From b6d18ccc813d9f35b080795de764b1730702981a Mon Sep 17 00:00:00 2001
From: Dirk Thomas <dirk-thomas@users.noreply.github.com>
Date: Thu, 19 Sep 2019 13:15:19 -0700
Subject: [PATCH] add more context to exception message (#858)

* add more context to exception message

Signed-off-by: Dirk Thomas <dirk-thomas@users.noreply.github.com>

* fix linter warnings

Signed-off-by: Dirk Thomas <dirk-thomas@users.noreply.github.com>
---
 rclcpp/src/rclcpp/time.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/rclcpp/src/rclcpp/time.cpp b/rclcpp/src/rclcpp/time.cpp
index 980b6a5..b7f0bd2 100644
--- a/rclcpp/src/rclcpp/time.cpp
+++ b/rclcpp/src/rclcpp/time.cpp
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include <limits>
+#include <string>
 #include <utility>
 
 #include "rclcpp/clock.hpp"
@@ -194,7 +195,10 @@ Duration
 Time::operator-(const rclcpp::Time & rhs) const
 {
   if (rcl_time_.clock_type != rhs.rcl_time_.clock_type) {
-    throw std::runtime_error("can't subtract times with different time sources");
+    throw std::runtime_error(
+            std::string("can't subtract times with different time sources [") +
+            std::to_string(rcl_time_.clock_type) + " != " +
+            std::to_string(rhs.rcl_time_.clock_type) + "]");
   }
 
   if (rclcpp::sub_will_overflow(rcl_time_.nanoseconds, rhs.rcl_time_.nanoseconds)) {