哪个变量导致分段错误？

Question

尝试调试 MQTT Paho 库中未处理的异常。无法弄清楚哪个确切的变量会引起分段错误。变量 m 和 ma 不为 NULL。不确定{...} 在m->c->connect_state 中的含义。

如何知道是哪个变量引发了问题？

如何解决这个问题？

MQTTClient.c中的函数代码：

int MQTTClient_setCallbacks(MQTTClient handle, void* context, MQTTClient_connectionLost* cl,
                                                        MQTTClient_messageArrived* ma, MQTTClient_deliveryComplete* dc)
{
    int rc = MQTTCLIENT_SUCCESS;
    MQTTClients* m = handle;

    FUNC_ENTRY;
    Thread_lock_mutex(mqttclient_mutex);

    if (m == NULL || ma == NULL || m->c->connect_state != NOT_IN_PROGRESS)
        rc = MQTTCLIENT_FAILURE;
    else
    {
        m->context = context;
        m->cl = cl;
        m->ma = ma;
        m->dc = dc;
    }

    Thread_unlock_mutex(mqttclient_mutex);
    FUNC_EXIT_RC(rc);
    return rc;
}

此代码来自官方 Paho 库： https://github.com/eclipse/paho.mqtt.c/blob/master/src/MQTTClient.c 以及为什么他们做出这样的任务： MQTTClients* m = 句柄；

Answer 1

如何知道是哪个变量引发了问题？

替换

if (m == NULL || ma == NULL || m->c->connect_state != NOT_IN_PROGRESS)
    rc = MQTTCLIENT_FAILURE;

暂时与

if (m == NULL)
    rc = MQTTCLIENT_FAILURE;

else if (ma == NULL)
    rc = MQTTCLIENT_FAILURE;

else if (m->c->connect_state != NOT_IN_PROGRESS)
    rc = MQTTCLIENT_FAILURE;

现在您可以看到是哪个变量导致了问题。