Up to Autoconf 2.13, the replacement of functions was triggered via the
LIBOBJS. Since Autoconf 2.50, the macro
AC_LIBOBJ should be used instead (see 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
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:
When used with Automake 1.10 or newer, a suitable value for
LIBOBJDIRis set so that the
LTLIBOBJScan be referenced from any Makefile.am. Even without Automake, arranging for
LIBOBJDIRto be set correctly enables referencing
LTLIBOBJSin another directory. The
LIBOBJDIRfeature is experimental.