[onert] Add API function for retrieving last error message

This commit adds dedicated API function nnfw_get_last_error_message()
for retrieving last error message in case when other functions return
status code other than NNFW_STATUS_NO_ERROR.

ONE-DCO-1.0-Signed-off-by: Arkadiusz Bokowy <[email protected]>

Author: arkq

runtime/onert/api/nnfw/include/nnfw.h

@@ -212,6 +212,17 @@ NNFW_STATUS nnfw_create_session(nnfw_session **session);
  */
 NNFW_STATUS nnfw_close_session(nnfw_session *session);
 
+/**
+ * @brief Get the last error message
+ *
+ * This function retrieves the last error message occurred in the session.
+ *
+ * @param[in] session session to be queried on.
+ * @return    The last error message string. The returned pointer is valid only
+ *            until the next API call with the same session.
+ */
+const char *nnfw_get_last_error_message(nnfw_session *session);
+
 /**
  * @brief     Load model from path to model or nnpackage
  *

runtime/onert/api/nnfw/src/APIImpl.cc

@@ -69,6 +69,13 @@ NNFW_STATUS nnfw_close_session(nnfw_session *session)
   return NNFW_STATUS_NO_ERROR;
 }
 
+const char *nnfw_get_last_error_message(nnfw_session *session)
+{
+  if (session == NULL)
+    return "Session is NULL";
+  return reinterpret_cast<Session *>(session)->get_last_error_message().c_str();
+}
+
 NNFW_STATUS nnfw_load_model_from_file(nnfw_session *session, const char *path)
 {
   NNFW_RETURN_ERROR_IF_NULL(session);