static bool sync_with_stdio(bool sync = true);The static member function stores a stdio sync flag, which is initially true. When true, this flag ensures that operations
on the same file are properly synchronized between the iostreams functions and those defined in the Standard C library.
Otherwise, synchronization may or may not be guaranteed, but performance may be improved. The function stores
sync in the stdio sync flag and returns its previous stored value. You can call it reliably only before performing any
operations on the standard streams.