@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.