> My guess for the real problem at hands is that for either direction of 
> dependencies ("up" using +REQUIRED_BY or "down" using @depends lines and 
> whatnot in +CONTENTS files), they only give data for one level, and care 
> needs to be taken to walk the tree recursively.
> 
> AFAIK this was never implemented for the places of pkgsrc and pkg_* when 
> that change was made in pkgsrc, and it _may_ be the problem at hands.

I already recurse things, when new dependencies are added, they are
considered as a new pkg to upgrade so I find pkgs depending on it.
And yes, parsing a text file is _much much_ faster than calling make,
but if I can solve many problems using make, I'm open to suggestion.
I think the good way is to do "up" method, when you want to upgrade
gtk+, the dependencies that matter are sylpheed, not xorg...

In this little prog, one package is one object, and adding some kind of
cache to properties (for them to be computed once) is _very_ easy, just
it adds code, and now the only researched behaviour is correctness, not
speed.

One solution could be to call show-var VARNAME=DEPENDS on *all*
packages who are in /var/db/pkg and then do the job with reverse
information built... do you think it will be better ?

Thanks for all your comments :)

Fabien Devaux.