Re: xattr.h wonkiness

[Serge Hallyn <serge.hallyn@ubuntu.com>]

Quoting Carlos O'Donell (carlos@systemhalted.org):
> On Thu, Mar 6, 2014 at 6:06 PM, Serge Hallyn <serge.hallyn@ubuntu.com> wrote:
> > Quoting Carlos O'Donell (carlos@systemhalted.org):
> >> On Fri, Feb 21, 2014 at 6:42 PM, Serge Hallyn <serge.hallyn@ubuntu.com> wrote:
> >> > Hi, would a simple patchl ike this to misc/sys/xattr.h be
> >> > acceptable?  This showed up in a failure to build (of at least
> >> > qemu, and aiui lots of other pkgs) after merging a new libcap2
> >> > where sys/capability.h #included linux/xattr.h.  It's being
> >> > worked around by patching libcap2 to #include sys/xattr.h
> >> > first, but presumably this will cause other breakages.
> >>
> >> Please follow the accepted practice for fixing coordination between
> >> userspace and Linux kernel headers.
> >>
> >> Upstream glibc and the Linux kernel have already worked out a
> >> mechanical solution to this problem, and we need people to work out
> >> the patches and post them upstream.
> >>
> >> The solution is to coordinate the conflicting headers following this template:
> >> https://sourceware.org/glibc/wiki/Synchronizing_Headers
> >
> > Thanks for the information.  I tested the two patches at
> > http://people.canonical.com/~serge/xattr-kernel-libc-fix/ and they
> > seem to do the right thing.  I'll send them out if they look ok.
> 
> Let me warn you that the glibc patch won't get accepted as-is.
> 
> You are adding a #ifdef for a Linux-specific define in OS-agnostic code.
> 
> Look at: https://sourceware.org/ml/libc-alpha/2013-08/msg00209.html

Yeah I had noticed that that patch (part of the linux part of which
was reverted :) used __USE_KERNEL_*, but I didn't see where that
was defined, and https://sourceware.org/glibc/wiki/Synchronizing_Headers
specifically said to use #if !__UAPI*.

No biggie, if I'm otherwise on the right track, I'll change that before
submitting.

thanks,
-serge

> See how we adjust a Linux-specific header to define an OS-agnostic
> variable to use in the OS-agnostic code e.g. __USE_FOO.
> 
> Cheers,
> Carlos.