src/xradius_cache.c: In function 'xrad_cache_dbm_post_config':
src/xradius_cache.c:146:22: error: 'unixd_config' undeclared (first use in this function)
         chown(path1, unixd_config.user_id, -1);
                      ^
src/xradius_cache.c:146:22: note: each undeclared identifier is reported only once for each function it appears in
src/xradius_cache.c: In function 'xrad_cache_dbm_check':
src/xradius_cache.c:200:22: warning: format '%d' expects argument of type 'int', but argument 8 has type 'apr_size_t' [-Wformat=]
                      dbmval.dsize);        

Solution is adding “#define unixd_config ap_unixd_config”, for more info see https://httpd.apache.org/docs/2.4/developer/new_api_2_4.html .

***************
*** 9,28 ****
--- 9,29 ----
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License is distributed on an "AS IS" BASIS,
   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   *  See the License for the specific language governing permissions and
   *  limitations under the License.
   *
   */
  
  #include "mod_auth_xradius.h"
+ #define unixd_config ap_unixd_config
  
  /**
   * Removes upto 128 Expired Sessions Per Call.
   * To Reset all Sessions, you can safely delete the DBM files used by the module.
   */
  int xrad_cache_dbm_expire(server_rec *s, xrad_serverconf_rec* sc, 
                            apr_pool_t* p, apr_time_t current_time)
  {
      apr_status_t rv;
      apr_dbm_t *dbm;