diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0d49236..85670b5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -61,7 +61,7 @@ set(PROJECT_VERSION "${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}.${PROJECT
 set(CMAKE_C_STANDARD 17)
 set(CMAKE_C_STANDARD_REQUIRED ON)
 set(CMAKE_C_EXTENSIONS ON) # GNU extensions and POSIX standard
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS ON)
 
diff --git a/include/collect-c/common.h b/include/collect-c/common.h
index 4b86096..797261f 100644
--- a/include/collect-c/common.h
+++ b/include/collect-c/common.h
@@ -4,7 +4,7 @@
  * Purpose: Common elements.
  *
  * Created: 5th February 2025
- * Updated: 14th February 2025
+ * Updated: 15th February 2025
  *
  * ////////////////////////////////////////////////////////////////////// */
 
@@ -14,6 +14,7 @@
  */
 
 #include <collect-c/common/macros.h>
+#include <collect-c/common/mem_api.h>
 #ifndef __cplusplus
 # include <collect-c/common/version.h>
 #endif
diff --git a/include/collect-c/common/mem_api.h b/include/collect-c/common/mem_api.h
new file mode 100644
index 0000000..9ade3ae
--- /dev/null
+++ b/include/collect-c/common/mem_api.h
@@ -0,0 +1,87 @@
+/* /////////////////////////////////////////////////////////////////////////
+ * File:    collect-c/common/mem_api.h
+ *
+ * Purpose: Memory API.
+ *
+ * Created: 14th February 2025
+ * Updated: 15th February 2025
+ *
+ * ////////////////////////////////////////////////////////////////////// */
+
+
+/* /////////////////////////////////////////////////////////////////////////
+ * includes
+ */
+
+#include <stdlib.h>
+
+
+/* /////////////////////////////////////////////////////////////////////////
+ * compatibility
+ */
+
+
+/* /////////////////////////////////////////////////////////////////////////
+ * API types
+ */
+
+typedef void* (*collect_c_mem_pfn_alloc)(void* param, size_t cb_new);
+typedef void* (*collect_c_mem_pfn_realloc)(void* param, void* pv_curr, size_t cb_curr, size_t cb_new);
+typedef void (*collect_c_mem_pfn_free)(void* param, void* pv_curr, size_t cb_curr);
+
+struct collect_c_mem_api_t
+{
+    collect_c_mem_pfn_alloc     pfn_alloc;
+    collect_c_mem_pfn_realloc   pfn_realloc;
+    collect_c_mem_pfn_free      pfn_free;
+    void*                       param;
+};
+#ifndef __cplusplus
+typedef struct collect_c_mem_api_t                          collect_c_mem_api_t;
+#endif
+
+
+/* /////////////////////////////////////////////////////////////////////////
+ * API functions
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void*
+collect_c_mem_std_alloc(
+    void*   param
+,   size_t  cb_new
+);
+
+void*
+collect_c_mem_std_realloc(
+    void*   param
+,   void*   pv_curr
+,   size_t  cb_curr
+,   size_t  cb_new
+);
+
+void
+collect_c_mem_std_free(
+    void*   param
+,   void*   pv_curr
+,   size_t  cb_curr
+);
+
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+
+/* /////////////////////////////////////////////////////////////////////////
+ * inclusion control
+ */
+
+#pragma once
+
+
+/* ///////////////////////////// end of file //////////////////////////// */
+
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index ad711ce..deb49a2 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -5,7 +5,7 @@
 # Purpose:  CMake lists file for collect-c library
 #
 # Created:  4th February 2025
-# Updated:  11th February 2025
+# Updated:  14th February 2025
 #
 # ######################################################################## #
 
@@ -42,6 +42,7 @@ endif()
 set(CORE_SRCS
 	circq.c
 	dlist.c
+	mem_api.c
 	vec.c
 	version.c
 )
diff --git a/src/dlist.c b/src/dlist.c
index ffc11de..fedc714 100644
--- a/src/dlist.c
+++ b/src/dlist.c
@@ -17,10 +17,7 @@
 
 #include <errno.h>
 #include <assert.h>
-#include <stdbool.h>
 #include <stddef.h>
-#include <stdlib.h>
-#include <string.h>
 
 
 /* /////////////////////////////////////////////////////////////////////////
diff --git a/src/mem_api.c b/src/mem_api.c
new file mode 100644
index 0000000..cb50745
--- /dev/null
+++ b/src/mem_api.c
@@ -0,0 +1,72 @@
+/* /////////////////////////////////////////////////////////////////////////
+ * File:    src/mem_api.c
+ *
+ * Purpose: Memory API.
+ *
+ * Created: 14th February 2025
+ * Updated: 15th February 2025
+ *
+ * ////////////////////////////////////////////////////////////////////// */
+
+
+/* /////////////////////////////////////////////////////////////////////////
+ * includes
+ */
+
+#include <collect-c/common/mem_api.h>
+
+#include <stdlib.h>
+
+
+/* /////////////////////////////////////////////////////////////////////////
+ * API functions
+ */
+
+void*
+collect_c_mem_std_alloc(
+    void*   param
+,   size_t  cb_new
+)
+{
+    ((void)&param);
+
+/*
+    if (0 != cb_new)
+    {
+        return NULL;
+    }
+*/
+
+    return malloc(cb_new);
+}
+
+void*
+collect_c_mem_std_realloc(
+    void*   param
+,   void*   pv_curr
+,   size_t  cb_curr
+,   size_t  cb_new
+)
+{
+    ((void)&param);
+    ((void)&cb_curr);
+
+    return realloc(pv_curr, cb_new);
+}
+
+void
+collect_c_mem_std_free(
+    void*   param
+,   void*   pv_curr
+,   size_t  cb_curr
+)
+{
+    ((void)&param);
+    ((void)&cb_curr);
+
+    free(pv_curr);
+}
+
+
+/* ///////////////////////////// end of file //////////////////////////// */
+
diff --git a/src/vec.c b/src/vec.c
index 4f5de96..ae30bc3 100644
--- a/src/vec.c
+++ b/src/vec.c
@@ -4,7 +4,7 @@
  * Purpose: Vector container.
  *
  * Created: 5th February 2025
- * Updated: 10th February 2025
+ * Updated: 14th February 2025
  *
  * ////////////////////////////////////////////////////////////////////// */
 
@@ -412,8 +412,6 @@ collect_c_v_push_front_by_ref(
             return 0;
         }
     }
-
-    return -1;
 }