Re: AC_DEFUN_ONCE semantics

[Ralf Wildenhues]

Hi Eric,

* Eric Blake wrote on Mon, Jan 26, 2009 at 06:09:28PM CET:
> * lib/m4sugar/m4sugar.m4 (m4_defun_once): Rewrite to be no-op,
> rather than warning, on second use, and make sure first use never
> occurs out of order.

This means that the user may practically never directly call a
defun_once'd macro within a shell conditional, right?  Sounds
like a backward incompatibility to me, hopefully a small one.

Thanks,
Ralf