The echo utility shall not recognize the "--" argument in the manner specified by Guideline 10 of XBD Utility Syntax Guidelines; "--" shall be recognized as a string operand.

All builtin commands other than ‘echo’ and precommand modifiers, even those that have no options, can be given the argument ‘--’ to terminate option processing. This indicates that the following words are non-option arguments, but is otherwise ignored. This is useful in cases where arguments to the command may begin with ‘-’. For historical reasons, most builtin commands (including ‘echo’) also recognize a single ‘-’ in a separate word for this purpose; note that this is less standard and use of ‘--’ is recommended.