Re: iconv.m4: avoid warning

[Bruno Haible]

Hi Eric,

> Typo in the ChangeLog; s/AM_DEFUN_ONCE/AC_DEFUN_ONCE/

Oops. Fixed now. Thanks.

> > +m4_version_prereq([2.64],[AC_DEFUN_ONCE],[AC_DEFUN])([AM_ICONV],
> 
>  ... rather than have a version check, I'd rather see:
> 
> m4_ifdef([AC_DEFUN_ONCE],[AC_DEFUN_ONCE],[AC_DEFUN])([AM_ICONV],

Remember that AC_DEFUN_ONCE existed all the time in autoconf, since 2.52
or earlier, but it was not really usable before 2.64. (See autoconf/NEWS.)
With this m4_ifdef, equivalent to an unconditional use of AC_DEFUN_ONCE,
users of autoconf < 2.64 without gnulib would encounter warnings that
they have not seen so far.

> That's great for gettext, where you don't require autoconf 2.64 but also
> don't guarantee AC_DEFUN_ONCE.  But what about for gnulib, where we
> guarantee that even with autoconf 2.59, we have a working AC_DEFUN_ONCE?

I don't see how to test for a new vs. an old definition of AC_DEFUN_ONCE.
Therefore these users will have a warning occasionally. But users of gnulib
tend to live on the "bleeding edge" and can afford to install autoconf 2.64.

Bruno