Support this binding retrieval for backtrace frames (#4669)

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

jerry-core/api/jerry.c

@@ -5276,6 +5276,26 @@ jerry_backtrace_get_function (jerry_backtrace_frame_t *frame_p) /**< frame point
   return NULL;
 } /* jerry_backtrace_get_function */
 
+/**
+ * Initialize and return with the 'this' binding private field of a backtrace frame.
+ * The 'this' binding is a hidden value passed to the called function. As for arrow
+ * functions, the 'this' binding is assigned at function creation.
+ *
+ * @return pointer to the 'this' binding - if the binding is available,
+ *         NULL - otherwise
+ */
+const jerry_value_t *
+jerry_backtrace_get_this (jerry_backtrace_frame_t *frame_p) /**< frame pointer */
+{
+  if (frame_p->frame_type == JERRY_BACKTRACE_FRAME_JS)
+  {
+    frame_p->this_binding = frame_p->context_p->this_binding;
+    return &frame_p->this_binding;
+  }
+
+  return NULL;
+} /* jerry_backtrace_get_this */
+
 /**
  * Returns true, if the code bound to the backtrace frame is strict mode code.
  *

jerry-core/include/jerryscript-core.h

@@ -350,6 +350,7 @@ void jerry_backtrace_capture (jerry_backtrace_callback_t callback, void *user_p)
 jerry_backtrace_frame_types_t jerry_backtrace_get_frame_type (jerry_backtrace_frame_t *frame_p);
 const jerry_backtrace_location_t *jerry_backtrace_get_location (jerry_backtrace_frame_t *frame_p);
 const jerry_value_t *jerry_backtrace_get_function (jerry_backtrace_frame_t *frame_p);
+const jerry_value_t *jerry_backtrace_get_this (jerry_backtrace_frame_t *frame_p);
 bool jerry_backtrace_is_strict (jerry_backtrace_frame_t *frame_p);
 
 /**

jerry-core/vm/vm-defines.h

@@ -157,6 +157,7 @@ struct jerry_backtrace_frame_internal_t
   uint8_t frame_type; /**< frame type */
   jerry_backtrace_location_t location; /**< location information */
   ecma_value_t function; /**< function reference */
+  ecma_value_t this_binding; /**< this binding passed to the function */
 };
 
 /**