Re: [gentoo-dev] Re: Implicit system dependency

[Andrew Savchenko]

Hi,

On Fri, 14 Nov 2014 07:20:50 -0500 Anthony G. Basile wrote:
> On 11/13/14 23:15, Zac Medico wrote:
> > On 11/13/2014 08:01 PM, Rich Freeman wrote:
> >> On Thu, Nov 13, 2014 at 9:38 PM, Michael Palimaka <kensington@g.o> wrote:
> >>> On 14/11/14 11:06, Rich Freeman wrote:
> >>>> Well, the idea would be to maintain the virtual INSTEAD of @system, or
> >>>> have @system just pull in the virtual and make some arch-specific
> >>>> additions.
> >>> Will that work? Some profiles remove packages from the base @system and
> >>> replace it with their own implementations (eg. BSD).
> >> Maybe.  The thing is that a package either depends on something or it
> >> doesn't.  If it really does depend on something, then the fact that it
> >> isn't available on BSD/etc isn't going to magically make the package
> >> work.  We just loosely define system dependencies in a way that makes
> >> them work 98% of the time, basically accepting that things are going
> >> to break and we get away with it because few of our users actually run
> >> on BSD/etc.
> >>
> >> If it is just a matter of preference then a profile could install an
> >> alternative package that is in a virtual.  However, this won't work if
> >> everybody still uses some convenience virtual that pulls in bash/etc
> >> and the BSD folks don't want to install bash unnecessarily.
> > Maybe I'm missing something, but if you are using virtuals, then you can
> > make the deps conditional on profile forced/masked flags like
> > userland_BSD and userland_GNU if necessary. These behave like normal USE
> > flags, aside from the fact the they are forced or masked by profiles.
>
> Sorry Zac, I posted my reply before I read this.  This is essentially
> the point I was making.  However, I think this will be cumbersome.  With
> the current way we do things, its easy to delete packages from @system
> by just doing '-*sys-apps/man-pages' (for example) in a profile's
> packages file.  It is not so easy to delete from a DEPEND string, so I
> foresee some tricky if logic here.

There is another drawback of using virtuals instead of @system set.
For old systems (in practical terms they are systems not updated
@world for more than several month) it is wise to update kernel,
@system and only afterwards whole @world.

Virtuals will not catch updates in underlying packages if --deep is
not used and it can't be used, because some packages from @system
may indirectly depend on packages from @world (e.g. cairo, qt or
xorg) which will trigger half of the @world update with -D @system
which makes it impossible and impractical to use -D @system before
full @world update on old setups.

We already have this problem with virtua/libc: it is not updated at
all, so when I run emerge -uav @system for the purposes described
above I have to manually add sys-devel/glibc to the list.

If @system will be removed at all, it will be much harder to
perform deep and large @world updates. Practically users willing to
update old systems will have to write and manage @system set on
their own.

Best regards,
Andrew Savchenko