MicroXRCEDDSGen pollutes global defines with constants

[Ryanf55]

Hello,

I am looking to see if there an alternative to message constants that aren't global defines.

Sample Message from ROS REP-147:

• https://github.com/ArduPilot/ardupilot/blob/eaf20db6ea635eabfc1a8b85d5dca63399a174e6/Tools/ros2/ardupilot_msgs/msg/GlobalPosition.msg#L21
• https://github.com/ArduPilot/ardupilot/blob/eaf20db6ea635eabfc1a8b85d5dca63399a174e6/libraries/AP_DDS/Idl/ardupilot_msgs/msg/GlobalPosition.idl#L31

This generates GlobalPosition.h

// Copyright 2016 Proyectos y Sistemas de Mantenimiento SL (eProsima).
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/*!
 * @file GlobalPosition.h
 * This header file contains the declaration of the described types in the IDL file.
 *
 * This file was generated by the tool microxrceddsgen.
 */

#ifndef _GlobalPosition_H_
#define _GlobalPosition_H_

#ifdef __cplusplus
extern "C"
{
#endif

#include <stdint.h>
#include <stdbool.h>
#include "geometry_msgs/msg/Twist.h"
#include "std_msgs/msg/Header.h"

#define FRAME_GLOBAL_INT 5
#define FRAME_GLOBAL_REL_ALT 6
#define FRAME_GLOBAL_TERRAIN_ALT 11
#define IGNORE_LATITUDE 1
#define IGNORE_LONGITUDE 2
#define IGNORE_ALTITUDE 4
#define IGNORE_VX 8
#define IGNORE_VY 16
#define IGNORE_VZ 32
#define IGNORE_AFX 64
#define IGNORE_AFY 128
#define IGNORE_AFZ 256
#define FORCE 512
#define IGNORE_YAW 1024
#define IGNORE_YAW_RATE 2048
typedef struct ardupilot_msgs_msg_GlobalPosition
{
    std_msgs_msg_Header header;

    uint8_t coordinate_frame;

    uint16_t type_mask;

    double latitude;

    double longitude;

    float altitude;

    geometry_msgs_msg_Twist velocity;

    geometry_msgs_msg_Twist acceleration_or_force;

    float yaw;

} ardupilot_msgs_msg_GlobalPosition;

struct ucdrBuffer;
bool ardupilot_msgs_msg_GlobalPosition_serialize_topic(struct ucdrBuffer* writer, const ardupilot_msgs_msg_GlobalPosition* topic);
bool ardupilot_msgs_msg_GlobalPosition_deserialize_topic(struct ucdrBuffer* reader, ardupilot_msgs_msg_GlobalPosition* topic);
uint32_t ardupilot_msgs_msg_GlobalPosition_size_of_topic(const ardupilot_msgs_msg_GlobalPosition* topic, uint32_t size);

#ifdef __cplusplus
}
#endif

#endif // _GlobalPosition_H_

AND

GlobalPosition.c

// Copyright 2016 Proyectos y Sistemas de Mantenimiento SL (eProsima).
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/*!
 * @file GlobalPosition.h
 * This header file contains the declaration of the described types in the IDL file.
 *
 * This file was generated by the tool microxrceddsgen.
 */

#include "GlobalPosition.h"

#include <ucdr/microcdr.h>
#include <string.h>


bool ardupilot_msgs_msg_GlobalPosition_serialize_topic(ucdrBuffer* writer, const ardupilot_msgs_msg_GlobalPosition* topic)
{
    bool success = true;

        success &= std_msgs_msg_Header_serialize_topic(writer, &topic->header);

        success &= ucdr_serialize_uint8_t(writer, topic->coordinate_frame);

        success &= ucdr_serialize_uint16_t(writer, topic->type_mask);

        success &= ucdr_serialize_double(writer, topic->latitude);

        success &= ucdr_serialize_double(writer, topic->longitude);

        success &= ucdr_serialize_float(writer, topic->altitude);

        success &= geometry_msgs_msg_Twist_serialize_topic(writer, &topic->velocity);

        success &= geometry_msgs_msg_Twist_serialize_topic(writer, &topic->acceleration_or_force);

        success &= ucdr_serialize_float(writer, topic->yaw);


    return success && !writer->error;
}

bool ardupilot_msgs_msg_GlobalPosition_deserialize_topic(ucdrBuffer* reader, ardupilot_msgs_msg_GlobalPosition* topic)
{
    bool success = true;

        success &= std_msgs_msg_Header_deserialize_topic(reader, &topic->header);

        success &= ucdr_deserialize_uint8_t(reader, &topic->coordinate_frame);

        success &= ucdr_deserialize_uint16_t(reader, &topic->type_mask);

        success &= ucdr_deserialize_double(reader, &topic->latitude);

        success &= ucdr_deserialize_double(reader, &topic->longitude);

        success &= ucdr_deserialize_float(reader, &topic->altitude);

        success &= geometry_msgs_msg_Twist_deserialize_topic(reader, &topic->velocity);

        success &= geometry_msgs_msg_Twist_deserialize_topic(reader, &topic->acceleration_or_force);

        success &= ucdr_deserialize_float(reader, &topic->yaw);


    return success && !reader->error;
}

uint32_t ardupilot_msgs_msg_GlobalPosition_size_of_topic(const ardupilot_msgs_msg_GlobalPosition* topic, uint32_t size)
{
    uint32_t previousSize = size;
        size += std_msgs_msg_Header_size_of_topic(&topic->header, size);

        size += ucdr_alignment(size, 1) + 1;

        size += ucdr_alignment(size, 2) + 2;

        size += ucdr_alignment(size, 8) + 8;

        size += ucdr_alignment(size, 8) + 8;

        size += ucdr_alignment(size, 4) + 4;

        size += geometry_msgs_msg_Twist_size_of_topic(&topic->velocity, size);

        size += geometry_msgs_msg_Twist_size_of_topic(&topic->acceleration_or_force, size);

        size += ucdr_alignment(size, 4) + 4;


    return size - previousSize;
}

The defines in header then conflict with an enum field in another library:

https://github.com/ArduPilot/ardupilot/blob/eaf20db6ea635eabfc1a8b85d5dca63399a174e6/libraries/AP_Servo_Telem/AP_Servo_Telem.h#L45

Are there any other alternatives to global defines for these constants that could be adopted?

In ArduPilot, we can use C++, so we can use static constexpr and wrap things in namespace declarations. Any ideas? On a large codebase, the usage of defines for constants that are normally scoped to the namespace of the message is not feasible.