Fix check for new libltdl (was: [libtool 2.1a] testsuite: 25 49 failed)

[Ralf Wildenhues]

* quoting myself, from Fri, Feb 16, 2007 at 02:11:34PM CET:
> 
> There is still another failure in libltdl/m4/ltdl.m4: it won't reject
> the external libltdl if only libtldl.so is new enough but ltdl.h is too
> old (can happen if LDFLAGS was set correctly but CPPFLAGS wasn't).  In
> that case there will be a link error due to `lt_preloaded_symbols' being
> undefined.  Guess I'll fix that too...

I'm applying the following patch, which hopefully improves things in
this area.

Cheers,
Ralf

2007-02-19  Ralf Wildenhues  <address@hidden>

        * libltdl/m4/ltdl.m4 (LT_WITH_LTDL): Fix detection of new enough
        libltdl by actually checking for the declaration of
        lt_dlinterface_register in ltdl.h with AC_CHECK_DECL.
        Remove redundant configure output line.

Index: libltdl/m4/ltdl.m4
===================================================================
RCS file: /cvsroot/libtool/libtool/libltdl/m4/ltdl.m4,v
retrieving revision 1.31
diff -u -r1.31 ltdl.m4
--- libltdl/m4/ltdl.m4  27 Jan 2007 16:45:38 -0000      1.31
+++ libltdl/m4/ltdl.m4  19 Feb 2007 09:08:00 -0000
@@ -5,7 +5,7 @@
 # unlimited permission to copy and/or distribute it, with or without
 # modifications, as long as this notice is preserved.
 
-# serial 11 LTDL_INIT
+# serial 12 LTDL_INIT
 
 # LT_CONFIG_LTDL_DIR(DIRECTORY, [LTDL-MODE])
 # ------------------------------------------
@@ -182,18 +182,17 @@
 if test "x$with_included_ltdl" != xyes; then
   # We are not being forced to use the included libltdl sources, so
   # decide whether there is a useful installed version we can use.
-  lt_dlinterface_register_found=no
   AC_CHECK_HEADER([ltdl.h],
-      [AC_CHECK_LIB([ltdl], [lt_dlinterface_register],
-          [with_included_ltdl=no],
-          [with_included_ltdl=yes])],
-
-      [],
+      [AC_CHECK_DECL([lt_dlinterface_register],
+          [AC_CHECK_LIB([ltdl], [lt_dlinterface_register],
+              [with_included_ltdl=no],
+              [with_included_ltdl=yes])],
+          [with_included_ltdl=yes],
+          [AC_INCLUDES_DEFAULT
+           #include <ltdl.h>])],
+      [with_included_ltdl=yes],
       [AC_INCLUDES_DEFAULT]
   )
-  AC_MSG_CHECKING([for lt_dlinterface_register in ltdl.h])
-  test "x$with_included_ltdl" = xno && lt_dlinterface_register_found=yes
-  AC_MSG_RESULT([$lt_dlinterface_register_found])
 fi
 
 if test "x$enable_ltdl_install" != xyes; then