FYI: detect missing Autoconf from configure

[Alexandre Duret-Lutz]

configure failed to report that Autoconf wasn't installed, because
`$AUTOCONF' uses the missing scripts.

I'm checking this in (HEAD & branch-1-7).

2002-12-01  Alexandre Duret-Lutz  <address@hidden>

        * configure.in: Do not use missing while checking for Autoconf's
        version, otherwise we won't notice that Autoconf isn't installed.
        Augment the error message with a few questions to help users.

Index: configure.in
===================================================================
RCS file: /cvs/automake/automake/configure.in,v
retrieving revision 1.120.2.3
diff -u -r1.120.2.3 configure.in
--- configure.in        16 Oct 2002 20:29:49 -0000      1.120.2.3
+++ configure.in        1 Dec 2002 10:47:45 -0000
@@ -24,6 +24,11 @@
 AC_CONFIG_SRCDIR(automake.in)
 AC_CONFIG_AUX_DIR(lib)
 
+# Save the AUTOCONF setting before AM_INIT_AUTOMAKE overrides it;
+# this way we can run Autoconf tests from configure without being
+# bothered by `missing'.
+am_AUTOCONF=${AUTOCONF-autoconf}
+
 AM_INIT_AUTOMAKE([1.6 dist-bzip2])
 
 # The API version is the base version.  We must guarantee
@@ -61,8 +66,10 @@
 # autom4te.cache).
 mkdir conftest
 echo 'AC''_PREREQ(2.54)' > conftest/conftest.ac
-AM_RUN_LOG([cd conftest && eval $AUTOCONF -o /dev/null conftest.ac]) || {
-   AC_MSG_ERROR([Autoconf 2.54 or better is required])
+AM_RUN_LOG([cd conftest && eval $am_AUTOCONF -o /dev/null conftest.ac]) || {
+   AC_MSG_ERROR([Autoconf 2.54 or better is required.
+  Is it installed?  Is it in your PATH?  (try running `autoconf --version')
+  Is it working?  See also config.log for error messages before this one.])
 }
 rm -rf conftest
 
-- 
Alexandre Duret-Lutz