Invalid makefile generated for projects whith files with the same name in separate directories

Imagine you have a project with two .cpp files in separate folders, for instance:

  1)  generate/workflow.cpp

  2) dataflow/workflow.cpp

These two files are listed in the .pro project file as source files.

When you build the project, the same ouput workflow.o is generated for both files, which means that one of the file appears to not be compiled at link time, which leads to undefined symbols.

The workaround is of course to rename one of the file, but I lost many hours scratching my head about this problem.
Please note that this may occur with file names that differ by the case of some chars. Linux file system, being case sensitive, is not affected in that particular case.