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From: Andrey Moshbear <andrey.vul@gmail.com>
Date: Tue, 15 Nov 2011 14:36:11 -0500
Message-ID: <CAFnZeoTVtgcAJyyQfuhUvsH00TpMb50PQ1pJJy_TMoMXEWqzCw@mail.gmail.com>
Subject: Re: [gentoo-user] Upgrading gcc: both 4.4 and 4.5 needed?
To: gentoo-user@lists.gentoo.org
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On Tue, Nov 15, 2011 at 13:58, Jarry <mr.jarry@gmail.com> wrote:
> Hi,
> today I upgraded gcc from 4.4.5 to the last stable version
> 4.5.3-r1. I followed "Gentoo GCC Upgrade Guide":
>
> # emerge -uav gcc
> # gcc-config 2
> # env-update && source /etc/profile
> # emerge --oneshot libtool
>
> # emerge --depclean
> # revdep-rebuild
>
> But at the and I noticed gcc 4.4 has not been unmerged
> and my "world" file is somehow larger. To my surprise,
> it contains these lines:
>
> sys-devel/gcc
> sys-devel/gcc:4.4
>
> I did full backup before, so I compared world-file before
> and after gcc-upgrade just to find out, these two lines
> have been really inserted now, during gcc-upgrade. And my
> question is: what does it mean? Does my system need now
> both gcc 4.4 and 4.5? Why is actually gcc in world-file,
> when it is part of system?
>

Because your forgot the -1 / --oneshot flag when manually upgrading gcc.
However, in system, multiple gcc slots do  not exist, so if you need gcc:4.4 for
backwards compatibility or gcc:4.6 for forwards compatibility, it'll show up in
your world file.