[Suggestion] Code-modification to improve the compatibility with the latest version of the compilation environment

[GoesM]

[Suggestion] for code-modification for Navigation2 [within ROS2-humble, Ubuntu 22.04]

To improve the compatibility of navigation2-[ROS2-humble] with the latest version of the compilation environment

Problem Description

For most current versions of compilers, nav2_ costmap_ 2d package often fails to compile smoothly,

Compiling ROS2 humble navigation2 using the latest version of gcc (such as gcc-11,gcc-12) or LLVM compiler (such as clang-11, clang-12, clang-14) will result in the following error:

/...../lib/gcc/x86_64-linux-gnu/11/../../../../include/c++/11/bits/stl_pair.h:314:17: error: the parameter for this explicitly-defaulted copy constructor is const, but a member or base requires it to be non-const
      constexpr pair(const pair&) = default;    ///< Copy constructor

The compilation instructions we used are as follows

we had tried CC&CXX as clang-11, clang-12, clang-14, gcc-11, gcc-12 and so on, our compilation instruction format is similar to:

source /opt/ros/humble/setup.bash
export CC=/usr/bin/clang
export CXX=/usr/bin/clang++
colcon build \
	--cmake-clean-cache \
	--cmake-args \
		-DBUILD_TESTING=OFF \
		-DCMAKE_CXX_STANDARD=17 \
		-DCMAKE_CXX_FLAGS="${CMAKE_CXX_FLAGS} \
			-w -Wno-error -Wno-everything" \
		-DCMAKE_C_FLAGS="${CMAKE_C_FLAGS}  \
			-w -Wno-error -Wno-format-security"

It seems that only gcc-9 could complie the program smoothly, however it's a very old version

Our Suggestions for Modification

suggestion for [nav2_costmap_2d] pkg

here's our core suggestion

In navigation2/nav2_costmap_2d/include/nav2_costmap_2d/denoise/image.hpp, modify the variable type as const:

The specific modification location is indicated in the following code comments:

template<class T>
class Image
{
public:
   ...
  /**
   * @brief Create image referencing to the other
   * Share image data between new and old object.
   * Changing data in a new object will affect the given one and vice versa
   */
//Image(Image & other)
  Image(const Image & other); // add " const " here !!!
   ...

template<class T>
//Image<T>::Image(Image & other) 
Image<T>::Image(const Image & other) // add " const " here !!!
: data_start_{other.data_start_},
  rows_{other.rows_}, columns_{other.columns_}, step_{other.step_} {}

   ...

suggestion for [nav2_mppi_controller] CMakelist.txt

here's just a weak suggestion
In navigation2/nav2_mppi_controller/CMakelist.txt: Suggest adding a C++standard judgment

because it seems like that -fconcepts is not supported by other C++ standards except C++20

foreach(lib IN LISTS libraries)
  #target_compile_options(${lib} PUBLIC -fconcepts) 
  target_compile_options(${lib} PUBLIC) # we delete -fconcepts
  target_include_directories(${lib} PUBLIC include ${xsimd_INCLUDE_DIRS} ${OpenMP_INCLUDE_DIRS})
  target_link_libraries(${lib} xtensor xtensor::optimize xtensor::use_xsimd)
  ament_target_dependencies(${lib} ${dependencies_pkgs})
endforeach()

Looking forward to your reply ^_^

[jay-waves]

Meet the same problem compiling nav2 with Clang 14 using C++17 standard.

[SteveMacenski]

Your PR looks fine - just needs to be targeted to the right place. I'll backport to Humble once its in main.

[SteveMacenski]

Merging