+# urcu - check that URCU lib is at least version 0.5.4
+AC_CHECK_LIB([urcu-bp], [rcu_bp_before_fork], [], [AC_MSG_ERROR([liburcu 0.5.4 or newer is needed, please update your version or use [LDFLAGS]=-Ldir to specify the right location.])])
+
+# urcu - check that URCU lib is at least version 0.5
+AC_CHECK_DECL([cds_list_add(0, 0)], [], [AC_MSG_ERROR([liburcu 0.5 or newer is needed, please update your version or use [LDFLAGS]=-Ldir to specify the right location.])], [[#include <urcu/list.h>]])
+
+
+
+# Check for various supplementary host information (beyond the
+# triplet) which might affect the library format choices. E.g., we
+# can be building with `i686-unknown-linux-gnu-gcc -m64'
+
+case "${host}" in
+changequote(,)dnl
+ i[34567]86-*-linux*)
+changequote([,])dnl
+ AC_CACHE_CHECK([if building for x86-64], [ust_cv_i386_is_x86_64],
+ [save_CPPFLAGS="$CPPFLAGS"
+ CPPFLAGS="$CPPFLAGS $CFLAGS"
+ AC_EGREP_CPP([got it], [
+#if __x86_64__
+got it
+#endif
+ ], [ust_cv_i386_is_x86_64=yes],
+ [ust_cv_i386_is_x86_64=no])
+ CPPFLAGS="$save_CPPFLAGS"])
+ ;;
+esac