Debugging ros2 libraries

Question

I am trying to understand custom memory allocators for ROS2. To understand the functioning of tlsf I am using tlsf_example wrapper project present in src/ros2/realtime_support. I have added dummy print statements to src/ros2/tlsf/tlsf/src/tlsf.c, to just verify if my changes are being applied. The colcon command I ran to build is colcon build --cmake-args -DCMAKE_BUILD_TYPE=Debug --packages-select tlsf tlsf_cpp. I am running the binary present in src/install/tlsf_cpp/lib/tlsf_cpp. But I don't see any of my changes being outputed to terminal. I also tried using gdb but I am not getting any source line info for tlsf_malloc function defined in tlsf.c file.

CMakeLists.txt file for tlsf.c

cmake_minimum_required(VERSION 3.5)

project(tlsf)

if(WIN32 OR APPLE OR ANDROID)
  message(STATUS "tlsf allocator does not target Windows, OSX or Android, skipping...")
  return()
endif()

# Default to C11
if(NOT CMAKE_C_STANDARD)
  set(CMAKE_C_STANDARD 11)
endif()
if(CMAKE_COMPILER_IS_GNUCC OR CMAKE_C_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic -g -O0)
endif()

find_package(ament_cmake REQUIRED)

add_library(${PROJECT_NAME} STATIC src/tlsf.c src/target.h include/tlsf/tlsf.h)
target_include_directories(${PROJECT_NAME} PUBLIC
  "$<BUILD_INTERFACE:${CMAKE_SOURCE_DIR}/include/tlsf>"
  "$<INSTALL_INTERFACE:include/${PROJECT_NAME}>")
set_target_properties(${PROJECT_NAME} PROPERTIES C_VISIBILITY_PRESET hidden)

ament_export_targets(export_${PROJECT_NAME})

# Disable linting for now.
#if(BUILD_TESTING)
#  find_package(ament_lint_auto REQUIRED)
#  ament_lint_auto_find_test_dependencies()
#endif()

ament_package()

install(DIRECTORY include/
  DESTINATION include/${PROJECT_NAME}
)

install(
  TARGETS ${PROJECT_NAME}
  EXPORT export_${PROJECT_NAME}
  ARCHIVE DESTINATION lib
  LIBRARY DESTINATION lib
  RUNTIME DESTINATION bin
)

I am sure that the build command touches tlsf.c file after changes but I am unable to observe any changes in the output. I want to know whether the application I am running actually links to the changed file, is there any way to achieve this? What changes should I do to the CMakeLists.txt file for tlsf? Is the binary I ran the correct binary to expect changes? Also how can I debug tlsf_malloc function in ROS2? I have very little idea about ROS build system, any resources to learn more about it are welcome.

Answer 1

In cmake, add_library() is used to build a library. It does not link it into the project executable. target_link_libraries() does that.

https://cmake.org/cmake/help/latest/command/add_library.html

If the compiler can see both a shared library and a static library with the same library name, I don't recall what the compiler does. You may need to explicitly provide the .a suffix to tell the compiler to use the static version.