protected part of system headers shall NEVER be >> accessed by userland. It is a fault to have them present in >> /usr/include. Linux got it right there, all those part are removed >> upon headers' installation. >> >> =A0- Arnaud > > Then lsof would NOT be compilable / usable at all, as it delves into > /dev/kmem to get information. > AFAIK, Linux is capable of supporting lsof in a backward compatible manner, without exposing its internal guts. FWIW, KVM is a bad kernel/userland interface, as it does not guarantee backward compatibility. > And it **NEEDS** to know what the structures are. > No, not kernel-only structure. Now, if these structure are not meant to be kernel only, move them out of _KERNEL area, but beware of backward compatibility issue in the future. > That is unless someone(tm) writes the Kernel interfaces to get the info. > Yes, this is the core of the problem and a classical chicken/eggs problem solves the very wrongest way. At some point, I thought to modify the build system to pass kernel's headers through unifdef(1), but I quickly forgot about that: % git grep 'define _KERNEL' * | grep -v '^sys' | wc -l 27 - Arnaud
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