[boost] [filesystem] On POSIX, any reliable way to find file size?

There have been requests for a Boost.Filesystem function which returns file size. But I don't want to provide such a function if it will be unreliable. On POSIX compliant 32-bit systems, is there any reliable way to find the size of a file? It looks to me as if stat::st_size's type of off_t isn't large enough on 32-bit systems to cope with large file sizes. Am I wrong, or missing something? How big is the largest possible file on, say, Linux? Isn't it larger than the 2 gigs a 32-bit signed integer can represent? --Beman