Hi Nick,
>In what sense is the "struct bar" type defined?
None.
I did not say that the "struct bar" type is defined.
It's also not used or referenced.
>Because if "struct bar" is not defined, then how can "struct bar *" be defined?
The definition of "struct bar*" is not dependent upon the definition of "struct bar".
Pointers are fundamental data types.
>Is it ok to to have pointer-type whose base type is not (or incompletely) defined?
Assuming you are using "base type" in a contextually liberal sense for "reference type", instead of the inheritance sense of C++...
Yes, it's ok -- for a lot of operations. What you are dealing with is a pointer. A pointer is a fundamental data type.
What you cannot do is increment/decrement the pointer, use array access, or access the (undefined, unknown) members, or dereference the pointer in any other fashion[1].
--Eljay
[1] Well, you can dereference it using casting techniques to a defined, known type. But that's slight-of-hand.
