Issue compiling generated C++ sources due to -Wnarrowing error on max CDR size of struct

[m-mead]

Hi, I am running into an issue when compiling generated C++ sources that have been generated from IDL files using fastddsgen. The error is a -Wnarrowing compiler error that is generated because the generated CDR size of a struct is greater than can fit in a uint32_t.

I need help understanding why a type’s generated _max_cdr_typesize could be so large.

The IDL have been successfully used with the CycloneDDS toolchain.

Software versions

• Foonathan_memory_vendor v1.3.1
• Fast-CDR: v2.2.1
• Fast-DDS: v2.14.1
• Fast-DDS-Gen: v3.3.0
• GCC: 9.4.0
• Ubuntu: 20.04

Compiler error

root@79074fa071b4:/workspace/build# make -j16 epromisa_dds_messages
Generating ePromisa FastDDS C++ sources for dds_object_track_array.idl
openjdk version "11.0.22" 2024-01-16
OpenJDK Runtime Environment (build 11.0.22+7-post-Ubuntu-0ubuntu220.04.1)
OpenJDK 64-Bit Server VM (build 11.0.22+7-post-Ubuntu-0ubuntu220.04.1, mixed mode)
Processing the file dds_object_track_array.idl...
Generating Type definition files...
Generating TopicDataTypes files...
Adding project: dds_object_track_array.idl
Building CXX object utils/dds/CMakeFiles/epromisa_dds_messages.dir/dds_object_track_array.cxx.o
Building CXX object utils/dds/CMakeFiles/epromisa_dds_messages.dir/dds_object_track_arrayPubSubTypes.cxx.o
In file included from /workspace/build/utils/dds/dds_object_track_arrayCdrAux.ipp:25,
                 from /workspace/build/utils/dds/dds_object_track_array.cxx:1009:
/workspace/build/utils/dds/dds_object_track_arrayCdrAux.hpp:39:80: error: narrowing conversion of ‘6083028363212’ from ‘long unsigned int’ to ‘uint32_t’ {aka ‘unsigned int’} [-Wnarrowing]
   39 | constexpr uint32_t dds_object_track_array_msg_max_cdr_typesize {6083028363212UL};
      |                                                                                ^
/workspace/build/utils/dds/dds_object_track_arrayCdrAux.hpp:48:72: error: narrowing conversion of ‘60830283632’ from ‘long unsigned int’ to ‘uint32_t’ {aka ‘unsigned int’} [-Wnarrowing]
   48 | constexpr uint32_t dds_object_track_msg_max_cdr_typesize {60830283632UL};
      |                                                                        ^
make[3]: *** [utils/dds/CMakeFiles/epromisa_dds_messages.dir/build.make:89: utils/dds/CMakeFiles/epromisa_dds_messages.dir/dds_object_track_array.cxx.o] Error 1
make[3]: *** Waiting for unfinished jobs....
In file included from /workspace/build/utils/dds/dds_object_track_arrayPubSubTypes.cxx:26:
/workspace/build/utils/dds/dds_object_track_arrayCdrAux.hpp:39:80: error: narrowing conversion of ‘6083028363212’ from ‘long unsigned int’ to ‘uint32_t’ {aka ‘unsigned int’} [-Wnarrowing]
   39 | constexpr uint32_t dds_object_track_array_msg_max_cdr_typesize {6083028363212UL};
      |                                                                                ^
/workspace/build/utils/dds/dds_object_track_arrayCdrAux.hpp:48:72: error: narrowing conversion of ‘60830283632’ from ‘long unsigned int’ to ‘uint32_t’ {aka ‘unsigned int’} [-Wnarrowing]
   48 | constexpr uint32_t dds_object_track_msg_max_cdr_typesize {60830283632UL};
      |                                                                        ^
make[3]: *** [utils/dds/CMakeFiles/epromisa_dds_messages.dir/build.make:103: utils/dds/CMakeFiles/epromisa_dds_messages.dir/dds_object_track_arrayPubSubTypes.cxx.o] Error 1
make[2]: *** [CMakeFiles/Makefile2:1929: utils/dds/CMakeFiles/epromisa_dds_messages.dir/all] Error 2
make[1]: *** [CMakeFiles/Makefile2:1936: utils/dds/CMakeFiles/epromisa_dds_messages.dir/rule] Error 2
make: *** [Makefile:192: epromisa_dds_messages] Error 2

How the sources are being generated

We have a custom CMake function which generates a shared library by first invoking fastddsgen to generate C++ sources from the IDL, and then adds those generates sources to the CMake target.

# CMake function used to generate target
function(epromisa_dds_generate_shared_library)
    set(oneValueArgs TARGET SOURCE_DIR BINARY_DIR)
    set(multiValueArgs FILES)

    cmake_parse_arguments(PARSED_ARG "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})

    if(NOT fastcdr_FOUND)
        find_package(fastcdr 2 REQUIRED)
    endif()

    if(NOT fastrtps_FOUND)
        find_package(fastrtps 2.12 REQUIRED)
    endif()

    set(ALL_GENERATED_FILES)

    foreach(IDL_FILE ${PARSED_ARG_FILES})
        get_filename_component(FILENAME ${IDL_FILE} NAME_WE)

        set(GENERERATED_HPP_FILES ${FILENAME}.h ${FILENAME}PubSubTypes.h)
        set(GENERERATED_CPP_FILES ${FILENAME}.cxx ${FILENAME}PubSubTypes.cxx)

        list(APPEND ALL_GENERATED_FILES ${GENERERATED_HPP_FILES})
        list(APPEND ALL_GENERATED_FILES ${GENERERATED_CPP_FILES})
    endforeach()

    add_custom_command(
        OUTPUT ${ALL_GENERATED_FILES}
        COMMAND fastddsgen -replace -d ${PARSED_ARG_BINARY_DIR} ${PARSED_ARG_FILES}
        WORKING_DIRECTORY ${PARSED_ARG_SOURCE_DIR}
        DEPENDS ${PARSED_ARG_FILES}
        COMMENT "Generating ePromisa FastDDS C++ sources for ${PARSED_ARG_FILES}"
    )

    add_library(${PARSED_ARG_TARGET} SHARED
        ${ALL_GENERATED_FILES}
    )

    set_target_properties(${PARSED_ARG_TARGET}
        PROPERTIES
            POSITION_INDEPENDENT_CODE ON
    )

    target_include_directories(${PARSED_ARG_TARGET}
        PUBLIC
            ${PARSED_ARG_SOURCE_DIR}
            ${PARSED_ARG_BINARY_DIR}
    )

    target_link_libraries(${PARSED_ARG_TARGET}
        fastrtps
        fastdds::optionparser
        fastcdr
    )
endfunction()

# Generating a shared library from IDL files.
epromisa_dds_generate_shared_library(
    TARGET
        epromisa_dds_messages
    SOURCE_DIR
        ${PROJECT_SOURCE_DIR}
    BINARY_DIR
        ${PROJECT_BINARY_DIR}
    FILES
        dds_object_track_array.idl
)

install(TARGETS epromisa_dds_messages LIBRARY DESTINATION lib)

IDL files

#ifndef DDS_OBJECT_TRACK_ARRAY_H
#define DDS_OBJECT_TRACK_ARRAY_H

module dds_point3d {
    struct msg {
        int16 x;
        int16 y;
        int16 z;
    };
};

module dds_short_point3d {
    @final
    struct msg {
        int16 x;
        int16 y;
        int16 z;
    };
};

module dds_triangle {
    @final
    struct msg {
        sequence<dds_short_point3d::msg> vertices;
    };
};

module dds_mesh {
    @appendable
    struct msg {
        sequence<dds_triangle::msg> triangles;
    };
};

module dds_object {
    @appendable struct msg {
        sequence<dds_point3d::msg> points;
        sequence<dds_mesh::msg> meshes;
    };
};

module dds_object_array {
    @appendable
    struct msg {
        sequence<dds_object::msg> objects;
    };
};

module dds_object_track {
    @appendable
    struct msg {
        dds_object::msg object_;
        sequence<dds_object_array::msg> detections;
    };
};

module dds_object_track_array {
    @appendable
    struct msg {
        sequence<dds_object_track::msg> tracks;
    };
};

#endif

[m-mead]

We solved this issue by setting bounds on the sequence fields in the IDL. It seems that leaving the sequence max size unspecified results in a large max CDR size.

Solution to limit the sequence size for others in the future:

module dds_object_track_array {
    @appendable
    struct msg {
        sequence<dds_object_track::msg, 10> tracks;
    };
};