[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: The load path
From: |
Rob Browning |
Subject: |
Re: The load path |
Date: |
Sun, 07 Nov 2004 15:16:50 -0600 |
User-agent: |
Gnus/5.1006 (Gnus v5.10.6) Emacs/21.3 (gnu/linux) |
Neil Jerram <address@hidden> writes:
> Agreed. I'd just note that versioning also has to cope with the case
> where an add-on package A also provides an interface that further
> packages {B, C, ...} may use, so there is also a requirement for
> handling multiple installed versions of A, and for {B, C, ...} to be
> able to get the version that they need.
>
> Unfortunately, I have no idea at this point how to solve such a
> problem!
One of the simplest ways I can think of to handle this (athough it's
not all that pretty) is for packages to just put something like a
"soname" in the module name. i.e. (use-modules (foo-1)). Then when
the API changes incompatibly, the author just changes the module name
to foo-2. This is already the best way to solve the dynamic linking
problem, given the currently available dynamic linking facilities like
libltdl. i.e. (dynamic-link "libfoo-2").
As far as use-modules is concerned, I can also imagine adding
something fancier like (use-modules (foo #:version 4)), which might
have more sophisticated semantics (like ld.so or something else).
There's a further complication if you want to try to handle problems
created when only some of the packages on a system have been upgraded
and there are multiple levels of dependencies,
A -> B -> D (-> means "depends on")
A -> C -> D
but the currently installed version of B depends on a different
version of D than the currently installed version of C. This is also
a problem in the shared library arena, and as far as I know the
primary solution right now is to just say "don't do that". A
distribution like Debian tries to make sure that the transition period
where such situations exists is a short as possible and only happens
in unstable (and maybe testing).
In any case, I suspect all of this will be the subject of some future
discussion.
--
Rob Browning
rlb @defaultvalue.org and @debian.org; previously @cs.utexas.edu
GPG starting 2002-11-03 = 14DD 432F AE39 534D B592 F9A0 25C8 D377 8C7E 73A4
- Re: The load path, (continued)
- Re: The load path, Andreas Rottmann, 2004/11/05
- Re: The load path, Greg Troxel, 2004/11/05
- Re: The load path, Neil Jerram, 2004/11/05
- Re: The load path, Rob Browning, 2004/11/06
- Re: The load path, Andreas Vögele, 2004/11/06
- Re: The load path, Neil Jerram, 2004/11/06
- Re: The load path, Rob Browning, 2004/11/06
- Re: The load path, Neil Jerram, 2004/11/07
- Re: The load path,
Rob Browning <=
- Re: The load path, Paul Jarc, 2004/11/09
- Re: The load path, Andy Wingo, 2004/11/11
- Re: The load path, Greg Troxel, 2004/11/11
- Re: The load path, Neil Jerram, 2004/11/12
- Re: The load path, Greg Troxel, 2004/11/12
- Re: The load path, Rob Browning, 2004/11/12
- Re: The load path, Greg Troxel, 2004/11/13
- Re: The load path, Neil Jerram, 2004/11/14
- Re: The load path, Greg Troxel, 2004/11/14
- Re: The load path, Neil Jerram, 2004/11/18