two more Autoconf problems [Was: cache variable documentation]

[Peter Breitenlohner]

On Thu, 15 Oct 2009, Eric Blake wrote:

> Thanks; I squashed the two fixes into one commit, added a ChangeLog, and
> applied.

Hi Eric,

thanks.

----------------

I'd like to report two more Autoconf problems. Both are, however, uncritical
and should not delay the release of 2.65.

---------

(1) Some time ago I mad a mistake and wrote

AC_ARG_WITH([yyy=DIR],
            AS_HELP_STRING([--with-yyy],
                           [Use DIR for ...]))
instead of

AC_ARG_WITH([yyy],
            AS_HELP_STRING([--with-yyy=DIR],
                           [Use DIR for ...]))

with fairly strange results and hard-to-interprete error/warning messages.
IMHO the macros AC_ARG_{WITH,ENABLE} ought to either check or sanitize their
first argument.

---------

(2) I use a multi-line output variable to generate a complete make rule,
i.e., something like

RULE='TARGET: DEPENDENCIES
        COMMAND'
AC_SUBST([RULE])
AM_SUBST_NOTMAKE([RULE])

in configure.ac and

@RULE@

in Makefile.am, and this nicely generates rules used to rebuild other parts
of the tree.

There is, however, a minor problem: The list of output variables in
config.log is sorted after expanding all variables with a rather unwanted
effect on multi-line values.  This isn't really a problem except when
debugging complex macros.

I think the code, in general.m4 starting with AS_BOX([Output variables.]),
could easily be modified to first sort the variable names and insert their
values afterwards.

----------------

Regards
Peter Breitenlohner <address@hidden>