+dnl define the LDFLAGS_NOUNDEFINED variable with the correct value for
+dnl the current linker to avoid undefined references in a shared object.
+AC_DEFUN([CC_NOUNDEFINED], [
+ dnl We check $host for which systems to enable this for.
+ AC_REQUIRE([AC_CANONICAL_HOST])
+
+ case $host in
+ dnl FreeBSD (et al.) does not complete linking for shared objects when pthreads
+ dnl are requested, as different implementations are present; to avoid problems
+ dnl use -Wl,-z,defs only for those platform not behaving this way.
+ *-freebsd* | *-openbsd*) ;;
+ *)
+ dnl First of all check for the --no-undefined variant of GNU ld. This allows
+ dnl for a much more readable command line, so that people can understand what
+ dnl it does without going to look for what the heck -z defs does.
+ for possible_flags in "-Wl,--no-undefined" "-Wl,-z,defs"; do
+ CC_CHECK_LDFLAGS([$possible_flags], [LDFLAGS_NOUNDEFINED="$possible_flags"])
+ break
+ done
+ ;;
+ esac
+
+ AC_SUBST([LDFLAGS_NOUNDEFINED])
+])
+