Re: x86_64 and x86 userland

[Ralf Wildenhues]

Hi Noah, others,

Sorry for the long response delay.  And thank you everyone for providing
useful information.

* Noah Misch wrote on Tue, May 03, 2005 at 03:57:07AM CEST:
> On Mon, May 02, 2005 at 10:31:57AM +0200, 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).
> > 
> > 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.
> 
> The compiler generates x86 binaries but defines __x86_64__?  Weird.

Now that you mention it, I don't think it does.  It might just be a bug
in the configuration of the package, but I'm not sure yet.  I'll go and
check this.

> > 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?  
> 
> Maybe.  If the sole purpose of host triplets was to characterize the binary 
> $CC
> produces, then that would be highly appropriate.  They serve other purposes as
> well, though.

ACK.  Others also rightly pointed out that such a change may be
inappropriate (but a config.site entry may just be an easy hack).

Will report back when I have more to report.

Regards,
Ralf