From c0af872c18ca827ce867c4f83a8d3c956e4e5dfd Mon Sep 17 00:00:00 2001
From: Rohan Agrawal <send2arohan@gmail.com>
Date: Thu, 22 Dec 2016 13:56:44 -0800
Subject: [PATCH] Warn on second call of register_param_change_callback (#297)

---
 rclcpp/src/rclcpp/node_interfaces/node_parameters.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/rclcpp/src/rclcpp/node_interfaces/node_parameters.cpp b/rclcpp/src/rclcpp/node_interfaces/node_parameters.cpp
index 2d0016f..61a79f0 100644
--- a/rclcpp/src/rclcpp/node_interfaces/node_parameters.cpp
+++ b/rclcpp/src/rclcpp/node_interfaces/node_parameters.cpp
@@ -226,5 +226,9 @@ NodeParameters::list_parameters(const std::vector<std::string> & prefixes, uint6
 void
 NodeParameters::register_param_change_callback(ParametersCallbackFunction callback)
 {
+  if (parameters_callback_) {
+    fprintf(stderr, "Warning: param_change_callback already registered, "
+      "overwriting previous callback\n");
+  }
   parameters_callback_ = callback;
 }