Additional checking around the timer.

rclcpp/CMakeLists.txt

@@ -329,6 +329,7 @@ if(BUILD_TESTING)
     ament_target_dependencies(test_utilities
       "rcl")
     target_link_libraries(test_utilities ${PROJECT_NAME})
+  endif()
 
   ament_add_gtest(test_multi_threaded_executor test/executors/test_multi_threaded_executor.cpp
     APPEND_LIBRARY_DIRS "${append_library_dirs}")
@@ -337,7 +338,15 @@ if(BUILD_TESTING)
       "rcl")
     target_link_libraries(test_multi_threaded_executor ${PROJECT_NAME})
   endif()
-endif()
+
+  ament_add_gtest(test_single_threaded_executor test/executors/test_single_threaded_executor.cpp
+    APPEND_LIBRARY_DIRS "${append_library_dirs}")
+  if(TARGET test_single_threaded_executor)
+    ament_target_dependencies(test_single_threaded_executor
+      "rcl")
+    target_link_libraries(test_single_threaded_executor ${PROJECT_NAME})
+  endif()
+endif(BUILD_TESTING)
 
 ament_package(
   CONFIG_EXTRAS rclcpp-extras.cmake

rclcpp/include/rclcpp/executor.hpp

@@ -22,6 +22,7 @@
 #include <iostream>
 #include <list>
 #include <memory>
+#include <set>
 #include <string>
 #include <vector>
 
@@ -351,6 +352,7 @@ class Executor
   RCLCPP_DISABLE_COPY(Executor)
 
   std::vector<rclcpp::node_interfaces::NodeBaseInterface::WeakPtr> weak_nodes_;
+  std::set<rclcpp::TimerBase::SharedPtr> taken_timers_;
 };
 
 }  // namespace executor

rclcpp/src/rclcpp/executor.cpp

@@ -36,16 +36,16 @@ using rclcpp::executor::ExecutorArgs;
 using rclcpp::executor::FutureReturnCode;
 
 Executor::Executor(const ExecutorArgs & args)
-: spinning(false),
+  : spinning(false),
   memory_strategy_(args.memory_strategy)
 {
   rcl_guard_condition_options_t guard_condition_options = rcl_guard_condition_get_default_options();
   if (rcl_guard_condition_init(
       &interrupt_guard_condition_, guard_condition_options) != RCL_RET_OK)
   {
     throw std::runtime_error(
-            std::string("Failed to create interrupt guard condition in Executor constructor: ") +
-            rcl_get_error_string_safe());
+      std::string("Failed to create interrupt guard condition in Executor constructor: ") +
+      rcl_get_error_string_safe());
   }
 
   // The number of guard conditions is always at least 2: 1 for the ctrl-c guard cond,
@@ -251,6 +251,10 @@ Executor::execute_any_executable(AnyExecutable::SharedPtr any_exec)
   }
   if (any_exec->timer) {
     execute_timer(any_exec->timer);
+    auto it = taken_timers_.find(any_exec->timer);
+    if (it != taken_timers_.end()) {
+      taken_timers_.erase(it);
+    }
   }
   if (any_exec->subscription) {
     execute_subscription(any_exec->subscription);
@@ -281,7 +285,7 @@ Executor::execute_subscription(
   rmw_message_info_t message_info;
 
   auto ret = rcl_take(subscription->get_subscription_handle().get(),
-      message.get(), &message_info);
+    message.get(), &message_info);
   if (ret == RCL_RET_OK) {
     message_info.from_intra_process = false;
     subscription->handle_message(message, message_info);
@@ -379,7 +383,7 @@ Executor::wait_for_work(std::chrono::nanoseconds timeout)
     weak_nodes_.erase(
       remove_if(
         weak_nodes_.begin(), weak_nodes_.end(),
-        [](rclcpp::node_interfaces::NodeBaseInterface::WeakPtr i)
+        [] (rclcpp::node_interfaces::NodeBaseInterface::WeakPtr i)
         {
           return i.expired();
         }
@@ -407,40 +411,40 @@ Executor::wait_for_work(std::chrono::nanoseconds timeout)
       &wait_set_, memory_strategy_->number_of_ready_subscriptions()) != RCL_RET_OK)
   {
     throw std::runtime_error(
-            std::string("Couldn't resize the number of subscriptions in wait set : ") +
-            rcl_get_error_string_safe());
+      std::string("Couldn't resize the number of subscriptions in wait set : ") +
+      rcl_get_error_string_safe());
   }
 
   if (rcl_wait_set_resize_services(
       &wait_set_, memory_strategy_->number_of_ready_services()) != RCL_RET_OK)
   {
     throw std::runtime_error(
-            std::string("Couldn't resize the number of services in wait set : ") +
-            rcl_get_error_string_safe());
+      std::string("Couldn't resize the number of services in wait set : ") +
+      rcl_get_error_string_safe());
   }
 
   if (rcl_wait_set_resize_clients(
       &wait_set_, memory_strategy_->number_of_ready_clients()) != RCL_RET_OK)
   {
     throw std::runtime_error(
-            std::string("Couldn't resize the number of clients in wait set : ") +
-            rcl_get_error_string_safe());
+      std::string("Couldn't resize the number of clients in wait set : ") +
+      rcl_get_error_string_safe());
   }
 
   if (rcl_wait_set_resize_guard_conditions(
       &wait_set_, memory_strategy_->number_of_guard_conditions()) != RCL_RET_OK)
   {
     throw std::runtime_error(
-            std::string("Couldn't resize the number of guard_conditions in wait set : ") +
-            rcl_get_error_string_safe());
+      std::string("Couldn't resize the number of guard_conditions in wait set : ") +
+      rcl_get_error_string_safe());
   }
 
   if (rcl_wait_set_resize_timers(
       &wait_set_, memory_strategy_->number_of_ready_timers()) != RCL_RET_OK)
   {
     throw std::runtime_error(
-            std::string("Couldn't resize the number of timers in wait set : ") +
-            rcl_get_error_string_safe());
+      std::string("Couldn't resize the number of timers in wait set : ") +
+      rcl_get_error_string_safe());
   }
 
   if (!memory_strategy_->add_handles_to_wait_set(&wait_set_)) {
@@ -522,10 +526,12 @@ Executor::get_next_timer(AnyExecutable::SharedPtr any_exec)
       }
       for (auto & timer_ref : group->get_timer_ptrs()) {
         auto timer = timer_ref.lock();
-        if (timer && timer->is_ready()) {
+
+        if (timer && timer->is_ready() && taken_timers_.count(timer) == 0) {
           any_exec->timer = timer;
           any_exec->callback_group = group;
           node = get_node_by_group(group);
+          taken_timers_.insert(timer);
           return;
         }
       }
@@ -603,7 +609,7 @@ rclcpp::executor::operator<<(std::ostream & os, const FutureReturnCode & future_
 }
 
 std::string
-rclcpp::executor::to_string(const FutureReturnCode &future_return_code)
+rclcpp::executor::to_string(const FutureReturnCode & future_return_code)
 {
   using enum_type = std::underlying_type<FutureReturnCode>::type;
   std::string prefix = "Unknown enum value (";