diff --git a/rcl/include/rcl/allocator.h b/rcl/include/rcl/allocator.h
index e9014b6..ce32052 100644
--- a/rcl/include/rcl/allocator.h
+++ b/rcl/include/rcl/allocator.h
@@ -20,6 +20,7 @@ extern "C"
 {
 #endif
 
+#include "rcl/macros.h"
 #include "rcl/types.h"
 #include "rcl/visibility_control.h"
 
@@ -61,6 +62,7 @@ typedef struct rcl_allocator_t
  * This function is lock-free.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_allocator_t
 rcl_get_default_allocator();
 
@@ -69,6 +71,7 @@ rcl_get_default_allocator();
  * function pointer fields.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 void *
 rcl_reallocf(void * pointer, size_t size, rcl_allocator_t * allocator);
 
diff --git a/rcl/include/rcl/guard_condition.h b/rcl/include/rcl/guard_condition.h
index 79b4d1d..c1f6c1a 100644
--- a/rcl/include/rcl/guard_condition.h
+++ b/rcl/include/rcl/guard_condition.h
@@ -20,6 +20,7 @@ extern "C"
 {
 #endif
 
+#include "rcl/macros.h"
 #include "rcl/node.h"
 #include "rcl/visibility_control.h"
 
@@ -41,6 +42,7 @@ typedef struct rcl_guard_condition_options_t
 
 /// Return a rcl_guard_condition_t struct with members set to NULL.
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_guard_condition_t
 rcl_get_zero_initialized_guard_condition();
 
@@ -84,6 +86,7 @@ rcl_get_zero_initialized_guard_condition();
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_guard_condition_init(
   rcl_guard_condition_t * guard_condition,
@@ -106,6 +109,7 @@ rcl_guard_condition_init(
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_guard_condition_fini(rcl_guard_condition_t * guard_condition, rcl_node_t * node);
 
@@ -115,6 +119,7 @@ rcl_guard_condition_fini(rcl_guard_condition_t * guard_condition, rcl_node_t * n
  * This function is lock-free.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_guard_condition_options_t
 rcl_guard_condition_get_default_options();
 
@@ -136,6 +141,7 @@ rcl_guard_condition_get_default_options();
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_guard_condition_trigger(const rcl_guard_condition_t * guard_condition);
 
@@ -157,6 +163,7 @@ rcl_guard_condition_trigger(const rcl_guard_condition_t * guard_condition);
  * \return rmw guard_condition handle if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rmw_guard_condition_t *
 rcl_guard_condition_get_rmw_handle(const rcl_guard_condition_t * guard_condition);
 
diff --git a/rcl/include/rcl/macros.h b/rcl/include/rcl/macros.h
new file mode 100644
index 0000000..2399307
--- /dev/null
+++ b/rcl/include/rcl/macros.h
@@ -0,0 +1,33 @@
+// Copyright 2015 Open Source Robotics Foundation, Inc.
+//
+// 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.
+
+#ifndef RCL__MACROS_H_
+#define RCL__MACROS_H_
+
+#if __cplusplus
+extern "C"
+{
+#endif
+
+#ifndef _WIN32
+# define RCL_WARN_UNUSED __attribute__((warn_unused_result))
+#else
+# define RCL_WARN_UNUSED _Check_return_
+#endif
+
+#if __cplusplus
+}
+#endif
+
+#endif  // RCL__MACROS_H_
diff --git a/rcl/include/rcl/node.h b/rcl/include/rcl/node.h
index 6f6c54a..9850810 100644
--- a/rcl/include/rcl/node.h
+++ b/rcl/include/rcl/node.h
@@ -23,6 +23,7 @@ extern "C"
 #include <stdint.h>
 
 #include "rcl/allocator.h"
+#include "rcl/macros.h"
 #include "rcl/types.h"
 #include "rcl/visibility_control.h"
 
@@ -59,6 +60,7 @@ typedef struct rcl_node_options_t
 
 /// Return a rcl_node_t struct with members initialized to NULL.
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_node_t
 rcl_get_zero_initialized_node();
 
@@ -106,6 +108,7 @@ rcl_get_zero_initialized_node();
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_node_init(rcl_node_t * node, const char * name, const rcl_node_options_t * options);
 
@@ -124,6 +127,7 @@ rcl_node_init(rcl_node_t * node, const char * name, const rcl_node_options_t * o
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_node_fini(rcl_node_t * node);
 
@@ -146,6 +150,7 @@ rcl_node_get_default_options();
  * \return name string if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 const char *
 rcl_node_get_name(const rcl_node_t * node);
 
@@ -163,6 +168,7 @@ rcl_node_get_name(const rcl_node_t * node);
  * \return options struct if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 const rcl_node_options_t *
 rcl_node_get_options(const rcl_node_t * node);
 
@@ -185,6 +191,7 @@ rcl_node_get_options(const rcl_node_t * node);
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_node_get_domain_id(const rcl_node_t * node, size_t * domain_id);
 
@@ -207,6 +214,7 @@ rcl_node_get_domain_id(const rcl_node_t * node, size_t * domain_id);
  * \return rmw node handle if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rmw_node_t *
 rcl_node_get_rmw_handle(const rcl_node_t * node);
 
@@ -226,6 +234,7 @@ rcl_node_get_rmw_handle(const rcl_node_t * node);
  * \return rcl instance id captured at node creation or 0 if there was an error
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 uint64_t
 rcl_node_get_rcl_instance_id(const rcl_node_t * node);
 
diff --git a/rcl/include/rcl/publisher.h b/rcl/include/rcl/publisher.h
index 2cc4583..6cc5d8b 100644
--- a/rcl/include/rcl/publisher.h
+++ b/rcl/include/rcl/publisher.h
@@ -22,6 +22,7 @@ extern "C"
 
 #include "rosidl_generator_c/message_type_support.h"
 
+#include "rcl/macros.h"
 #include "rcl/node.h"
 #include "rcl/visibility_control.h"
 
@@ -51,6 +52,7 @@ typedef struct rcl_publisher_options_t
  * being allocated on the heap.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_publisher_t
 rcl_get_zero_initialized_publisher();
 
@@ -126,6 +128,7 @@ rcl_get_zero_initialized_publisher();
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_publisher_init(
   rcl_publisher_t * publisher,
@@ -150,11 +153,13 @@ rcl_publisher_init(
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_publisher_fini(rcl_publisher_t * publisher, rcl_node_t * node);
 
 /// Return the default publisher options in a rcl_publisher_options_t.
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_publisher_options_t
 rcl_publisher_get_default_options();
 
@@ -203,6 +208,7 @@ rcl_publisher_get_default_options();
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_publish(const rcl_publisher_t * publisher, const void * ros_message);
 
@@ -222,6 +228,7 @@ rcl_publish(const rcl_publisher_t * publisher, const void * ros_message);
  * \return name string if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 const char *
 rcl_publisher_get_topic_name(const rcl_publisher_t * publisher);
 
@@ -241,6 +248,7 @@ rcl_publisher_get_topic_name(const rcl_publisher_t * publisher);
  * \return options struct if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 const rcl_publisher_options_t *
 rcl_publisher_get_options(const rcl_publisher_t * publisher);
 
@@ -262,6 +270,7 @@ rcl_publisher_get_options(const rcl_publisher_t * publisher);
  * \return rmw publisher handle if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rmw_publisher_t *
 rcl_publisher_get_rmw_handle(const rcl_publisher_t * publisher);
 
diff --git a/rcl/include/rcl/rcl.h b/rcl/include/rcl/rcl.h
index 21d5f04..0257473 100644
--- a/rcl/include/rcl/rcl.h
+++ b/rcl/include/rcl/rcl.h
@@ -20,6 +20,7 @@ extern "C"
 {
 #endif
 
+#include "rcl/macros.h"
 #include "rcl/node.h"
 #include "rcl/publisher.h"
 #include "rcl/subscription.h"
@@ -60,6 +61,7 @@ extern "C"
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_init(int argc, char ** argv, rcl_allocator_t allocator);
 
@@ -88,6 +90,7 @@ rcl_init(int argc, char ** argv, rcl_allocator_t allocator);
  *         RCL_RET_ERROR if an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_shutdown();
 
@@ -102,6 +105,7 @@ rcl_shutdown();
  * \return a unique id specific to this rcl instance, or 0 if not initialized.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 uint64_t
 rcl_get_instance_id();
 
@@ -112,6 +116,7 @@ rcl_get_instance_id();
  * atomic_is_lock_free() returns true for atomic_uint_least64_t.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 bool
 rcl_ok();
 
diff --git a/rcl/include/rcl/subscription.h b/rcl/include/rcl/subscription.h
index 1c376dc..a417248 100644
--- a/rcl/include/rcl/subscription.h
+++ b/rcl/include/rcl/subscription.h
@@ -22,6 +22,7 @@ extern "C"
 
 #include "rosidl_generator_c/message_type_support.h"
 
+#include "rcl/macros.h"
 #include "rcl/node.h"
 #include "rcl/visibility_control.h"
 
@@ -53,6 +54,7 @@ typedef struct rcl_subscription_options_t
  * is being allocated on the heap.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_subscription_t
 rcl_get_zero_initialized_subscription();
 
@@ -127,6 +129,7 @@ rcl_get_zero_initialized_subscription();
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_subscription_init(
   rcl_subscription_t * subscription,
@@ -153,11 +156,13 @@ rcl_subscription_init(
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_subscription_fini(rcl_subscription_t * subscription, rcl_node_t * node);
 
 /// Return the default subscription options in a rcl_subscription_options_t.
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_subscription_options_t
 rcl_subscription_get_default_options();
 
@@ -204,6 +209,7 @@ rcl_subscription_get_default_options();
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_take(
   const rcl_subscription_t * subscription,
@@ -227,6 +233,7 @@ rcl_take(
  * \return name string if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 const char *
 rcl_subscription_get_topic_name(const rcl_subscription_t * subscription);
 
@@ -246,6 +253,7 @@ rcl_subscription_get_topic_name(const rcl_subscription_t * subscription);
  * \return options struct if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 const rcl_subscription_options_t *
 rcl_subscription_get_options(const rcl_subscription_t * subscription);
 
@@ -269,6 +277,7 @@ rcl_subscription_get_options(const rcl_subscription_t * subscription);
  * \return rmw subscription handle if successful, otherwise NULL
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rmw_subscription_t *
 rcl_subscription_get_rmw_handle(const rcl_subscription_t * subscription);
 
diff --git a/rcl/include/rcl/time.h b/rcl/include/rcl/time.h
index c80c63e..60ccf5d 100644
--- a/rcl/include/rcl/time.h
+++ b/rcl/include/rcl/time.h
@@ -20,6 +20,7 @@ extern "C"
 {
 #endif
 
+#include "rcl/macros.h"
 #include "rcl/types.h"
 #include "rcl/visibility_control.h"
 
@@ -93,6 +94,7 @@ typedef struct rcl_duration_t
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_system_time_point_now(rcl_system_time_point_t * now);
 
@@ -117,6 +119,7 @@ rcl_system_time_point_now(rcl_system_time_point_t * now);
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_steady_time_point_now(rcl_steady_time_point_t * now);
 
diff --git a/rcl/include/rcl/timer.h b/rcl/include/rcl/timer.h
index a8b72a0..8753356 100644
--- a/rcl/include/rcl/timer.h
+++ b/rcl/include/rcl/timer.h
@@ -23,6 +23,7 @@ extern "C"
 #include <stdbool.h>
 
 #include "rcl/allocator.h"
+#include "rcl/macros.h"
 #include "rcl/time.h"
 #include "rcl/types.h"
 #include "rmw/rmw.h"
@@ -51,6 +52,7 @@ typedef void (* rcl_timer_callback_t)(rcl_timer_t *, uint64_t);
 
 /// Return a zero initialized timer.
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_timer_t
 rcl_get_zero_initialized_timer();
 
@@ -112,6 +114,7 @@ rcl_get_zero_initialized_timer();
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_init(
   rcl_timer_t * timer,
@@ -136,6 +139,7 @@ rcl_timer_init(
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_fini(rcl_timer_t * timer);
 
@@ -169,6 +173,7 @@ rcl_timer_fini(rcl_timer_t * timer);
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_call(rcl_timer_t * timer);
 
@@ -193,6 +198,7 @@ rcl_timer_call(rcl_timer_t * timer);
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_is_ready(const rcl_timer_t * timer, bool * is_ready);
 
@@ -222,6 +228,7 @@ rcl_timer_is_ready(const rcl_timer_t * timer, bool * is_ready);
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_get_time_until_next_call(const rcl_timer_t * timer, int64_t * time_until_next_call);
 
@@ -248,6 +255,7 @@ rcl_timer_get_time_until_next_call(const rcl_timer_t * timer, int64_t * time_unt
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_get_time_since_last_call(const rcl_timer_t * timer, uint64_t * time_since_last_call);
 
@@ -268,6 +276,7 @@ rcl_timer_get_time_since_last_call(const rcl_timer_t * timer, uint64_t * time_si
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_get_period(const rcl_timer_t * timer, uint64_t * period);
 
@@ -292,6 +301,7 @@ rcl_timer_get_period(const rcl_timer_t * timer, uint64_t * period);
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_exchange_period(const rcl_timer_t * timer, uint64_t new_period, uint64_t * old_period);
 
@@ -308,6 +318,7 @@ rcl_timer_exchange_period(const rcl_timer_t * timer, uint64_t new_period, uint64
  * \return function pointer to the callback, or NULL if an error occurred
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_timer_callback_t
 rcl_timer_get_callback(const rcl_timer_t * timer);
 
@@ -326,6 +337,7 @@ rcl_timer_get_callback(const rcl_timer_t * timer);
  * \return function pointer to the old callback, or NULL if an error occurred
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_timer_callback_t
 rcl_timer_exchange_callback(rcl_timer_t * timer, const rcl_timer_callback_t new_callback);
 
@@ -347,6 +359,7 @@ rcl_timer_exchange_callback(rcl_timer_t * timer, const rcl_timer_callback_t new_
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_cancel(rcl_timer_t * timer);
 
@@ -368,6 +381,7 @@ rcl_timer_cancel(rcl_timer_t * timer);
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_is_canceled(const rcl_timer_t * timer, bool * is_canceled);
 
@@ -387,6 +401,7 @@ rcl_timer_is_canceled(const rcl_timer_t * timer, bool * is_canceled);
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_timer_reset(rcl_timer_t * timer);
 
diff --git a/rcl/include/rcl/visibility_control.h b/rcl/include/rcl/visibility_control.h
index 24b3a25..85e3b16 100644
--- a/rcl/include/rcl/visibility_control.h
+++ b/rcl/include/rcl/visibility_control.h
@@ -1,4 +1,4 @@
-// Copyright 2014 Open Source Robotics Foundation, Inc.
+// Copyright 2015 Open Source Robotics Foundation, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
diff --git a/rcl/include/rcl/wait.h b/rcl/include/rcl/wait.h
index ca67d19..c36300d 100644
--- a/rcl/include/rcl/wait.h
+++ b/rcl/include/rcl/wait.h
@@ -23,8 +23,9 @@ extern "C"
 #include <stdbool.h>
 #include <stddef.h>
 
-#include "rcl/subscription.h"
 #include "rcl/guard_condition.h"
+#include "rcl/macros.h"
+#include "rcl/subscription.h"
 #include "rcl/timer.h"
 #include "rcl/types.h"
 #include "rcl/visibility_control.h"
@@ -49,6 +50,7 @@ typedef struct rcl_wait_set_t
 
 /// Return a rcl_wait_set_t struct with members set to NULL.
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_wait_set_t
 rcl_get_zero_initialized_wait_set();
 
@@ -93,6 +95,7 @@ rcl_get_zero_initialized_wait_set();
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_init(
   rcl_wait_set_t * wait_set,
@@ -121,6 +124,7 @@ rcl_wait_set_init(
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_fini(rcl_wait_set_t * wait_set);
 
@@ -138,6 +142,7 @@ rcl_wait_set_fini(rcl_wait_set_t * wait_set);
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_get_allocator(const rcl_wait_set_t * wait_set, rcl_allocator_t * allocator);
 
@@ -157,6 +162,7 @@ rcl_wait_set_get_allocator(const rcl_wait_set_t * wait_set, rcl_allocator_t * al
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_add_subscription(
   rcl_wait_set_t * wait_set,
@@ -178,6 +184,7 @@ rcl_wait_set_add_subscription(
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_clear_subscriptions(rcl_wait_set_t * wait_set);
 
@@ -207,6 +214,7 @@ rcl_wait_set_clear_subscriptions(rcl_wait_set_t * wait_set);
  *         RCL_RET_ERROR if an unspecified error occurs.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_resize_subscriptions(rcl_wait_set_t * wait_set, size_t size);
 
@@ -215,6 +223,7 @@ rcl_wait_set_resize_subscriptions(rcl_wait_set_t * wait_set, size_t size);
  * \see rcl_wait_set_add_subscription
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_add_guard_condition(
   rcl_wait_set_t * wait_set,
@@ -225,6 +234,7 @@ rcl_wait_set_add_guard_condition(
  * \see rcl_wait_set_clear_subscriptions
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_clear_guard_conditions(rcl_wait_set_t * wait_set);
 
@@ -233,6 +243,7 @@ rcl_wait_set_clear_guard_conditions(rcl_wait_set_t * wait_set);
  * \see rcl_wait_set_resize_subscriptions
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_resize_guard_conditions(rcl_wait_set_t * wait_set, size_t size);
 
@@ -241,6 +252,7 @@ rcl_wait_set_resize_guard_conditions(rcl_wait_set_t * wait_set, size_t size);
  * \see rcl_wait_set_add_subscription
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_add_timer(
   rcl_wait_set_t * wait_set,
@@ -251,6 +263,7 @@ rcl_wait_set_add_timer(
  * \see rcl_wait_set_clear_subscriptions
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_clear_timers(rcl_wait_set_t * wait_set);
 
@@ -259,6 +272,7 @@ rcl_wait_set_clear_timers(rcl_wait_set_t * wait_set);
  * \see rcl_wait_set_resize_subscriptions
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait_set_resize_timers(rcl_wait_set_t * wait_set, size_t size);
 
@@ -352,6 +366,7 @@ rcl_wait_set_resize_timers(rcl_wait_set_t * wait_set, size_t size);
  *         RCL_RET_ERROR an unspecified error occur.
  */
 RCL_PUBLIC
+RCL_WARN_UNUSED
 rcl_ret_t
 rcl_wait(rcl_wait_set_t * wait_set, int64_t timeout);
 
diff --git a/rcl/src/rcl/wait.c b/rcl/src/rcl/wait.c
index a214673..0323963 100644
--- a/rcl/src/rcl/wait.c
+++ b/rcl/src/rcl/wait.c
@@ -55,14 +55,18 @@ __wait_set_is_valid(const rcl_wait_set_t * wait_set)
 static void
 __wait_set_clean_up(rcl_wait_set_t * wait_set, rcl_allocator_t allocator)
 {
+  rcl_ret_t ret;
   if (wait_set->subscriptions) {
-    rcl_wait_set_resize_subscriptions(wait_set, 0);
+    ret = rcl_wait_set_resize_subscriptions(wait_set, 0);
+    assert(ret == RCL_RET_OK);  // Defensive, shouldn't fail with size 0.
   }
   if (wait_set->guard_conditions) {
-    rcl_wait_set_resize_guard_conditions(wait_set, 0);
+    ret = rcl_wait_set_resize_guard_conditions(wait_set, 0);
+    assert(ret == RCL_RET_OK);  // Defensive, shouldn't fail with size 0.
   }
   if (wait_set->timers) {
-    rcl_wait_set_resize_timers(wait_set, 0);
+    ret = rcl_wait_set_resize_timers(wait_set, 0);
+    assert(ret == RCL_RET_OK);  // Defensive, shouldn't fail with size 0.
   }
   if (wait_set->impl) {
     allocator.deallocate(wait_set->impl, allocator.state);
@@ -416,8 +420,11 @@ rcl_wait(rcl_wait_set_t * wait_set, int64_t timeout)
   // Check for timeout.
   if (ret == RMW_RET_TIMEOUT) {
     // Assume none were set (because timeout was reached first), and clear all.
-    rcl_wait_set_clear_subscriptions(wait_set);
-    rcl_wait_set_clear_guard_conditions(wait_set);
+    rcl_ret_t rcl_ret;
+    rcl_ret = rcl_wait_set_clear_subscriptions(wait_set);
+    assert(rcl_ret == RCL_RET_OK);  // Defensive, shouldn't fail with valid wait_set.
+    rcl_ret = rcl_wait_set_clear_guard_conditions(wait_set);
+    assert(rcl_ret == RCL_RET_OK);  // Defensive, shouldn't fail with valid wait_set.
     return RCL_RET_TIMEOUT;
   }
   // Set corresponding rcl subscription handles NULL.