A segment error occurred after the conn_lost() was executed

[okyihu]

HI,SIR A segment fault occurred after the conn_lost() was executed , once I called MQTTClient_connect(client, &conn_opts) in conn_lost() function , the programe could re-connect the broker, but immediately a segment fault occured , why, what am I doing wrong. more information : just now I re-compile this program with gcc and run it on unbuntu desktop system , this program run correctly ,no segment fault . so strange.

My code is :

include "stdlib.h"

include "string.h"

include "unistd.h"

include "MQTTClient.h"

include "mqtt_req_proc.h"

// Enable or disable SSL/TLS connection (1 for SSL/TLS, 0 for TCP)

define USE_SSL 0

if USE_SSL

define ADDRESS "ssl://broker.emqx.io:8883"

else

// #define ADDRESS "tcp://47.106.203.236:1883"

define ADDRESS "tcp://112.74.85.63:1883"

// #define ADDRESS "b187a1e0.ala.dedicated.aliyun.emqxcloud.cn:1883"

endif

define USERNAME "steve"

define PASSWORD "Zrr_4410693"

define CLIENTID "c-client"

define QOS 0

define PUB_TOPIC "192.168.1.103_internal_service"

define SUB_TOPIC "192.168.1.103_public_service"

define TIMEOUT 10000L

MQTTClient_SSLOptions configureSSLOptions() { MQTTClient_SSLOptions ssl_opts = MQTTClient_SSLOptions_initializer; ssl_opts.enableServerCertAuth = 1; // ssl_opts.trustStore = CA_CERTIFICATE_FILE; return ssl_opts; }

void publish(MQTTClient client, char topic, char payload) { MQTTClient_message message = MQTTClient_message_initializer; message.payload = payload; message.payloadlen = strlen(payload); message.qos = QOS; message.retained = 1; MQTTClient_deliveryToken token; MQTTClient_publishMessage(client, topic, &message, &token); MQTTClient_waitForCompletion(client, token, TIMEOUT); printf("Send %s to topic %s \n", payload, PUB_TOPIC); } int request_completed = 0; int on_message(void context, char topicName, int topicLen, MQTTClient_message message) { char payload = message->payload; // printf("Received %s from %s topic \n", payload, topicName);

    request_completed = 1;
    MQTTClient_freeMessage(&message);
    MQTTClient_free(topicName);
    return 1;

}

void conn_lost(void context, char cause) { printf("\nConnection lost\n"); printf(" cause: %s\n", cause); int rc; MQTTClient client = (MQTTClient )context;

MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
     conn_opts.username = USERNAME;
    conn_opts.password = PASSWORD;
conn_opts.keepAliveInterval = 10;
conn_opts.cleansession = 1;

while (1)
{
            rc= MQTTClient_connect(client, &conn_opts);
    if (rc == MQTTCLIENT_SUCCESS)
    {
        printf("Reconnection Successful\n");
        break;
    }
    else
    {
        printf("Failed to connect, return code %d\n", rc);
    }
    sleep(10);
}

while (1)
{
    if (MQTTClient_subscribe(client, SUB_TOPIC, QOS) == MQTTCLIENT_SUCCESS)
    {
        printf("Resubscribe Successful\n");
        break;
    }
    else
    {
        printf("Resubscribe Failure\n");
    }
    sleep(1);
}

}

int main(int argc, char *argv[]) { int rc; MQTTClient client;

     MQTTClient_create(&client, ADDRESS, CLIENTID, MQTTCLIENT_PERSISTENCE_NONE, NULL);

    MQTTClient_connectOptions conn_opts = MQTTClient_connectOptions_initializer;
    conn_opts.username = USERNAME;
    conn_opts.password = PASSWORD;

if USE_SSL

    MQTTClient_SSLOptions ssl_opts = configureSSLOptions();
    conn_opts.ssl = &ssl_opts;

endif

    conn_opts.keepAliveInterval = 10;
    conn_opts.cleansession = 1;
    MQTTClient_setCallbacks(client, client, conn_lost, on_message, NULL);
    if ((rc = MQTTClient_connect(client, &conn_opts)) != MQTTCLIENT_SUCCESS)
    {
            printf("Failed to connect, return code %d\n", rc);
            exit(-1);

    }
    else
    {
            printf("Connected to MQTT Broker!\n");
    }
    // subscribe topic
    MQTTClient_subscribe(client, SUB_TOPIC, QOS);

    while (1)
    {
            if (request_completed)
            {
                    request_completed = 0;
                    publish(client, PUB_TOPIC, res);  
            }
    }
    MQTTClient_unsubscribe(client, TOPIC);
    MQTTClient_disconnect(client, TIMEOUT);
    MQTTClient_destroy(&client);
    return rc;

}

[icraggs]

The first thing is that the cause field in the connectionLost callback can be null, so it should be checked for that before printing.

Next, the program should not spend a long time in callbacks, which means no sleeping. The only API call allowed in connectionLost is connect - no subscribe or any other.

[SeaAndSand]

"The only API call allowed in connectionLost is connect。" How should understand this sentence? In fact, I called B client's publish function in A client's connlost. When A client triggers connlost, it crashes very easily.

[19:13:25.384]Program received signal SIGSEGV, Segmentation fault. [19:13:25.384]malloc_consolidate (av=av@entry=0x75b00010) at malloc.c:4141 [19:13:25.384]4141    malloc.c: No such file or directory. 19:13:29.134 bt [19:13:29.134]#0  malloc_consolidate (av=av@entry=0x75b00010) at malloc.c:4141 [19:13:29.134]#1  0x76edd538 in _int_free (av=0x75b00010, p=, have_lock=0) at malloc.c:4049 [19:13:29.134]#2  0x76e757c4 in MQTTProperties_free () from /usr/lib/libpaho-mqtt3c.so.1 [19:13:29.134]Backtrace stopped: previous frame identical to this frame (corrupt stack?)