Re: Partial autoconf transition thoughts

[Nathanael Nerode <neroden@twcny.rr.com>]

Alexandre said:
>I.e., assume you're always cross compiling?  That would be a
Actually, assume you're always Canadian cross compiling. :-)  Except 
when you aren't.

>reasonable approach too, but there are some tests that you can't
>possibly do in the cross case, autoconf lets you actually do them in
>the native case as long as you set a safe default or alternate test
>for the cross case.

And when I write my own tests for these circumstances, I would guard 
them by one of build=host or build=target, depending on which is correct 
under the circumstances.  

This generally tests in the correct situations, and is if anything too
conservative (assuming untestability when build=i686-pc-linux-gnu 
and host=i386-pc-linux-gnu).

I suppose the idea behind the proposal is that you can always 
force nativeness by not specifying 'host' (since it defaults to build); 
but there's no clear way to force 'crossness' when host=build.

But why would you *want* to?

Perhaps you have two machines with the same canonical name, but 
differing in the particular feature.  This is most likely due to a bug 
in config.guess or config.sub, which is Not Autoconf's Problem.  

Otherwise, the feature is probably one where I don't *want* autoconf to 
decide based on my particular build machine; it will presumably make 
the produced program quite unportable, and will likely break if I make 
some small change to my machine's configuration.  Such a feature 
probably deserves its own --with option and notes in the documentation, 
and should certainly be defaulted to the 'baseline' option, not to 
whatever's on my machine today.

So the only use case I can think of for 'forcing crossness' when 
build=host depends on either bugs in config.* or poor 'configure' 
design.

Hmm.  Now who should I say this to?

Akim, I guess, but he still hasn't done anything with the autoconf patch 
I sent him a long while ago.

--Nathanael