On Tuesday, June 9, 2015, Peter Stephenson <p.stephenson@samsung.com> wrote:
>
>
> I can't remember why POSIX_ARGZERO isn't on, or even if there was
> actually a reason.
>
>
The doc actually does explain this, for once.

For compatibility with previous versions of the shell, emulations use
NO_FUNCTION_ARGZERO instead of POSIX_ARGZERO, which may result in
unexpected scoping of $0 if the emulation mode is changed inside a function
or script.