On Friday 07 December 2007, Stepan Kasal wrote:
> Hello Mike,
>
> On Wed, Dec 05, 2007 at 03:17:11PM -0500, Mike Frysinger wrote:
> > > On Tue, Dec 04, 2007 at 07:25:28PM -0500, Mike Frysinger wrote:
> > > > this structure isnt portable shell:
> > > > : ${VAR='foo'}
> >
> > i dont have any documentation to back up my claim, just code. ive never
> > seen this construct in autoconf generated code [...]
>
> ... yet there is one instance in every configure script:
> : ${CONFIG_STATUS=./config.status}
>
> But I admit that's not much. ;-)
>
> > especially considering this:
> > - older automake used the form
> >
> > : ${VAR='foo'}
> >
> > - newer automake switched same code base to use
> > test "${VAR+set}" = set || VAR="foo"
>
> I searched the Automake git and found one such changed, see the patch
> attached to this mail.
>
> The comment explains that the intention was to expand the variable.
> IOW they wanted to change
>
> : ${CCAS='$(CC)'}
>
> to
>
> : ${CCAS="$CC"}
>
> But since the _latter_ can cause problems on some weird systems, it
> had to be rewritten using the ${VAR+set} pattern.
>
> BTW, I would not hesitate to use the latter form in
> util-linux-ng/configure.ac, because IMHO the portability scope
> of util-linux-ng is not as wide as the scope of the Autoconf itself.
> (IOW, I think that no one builds util-linux-ng on Ultrix, which is the
> only patform known to have problems wit ${CCAS="$CC"}.)
while i agree in general that the target consumers of newer util-linux could
probably get by with POSIX shell and not portable shell, i think it's best if
we stick to "common" conventions that autotool / portable shell uses so as to
reduce confusion/gotchas to new comers.
other than the fact that it sucks we have to explicitly enumerate variables
for every program, i think an updated patch would be OK.
gnulib does something similar:
gl_INCLUDE_EXCLUDE_PROG([prog_var_name], [list of progs])
and then at the bottom it runs [list of progs] through a loop ... perhaps we
could do something like that ... or maybe it'll just complicate things ...
-mike
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