Reinstall all ports after Xcode 4.1 -> 4.2 upgrade?

[Christoph Deil]

Hi,

I just updated XCode from 4.1 to 4.2 on Lion.
Do I have to reinstall all ports because the XCode compilers changed?
( I did follow the migration guide and reinstalled everything when I switched to Lion. )

I'd also be interested to understand why exactly this is / isn't necessary, given that ports are built with the Macports compilers, but these themselves are build with the XCode compilers.

Thanks!
Christoph