-extern int system (const char *);
-
-static int os_init (host_callback *);
-static int os_shutdown (host_callback *);
-static int os_unlink (host_callback *, const char *);
-static long os_time (host_callback *, long *);
-static int os_system (host_callback *, const char *);
-static int os_rename (host_callback *, const char *, const char *);
-static int os_write_stdout (host_callback *, const char *, int);
-static void os_flush_stdout (host_callback *);
-static int os_write_stderr (host_callback *, const char *, int);
-static void os_flush_stderr (host_callback *);
-static int os_write (host_callback *, int, const char *, int);
-static int os_read_stdin (host_callback *, char *, int);
-static int os_read (host_callback *, int, char *, int);
-static int os_open (host_callback *, const char *, int);
-static int os_lseek (host_callback *, int, long, int);
-static int os_isatty (host_callback *, int);
-static int os_get_errno (host_callback *);
-static int os_close (host_callback *, int);
-static void os_vprintf_filtered (host_callback *, const char *, va_list);
-static void os_evprintf_filtered (host_callback *, const char *, va_list);
-static void os_error (host_callback *, const char *, ...)
-#ifdef __GNUC__
- __attribute__ ((__noreturn__))
-#endif
- ;
-static int fdmap (host_callback *, int);
-static int fdbad (host_callback *, int);
-static int wrap (host_callback *, int);
-