Implement common external function handlers in jerry-ext (#1787)

Added `handler` module to `jerry-ext` to contain implementation of
commonly used external function handlers: `assert`, `gc`, and
`print`.

Also adapted jerry-main to use jerry-ext/handler

JerryScript-DCO-1.0-Signed-off-by: Akos Kiss akiss@inf.u-szeged.hu

jerry-ext/handler/handler-assert.c

@@ -0,0 +1,45 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "jerryscript-ext/handler.h"
+#include "jerryscript-port.h"
+
+/**
+ * Assert for scripts. The routine calls jerry_port_fatal on assertion failure.
+ *
+ * @return true - if only one argument was passed and that argument was a boolean true.
+ *         Note that the function does not return otherwise.
+ */
+jerry_value_t
+jerryx_handler_assert (const jerry_value_t func_obj_val, /**< function object */
+                       const jerry_value_t this_p, /**< this arg */
+                       const jerry_value_t args_p[], /**< function arguments */
+                       const jerry_length_t args_cnt) /**< number of function arguments */
+{
+  (void) func_obj_val; /* unused */
+  (void) this_p; /* unused */
+
+  if (args_cnt == 1
+      && jerry_value_is_boolean (args_p[0])
+      && jerry_get_boolean_value (args_p[0]))
+  {
+    return jerry_create_boolean (true);
+  }
+  else
+  {
+    jerry_port_log (JERRY_LOG_LEVEL_ERROR, "Script Error: assertion failed\n");
+    jerry_port_fatal (ERR_FAILED_INTERNAL_ASSERTION);
+  }
+} /* jerryx_handler_assert */