FILE (ab)use

FILE is an opaque object:
stdio interface depends only on the pointer
copying FILE is explicitly implementation defined behaviour
DragonFly slightly violates ISO C99: FILE is incomplete
catches many abuses (misc/screen for example)
stdin, stdout and stderr can be implemented in different ways
NetBSD has FILE foo[3], stdin == &foo[0]
DragonFly has FILE *stdin => invalid for file scope assignments