Agent has crashed when using UXR_REUSE flag on entity's creation

[bhlt]

Change creation mode from UXR_REPLACE to UXR_RESUE in RequestAdder example, then the DDS Agent has been aborted when I run this example app secondly!!! Modify:

const char* participant_xml = "<dds>"
            "<participant>"
            "<rtps>"
            "<name>default_xrce_participant</name>"
            "</rtps>"
            "</participant>"
            "</dds>";
    uint16_t participant_req = uxr_buffer_create_participant_xml(&session, reliable_out, participant_id, 0,
                    participant_xml, UXR_REPLACE);

    replier_id = uxr_object_id(0x01, UXR_REPLIER_ID);
    const char* replier_xml = "<dds>"
            "<replier profile_name=\"my_requester\""
            "service_name=\"service_name\""
            "request_type=\"request_type\""
            "reply_type=\"reply_type\">"
            "</replier>"
            "</dds>";
    uint16_t replier_req = uxr_buffer_create_replier_xml(&session, reliable_out, replier_id, participant_id,
                    replier_xml, UXR_REPLACE);

runing twice, Agent is aborted, as below:

terminate called after throwing an instance of 'dds::xrce::XRCETypesException'
  what():  This member is not been selected

the Agent backtrace is:

(gdb) bt
#0  __pthread_kill_implementation (no_tid=0, signo=6, threadid=140737211524672) at ./nptl/pthread_kill.c:44
#1  __pthread_kill_internal (signo=6, threadid=140737211524672) at ./nptl/pthread_kill.c:78
#2  __GI___pthread_kill (threadid=140737211524672, signo=signo@entry=6) at ./nptl/pthread_kill.c:89
#3  0x00007ffff7331476 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#4  0x00007ffff73177f3 in __GI_abort () at ./stdlib/abort.c:79
#5  0x00007ffff75b9bbe in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#6  0x00007ffff75c524c in ?? () from /lib/x86_64-linux-gnu/libstdc++.so.6
#7  0x00007ffff75c52b7 in std::terminate() () from /lib/x86_64-linux-gnu/libstdc++.so.6
#8  0x00007ffff75c5518 in __cxa_throw () from /lib/x86_64-linux-gnu/libstdc++.so.6
#9  0x00007ffff7d0b846 in dds::xrce::OBJK_Representation3Formats::object_reference[abi:cxx11]() const (this=0x7fffef7fda80) at /projects/git/Micro-XRCE-DDS-Agent/src/cpp/types/XRCETypes.cpp:1333
#10 0x00007ffff7d03f14 in eprosima::uxr::Requester::matched (this=0x7fffe010b990, new_object_rep=...) at /projects/git/Micro-XRCE-DDS-Agent/src/cpp/requester/Requester.cpp:103
#11 0x00007ffff7ce5e99 in eprosima::uxr::ProxyClient::create_object (this=0x7fffe0000b80, creation_mode=..., objectid_prefix=..., object_representation=...)
    at /projects/git/Micro-XRCE-DDS-Agent/src/cpp/client/ProxyClient.cpp:140

Can tell me what the problem is?

[pablogs9]

Is your entity created so it can be replaced?

https://micro-xrce-dds.docs.eprosima.com/en/latest/client.html?highlight=UXR_REPLACE#creation-policy-table

[bhlt]

It works when using UXR_REPLACE mode

[pablogs9]

In order to use UXR_RESUE the entities must exist in order to be reusable.

[bhlt]

I thought the entities has existed, because it's normal at the first running, but Agent crashed after trying again.

[pablogs9]

Please provide full code to replicate this issue so we can reproduce the error.

[bhlt]

this is examples/RequestAdder/main.c, I change UXR_REPLACE to UXR_REUSE:

// Copyright 2017 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.

#include <uxr/client/client.h>

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <inttypes.h>

#define STREAM_HISTORY  8
#define BUFFER_SIZE     UXR_CONFIG_UDP_TRANSPORT_MTU* STREAM_HISTORY

void on_reply(
        uxrSession* session,
        uxrObjectId object_id,
        uint16_t request_id,
        uint16_t reply_id,
        ucdrBuffer* ub,
        uint16_t length,
        void* args)
{
    (void) session;
    (void) object_id;
    (void) request_id;
    (void) length;
    (void) args;

    uint64_t result;
    ucdr_deserialize_uint64_t(ub, &result);

#ifdef WIN32
    printf("Reply received: %I64u [id: %d]\n", result, reply_id);
#else
    printf("Reply received: %" PRIu64 " [id: %d]\n", result, reply_id);
#endif /* ifdef WIN32 */
}

int main(
        int args,
        char** argv)
{
    if (3 > args || 0 == atoi(argv[2]))
    {
        printf("usage: program [-h | --help] | ip port [key]\n");
        return 0;
    }

    char* ip = argv[1];
    char* port = argv[2];
    uint32_t key = (args == 4) ? (uint32_t)atoi(argv[3]) : 0xAAAABBBB;

    // Transport
    uxrUDPTransport transport;
    if (!uxr_init_udp_transport(&transport, UXR_IPv4, ip, port))
    {
        printf("Error at init transport.\n");
        return 1;
    }

    // Session
    uxrSession session;
    uxr_init_session(&session, &transport.comm, key);
    uxr_set_reply_callback(&session, on_reply, false);
    if (!uxr_create_session(&session))
    {
        printf("Error at init session.\n");
        return 1;
    }

    // Streams
    uint8_t output_reliable_stream_buffer[BUFFER_SIZE];
    uxrStreamId reliable_out = uxr_create_output_reliable_stream(&session, output_reliable_stream_buffer, BUFFER_SIZE,
                    STREAM_HISTORY);

    uint8_t input_reliable_stream_buffer[BUFFER_SIZE];
    uxrStreamId reliable_in = uxr_create_input_reliable_stream(&session, input_reliable_stream_buffer, BUFFER_SIZE,
                    STREAM_HISTORY);

    // Create entities
    uxrObjectId participant_id = uxr_object_id(0x01, UXR_PARTICIPANT_ID);
    const char* participant_xml = "<dds>"
            "<participant>"
            "<rtps>"
            "<name>default_xrce_participant</name>"
            "</rtps>"
            "</participant>"
            "</dds>";
    uint16_t participant_req = uxr_buffer_create_participant_xml(&session, reliable_out, participant_id, 0,
                    participant_xml, UXR_REUSE);
                    // participant_xml, UXR_REPLACE);

    uxrObjectId requester_id = uxr_object_id(0x01, UXR_REQUESTER_ID);
    const char* requester_xml = "<dds>"
            "<requester profile_name=\"my_requester\""
            "service_name=\"service_name\""
            "request_type=\"request_type\""
            "reply_type=\"reply_type\">"
            "</requester>"
            "</dds>";
    uint16_t requester_req = uxr_buffer_create_requester_xml(&session, reliable_out, requester_id, participant_id,
                    requester_xml, UXR_REUSE);
                    // requester_xml, UXR_REPLACE);

    // Send create entities message and wait its status
    uint8_t status[2];
    uint16_t requests[2] = {
        participant_req, requester_req
    };
    if (!uxr_run_session_until_all_status(&session, 1000, requests, status, 2))
    {
        printf("Error at create entities: participant: %i requester: %i\n", status[0], status[1]);
        return 1;
    }

    // Request replies
    uxrDeliveryControl delivery_control = {
        0
    };
    delivery_control.max_samples = UXR_MAX_SAMPLES_UNLIMITED;
    uxr_buffer_request_data(&session, reliable_out, requester_id, reliable_in,
            &delivery_control);

    // Write requests
    bool connected = true;
    uint32_t count = 0;
    while (connected)
    {
        uint8_t request[2 * 4] = {
            0
        };
        ucdrBuffer ub;

        ucdr_init_buffer(&ub, request, sizeof(request));
        ucdr_serialize_uint32_t(&ub, count);
        ucdr_serialize_uint32_t(&ub, count);

        uint16_t request_id = uxr_buffer_request(&session, reliable_out, requester_id, request, sizeof(request));
        printf("Request sent: (%d + %d) [id: %d]\n", count, count, request_id);
        connected = uxr_run_session_time(&session, 1000);

        ++count;
    }

    return 0;
}

[pablogs9]

Which version of the Micro XRCE-DDS Agent and Client are you using? I have just replicated your code and I have found no error.

Please provide complete replication instructions.

[bhlt]

Client version: 2.2.0 Agent vsersion: 2.2.0 build environment : Ubuntu 22.04, gcc 11.3.0, cmake 3.24.2 runtime environment: Ubuntu 22.04 Build agent without any modification, then modify examples/RequestAdder/main.c as mentioned above before client building. start agent in shell by command "MicroXRCEAgent udp4 -p 2022" start example client in another shell by command "RequestAdder 127.0.0.1 2022", then stop the client by Ctrl+C; start again by the same way. At this time, we can discover the Agent has crashed.

[pablogs9]

Hello @bhlt I have found the bug, we are working on it here: https://github.com/eProsima/Micro-XRCE-DDS-Agent/pull/318

I will notify when we merge it

[bhlt]

Thanks @pablogs9