diff --git a/jerry-core/api/jerry.c b/jerry-core/api/jerry.c
index 0ffa623a9..6a48c6d18 100644
--- a/jerry-core/api/jerry.c
+++ b/jerry-core/api/jerry.c
@@ -48,6 +48,14 @@ JERRY_STATIC_ASSERT ((int) ECMA_ERROR_COMMON == (int) JERRY_ERROR_COMMON
                      && (int) ECMA_ERROR_URI == (int) JERRY_ERROR_URI,
                      ecma_standard_error_t_must_be_equal_to_jerry_error_t);
 
+JERRY_STATIC_ASSERT ((int) ECMA_INIT_EMPTY == (int) JERRY_INIT_EMPTY
+                     && (int) ECMA_INIT_SHOW_OPCODES == (int) JERRY_INIT_SHOW_OPCODES
+                     && (int) ECMA_INIT_SHOW_REGEXP_OPCODES == (int) JERRY_INIT_SHOW_REGEXP_OPCODES
+                     && (int) ECMA_INIT_MEM_STATS == (int) JERRY_INIT_MEM_STATS
+                     && (int) ECMA_INIT_MEM_STATS_SEPARATE == (int) JERRY_INIT_MEM_STATS_SEPARATE
+                     && (int) ECMA_INIT_DEBUGGER == (int) JERRY_INIT_DEBUGGER,
+                     ecma_init_flag_t_must_be_equal_to_jerry_init_flag_t);
+
 #ifndef JERRY_JS_PARSER
 #error JERRY_JS_PARSER must be defined with 0 (disabled) or 1 (enabled)
 #elif !JERRY_JS_PARSER && !defined (JERRY_ENABLE_SNAPSHOT_EXEC)
@@ -169,11 +177,11 @@ jerry_init (jerry_init_flag_t flags) /**< combination of Jerry flags */
  */
 void
 jerry_init_with_user_context (jerry_init_flag_t flags,  /**< combination of Jerry flags */
-                              jerry_user_context_init_cb init_cb, /**< callback to call to create the user context or
-                                                                    *  NULL, in which case no user context will be
-                                                                    *  created */
-                              jerry_user_context_deinit_cb deinit_cb) /**< callback to call to free the user context or
-                                                                        *  NULL if it does not need to be freed */
+                              jerry_user_context_init_t init_cb, /**< callback to call to create the user context or
+                                                                   *  NULL, in which case no user context will be
+                                                                   *  created */
+                              jerry_user_context_deinit_t deinit_cb) /**< callback to call to free the user context or
+                                                                       *  NULL if it does not need to be freed */
 {
   jerry_init (flags);
   JERRY_CONTEXT (user_context_p) = (init_cb ? init_cb () : NULL);
@@ -956,7 +964,7 @@ jerry_create_external_function (jerry_external_handler_t handler_p) /**< pointer
 {
   jerry_assert_api_available ();
 
-  ecma_object_t *func_obj_p = ecma_op_create_external_function_object ((ecma_external_pointer_t) handler_p);
+  ecma_object_t *func_obj_p = ecma_op_create_external_function_object (handler_p);
   return ecma_make_object_value (func_obj_p);
 } /* jerry_create_external_function */
 
@@ -2076,7 +2084,7 @@ jerry_get_object_native_pointer (const jerry_value_t obj_val, /**< object to get
 
   if (out_native_info_p)
   {
-    *out_native_info_p = (const jerry_object_native_info_t *) native_pointer_p->info_p;
+    *out_native_info_p = (const jerry_object_native_info_t *) native_pointer_p->u.info_p;
   }
 
   return true;
diff --git a/jerry-core/debugger/jerry-debugger-ws.c b/jerry-core/debugger/jerry-debugger-ws.c
index 29e3603c4..5d16b00d8 100644
--- a/jerry-core/debugger/jerry-debugger-ws.c
+++ b/jerry-core/debugger/jerry-debugger-ws.c
@@ -314,7 +314,7 @@ jerry_debugger_accept_connection (void)
   struct sockaddr_in addr;
   socklen_t sin_size = sizeof (struct sockaddr_in);
 
-  JERRY_ASSERT (JERRY_CONTEXT (jerry_init_flags) & JERRY_INIT_DEBUGGER);
+  JERRY_ASSERT (JERRY_CONTEXT (jerry_init_flags) & ECMA_INIT_DEBUGGER);
 
   addr.sin_family = AF_INET;
   addr.sin_port = htons (JERRY_DEBUGGER_PORT);
diff --git a/jerry-core/ecma/base/ecma-gc.c b/jerry-core/ecma/base/ecma-gc.c
index e08ea0d98..3160dd36b 100644
--- a/jerry-core/ecma/base/ecma-gc.c
+++ b/jerry-core/ecma/base/ecma-gc.c
@@ -408,22 +408,20 @@ ecma_gc_free_native_pointer (ecma_property_t *property_p, /**< property */
 
   if (id == LIT_INTERNAL_MAGIC_STRING_NATIVE_HANDLE)
   {
-    if (native_pointer_p->info_p != NULL)
+    if (native_pointer_p->u.callback_p != NULL)
     {
-      ecma_external_pointer_t freecb_p = (ecma_external_pointer_t) native_pointer_p->info_p;
-      ((jerry_object_free_callback_t) freecb_p) ((uintptr_t) native_pointer_p->data_p);
+      native_pointer_p->u.callback_p ((uintptr_t) native_pointer_p->data_p);
     }
   }
   else
   {
-    if (native_pointer_p->info_p != NULL)
+    if (native_pointer_p->u.info_p != NULL)
     {
-      jerry_object_free_callback_t free_cb;
-      free_cb = (jerry_object_free_callback_t) ((const jerry_object_native_info_t *) native_pointer_p->info_p)->free_cb;
+      ecma_object_native_free_callback_t free_cb = native_pointer_p->u.info_p->free_cb;
 
       if (free_cb != NULL)
       {
-        free_cb ((uintptr_t) native_pointer_p->data_p);
+        free_cb (native_pointer_p->data_p);
       }
     }
   }
diff --git a/jerry-core/ecma/base/ecma-globals.h b/jerry-core/ecma/base/ecma-globals.h
index a1353e659..e2f0b8757 100644
--- a/jerry-core/ecma/base/ecma-globals.h
+++ b/jerry-core/ecma/base/ecma-globals.h
@@ -53,6 +53,19 @@
  * @}
  */
 
+/**
+ * JerryScript init flags.
+ */
+typedef enum
+{
+  ECMA_INIT_EMPTY               = (0u),      /**< empty flag set */
+  ECMA_INIT_SHOW_OPCODES        = (1u << 0), /**< dump byte-code to log after parse */
+  ECMA_INIT_SHOW_REGEXP_OPCODES = (1u << 1), /**< dump regexp byte-code to log after compilation */
+  ECMA_INIT_MEM_STATS           = (1u << 2), /**< dump memory statistics */
+  ECMA_INIT_MEM_STATS_SEPARATE  = (1u << 3), /**< dump memory statistics and reset peak values after parse */
+  ECMA_INIT_DEBUGGER            = (1u << 4), /**< enable all features required by debugging */
+} ecma_init_flag_t;
+
 /**
  * Type of ecma value
  */
@@ -195,13 +208,53 @@ typedef int32_t ecma_integer_value_t;
  */
 typedef uintptr_t ecma_external_pointer_t;
 
+/**
+ * Callback which tells whether the ECMAScript execution should be stopped.
+ */
+typedef ecma_value_t (*ecma_vm_exec_stop_callback_t) (void *user_p);
+
+/**
+ * Function type for user context deallocation
+ */
+typedef void (*ecma_user_context_deinit_t) (void *user_context_p);
+
+/**
+ * Type of an external function handler.
+ */
+typedef ecma_value_t (*ecma_external_handler_t) (const ecma_value_t function_obj,
+                                                 const ecma_value_t this_val,
+                                                 const ecma_value_t args_p[],
+                                                 const ecma_length_t args_count);
+
+/**
+ * Native free callback of an object (deprecated).
+ */
+typedef void (*ecma_object_free_callback_t) (const uintptr_t native_p);
+
+/**
+ * Native free callback of an object.
+ */
+typedef void (*ecma_object_native_free_callback_t) (void *native_p);
+
+/**
+ * Type information of a native pointer.
+ */
+typedef struct
+{
+  ecma_object_native_free_callback_t free_cb; /**< the free callback of the native pointer */
+} ecma_object_native_info_t;
+
 /**
  * Representation for native pointer data.
  */
 typedef struct
 {
   void *data_p; /**< points to the data of the object */
-  void *info_p; /**< free info or callback */
+  union
+  {
+    ecma_object_free_callback_t callback_p; /**< callback */
+    ecma_object_native_info_t *info_p; /**< native info */
+  } u;
 } ecma_native_pointer_t;
 
 /**
@@ -720,7 +773,7 @@ typedef struct
       ecma_length_t args_length; /**< length of arguments */
     } bound_function;
 
-    ecma_external_pointer_t external_function; /**< external function */
+    ecma_external_handler_t external_handler_cb; /**< external function */
   } u;
 } ecma_extended_object_t;
 
diff --git a/jerry-core/ecma/base/ecma-helpers-external-pointers.c b/jerry-core/ecma/base/ecma-helpers-external-pointers.c
index bd81ec35f..6a5ad2b56 100644
--- a/jerry-core/ecma/base/ecma-helpers-external-pointers.c
+++ b/jerry-core/ecma/base/ecma-helpers-external-pointers.c
@@ -72,7 +72,7 @@ ecma_create_native_property (ecma_object_t *obj_p, /**< object to create propert
   JERRY_ASSERT (ECMA_STRING_IS_REF_EQUALS_TO_ONE (&name));
 
   native_pointer_p->data_p = data_p;
-  native_pointer_p->info_p = info_p;
+  native_pointer_p->u.info_p = info_p;
 
   return is_new;
 } /* ecma_create_native_property */
diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-promise.c b/jerry-core/ecma/builtin-objects/ecma-builtin-promise.c
index f8e4ca4ed..3438bde28 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-promise.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-promise.c
@@ -496,7 +496,7 @@ ecma_builtin_promise_do_all (ecma_value_t array, /**< the array for all */
 
     /* k. */
     ecma_object_t *res_ele_p;
-    res_ele_p = ecma_op_create_external_function_object ((ecma_external_pointer_t) ecma_builtin_promise_all_handler);
+    res_ele_p = ecma_op_create_external_function_object (ecma_builtin_promise_all_handler);
     /* l. */
     ecma_op_object_put (res_ele_p,
                         str_already_called,
diff --git a/jerry-core/ecma/operations/ecma-function-object.c b/jerry-core/ecma/operations/ecma-function-object.c
index ff0f9ccf1..a5a1b4f2a 100644
--- a/jerry-core/ecma/operations/ecma-function-object.c
+++ b/jerry-core/ecma/operations/ecma-function-object.c
@@ -310,7 +310,7 @@ ecma_op_function_try_lazy_instantiate_property (ecma_object_t *object_p, /**< th
  * @return pointer to newly created external function object
  */
 ecma_object_t *
-ecma_op_create_external_function_object (ecma_external_pointer_t code_p) /**< pointer to external native handler */
+ecma_op_create_external_function_object (ecma_external_handler_t handler_cb) /**< pointer to external native handler */
 {
   ecma_object_t *prototype_obj_p = ecma_builtin_get (ECMA_BUILTIN_ID_FUNCTION_PROTOTYPE);
 
@@ -328,7 +328,7 @@ ecma_op_create_external_function_object (ecma_external_pointer_t code_p) /**< po
    */
 
   ecma_extended_object_t *ext_func_obj_p = (ecma_extended_object_t *) function_obj_p;
-  ext_func_obj_p->u.external_function = code_p;
+  ext_func_obj_p->u.external_handler_cb = handler_cb;
 
   ecma_string_t *magic_string_prototype_p = ecma_get_magic_string (LIT_MAGIC_STRING_PROTOTYPE);
   ecma_builtin_helper_def_prop (function_obj_p,
@@ -536,12 +536,11 @@ ecma_op_function_call (ecma_object_t *func_obj_p, /**< Function object */
   else if (ecma_get_object_type (func_obj_p) == ECMA_OBJECT_TYPE_EXTERNAL_FUNCTION)
   {
     ecma_extended_object_t *ext_func_obj_p = (ecma_extended_object_t *) func_obj_p;
-    jerry_external_handler_t handler_p = (jerry_external_handler_t) ext_func_obj_p->u.external_function;
 
-    ret_value = handler_p (ecma_make_object_value (func_obj_p),
-                           this_arg_value,
-                           arguments_list_p,
-                           arguments_list_len);
+    ret_value = ext_func_obj_p->u.external_handler_cb (ecma_make_object_value (func_obj_p),
+                                                       this_arg_value,
+                                                       arguments_list_p,
+                                                       arguments_list_len);
   }
   else
   {
diff --git a/jerry-core/ecma/operations/ecma-function-object.h b/jerry-core/ecma/operations/ecma-function-object.h
index 84ca80935..a52c5b193 100644
--- a/jerry-core/ecma/operations/ecma-function-object.h
+++ b/jerry-core/ecma/operations/ecma-function-object.h
@@ -42,7 +42,7 @@ ecma_property_t *
 ecma_op_function_try_lazy_instantiate_property (ecma_object_t *object_p, ecma_string_t *property_name_p);
 
 ecma_object_t *
-ecma_op_create_external_function_object (ecma_external_pointer_t code_p);
+ecma_op_create_external_function_object (ecma_external_handler_t handler_cb);
 
 ecma_value_t
 ecma_op_function_call (ecma_object_t *func_obj_p, ecma_value_t this_arg_value,
diff --git a/jerry-core/ecma/operations/ecma-promise-object.c b/jerry-core/ecma/operations/ecma-promise-object.c
index 321e351d8..1b4abe579 100644
--- a/jerry-core/ecma/operations/ecma-promise-object.c
+++ b/jerry-core/ecma/operations/ecma-promise-object.c
@@ -416,7 +416,7 @@ ecma_promise_create_resolving_functions (ecma_object_t *object_p) /**< the promi
   ecma_init_ecma_magic_string (&str_already_resolved, LIT_INTERNAL_MAGIC_STRING_ALREADY_RESOLVED);
   /* 2. */
   ecma_object_t *resolve_p;
-  resolve_p = ecma_op_create_external_function_object ((ecma_external_pointer_t) ecma_promise_resolve_handler);
+  resolve_p = ecma_op_create_external_function_object (ecma_promise_resolve_handler);
 
   /* 3. */
   ecma_op_object_put (resolve_p,
@@ -430,7 +430,7 @@ ecma_promise_create_resolving_functions (ecma_object_t *object_p) /**< the promi
                       false);
   /* 5. */
   ecma_object_t *reject_p;
-  reject_p = ecma_op_create_external_function_object ((ecma_external_pointer_t) ecma_promise_reject_handler);
+  reject_p = ecma_op_create_external_function_object (ecma_promise_reject_handler);
   /* 6. */
   ecma_op_object_put (reject_p,
                       &str_promise,
diff --git a/jerry-core/include/jerryscript-core.h b/jerry-core/include/jerryscript-core.h
index 0024b0ca1..0c9a3001b 100644
--- a/jerry-core/include/jerryscript-core.h
+++ b/jerry-core/include/jerryscript-core.h
@@ -198,12 +198,12 @@ typedef bool (*jerry_object_property_foreach_t) (const jerry_value_t property_na
 /**
  * Function type for user context allocation
  */
-typedef void *(*jerry_user_context_init_cb) (void);
+typedef void *(*jerry_user_context_init_t) (void);
 
 /**
  * Function type for user context deallocation
  */
-typedef void (*jerry_user_context_deinit_cb) (void *user_context_p);
+typedef void (*jerry_user_context_deinit_t) (void *user_context_p);
 
 /**
  * Type information of a native pointer.
@@ -218,8 +218,8 @@ typedef struct
  */
 void jerry_init (jerry_init_flag_t flags);
 void jerry_init_with_user_context (jerry_init_flag_t flags,
-                                   jerry_user_context_init_cb init_cb,
-                                   jerry_user_context_deinit_cb deinit_cb);
+                                   jerry_user_context_init_t init_cb,
+                                   jerry_user_context_deinit_t deinit_cb);
 void jerry_cleanup (void);
 void jerry_register_magic_strings (const jerry_char_ptr_t *ex_str_items_p, uint32_t count,
                                    const jerry_length_t *str_lengths_p);
diff --git a/jerry-core/jcontext/jcontext.h b/jerry-core/jcontext/jcontext.h
index 32f49b32f..16342ce47 100644
--- a/jerry-core/jcontext/jcontext.h
+++ b/jerry-core/jcontext/jcontext.h
@@ -62,7 +62,7 @@ typedef struct
   ecma_object_t *ecma_global_lex_env_p; /**< global lexical environment */
   vm_frame_ctx_t *vm_top_context_p; /**< top (current) interpreter context */
   void *user_context_p; /**< user-provided context-specific pointer */
-  jerry_user_context_deinit_cb user_context_deinit_cb; /**< user-provided deleter for context-specific pointer */
+  ecma_user_context_deinit_t user_context_deinit_cb; /**< user-provided deleter for context-specific pointer */
   size_t ecma_gc_objects_number; /**< number of currently allocated objects */
   size_t ecma_gc_new_objects; /**< number of newly allocated objects since last GC session */
   size_t jmem_heap_allocated_size; /**< size of allocated regions */
@@ -88,8 +88,8 @@ typedef struct
   uint32_t vm_exec_stop_frequency; /**< reset value for vm_exec_stop_counter */
   uint32_t vm_exec_stop_counter; /**< down counter for reducing the calls of vm_exec_stop_cb */
   void *vm_exec_stop_user_p; /**< user pointer for vm_exec_stop_cb */
-  jerry_vm_exec_stop_callback_t vm_exec_stop_cb; /**< user function which returns whether the
-                                                  *   ECMAScript execution should be stopped */
+  ecma_vm_exec_stop_callback_t vm_exec_stop_cb; /**< user function which returns whether the
+                                                 *   ECMAScript execution should be stopped */
 #endif /* JERRY_VM_EXEC_STOP */
 
 #ifdef JERRY_DEBUGGER
diff --git a/jerry-core/jmem/jmem-allocator.c b/jerry-core/jmem/jmem-allocator.c
index a99dc19c5..a3400b924 100644
--- a/jerry-core/jmem/jmem-allocator.c
+++ b/jerry-core/jmem/jmem-allocator.c
@@ -42,7 +42,7 @@ jmem_finalize (void)
   jmem_pools_finalize ();
 
 #ifdef JMEM_STATS
-  if (JERRY_CONTEXT (jerry_init_flags) & JERRY_INIT_MEM_STATS)
+  if (JERRY_CONTEXT (jerry_init_flags) & ECMA_INIT_MEM_STATS)
   {
     jmem_stats_print ();
   }
diff --git a/jerry-core/jrt/jrt.h b/jerry-core/jrt/jrt.h
index c667a0dc4..583d3136a 100644
--- a/jerry-core/jrt/jrt.h
+++ b/jerry-core/jrt/jrt.h
@@ -19,7 +19,6 @@
 #include <stdio.h>
 #include <string.h>
 
-#include "jerryscript.h"
 #include "jerryscript-port.h"
 #include "jrt-types.h"
 
diff --git a/jerry-core/parser/js/js-parser.c b/jerry-core/parser/js/js-parser.c
index cd15cfdf0..0bc933558 100644
--- a/jerry-core/parser/js/js-parser.c
+++ b/jerry-core/parser/js/js-parser.c
@@ -1901,7 +1901,7 @@ parser_parse_source (const uint8_t *source_p, /**< valid UTF-8 source code */
 #endif /* !JERRY_NDEBUG */
 
 #ifdef PARSER_DUMP_BYTE_CODE
-  context.is_show_opcodes = (JERRY_CONTEXT (jerry_init_flags) & JERRY_INIT_SHOW_OPCODES);
+  context.is_show_opcodes = (JERRY_CONTEXT (jerry_init_flags) & ECMA_INIT_SHOW_OPCODES);
   context.total_byte_code_size = 0;
 
   if (context.is_show_opcodes)
diff --git a/jerry-core/parser/regexp/re-compiler.c b/jerry-core/parser/regexp/re-compiler.c
index cae945d71..433e88169 100644
--- a/jerry-core/parser/regexp/re-compiler.c
+++ b/jerry-core/parser/regexp/re-compiler.c
@@ -601,7 +601,7 @@ re_compile_bytecode (const re_compiled_code_t **out_bytecode_p, /**< [out] point
   else
   {
 #ifdef REGEXP_DUMP_BYTE_CODE
-    if (JERRY_CONTEXT (jerry_init_flags) & JERRY_INIT_SHOW_REGEXP_OPCODES)
+    if (JERRY_CONTEXT (jerry_init_flags) & ECMA_INIT_SHOW_REGEXP_OPCODES)
     {
       re_dump_bytecode (&bc_ctx);
     }