diff --git a/docs/01.CONFIGURATION.md b/docs/01.CONFIGURATION.md
index 1a263e73fa..506d280bfb 100644
--- a/docs/01.CONFIGURATION.md
+++ b/docs/01.CONFIGURATION.md
@@ -155,7 +155,7 @@ Enabling this feature provides detailed error messages where available, like lin
 
 ### Logging
 
-This option can be used to enable log messages during runtime. When enabled the engine will use the `jerry_port_log` port API function to print relevant log messages.
+This option can be used to enable log messages during runtime. When enabled the engine will use the `jerry_port_log_buffer` port API function to print relevant log messages.
 This feature is disabled by default.
 
 | Options |                                              |
diff --git a/docs/05.PORT-API.md b/docs/05.PORT-API.md
index 9feecf2565..015bbb6f0c 100644
--- a/docs/05.PORT-API.md
+++ b/docs/05.PORT-API.md
@@ -119,8 +119,11 @@ void jerry_port_context_free (void);
  *
  * The implementation can decide whether error and debug messages are logged to
  * the console, or saved to a database or to a file.
+ *
+ * @param buffer_p: input buffer
+ * @param buffer_size: data size
  */
-void jerry_port_log (const char *message_p);
+void jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size);
 ```
 
 ```c
diff --git a/jerry-core/api/jerryscript.c b/jerry-core/api/jerryscript.c
index 5a874a3f32..aea81a19b8 100644
--- a/jerry-core/api/jerryscript.c
+++ b/jerry-core/api/jerryscript.c
@@ -5083,49 +5083,33 @@ jerry_log_set_level (jerry_log_level_t level)
  * Log a zero-terminated string message.
  *
  * @param str_p: message
+ * @param str_size: size of message
  */
 static void
-jerry_log_string (const char *str_p)
+jerry_log_string (const jerry_char_t *str_p, jerry_size_t str_size)
 {
-  jerry_port_log (str_p);
+  jerry_port_log_buffer (str_p, str_size);
 
 #if JERRY_DEBUGGER
   if (jerry_debugger_is_connected ())
   {
-    jerry_debugger_send_string (JERRY_DEBUGGER_OUTPUT_RESULT,
-                                JERRY_DEBUGGER_OUTPUT_LOG,
-                                (const uint8_t *) str_p,
-                                strlen (str_p));
+    jerry_debugger_send_string (JERRY_DEBUGGER_OUTPUT_RESULT, JERRY_DEBUGGER_OUTPUT_LOG, str_p, str_size);
   }
 #endif /* JERRY_DEBUGGER */
 } /* jerry_log_string */
 
 /**
- * Log a fixed-size string message.
+ * Log a zero-terminated number string message.
  *
- * @param str_p: message
- * @param size: size
- * @param buffer_p: buffer to use
+ * @param cursor_p: the number string cursor
+ * @param buffer_p: buffer used to construct the number string
  */
 static void
-jerry_log_string_fixed (const char *str_p, size_t size, char *buffer_p)
+jerry_log_cursor (const jerry_char_t *cursor_p, jerry_char_t *buffer_p)
 {
-  const size_t batch_size = JERRY_LOG_BUFFER_SIZE - 1;
-
-  while (size > batch_size)
-  {
-    memcpy (buffer_p, str_p, batch_size);
-    buffer_p[batch_size] = '\0';
-    jerry_log_string (buffer_p);
-
-    str_p += batch_size;
-    size -= batch_size;
-  }
-
-  memcpy (buffer_p, str_p, size);
-  buffer_p[size] = '\0';
-  jerry_log_string (buffer_p);
-} /* jerry_log_string_fixed */
+  jerry_char_t *tail_p = buffer_p + JERRY_LOG_BUFFER_SIZE - 1;
+  jerry_log_string (cursor_p, (jerry_size_t) (tail_p - cursor_p));
+} /* jerry_log_cursor */
 
 /**
  * Format an unsigned number.
@@ -5138,11 +5122,13 @@ jerry_log_string_fixed (const char *str_p, size_t size, char *buffer_p)
  *
  * @return formatted number as string
  */
-static char *
-jerry_format_unsigned (unsigned int num, uint8_t width, char padding, uint8_t radix, char *buffer_p)
+static jerry_char_t *
+jerry_format_unsigned (unsigned int num, uint8_t width, jerry_char_t padding, uint8_t radix, jerry_char_t *buffer_p)
 {
-  static const char digits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };
-  char *cursor_p = buffer_p + JERRY_LOG_BUFFER_SIZE;
+  static const jerry_char_t digits[] = {
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'
+  };
+  jerry_char_t *cursor_p = buffer_p + JERRY_LOG_BUFFER_SIZE;
   *(--cursor_p) = '\0';
   uint8_t count = 0;
 
@@ -5172,8 +5158,8 @@ jerry_format_unsigned (unsigned int num, uint8_t width, char padding, uint8_t ra
  *
  * @return formatted number as string
  */
-static char *
-jerry_format_int (int num, uint8_t width, char padding, char *buffer_p)
+static jerry_char_t *
+jerry_format_int (int num, uint8_t width, jerry_char_t padding, jerry_char_t *buffer_p)
 {
   if (num >= 0)
   {
@@ -5184,15 +5170,15 @@ jerry_format_int (int num, uint8_t width, char padding, char *buffer_p)
 
   if (padding == '0' && width > 0)
   {
-    char *cursor_p = jerry_format_unsigned ((unsigned) num, --width, padding, 10, buffer_p);
+    jerry_char_t *cursor_p = jerry_format_unsigned ((unsigned) num, --width, padding, 10, buffer_p);
     *(--cursor_p) = '-';
     return cursor_p;
   }
 
-  char *cursor_p = jerry_format_unsigned ((unsigned) num, 0, ' ', 10, buffer_p);
+  jerry_char_t *cursor_p = jerry_format_unsigned ((unsigned) num, 0, ' ', 10, buffer_p);
   *(--cursor_p) = '-';
 
-  char *indent_p = buffer_p + JERRY_LOG_BUFFER_SIZE - width - 1;
+  jerry_char_t *indent_p = buffer_p + JERRY_LOG_BUFFER_SIZE - width - 1;
 
   while (cursor_p > indent_p)
   {
@@ -5226,9 +5212,9 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
   }
 
   va_list vl;
-  char buffer_p[JERRY_LOG_BUFFER_SIZE];
-  uint32_t buffer_index = 0;
-  const char *cursor_p = format_p;
+  jerry_char_t buffer_p[JERRY_LOG_BUFFER_SIZE];
+  jerry_size_t buffer_index = 0;
+  const jerry_char_t *cursor_p = (const jerry_char_t *) format_p;
   va_start (vl, format_p);
 
   while (*cursor_p != '\0')
@@ -5236,7 +5222,7 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
     if (*cursor_p == '%' || buffer_index > JERRY_LOG_BUFFER_SIZE - 2)
     {
       buffer_p[buffer_index] = '\0';
-      jerry_log_string (buffer_p);
+      jerry_log_string (buffer_p, buffer_index);
       buffer_index = 0;
     }
 
@@ -5248,8 +5234,8 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
 
     ++cursor_p;
     uint8_t width = 0;
-    size_t precision = 0;
-    char padding = ' ';
+    jerry_size_t precision = 0;
+    jerry_char_t padding = ' ';
 
     if (*cursor_p == '0')
     {
@@ -5269,7 +5255,7 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
     }
     else if (*cursor_p == '.' && *(cursor_p + 1) == '*')
     {
-      precision = (size_t) va_arg (vl, int);
+      precision = (jerry_size_t) va_arg (vl, int);
       cursor_p += 2;
     }
 
@@ -5284,36 +5270,36 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
     {
       case 's':
       {
-        char *str_p = va_arg (vl, char *);
+        jerry_char_t *str_p = va_arg (vl, jerry_char_t *);
 
         if (precision == 0)
         {
-          jerry_log_string (str_p);
+          jerry_log_string (str_p, (jerry_size_t) strlen ((const char *) str_p));
           break;
         }
 
-        jerry_log_string_fixed (str_p, precision, buffer_p);
+        jerry_log_string (str_p, precision);
         break;
       }
       case 'c':
       {
         /* Arguments of types narrower than int are promoted to int for variadic functions */
-        buffer_p[buffer_index++] = (char) va_arg (vl, int);
+        buffer_p[buffer_index++] = (jerry_char_t) va_arg (vl, int);
         break;
       }
       case 'd':
       {
-        jerry_log_string (jerry_format_int (va_arg (vl, int), width, padding, buffer_p));
+        jerry_log_cursor (jerry_format_int (va_arg (vl, int), width, padding, buffer_p), buffer_p);
         break;
       }
       case 'u':
       {
-        jerry_log_string (jerry_format_unsigned (va_arg (vl, unsigned int), width, padding, 10, buffer_p));
+        jerry_log_cursor (jerry_format_unsigned (va_arg (vl, unsigned int), width, padding, 10, buffer_p), buffer_p);
         break;
       }
       case 'x':
       {
-        jerry_log_string (jerry_format_unsigned (va_arg (vl, unsigned int), width, padding, 16, buffer_p));
+        jerry_log_cursor (jerry_format_unsigned (va_arg (vl, unsigned int), width, padding, 16, buffer_p), buffer_p);
         break;
       }
       default:
@@ -5327,7 +5313,7 @@ jerry_log (jerry_log_level_t level, const char *format_p, ...)
   if (buffer_index > 0)
   {
     buffer_p[buffer_index] = '\0';
-    jerry_log_string (buffer_p);
+    jerry_log_string (buffer_p, buffer_index);
   }
 
   va_end (vl);
diff --git a/jerry-core/include/jerryscript-compiler.h b/jerry-core/include/jerryscript-compiler.h
index 4732f010f7..41117d237e 100644
--- a/jerry-core/include/jerryscript-compiler.h
+++ b/jerry-core/include/jerryscript-compiler.h
@@ -185,6 +185,13 @@ void *__cdecl _alloca (size_t _Size);
 #define JERRY_VLA(type, name, size) type name[size]
 #endif /* !JERRY_VLA */
 
+/**
+ * Helper to make sure unused parameters, variables, or expressions trigger no compiler warning.
+ */
+#ifndef JERRY_UNUSED
+#define JERRY_UNUSED(x) ((void) (x))
+#endif /* !JERRY_UNUSED */
+
 /**
  * @}
  */
diff --git a/jerry-core/include/jerryscript-port.h b/jerry-core/include/jerryscript-port.h
index 420ecd9bdf..cdcf9af7be 100644
--- a/jerry-core/include/jerryscript-port.h
+++ b/jerry-core/include/jerryscript-port.h
@@ -144,8 +144,11 @@ void jerry_port_context_free (void);
  *
  * The implementation can decide whether error and debug messages are logged to
  * the console, or saved to a database or to a file.
+ *
+ * @param buffer_p: input buffer that is a zero-terminated UTF-8 string
+ * @param buffer_size: data size
  */
-void jerry_port_log (const char *message_p);
+void jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size);
 
 /**
  * Print a buffer to standard output
diff --git a/jerry-core/jrt/jrt.h b/jerry-core/jrt/jrt.h
index 2c1f308d96..9c18653f81 100644
--- a/jerry-core/jrt/jrt.h
+++ b/jerry-core/jrt/jrt.h
@@ -30,11 +30,6 @@
  */
 #define JERRY_BITSINBYTE 8
 
-/*
- * Make sure unused parameters, variables, or expressions trigger no compiler warning.
- */
-#define JERRY_UNUSED(x) ((void) (x))
-
 #define JERRY_UNUSED_1(_1)                             JERRY_UNUSED (_1)
 #define JERRY_UNUSED_2(_1, _2)                         JERRY_UNUSED (_1), JERRY_UNUSED_1 (_2)
 #define JERRY_UNUSED_3(_1, _2, _3)                     JERRY_UNUSED (_1), JERRY_UNUSED_2 (_2, _3)
diff --git a/jerry-core/parser/js/common.c b/jerry-core/parser/js/common.c
index eafd167704..26287fc425 100644
--- a/jerry-core/parser/js/common.c
+++ b/jerry-core/parser/js/common.c
@@ -65,11 +65,7 @@ static void
 util_print_chars (const uint8_t *char_p, /**< character pointer */
                   size_t size) /**< size */
 {
-  while (size > 0)
-  {
-    JERRY_DEBUG_MSG ("%c", *char_p++);
-    size--;
-  }
+  JERRY_DEBUG_MSG ("%.*s", (int) size, char_p);
 } /* util_print_chars */
 
 /**
@@ -81,7 +77,7 @@ util_print_number (ecma_number_t num_p) /**< number to print */
   lit_utf8_byte_t str_buf[ECMA_MAX_CHARS_IN_STRINGIFIED_NUMBER];
   lit_utf8_size_t str_size = ecma_number_to_utf8_string (num_p, str_buf, sizeof (str_buf));
   str_buf[str_size] = 0;
-  JERRY_DEBUG_MSG ("%s", str_buf);
+  JERRY_DEBUG_MSG ("%.*s", (int) str_size, str_buf);
 } /* util_print_number */
 
 #if JERRY_BUILTIN_BIGINT
diff --git a/jerry-ext/common/jext-common.h b/jerry-ext/common/jext-common.h
index 946de890ba..afba6f35f9 100644
--- a/jerry-ext/common/jext-common.h
+++ b/jerry-ext/common/jext-common.h
@@ -22,11 +22,6 @@
 #include "jerryscript-port.h"
 #include "jerryscript.h"
 
-/*
- * Make sure unused parameters, variables, or expressions trigger no compiler warning.
- */
-#define JERRYX_UNUSED(x) ((void) (x))
-
 /*
  * Asserts
  *
@@ -70,7 +65,7 @@ void JERRY_ATTR_NORETURN jerry_unreachable (const char *file, const char *functi
   {                      \
     if (false)           \
     {                    \
-      JERRYX_UNUSED (x); \
+      JERRY_UNUSED (x);  \
     }                    \
   } while (0)
 
diff --git a/jerry-ext/debugger/debugger-common.c b/jerry-ext/debugger/debugger-common.c
index 9b03f2239b..3f2915df95 100644
--- a/jerry-ext/debugger/debugger-common.c
+++ b/jerry-ext/debugger/debugger-common.c
@@ -35,7 +35,7 @@ jerryx_debugger_after_connect (bool success) /**< tells whether the connection
     jerry_debugger_transport_close ();
   }
 #else /* !(defined (JERRY_DEBUGGER) && (JERRY_DEBUGGER == 1)) */
-  JERRYX_UNUSED (success);
+  JERRY_UNUSED (success);
 #endif /* defined (JERRY_DEBUGGER) && (JERRY_DEBUGGER == 1) */
 } /* jerryx_debugger_after_connect */
 
diff --git a/jerry-ext/debugger/debugger-serial.c b/jerry-ext/debugger/debugger-serial.c
index 3a4215f087..8a0c5ff204 100644
--- a/jerry-ext/debugger/debugger-serial.c
+++ b/jerry-ext/debugger/debugger-serial.c
@@ -402,7 +402,7 @@ jerryx_debugger_serial_create (const char *config) /**< specify the configuratio
 bool
 jerryx_debugger_serial_create (const char *config)
 {
-  JERRYX_UNUSED (config);
+  JERRY_UNUSED (config);
   return false;
 } /* jerryx_debugger_serial_create */
 
diff --git a/jerry-ext/debugger/debugger-tcp.c b/jerry-ext/debugger/debugger-tcp.c
index 8483470559..76cbc9a12d 100644
--- a/jerry-ext/debugger/debugger-tcp.c
+++ b/jerry-ext/debugger/debugger-tcp.c
@@ -399,7 +399,7 @@ jerryx_debugger_tcp_create (uint16_t port) /**< listening port */
 bool
 jerryx_debugger_tcp_create (uint16_t port)
 {
-  JERRYX_UNUSED (port);
+  JERRY_UNUSED (port);
   return false;
 } /* jerryx_debugger_tcp_create */
 
diff --git a/jerry-port/common/jerry-port-io.c b/jerry-port/common/jerry-port-io.c
index 26ae7c4445..eaa6633ca7 100644
--- a/jerry-port/common/jerry-port-io.c
+++ b/jerry-port/common/jerry-port-io.c
@@ -19,14 +19,11 @@
 
 #include "jerryscript-port.h"
 
-/**
- * Default implementation of jerry_port_log. Prints log messages to stderr.
- */
 void JERRY_ATTR_WEAK
-jerry_port_log (const char *message_p) /**< message */
+jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
 {
-  fputs (message_p, stderr);
-} /* jerry_port_log */
+  fwrite (buffer_p, 1, buffer_size, stderr);
+} /* jerry_port_log_buffer */
 
 void JERRY_ATTR_WEAK
 jerry_port_print_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
diff --git a/targets/baremetal-sdk/espressif/main/jerry-port.c b/targets/baremetal-sdk/espressif/main/jerry-port.c
index 6655b21874..e79dc9cbb2 100644
--- a/targets/baremetal-sdk/espressif/main/jerry-port.c
+++ b/targets/baremetal-sdk/espressif/main/jerry-port.c
@@ -30,14 +30,11 @@
 
 static const char ESP_JS_TAG[] = "JS";
 
-/**
- * Provide log message implementation for the engine.
- */
 void
-jerry_port_log (const char *message_p) /**< message */
+jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
 {
-  ESP_LOGI (ESP_JS_TAG, "%s", message_p);
-} /* jerry_port_log */
+  ESP_LOGI (ESP_JS_TAG, "%s", buffer_p);
+} /* jerry_port_log_buffer */
 
 /**
  * Implementation of jerry_port_fatal.
diff --git a/targets/os/mbedos/jerry-port.cpp b/targets/os/mbedos/jerry-port.cpp
index 9ba1383c48..cf7bc6f550 100644
--- a/targets/os/mbedos/jerry-port.cpp
+++ b/targets/os/mbedos/jerry-port.cpp
@@ -29,23 +29,20 @@ jerry_port_fatal (jerry_fatal_code_t code)
   exit ((int) code);
 } /* jerry_port_fatal */
 
-/**
- * Provide log message implementation for the engine.
- */
 void
-jerry_port_log (const char *message_p) /**< message */
+jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
 {
-  while (*message_p != '\0')
+  for (jerry_size_t i = 0; i < buffer_size; ++i)
   {
-    if (*message_p == '\n')
+    if (buffer_p[i] == '\n')
     {
       /* add CR for proper display in serial monitors */
       fputc ('\r', stderr);
     }
 
-    fputc (*message_p++, stderr);
+    fputc (buffer_p[i], stderr);
   }
-} /* jerry_port_log */
+} /* jerry_port_log_buffer */
 
 /**
  * Dummy function to get the time zone adjustment.
diff --git a/targets/os/nuttx/jerry-port.c b/targets/os/nuttx/jerry-port.c
index c4f65a44a6..f90c918826 100644
--- a/targets/os/nuttx/jerry-port.c
+++ b/targets/os/nuttx/jerry-port.c
@@ -19,14 +19,12 @@
 
 #include "jerryscript-port.h"
 
-/**
- * Default implementation of jerry_port_log. Prints log messages to stderr.
- */
 void
-jerry_port_log (const char *message_p) /**< message */
+jerry_port_log_buffer (const jerry_char_t *buffer_p, jerry_size_t buffer_size)
 {
-  (void) message_p;
-} /* jerry_port_log */
+  JERRY_UNUSED (buffer_p);
+  JERRY_UNUSED (buffer_size);
+} /* jerry_port_log_buffer */
 
 /**
  * Read a line from standard input as a zero-terminated string.
diff --git a/tests/unit-core/test-common.h b/tests/unit-core/test-common.h
index b6d83491c5..b34166d96c 100644
--- a/tests/unit-core/test-common.h
+++ b/tests/unit-core/test-common.h
@@ -25,8 +25,6 @@
 
 #include "jerryscript-port.h"
 
-#define JERRY_UNUSED(x) ((void) (x))
-
 #define TEST_ASSERT(x)                                           \
   do                                                             \
   {                                                              \
diff --git a/tests/unit-ext/test-common.h b/tests/unit-ext/test-common.h
index 5941f46184..562e9470cc 100644
--- a/tests/unit-ext/test-common.h
+++ b/tests/unit-ext/test-common.h
@@ -20,8 +20,6 @@
 
 #define ARRAY_SIZE(array) ((unsigned long) (sizeof (array) / sizeof ((array)[0])))
 
-#define JERRY_UNUSED(x) ((void) (x))
-
 #define TEST_ASSERT(x)                                           \
   do                                                             \
   {                                                              \