Re: [gentoo-dev] Cross Compilation and Dynamic Slots

[Ilya A. Volynets-Evenbakh]

Here are few of my comments/questions.

Let me try to understand multilib on MIPS example (which is probably 
most complex ABI screw-up case).
For starters, standrard mips toolchain, when compiled with multilibs 
enabled, is capable of producing
binaries for any ABI. At the same time, this imposes specific file 
system layout
(o32 libraries go into /lib /usr/lib /usr/lib/gcc-lib/lib, n32 - /lib32 
/usr/lib32 /usr/lib/gcc-lib/lib32, n64 -
/lib64 /usr/lib64 /usr/lib/gcc-lib/lib64).

On one hand this is good - different ABIs can coexist, and even mix in 
some cases. On the other hand
thus is bad - many programs do not expect to have libraried not in /lib 
/usr/lib places. As it is now,
I have special patch, that makes glibc and gcc use /lib /usr/lib layout 
when using N32 and not using
multilibs.

So, for one thing, we should probably add another variable - ABI - since 
ARCH will be mips in all three cases.

I'm not sure I understand what you mean by

 When keyword matching is 
done, they are search in order of ACCEPT_KEYWORDS and the first match is used 
when sourcing bashrc and when recording the installation into the installed 
package database.

How do we handle the case, where we have two different apps, depending 
on same lib, and
one is requested to be compiled as o32 and another as n32? And in 
general, how do we allow
user to specify which ABI he wants to use for this specific compile (Yes 
- it is possible some
will want to compile different apps with different ABIs - i.e. n32 is 
generally faster then n64
because it has lmaller pointer size, but for that same reason its 
addressing is limited. Thus
in order to utilize all 8G of ram in my origin, I will need certain apps 
to be n64).

I'll have more question later ;-)

    Ilya

>MULTILIB
>
>I'll use amd64 as the example. In the profile, bashrc would set aliases
>defining how to run gcc to create 32bit binaries when ARCH="x86". The
>profile's ACCEPT_KEYWORDS would be "amd64 x86". When keyword matching is
>done, they are search in order of ACCEPT_KEYWORDS and the first match is used
>when sourcing bashrc and when recording the installation into the installed
>package database.
>
>Any packages that the to be installed package depends on will then be
>installed using the accepted keyword.
>
>
>I'm sure there are a few issues remaining here. I think that most of them will
>be much easier to deal with, though. Feedback is greatly welcome.
>
>Regards,
>Jason Stubbs
>
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>
>
>


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