I was wondering:
If I have structure definitions, for example, like this:
struct Base { int foo; }; struct Derived { int foo; // int foo is comm
As you seem to be aiming at Object Oriented Programming in C I can suggest you to have a look at the following link:
http://www.planetpdf.com/codecuts/pdfs/ooc.pdf
It goes into detail about ways of handling oop principles in ANSI C.