Hello,

It seems you don't have created a project associated to your C++ file.
QMake requires a particular file your_project.pro, to be able to generate the Makefile.
Did you create a new project in QDevelop, containing your sources ?

You can generate automatically this project file with Qmake, in your project directory, or create a new project with QDevelop.

Command line : qmake -project your_directory

Hope this helps, and that I am clear too

Guilugi.