Re: [PATCH] Add an XSI replacement for func_split_short_opt.

[Ralf Wildenhues]

Hi Gary,

* Gary V. Vaughan wrote on Tue, Jun 29, 2010 at 05:09:29PM CEST:
> On 29 Jun 2010, at 21:03, Eric Blake wrote:
> > Ultimately, I'd like to fix m4sh to make it easier to probe/require XSI
> > support, but that will have to wait until after autoconf 2.66.
> 
> While that might turn out to be useful elsewhere (I wrote a quick esyscmd
> to check for the things that Libtool needs, so it's not difficult in
> principle), it's not useful for Autotools as things stand right now, since
> m4sh generally runs on the developers machine to generate scripts that are
> shipped and executed on the user's shell.
> 
> It might be nice if a future Autotools does the m4sh->sh generation from
> some AC_macros that expand at distribution time but are still executed on
> the user's machine - but then we are requiring that the user have modern
> GNU m4 available, which might not be smart.

I think m4sh can simply use code like

  if ( eval '$smart_works' ) >/dev/null 2>&1; then
    func_foo () { smart code; }
  else
    func_foo () { safe code; }
  fi

for code run a handful of times, without need for extra m4 magic, it's
just that libtool is easily run hundreds of times in a typical large
software build so it warrants optimization.

Cheers,
Ralf