Thanks Nicol. Your answer looks to be bang on the money. I believe that the developer simply wanted to 'add' a few member variables to an existing struct, and used inheritance exactly as you suggest to expose the base class's members. Your improved syntax for the assignment is much appreciated.

@rwong Nope, no constructors; just member variables in both.

@Deduplicator: alas, it doesn't work (at least not in MSVC): no acceptable conversion.