targets: zephyr: Reinstate "print" function and error printing. (#1851)

Re-add "print" function following resent refactors when it was moved
from jerry-core to jerry-ext. This is done in particular to keep
detailed messages on errors.

JerryScript-DCO-1.0-Signed-off-by: Paul Sokolovsky paul.sokolovsky@linaro.org

targets/zephyr/src/Makefile

@@ -17,6 +17,6 @@ $(info Compiling application)
 endif
 
 # Adding path for jerry script APIs
-ZEPHYRINCLUDE += -I$(JERRY_INCLUDE)
+ZEPHYRINCLUDE += $(JERRY_INCLUDE)
 
 obj-y += main-zephyr.o getline-zephyr.o jerry-port.o

targets/zephyr/src/jerry-port.c

@@ -72,3 +72,13 @@ jerry_port_get_time_zone (jerry_time_zone_t *tz_p)
 
   return true;
 } /* jerry_port_get_time_zone */
+
+/**
+ * Provide the implementation of jerryx_port_handler_print_char.
+ * Uses 'printf' to print a single character to standard output.
+ */
+void
+jerryx_port_handler_print_char (char c) /**< the character to print */
+{
+  printf ("%c", c);
+} /* jerryx_port_handler_print_char */

targets/zephyr/src/main-zephyr.c

@@ -22,9 +22,28 @@
 #include "getline-zephyr.h"
 
 #include "jerryscript.h"
+#include "jerryscript-port.h"
+#include "jerryscript-ext/handler.h"
 
 static jerry_value_t print_function;
 
+/**
+ * Register a JavaScript function in the global object.
+ */
+static void
+register_js_function (const char *name_p, /**< name of the function */
+                      jerry_external_handler_t handler_p) /**< function callback */
+{
+  jerry_value_t result_val = jerryx_handler_register_global ((const jerry_char_t *) name_p, handler_p);
+
+  if (jerry_value_has_error_flag (result_val))
+  {
+    jerry_port_log (JERRY_LOG_LEVEL_WARNING, "Warning: failed to register '%s' method.", name_p);
+  }
+
+  jerry_release_value (result_val);
+} /* register_js_function */
+
 static int shell_cmd_handler (char *source_buffer)
 {
   jerry_value_t ret_val;
@@ -69,6 +88,7 @@ void main (void)
 
   zephyr_getline_init ();
   jerry_init (JERRY_INIT_EMPTY);
+  register_js_function ("print", jerryx_handler_print);
   jerry_value_t global_obj_val = jerry_get_global_object ();
 
   jerry_value_t print_func_name_val = jerry_create_string ((jerry_char_t *) "print");