[fs.op.is.empty]

bool filesystem::is_empty(const path& p);
bool filesystem::is_empty(const path& p, error_code& ec);

Effects:

(1.1)
Determine file_status s, as if by status(p) or status(p, ec), respectively.
(1.2)
For the signature with argument ec, return false if an error occurred.
(1.3)
Otherwise, if is_directory(s):
- (1.3.1)
  Create a variable itr, as if by directory_iterator itr(p) or directory_iterator itr(p, ec), respectively.
- (1.3.2)
  For the signature with argument ec, return false if an error occurred.
- (1.3.3)
  Otherwise, return itr == directory_iterator().
(1.4)
Otherwise:
- (1.4.1)
  Determine uintmax_t sz, as if by file_size(p) or file_size(p, ec), respectively.
- (1.4.2)
  For the signature with argument ec, return false if an error occurred.
- (1.4.3)
  Otherwise, return sz == 0.

31 Input/output library [input.output]