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Re: [PATCH 0/2] First steps in making autoconf ensure a POSIX shell

From: Adrian Bunk
Subject: Re: [PATCH 0/2] First steps in making autoconf ensure a POSIX shell
Date: Sat, 10 Nov 2012 12:22:01 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

On Sat, Nov 10, 2012 at 10:00:17AM +0100, Stefano Lattarini wrote:
> On 11/10/2012 01:45 AM, Eric Blake wrote:
> >
> > [SNIP]
> >
> > What I'm thinking right now (but don't have the patch ready yet) is that
> > we will reinstate a spy that loudly warns if autoconf can't find a POSIX
> > shell, with a request for bug reports, and in parallel add a new macro
> > (maybe named AS_SHELL_POSIX) that other packages can use to require a
> > POSIX shell even with autoconf 2.70.  That is, using the new macro would
> > switch autoconf from spying to requiring POSIX, but packages that aren't
> > ready to require POSIX can still safely use 2.70, and the spy will help
> > us know if anyone is really stuck on a non-museum system where it matters.
> > 
> This is a good idea.  It might also scale well in case we'll decide to
> allow the user to request more POSIX or not-so-POSIX features from the
> shell: that could be implemented with a similar macro AS_SHELL_EXTRA
> (say), or, for finer control and granularity, by having AS_SHELL_POSIX
> take arguments specifying extra suggested or required features:
>        set-x-dont-corrupt-stderr=suggested
>        set-e-respects-exit-traps=required
>     ])

I'm a bit worried about the direction this discussion is taking,
IMHO adding AS_SHELL_POSIX would be a mistake.

The purpose should be to make software portable to as many systems as 
possible, not making it easy to exclude systems.

And the absolute worst case would be if automake would *ever*
use AS_SHELL_POSIX - that would completely defeat the purpose
of having it optional.

If it turns out that there are still systems that only have a 
not-so-POSIX shell, then whatever features are missing on such
systems must not be used.

Add a "spy that loudly warns" into autoconf 2.70 and wait 6-12 months
for the results. Then we'll know what features can safely be assumed
to be present on all systems.

> Thanks,
>   Stefano



       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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