The error message is clear: at the point the compiler encounters sizeof(struct Node) (or sizeof(nd), or whatever...) it doesn't know the size, because the complete declaration of struct Node is missing.
You could post the relevant code, in order to get better help.
"In testa che avete, Signor di Ceprano?"
Got two items to ask. First, is there a library available for c++ mfc that can write results to PDF?. libHARU is deoendent on zlib , libpng, etc. Like to try something more straight forward and free. secondly, is there a possibility to save a CDialog to PDF file?.