Re: [gentoo-dev] Dynamic Modularization

[Paul de Vrieze]

On Tuesday 02 August 2005 08:45, Keziah W wrote:
> Hi all,
> I got this idea and I'm not sure if it would be feasible, but if it is,
> it could lead to many Cool Things:
> Is there any reason not to have dynamic libraries for most of the
> changes made by USE flags, that are used only if present, and then the
> USE flags would just specify whether to compile that library?
>
> That way, one of the benefits would be that USE flags could be changed
> on the fly, and the whole system could be tweaked with minimal
> recompilation... but probably the biggest benefit would be the
> programming paradigm shift that this could affect, by pushing the
> packages toward a more dynamic, client-server module where the
> different parts of the package have separate purposes that they each
> independently achieve.
> This way, it could also make development a lot easier.
> As an example, lets use some fictional package "quux" that has optional
> support for Kde or Gnome.
> the quux-kde library and the quux-gnome library could be
> interchangable, and, from the point of view of the quux-core code, the
> same, allowing one programming interface to apply to both. Changes to
> quux's main system would just be in quux-core, and quux-kde and -gnome
> could remain the same, while if gnome support needed improvement, it
> would just be a matter of improving the quux-gnome library, with no
> risk of breaking the main system or causing undesired results
> elsewhere.
> This would also allow for more shared code, because two packages could
> use the same library in some cases.
>
> So, what do you think?

What you think about shows incomplete knowledge of the shared library 
system. In short you propose a plugin architecture. This is possible 
(though slower), but only if the application source actually is written 
to encompass this. The way dynamic libaries are normally used is just as 
if the code were internal to the application. With plugins (dlopened) it 
works with pointers to functions in some way. This means a layer of 
indirection, and the necessity for the program to be able to cope with 
the absense of said library. In short it is an option more appropriate 
for upstream to perform. In many cases it is just not appropriate. Global 
application of such a system is impossible though.

Paul

-- 
Paul de Vrieze
Gentoo Developer
Mail: pauldv@g.o
Homepage: http://www.devrieze.net