Hello, xdrawchem too seems incompatible with openbabel 3:
xdrawchem/ioiface.cpp: In member function ‘void IOIface::convertToChemData()’: xdrawchem/ioiface.cpp:122:21: error: invalid use of incomplete type ‘class OpenBabel::OBBond’ 122 | atom1 = bond->GetBeginAtom(); | ^~ ... xdrawchem/ioiface.cpp: In member function ‘bool IOIface::convertToOBMol()’: xdrawchem/ioiface.cpp:275:13: error: aggregate ‘OpenBabel::vector3 v’ has incomplete type and cannot be defined 275 | vector3 v; | ^ xdrawchem/ioiface.cpp:276:12: error: aggregate ‘OpenBabel::OBAtom atom’ has incomplete type and cannot be defined 276 | OBAtom atom; | ^~~~ Best, Andrius