Translations:Upgrading GCC/47/en
From Gentoo Wiki
If you are upgrading to GCC 4.1, or GCC 5.1, you would probably encounter ABI issues. To prevent this, the revdep-rebuild command should be run against the libstdc++.so.5 library when moving from GCC 3 to GCC 4.1, or libstdc++.so.6 when moving from GCC 4 to GCC 5.1.