[gentoo-user] Running programs compiled with a different gcc version

[Urs Schutz <u.schutz@bluewin.ch>]

Yesterday I manually compiled photivo, a camera raw file
converter and image editor. One of the requirements for
installing is gcc 4.6. So I manually unmasked gcc 4.6.3
and installed it with portage.
After switching gcc with gcc-config and . /etc/profile,
photivo compiled fine.
A test run showed that photivo is running fine.

I simply do not know enough about gcc and gentoo to leave
gcc at 4.6.3, and switched back to the stable 4.5 branch
(gcc-config and . /etc/profile again).

When I try to run photivo again I get an error:
photivo: /usr/lib/gcc/i686-pc-linux-gnu/4.5.3/libstdc++.so.6:
version `GLIBCXX_3.4.15' not found (required by photivo)

locate -i glibcxx shows no results.

My question is: Can I set some variables (e.g. in a bash
start script) that photivo thinks it is running on a system
with gcc 4.6? All the components are installed, as I can
switch gcc to 4.6.3 and run photivo as user.

I do not see any changes in environment variables before
and after switching gcc versions. What magic does
gcc-config do?

Urs