Compilation error on Windows with ROS Humble when downstream project is compiled with BUILD_SHARED_LIBS set to OFF

[traversaro]

Bug report

Required Info:

• Operating System:
  • Windows 10/11
• Installation type:
  • Binaries
• Version or commit hash:
  • https://github.com/ros2/ros2/releases/download/release-humble-20220523/ros2-humble-20220523-windows-release-amd64.zip
• DDS implementation:
  • fastrtps
• Client library (if applicable):
  • N/A

Steps to reproduce issue

See the CI.yml GitHub of the repo https://github.com/traversaro/test_static_lib_ros2_srv. In particular, this repo generate the library for a .srv file, and the important thing is that the CMake project is compiled with BUILD_SHARED_LIBS set to OFF .

Expected behavior

I would expect the compilation to end successfully, as it was happening in Galactic.

Actual behavior

The compilation fails with error:

Additional information

I think this is a regression of #87, where:

if(WIN32)
  target_compile_definitions(${rosidl_generate_interfaces_TARGET}${_target_suffix}
    PRIVATE "ROSIDL_TYPESUPPORT_FASTRTPS_CPP_BUILDING_DLL_${PROJECT_NAME}")
endif()

has been substituted with

set_target_properties(${rosidl_generate_interfaces_TARGET}${_target_suffix}
  PROPERTIES
    DEFINE_SYMBOL "ROSIDL_TYPESUPPORT_FASTRTPS_CPP_BUILDING_DLL_${PROJECT_NAME}"
    CXX_STANDARD 14)

However, this is not the fully story. The use of DEFINE_SYMBOL is actually correct in this context. The reason why everything is now failing is that the visibility header generated by this repo does not cover the case of a static libraries, for which the ROSIDL_TYPESUPPORT_FASTRTPS_CPP_PUBLIC_@PROJECT_NAME@ macro should evaluate to an empty string. Everything was working fine just because apparently in this case static libraries do not have problems if functions inside them are defined as __attribute__ ((dllexport)). The most complete fix would be to consider the static case in the visibility header macro (as done for example in the example at the end of https://gcc.gnu.org/wiki/Visibility), and pass to the library some kind of macro to indicate if the library is static or shared.