Build fails on Windows: Cannot open include file: 'sched.h'

[RobertoRoos]

I am trying to build and run the ROS2Control demo, but during building I run into the following error: Cannot open include file: 'sched.h'

I am following the instructions here: https://control.ros.org/master/doc/getting_started/getting_started.html#building-from-source
Using ROS2 Humble, with Windows 10.

The full build output is:

stdout_stderr.log

-- Selecting Windows SDK version 10.0.22621.0 to target Windows 10.0.19045.
-- Found ament_cmake: 1.3.5 (C:/dev/ros2_humble/share/ament_cmake/cmake)
-- Found rclcpp: 16.0.5 (C:/dev/ros2_humble/share/rclcpp/cmake)
-- Found rosidl_generator_c: 3.1.5 (C:/dev/ros2_humble/share/rosidl_generator_c/cmake)
-- Found rosidl_adapter: 3.1.5 (C:/dev/ros2_humble/share/rosidl_adapter/cmake)
-- Found rosidl_generator_cpp: 3.1.5 (C:/dev/ros2_humble/share/rosidl_generator_cpp/cmake)
-- Using all available rosidl_typesupport_c: rosidl_typesupport_fastrtps_c;rosidl_typesupport_introspection_c
-- Using all available rosidl_typesupport_cpp: rosidl_typesupport_fastrtps_cpp;rosidl_typesupport_introspection_cpp
-- Found rmw_implementation_cmake: 6.1.1 (C:/dev/ros2_humble/share/rmw_implementation_cmake/cmake)
-- Found rmw_fastrtps_cpp: 6.2.3 (C:/dev/ros2_humble/share/rmw_fastrtps_cpp/cmake)
-- Using RMW implementation 'rmw_fastrtps_cpp' as default
-- Found rclcpp_action: 16.0.5 (C:/dev/ros2_humble/share/rclcpp_action/cmake)
-- Found ament_cmake_gmock: 1.3.5 (C:/dev/ros2_humble/share/ament_cmake_gmock/cmake)
-- Found test_msgs: 1.2.1 (C:/dev/ros2_humble/share/test_msgs/cmake)
-- Found gmock sources under 'C:/dev/ros2_humble/src/gmock_vendor': C++ tests using 'Google Mock' will be built
-- Found ament_cmake_gtest: 1.3.5 (C:/dev/ros2_humble/share/ament_cmake_gtest/cmake)
-- Found gtest sources under 'C:/dev/ros2_humble/src/gtest_vendor': C++ tests using 'Google Test' will be built
-- Configuring done (4.1s)
-- Generating done (1.6s)
-- Build files have been written to: C:/Users/Name/project/ros2_control_ws/build/realtime_tools
MSBuild version 17.7.2+d6990bcfa for .NET Framework

1>Checking Build System
gmock.vcxproj -> C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\gmock\Release\gmock.lib
gmock_main.vcxproj -> C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\gmock\Release\gmock_main.lib
Building Custom Rule C:/Users/Name/project/ros2_control_ws/src/realtime_tools/CMakeLists.txt
realtime_tools.vcxproj -> C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\Release\realtime_tools.dll
Building Custom Rule C:/Users/Name/project/ros2_control_ws/src/realtime_tools/CMakeLists.txt
LINK : fatal error LNK1181: cannot open input file 'Release\realtime_tools.lib' [C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\realtime_box_tests.vcxproj]
Building Custom Rule C:/Users/Name/project/ros2_control_ws/src/realtime_tools/CMakeLists.txt
LINK : fatal error LNK1181: cannot open input file 'Release\realtime_tools.lib' [C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\realtime_buffer_tests.vcxproj]
Building Custom Rule C:/Users/Name/project/ros2_control_ws/src/realtime_tools/CMakeLists.txt
LINK : fatal error LNK1181: cannot open input file 'Release\realtime_tools.lib' [C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\realtime_clock_tests.vcxproj]
Building Custom Rule C:/Users/Name/project/ros2_control_ws/src/realtime_tools/CMakeLists.txt
LINK : fatal error LNK1181: cannot open input file 'Release\realtime_tools.lib' [C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\realtime_publisher_tests.vcxproj]
Building Custom Rule C:/Users/Name/project/ros2_control_ws/src/realtime_tools/CMakeLists.txt
LINK : fatal error LNK1181: cannot open input file 'Release\realtime_tools.lib' [C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\realtime_publisher_tests_non_polling.vcxproj]
Building Custom Rule C:/Users/Name/project/ros2_control_ws/src/realtime_tools/CMakeLists.txt
LINK : fatal error LNK1181: cannot open input file 'Release\realtime_tools.lib' [C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\realtime_server_goal_handle_tests.vcxproj]
Building Custom Rule C:/Users/Name/project/ros2_control_ws/src/realtime_tools/CMakeLists.txt
thread_priority.cpp
C:\Users\Users\Name\project\ros2_control_ws\src\realtime_tools\src\thread_priority.cpp(31,10): fatal error C1083: Cannot open include file: 'sched.h': No such file or directory [C:\Users\Users\Name\project\ros2_control_ws\build\realtime_tools\thread_priority.vcxproj]

I am not sure to what extend Windows is even supported for ROS2Control, I hope this issue won't do any harm. Thanks!

[bmagyar]

Windows support: we do have all the boilerplate for DLLs in place. Everything else should be handled by ament but we don't have a windows CI so no means really to keep things building. You are welcome to propose a fix, the Linux CIs should help guide you to a compatible solution.

[bmagyar]

Please no #IF Windows :D

[bmagyar]

I found a simple solution, using cygwin/mingw (aka anything coming from gcc and the POSIX world) will have compatible versions: https://stackoverflow.com/questions/27667552/porting-sched-h-to-windows

[AustinMooreT]

Sorry to comment on an old issue, but if someone is in my shoes I got things to at least build with msvc with a tiny bit of cheap hackery.
Sadly I don't have the luxury of a minimal gnu implementation. I know this isn't ideal, but it'll get you building and linking, and hopefully no runtime errors?

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4743d98..06e5e6a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,6 +3,9 @@ project(realtime_tools LANGUAGES CXX)

 if(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Clang)")
   add_compile_options(-Wall -Wextra)
+elseif (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
+  # windows needs a .lib with all of the exported symbols to link to a shared library
+  set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON)
 endif()

 set(THIS_PACKAGE_INCLUDE_DEPENDS
diff --git a/src/thread_priority.cpp b/src/thread_priority.cpp
index 72749e3..04e6960 100644
--- a/src/thread_priority.cpp
+++ b/src/thread_priority.cpp
@@ -28,7 +28,10 @@

 #include "realtime_tools/thread_priority.hpp"

+#ifdef __linux__
 #include <sched.h>
+#elif _WIN32
+#endif

 #include <cstring>
 #include <fstream>
@@ -37,20 +40,29 @@ namespace realtime_tools
 {
 bool has_realtime_kernel()
 {
+#ifdef __linux__
   std::ifstream realtime_file("/sys/kernel/realtime", std::ios::in);
   bool has_realtime = false;
   if (realtime_file.is_open()) {
     realtime_file >> has_realtime;
   }
   return has_realtime;
+#elif _WIN32
+  return false;  // TODO: is it possible to configure windows for realtime?
+#endif
 }

 bool configure_sched_fifo(int priority)
 {
+#ifdef __linux__
   struct sched_param schedp;
   memset(&schedp, 0, sizeof(schedp));
   schedp.sched_priority = priority;
   return !sched_setscheduler(0, SCHED_FIFO, &schedp);
+#elif _WIN32
+  return false;  // TODO: maybe add the ability to set proccess priority to realtime?
+                 // see https://stackoverflow.com/questions/27732280/porting-set-fifo-to-windows
+#endif
 }

 }  // namespace realtime_tools