fix: Fix data race in CallbackGroup::size() (#3056)

jmachowinski · Janosch Machowinski · web-flow · commit 4d950baa1528 · 2026-02-11T18:05:09.000+01:00
The computation of the size was not protected by a mutex, leading
to possible data races.

Signed-off-by: Janosch Machowinski &lt;J.Machowinski@cellumation.com&gt;
Co-authored-by: Janosch Machowinski &lt;J.Machowinski@cellumation.com&gt;
diff --git a/rclcpp/src/rclcpp/callback_group.cpp b/rclcpp/src/rclcpp/callback_group.cpp
@@ -59,6 +59,7 @@ CallbackGroup::type() const
 size_t
 CallbackGroup::size() const
 {
+  std::lock_guard<std::mutex> lock(mutex_);
   return
     subscription_ptrs_.size() +
     service_ptrs_.size() +

Original file line number	Diff line number	Diff line change
`@@ -59,6 +59,7 @@ CallbackGroup::type() const`
`59`	`59`	`size_t`
`60`	`60`	`CallbackGroup::size() const`
`61`	`61`	`{`
	`62`	`+ std::lock_guard<std::mutex> lock(mutex_);`
`62`	`63`	`return`
`63`	`64`	`subscription_ptrs_.size() +`
`64`	`65`	`service_ptrs_.size() +`