[AD] anonymous unions in C

["Peter Hull" <peterhull90@xxxxxxxxxx>]

Are anonymous unions allowed in standard C? I ask because there is one
in fshook-stdio.c, line 333
struct ALLEGRO_FS_ENTRY_STDIO {
...
   union {
      FILE *handle;
      DIR *dir;
   };
...
};

AFAIK it isn't, but from a bit of googling it seems like gcc and msvc
both allow it. Unfortunately I haven't got a proper reference book and
I'm a bit hazy on what's C89, C99 or whatever.

Pete