(autoconf.info)AC_LIBOBJ vs LIBOBJS


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17.6.4 `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.


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