Darwin Version

[Bachsau]

Brandon Allbery wrote on 02.10.2015 15:52:
> Dependencies. Port X compiles against new libSystem, depends on port Y
> that was linked against old libSystem, link fails because it tries to
> bring in both versions and they conflict. (Keeping around old libSystem
> versions is how you can still run applications built for 10.5 on
> 10.10/10.11.)
>
> This doesn't happen on Linux because glibc is obsessive about
> maintaining backward compatibility interfaces, so the older program
> links against the current glibc and uses compatibility interfaces from
> it; this works even for libraries. Apple doesn't care about backward
> compatibility enough to do things that way.
>

Thanks for this detailed answer. I might have been somewhat rude because 
I just didn't fully understand what the problem is. One reason I don't 
like the idea of recompiling everything is time, the other one being 
that I did some things to integrate macports into my system, like 
setting my shell to its bash and prefering it in /etc/paths, probably 
some other things I don't remember yet. I just wanted to avoid some trouble.