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Date: Thu, 3 Mar 2016 11:10:06 +0100
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: iproute2 & other software
* Rich Felker <dalias@...c.org> [2016-03-02 18:30:50 -0500]:
> On Wed, Mar 02, 2016 at 09:49:41PM +0100, Szabolcs Nagy wrote:
> > * Loganaden Velvindron <loganaden@...il.com> [2016-03-02 19:19:13 +0000]:
> > > "
> > > Sorry, I have to reject this.
> > > All include files in include/linux come from headers automatically
> > > generated from upstream
> > > Linux source. This is the only way to ensure long term ABI/API consistency
> > > with kernel.
> > >
> > > Either fix musl or submit patches to upstream kernel and get them merged.
> > > "
> > >
> > > Can we look into providing somekind of compatibility layer for header files
> > > so that it's easier to get upstream projects like iproute2 to support musl ?
> > >
> >
> > in theory the correct solution is to fix the kernel headers
> > so they don't collide with posix types in libc headers.
> >
> > in practice old kernel headers should work too and it's unlikely
> > that a complete uapi fix would be accepted into linux any time
> > soon so applications should avoid including both libc and kernel
> > headers into the same tu.
> >
> > unfortunately glibc added workarounds into libc and uapi headers
> > that make it seem as if mixing linux and libc headers work, so
> > now application programmers don't have the incentive to fix this.
> >
> > musl cannot use the same workarounds because they use ifdef __GLIBC__
> > (which is a major bug for linux uapi headers to depend on):
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/libc-compat.h
>
> Would it help for us to define the __UAPI_DEF_* macros? If so I'd be
no, because they are defined unconditionally in libc-compat.h,
however we could define _UAPI_LIBC_COMPAT_H to make the conflicting
type definitions disappear.
but that is still fragile: any libc header would disable all
typedefs, while in glibc the checks are more fine grained.
we could also submit a linux patch to make the non-__GLIBC__
case more reasonable (e.g. check for existing definition of
the macros).
> happy to look at a patch doing that. I don't think we should honor
> them for suppressing definitions in libc (i.e. for supporting
> inclusion of uapi headers _before_ libc ones) but it seems like we
> could support inclusion of the uapi headers _after_ libc ones by doing
> this with very little effort or maintenance cost.
>
> Rich
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