[C] struct, function pointers question

Hi, I've got certain way to do something, but can't get it to compile. This relevant source is attached, I really expected it to compile... The errors are: struct_question.c: In function `some_function': struct_question.c:23: arithmetic on pointer to an incomplete type struct_question.c:23: parse error before `{' I'm desperate... Can someone give me some pointers? (possibly literally ;-) --jeroen begin 666 struct_question.c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` end