Re: x86_64 and x86 userland

[Harald Dunkel]

Ralf Wildenhues wrote:
> I have a question regarding systems with more than one ABI, specifically
> x86_64.  If you consider for example the Debian distribution which has a
> x86_64 kernel, but a completely x86 userland, config.guess still gives
> you x86_64-unknown-linux-gnu as output.  (I have been told this, but not
> tried it myself).
> 

What do you mean by "a completely x86 userland"?

I am running Debian (amd64) on my PC at home. There are no
32bit applications on it. AFAIK this is different to some
other major Distros claiming "amd64".

_Optionally_ I can install 32bit libraries on Debian. But
there are several problems with this. Some libraries are
missing (e.g. qt and dsub, breaking Skype). Most of the
32bit libraries are in a bulky mega package "ia32libs".

> Now, if you configure a package and forget to add
>   --build=i686-pc-linux-gnu
> or maybe use the setarch tool to set personality (I do not even know how
> portable/available this is -- it exists in RedHat Fedora), it may break,
> e.g. because of the __x86_64__ preprocessor define.
> 
> Would it not make more sense to have config.guess return i686 instead of
> x86_64?  Is it just too late to make that change now?  How would it even
> be possible to detect a completely 32bit userland?
> 

I would say that config.guess is right by returning
x86_64. If it would return i686, then the build system
would incorrectly assume that the machine provides a
32bit development environment.

IMHO the 32bit world is not the "native environment" of
the amd64 CPU.


Just my $0.02.


Regards

Harri