System headers with clang?
ler at lerctr.org
Tue Oct 11 19:05:14 UTC 2011
On 10/11/2011 1:52 PM, Arnaud Lacombe wrote:
> On Tue, Oct 11, 2011 at 2:39 PM, Larry Rosenman<ler at lerctr.org> wrote:
>> On 10/11/2011 1:36 PM, Arnaud Lacombe wrote:
>>> On Tue, Oct 11, 2011 at 8:00 AM, Dimitry Andric<dim at freebsd.org> wrote:
>>>> On 2011-10-09 19:32, Larry Rosenman wrote:
>>>>> I had gotten a PR about sysutils/lsof not compiling with clang. I had
>>>>> 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 clang
>>>> The problem isn't that clang can't compile the system headers, but
>>>> normally these don't get included from userspace. And they certainly
>>>> won't work as expected when you define _KERNEL in userspace, as the lsof
>>>> port foolishly does. It probably can't be avoided in such a tool,
>>> #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.
>>> - 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.
Therein lies the rub. In order to do it's job, it DOES need to grovel
around in kernel only structures.
>> 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
> - Arnaud
This is not going to fix things until/unless someone(tm) takes the bull
by the horns, and writes
a userland<->kernel interface to get ALL the data that lsof currently
gathers from groveling around
I don't have the skills nor time to do that.
We can go around and around on this topic, but until/unless either the
clang headers/built-ins are changed to match
the system/kernel headers, or someone(tm) writes the interfaces, clang
will NOT be supported to compile sysutils/lsof.
Larry Rosenman http://www.lerctr.org/~ler
Phone: +1 512-248-2683 E-Mail: ler at lerctr.org
US Mail: 430 Valona Loop, Round Rock, TX 78681-3893
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