[m-rev.] diff: do not warn about obsolete autoconf macros

[Peter Wang]

On Mon, 07 Jun 2021 15:43:18 +1000 Julien Fischer <jfischer at opturion.com> wrote:
> 
> On Mon, 7 Jun 2021, Peter Wang wrote:
> 
> > On Mon, 07 Jun 2021 15:19:55 +1000 Julien Fischer <jfischer at opturion.com> wrote:
> >>
> >> From autoconf 2.70 onwards, obsolescence warnings are enabled by default.
> >> Recently I have fixed all the warnings we were getting, except for:
> >>
> >> 1. With autoconf 2.70 we get a warning about our use of AC_PROG_LEX;
> >> this cannot be avoided while preserving support for autoconf 2.69
> >
> > Can we use AC_PATH_PROG to search for flex instead?
> 
> The correct fix (as per the comment I added to configure.ac) is to use
> AC_PROG_LEX([noyywrap]), but that's only supported by 2.70+.
> 

If we don't make use of any of the portability checks done by
AC_PROG_LEX (and I think we don't) then we should be able to just search
for flex until we are ready to require autoconf 2.70.

But that's more work, so I don't mind if you just disable the warnings.

> >> 2. Warnings about escaping of quotes and double quotes, like:
> >>
> >>      warning: back quotes and double quotes must not be escaped in:
> >>      $as_me:${as_lineno-$LINENO}: WARNING: cannot find a working \`mkfifo' or \`mknod'
> >>
> >> I haven't (yet) found a way to avoid this warning and get a configure
> >> script that works :-(  Suggestions welcome.
> >
> > Does 'single quotes' work?
> 
> Yes, it works.  Doing that will mean that the configure output will use
> a different quoting style from configure --help (which is fine by me).

Me too. I'm a little surprised configure is still using `this quoting
style'.

Peter