File: autoconf.info,  Node: AC_LIBOBJ vs LIBOBJS,  Next: AC_ACT_IFELSE vs AC_TRY_ACT,  Prev: Hosts and Cross-Compilation,  Up: Autoconf 2.13

18.6.4 ‘AC_LIBOBJ’ vs. ‘LIBOBJS’
--------------------------------

Up to Autoconf 2.13, the replacement of functions was triggered via the
variable ‘LIBOBJS’.  Since Autoconf 2.50, the macro ‘AC_LIBOBJ’ should
be used instead (*note Generic Functions::).  Starting at Autoconf 2.53,
the use of ‘LIBOBJS’ is an error.

   This change is mandated by the unification of the GNU Build System
components.  In particular, the various fragile techniques used to parse
a ‘configure.ac’ are all replaced with the use of traces.  As a
consequence, any action must be traceable, which obsoletes critical
variable assignments.  Fortunately, ‘LIBOBJS’ was the only problem, and
it can even be handled gracefully (read, "without your having to change
something").

   There were two typical uses of ‘LIBOBJS’: asking for a replacement
function, and adjusting ‘LIBOBJS’ for Automake and/or Libtool.


   As for function replacement, the fix is immediate: use ‘AC_LIBOBJ’.
For instance:

     LIBOBJS="$LIBOBJS fnmatch.o"
     LIBOBJS="$LIBOBJS malloc.$ac_objext"

should be replaced with:

     AC_LIBOBJ([fnmatch])
     AC_LIBOBJ([malloc])


   When used with Automake 1.10 or newer, a suitable value for
‘LIBOBJDIR’ is set so that the ‘LIBOBJS’ and ‘LTLIBOBJS’ can be
referenced from any ‘Makefile.am’.  Even without Automake, arranging for
‘LIBOBJDIR’ to be set correctly enables referencing ‘LIBOBJS’ and
‘LTLIBOBJS’ in another directory.  The ‘LIBOBJDIR’ feature is
experimental.