Could you not go with standard iostreams for log4cxx then? I mean, given that iostreams tend to be entirely in headers, it seems like you could compile log4cxx with an iostreams library independant of what your customers have.
At least for the Microsoft platform, you are not allowed to mix old and standard iostream include files within a single executable or DLL. See http://msdn.microsoft.com/library/default.asp?url=/library/en-us/ vccore98/html/_core_differences_in_iostream_implementation.asp.
However, it think it is possible for an old iostream using application to use a DLL that uses standard iostream as long as the API does not involve any iostream types and the API include files don't include any iostream headers. I haven't had time to check it, but I think it is pretty likely that the API-level log4cxx include files likely include standard iostream library headers which would cause compile errors in calling applications that used old iostreams.
