Going back to my first error actually might be useful:
In file included from G__PWGCFfemtoscopy dictionary payload:16:
In file included from /cvmfs/alice.cern.ch/el6-x86_64/Packages/AliPhysics/vAN-20190309_ROOT6-1/include/AliAnalysisTaskFemto.h:46:
In file included from /cvmfs/alice.cern.ch/el6-x86_64/Packages/AliPhysics/vAN-20190309_ROOT6-1/include/AliFemtoEventReaderESDChain.h:11:
In file included from /cvmfs/alice.cern.ch/el6-x86_64/Packages/AliPhysics/vAN-20190309_ROOT6-1/include/AliFemtoV0.h:14:
In file included from /cvmfs/alice.cern.ch/el6-x86_64/Packages/AliPhysics/vAN-20190309_ROOT6-1/include/AliFemtoTypes.h:45:
In file included from /cvmfs/alice.cern.ch/el6-x86_64/Packages/AliPhysics/vAN-20190309_ROOT6-1/include/AliFemtoVector.h:35:
In file included from /cvmfs/alice.cern.ch/el6-x86_64/Packages/AliPhysics/vAN-20190309_ROOT6-1/include/AliFmThreeVectorD.h:18:
/cvmfs/alice.cern.ch/el6-x86_64/Packages/AliPhysics/vAN-20190309_ROOT6-1/include/AliFmThreeVector.h:812:1: error: redefinition of 'operator+'
operator+ (const AliFmThreeVector<T> &v1, const AliFmThreeVector<X> &v2)
^
/cvmfs/alice.cern.ch/el6-x86_64/Packages/AliPhysics/vAN-20190309_ROOT6-1/include/AliFmThreeVector.h:812:1: note: previous definition is here
operator+ (const AliFmThreeVector<T> &v1, const AliFmThreeVector<X> &v2)
^
Note the " previous definition is here" line is the same as the redefinition line. There are include-guards around the file.
The source code can be found here: {github} AliFmThreeVector.h (note it is not “my code” so don’t offer suggestions on how it could be cleaned/better organized - I certainly know.)