On Sat, 8 Oct 2011 11:33:07 +0000
Sven Vermeulen <swift@g.o> wrote:

> Hi guys
> 
> There is some FUD regarding GCC upgrades and I don't have the proper
> knowledge to write a correct document on GCC upgrades. As you are currently
> aware, we have a GCC upgrade guide [1], but it has seen its last update in
> 2008. Since then, things have undoubtedly changed.
> 
> What I can find on GCC upgrades and their apparent need (or no-need) for
> rebuilding stuff:

There are some packages that all need to be built with the same version of
GCC. The whole qt-* family is an example, or at least it was a year ago
(I'm not using KDE any more).  Luckily they tend to be bumped as a unit.

The biggest problem is building stuff with a newer version of gcc than the
"system" version, either outside of portage, or selectively changing back
with gcc-config.  Programs can get linked to symbols in (usually)
libstdc++.so.6 that have a symbol version that doesn't exist in the previous
release.  When you switch back to using that release as your system compiler,
the libstc++ library also gets switched out, and suddenly your
gcc-4.6-compiled firefox won't launch.  If you've ever gotten a bug report
like "libstdc++.so.6: version `GLIBCXX_3.4.15' not found" then you've dealt
with this.

This isn't a problem most users encounter, but some do like to try to rebuild
some of their system a bit at a time, and this is the reason why I usually
recommend they rebuild everything.  By making it an all or nothing affair,
they're less likely to try hopping back and forth between versions.


-- 
fonts, gcc-porting,                  it makes no sense how it makes no sense
toolchain, wxwidgets                           but i'll take it free anytime
@ gentoo.org                EFFD 380E 047A 4B51 D2BD C64F 8AA8 8346 F9A4 0662