How to best prevent autoreconf from recursing into a subdir

[Peter Breitenlohner]

Hi,

the TeX Live (TL) source tree contains the subdirectory util/dialog/ with a
proxy build system for the dialog sources in, e.g.,
util/dialog/dialog-1.1-20100428.

Building dialog is enabled or disabled when util/dialog/ is configured with
'--enable-build' or '--disable-build' respectively (as a consequence of
'--enable-dialog', the default, or '--disable-dialog' at the top-level).

While the dialog-1.1-20100428 build system is good to configure and compile
the program (with or without VPATH), several other targets required by
Automake are missing.  Thus the proxy build system.

Here an excerpt from our util/dialog/configure.ac:

> m4_define([dialog_version], [1.1-20100428])[]dnl using unmodified dialog source 
> tree
>
> ....
>
> DIALOG_TREE=[dialog-]dialog_version
> AC_SUBST([DIALOG_TREE])
>
> # Initialize the subdir machinery
> AC_CONFIG_SUBDIRS([])
>
> if test "x$enable_build" != xno || test -f config.force; then
>   # when building dialog, configure the subdir $DIALOG_TREE
>   # but prevent autoreconf from recursing into this subdir.
>   subdirs=$DIALOG_TREE
>   echo timestamp >config.force
> fi

NB: The file config.force may be created by running 'make' in util/dialog/,
thus building the program even when configured with '--disable-build'.

All this works fine, except that autoreconf (2.65 or 2.68) complains:

> autoreconf: Entering directory `dialog'
> Use of uninitialized value in split at BIN_DIR/autoreconf line 484, <GEN79> 
> line 4.
> autoreconf: Leaving directory `dialog'

===============

Question:

(1) is there a better (more correct) way to achieve the same result?

(2) is there a way to avoid that warning.

Regards
Peter Breitenlohner <address@hidden>