Hi,

I'm building a Qt project with QtCreator and wanted to use some old self-made headers for often used functions.

After including them via:
Qt Code: 
  1. #include "myHeader.h"
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I got some freaky errors containing
undefined reference to...
undefined reference to vtable...
Well, I know now, that I have to add the full path of my included headers AND the corresponding source files to the project-file.
Now, the included headers & sources are also shown in the treeview of QtCreator.

Well, what I'd like to know is: Why do I have to include these files like "normal" files of the project? I mean, I also include many other headers like <QApplication>, <QMessageBox> and so on. Why doesn't linker throw errors on these files too when I don't include them explicitly like I have to with my own headers/sources?

If someone could answer me this (simple) question?

Thank you in anticipation!
Binary