@mrjj No I don't have a .pro file so I am opening using a .qbs file @Bagavathi I have done as you said, and that has worked. (i.e. Upgrading gcc/g++ ) In the meantime I also discovered ( I am on Ubuntu ), that using command-line and 'make' works fine for all projects. So I am sorted. Thanks very much for your help. :-) John Montgomery, Glassel, Scotland.