Re: [gentoo-dev] Support for multiple ABIs for amd64 (64bit,32bit) in multilib overlay

[Robin H. Johnson]

On Sun, Oct 18, 2009 at 10:26:37PM -0400, Mike Frysinger wrote:
> On Sunday 18 October 2009 14:49:09 Thomas Sachau wrote:
> > Robin H. Johnson schrieb:
> > > On Mon, Oct 12, 2009 at 04:50:23PM -0400, Mike Frysinger wrote:
> > >> what exactly does this "lib32" do ?  naming USE flags according to
> > >> specific ABI implementations is a bad idea.  you have to forget special
> > >> casing anything to "lib32 vs lib64".  amd64, while the most common, is
> > >> hardly extensible.  we must handle multiple ABIs which easily might have
> > >> the same bitsize.
> > >
> > > The canonical example for this does still remain MIPS I believe.
> > >
> > > The most common ABIs in MIPS are:
> > > o32, n32 - Both in Gentoo releases
> > > n64 - Was experimentally done in Gentoo
> > > (default-linux/mips/2007.1-dev/generic-be/n64) o64, eabi, meabi, nubi -
> > > Not sure if they were were ever released in any way.
> > >
> > > Crossdev DOES support the full swath of these last I checked it.
> >
> > There is a difference between creating a toolchain and supporting all
> >  packages for that arch and every possible ABI you can crosscompile.
> >
> > Currently i only support amd64 since thats the only ARCH i know and have
> >  access to. If i get enough details to implement other ARCHes and some way
> >  to test it there, i might try it for those other ARCHes too.
> we're not asking you to implement support for these ABIs, just to keep in mind
> that any implementation that does not scale and/or hardcodes to a single set
> of ABIs isnt a proper solution
My main objection thusfar is hardcoding the names as lib64/lib32.

Is there any specific reason you're using the content of the
LIBDIR_${ABI} variable? Maybe using the $ABI string as the USE flag
would be better, in some form of USE_EXPAND manner (cannot use them raw
as I believe we still have some code in the form of 'use $ARCH', which
might not behave sanely if say both amd64 and x86 were set.

Egs:
multilib AMD64:
USE="abi_x86 abi_amd64"

Multilib PPC64:
USE="abi_ppc abi_ppc64"

Multilib MIPS (SGI hardware)
USE="abi_n32 abi_n64"

Possible valid multilib sets on MIPS are:
[n32,n64] - at least one Gentoo system like this has been built.
[o32,o64]
[eabi,meabi] - docs fuzzy
[nubi]

-- 
Robin Hugh Johnson
Gentoo Linux: Developer, Trustee & Infrastructure Lead
E-Mail     : robbat2@g.o
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