Hi Eric,
* Eric Blake wrote on Wed, Aug 25, 2010 at 12:22:00AM CEST:
> * lib/m4sugar/m4sh.m4 (_AS_SHELL_NULL_WORKS, _AS_SHELL_NULL_SPY):
> New macros.
> (AS_INIT): Use it.
> This is the cautious alternative. If we go with this patch, then
> 2.68 will be released without any use of ${a:<op>b} (for <op> in
> -, +, =, ?), except for the spy; and assuming no bug reports,
> then 2.69 can go ahead and use it at will by deleting _AS_SHELL_NULL_SPY
> and by moving _AS_SHELL_NULL_WORKS from _AS_DETECT_SUGGESTED over
> to _AS_DETECT_REQUIRED.
The patch looks good to me barring the minor nit below.
> The more aggressive approach is to assume that all shells that
> support shell functions also support : in variable substitutions;
I can't really judge this one well. If Paul doesn't know, Sven
Mascheck's pages are a good indicator.
> Should we also update tests/m4sh.at to add a test next
> to 'Negated classes in globbing' and 'Functions support'
> to reiterate this spy in the autoconf testsuite?
Yes, that would be good. Thanks!
> +# _AS_SHELL_NULL_SPY
> +# ------------------
> +# This temporary macro checks "in the wild" for shells that do not support
> +# null variable manipulation. FIXME: remove in the next release after 2.68.
> +m4_defun([_AS_SHELL_NULL_SPY],
> +[_AS_DETECT_SUGGESTED([_AS_SHELL_NULL_WORKS])
> +_AS_RUN([_AS_SHELL_NULL_WORKS]) || {
> + echo No shell found that supports \${a:-b}.
Please quote {a:-b} otherwise there is the slight chance that the { }
get removed if there is a file named '$a:-b' in the current directory.
Also, output to stderr?
Cheers,
Ralf
