哪个变量导致分段故障？ [英] Which variable cause segmentation fault?

问题描述

正在尝试调试MQTT Paho库中的未处理异常。不知道具体是哪个变量出现分段故障。变量m和ma不为空。不确定m->c->connect_state中的{...}是什么意思。

如何知道是哪个确切变量引发了问题？

如何解决此问题？

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 以及他们为什么会做出这样的任务： MQTTClients*m=句柄；

推荐答案

如何知道是哪个确切变量引发了问题？

替换

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

临时与

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;

现在您可以查看是哪个变量导致了问题。

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