Re: [PATCH] modernize AS_UNSET a bit

[Ralf Wildenhues]

Hi Paolo,

* Paolo Bonzini wrote on Tue, Oct 14, 2008 at 07:16:48AM CEST:
> This patch modernizes a bit what we assume about unset.  In particular,
> we assume that unset exists but might fail if the variable is not present.
> We also assume that the user won't unset MAIL and MAILCHECK; we do that
> in m4sh's initialization in a way that won't upset Bash 2.01 (did not
> test it though, I don't have that shell).
> 
> This in turn removes the need for _AS_UNSET_PREPARE.

Unfortunately, Libtool uses $as_unset, and I guess some other packages
do, too.  :-/

And I'm not *that* much of an old shell expert.  But
<http://www.in-ulm.de/~mascheck/bourne/> states that Version 7 sh didn't
have unset at all.

Darn, it also states that, while 'unset' was added in SVR2, ${var:-repl}
was already in System III.

Cheers,
Ralf