Following the guide, I download ros2 source code, and build whole ros2 successfully. However, when I download freertps to src/ros2/freertps, trigger build as below
$ament build src/ros2/freertps
Process package 'freertps' with context:
source_space => /home/jwang/ros2_ws/src/ros2/freertps
build_space => /home/jwang/ros2_ws/build/freertps
install_space => /home/jwang/ros2_ws/install
make_flags => -j8, -l8
build_tests => False
+++ Building 'freertps'
Running cmake because arguments have changed.
==> '. /home/jwang/ros2_ws/build/freertps/cmake__build.sh && /usr/bin/cmake /home/jwang/ros2_ws/src/ros2/freertps -DBUILD_TESTING=0 -DCMAKE_INSTALL_PREFIX=/home/jwang/ros2_ws/install' in '/home/jwang/ros2_ws/build/freertps'
-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is GNU 5.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found ament_cmake: 0.0.3 (/home/jwang/ros2_ws/install/share/ament_cmake/cmake)
-- Found PythonInterp: /usr/bin/python3 (found suitable version "3.5.2", minimum required is "3")
CMake Warning (dev) at /home/jwang/ros2_ws/install/share/ament_cmake_core/cmake/core/list_append_unique.cmake:30 (if):
Policy CMP0057 is not set: Support new IN_LIST if() operator. Run "cmake
--help-policy CMP0057" for policy details. Use the cmake_policy command to
set the policy and suppress this warning.
IN_LIST will be interpreted as an operator when the policy is set to NEW.
Since the policy is not set the OLD behavior will be used.
Call Stack (most recent call first):
/home/jwang/ros2_ws/install/share/ament_cmake_export_include_directories/cmake/ament_export_include_directories.cmake:41 (list_append_unique)
CMakeLists.txt:12 (ament_export_include_directories)
This warning is for project developers. Use -Wno-dev to suppress it.
CMake Error at /home/jwang/ros2_ws/install/share/ament_cmake_core/cmake/core/list_append_unique.cmake:30 (if):
if given arguments:
"NOT" "element" "IN_LIST" "_AMENT_EXPORT_RELATIVE_INCLUDE_DIRECTORIES"
Unknown arguments specified
Call Stack (most recent call first):
/home/jwang/ros2_ws/install/share/ament_cmake_export_include_directories/cmake/ament_export_include_directories.cmake:41 (list_append_unique)
CMakeLists.txt:12 (ament_export_include_directories)