diff --git a/configure.ac b/configure.ac
index fa0228b..fba0023 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,6 +1,6 @@
 dnl Process this file with autoconf to produce a configure script.
 
-AC_INIT(libtdata, 0.2.2)
+AC_INIT(libtdata, 0.2.3)
 
 AC_CONFIG_HEADERS([config.h])
 
@@ -12,6 +12,36 @@ AC_PROG_CC
 
 LT_INIT
 
+# Checks for pointer size.
+# TODO: Later this is irrelevant, and we should just bail on 32-bit platforms always
+AC_CHECK_SIZEOF([uintptr_t])
+if test "x$ac_cv_sizeof_uintptr_t" == "x"; then
+  AC_ERROR([Cannot determine size of uintptr_t])
+fi
+AC_SUBST(ac_cv_sizeof_uintptr_t)
+
+if test "${ac_cv_sizeof_uintptr_t}" = "4"; then
+   AC_DEFINE([BUILD_HOST_32BIT], 1, [Define to 1 if host is 32bit])
+fi
+
+dnl  **************************************
+dnl ***** tests for compiler built-ins *****
+dnl  **************************************
+
+AC_CACHE_CHECK([for __sync_bool_compare_and_swap_8],
+[ctrie_cv_func___sync_bool_compare_and_swap_8],
+[AC_LINK_IFELSE([
+typedef unsigned int uint64  __attribute__ ((mode (DI)));
+uint64 i;
+int main() { return __sync_bool_compare_and_swap (&i, 0, 1); }
+],
+[ctrie_cv_func___sync_bool_compare_and_swap_8=yes],
+[ctrie_cv_func___sync_bool_compare_and_swap_8=no])])
+if test "$ctrie_cv_func___sync_bool_compare_and_swap_8" = "yes"; then
+  AC_DEFINE([HAVE__SYNC_BOOL_COMPARE_AND_SWAP_8], 1,
+    [Define to 1 if the compiler provides the __sync_bool_compare_and_swap function for uint64])
+fi
+
 dnl  *****************
 dnl ***** options *****
 dnl  *****************
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 2263252..1e8f02b 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -15,7 +15,8 @@ lib_LTLIBRARIES = libtdata.la
 
 libtdata_la_SOURCES = \
 	avl.c lslist.c redblack.c splay.c \
-	tree.c usrtc.c bitwise.c idx_allocator.c
+	tree.c usrtc.c bitwise.c idx_allocator.c \
+	cas.c
 
 libtdata_la_LDFLAGS = 
 
diff --git a/lib/cas.c b/lib/cas.c
new file mode 100644
index 0000000..3a35d7c
--- /dev/null
+++ b/lib/cas.c
@@ -0,0 +1,51 @@
+/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 2; tab-width: 2 -*- */
+/*
+ * cas.c
+ * Copyright (C) 2015 Alexander Vdolainen <avdolainen@gmail.com>
+ *
+ * libtdata is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * libtdata is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.";
+ */
+
+#include <stdlib.h>
+#include <stdint.h>
+
+#include "../config.h"
+
+#if !defined (HAVE__SYNC_BOOL_COMPARE_AND_SWAP_8)
+#include <pthread.h>
+static pthread_mutex_t __sync_lock = PTHREAD_MUTEX_INITIALIZER;
+#endif
+
+#ifndef HAVE__SYNC_BOOL_COMPARE_AND_SWAP_8
+_Bool __sync_bool_compare_and_swap_8 (uint64_t*, uint64_t, uint64_t)
+__attribute__ ((visibility ("hidden")));
+
+_Bool __sync_bool_compare_and_swap_8 (uint64_t* ptr, uint64_t old, uint64_t new)
+{
+  int i;
+  _Bool ret;
+
+  i = pthread_mutex_lock(&sync_lock);
+
+  if(*ptr != old)    ret = 0;
+  else {
+    *ptr = new;
+    ret = 1;
+  }
+
+  i = pthread_mutex_unlock(&sync_lock);
+
+  return ret;
+}
+#endif