[gentoo-user] multiple gcc versions

[Matthias Langer]

I'm mainly in x86 and thus using gcc-3.3.6. However, as i do some
programming, i want to know if it is without greater problems possible,
to install gcc-3.4.4 additionally, so that i can make sure that the code
i'm writing is accepted by gcc-3.4.x too [i know that i can't expect my
code to work, as it is c++ stuff and the libs i'm using are compiled
with 3.3.6 - i only want to be sure that the code compiles cleanly].

Thanks,
Matthias Langer
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[Peter O'Connor]

It shouldn't be too much of a problem since they are different branches
of gcc and should be default install side by side. I run 3.4.4-r1 and
when I pretend to install 3.3.6

# emerge -p =gcc-3.3.6
[ebuild NS ] sys-devel/gcc-3.3.6

(from man emerge)
N = new, (not yet installed)
S = new, slot installation (side-by-side versions)

First of all you would need to make the 3.4.4 version available

echo "sys-devel/gcc ~x86" >> /etc/portage/package.keywords

Then try # emerge -p gcc to test how it will install the new version. If
it shows NS, it won't remove 3.3.6 at all. Otherwise you may want to
hold off installing.

Use gcc-config -l to check what version it is using after the install
and make sure it's set for 3.3.6, otherwise change it (that is assuming
you are still wanting 3.3.6 as default).

Depending on how you compile your programs you can use the gcc-3.4.4 and
g++-3.4.4 (ie g++-3.4.4 -o foo foo.cc) commands if you do it manually.

Or else you can use gcc-config to set 3.4.4 before compiling your code
to test if it compiles and then change back to 3.3.6 when you're done.
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