GammaLib

If you are using a a mac and installed the most recent update of OSX 10.9 (Mavericks), gammalib won’t compile anymore and the python bindings do not work either. This is due to a new compiler in Xcode 5.0.1 (which comes with the Mavericks update). The low level virtual machine (llvm) version has been changed to version 5.0. This implies that all packages you have installed on your mac are outdated and have to be recompiled with the new version (this includes e.g. the gcc compiler).
If you are using macports, there is a nice way to easy let this work getting done for you:
First update you macports definition by:

$ > sudo port selfupdate

then update all your old ports by typing:

$ > sudo port upgrade outdated

This update will stop with an error message about the llvm version. To continue, you have to remove this version and all its dependencies:

$ > sudo port uninstall —follow-dependents llvm-3.1

After finishing, rerun the following command:

$ > sudo port upgrade outdated

Note, that all this took me up to 4h. So consider doing this in parallel to something else