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Re: [Gnu-arch-users] Features command for arch

From: Matthieu Moy
Subject: Re: [Gnu-arch-users] Features command for arch
Date: Fri, 03 Sep 2004 00:03:50 +0200
User-agent: Gnus/5.1002 (Gnus v5.10.2) Emacs/21.2 (gnu/linux)

"Robert Anderson" <address@hidden> writes:

> I haven't really been keeping up with this discussion, but isn't
> all of this what 'configure' and configure scripts are for?

autoconf is an interesting hack that will allow you to deal with
software not having the feature proposed here.

For example, look at the way automake computes dependancies : It has a
knowledge base saying roughly

* With gcc < 3.0, do the first way,
* With gcc > 3.0, there are better features. Do another way,
* With Intel's compiler, there's a third way to do it,
* ...

It would be much easier for automake if it could just say

if ${CC} --has-feature "interesting feature like gcc 3.0"
   Do this way
   Do another way

No need for a specific knowledge base about different versions of your
tool to change the behavior of your software, but this requires
standardization of the "--has-feature" command in all possible ${CC}.

Furthermore, there are a number of contexts where the "features"
feature would be usefull, and where autoconf doesn't apply. For
example, if tla becomes extensible through an embedded language, then,
the language could have access to this information. A package written
to be portable could be used on several versions of tla without
recompilation/reconfiguration/... Considering a branched development
of tla, some code of tla could also use "features" to adapt itself to
another portion of code of the same executable. (then, you can't
detect automatically wether you have feature X at configure time,
because you don't have the executable yet)

Another example : you installed a tla front-end, and afterwards, you
upgrade/downgrade your version of tla. Then the front-end could adapt
itself to the new version of tla without having to re-run configure.


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