bool is_block_file(file_status s) noexcept;
Returns: s.type() == file_type::block.
bool is_block_file(const path& p);
bool is_block_file(const path& p, error_code& ec) noexcept;
Returns: is_block_file(status(p)) or is_block_file(status(p, ec)), respectively. The signature with argument ec returns false if an error occurs.
Throws: As specified in [fs.err.report].