哪个变量导致分段错误？

Question

正在尝试调试 MQTT Paho 库中未处理的异常。无法弄清楚哪个确切变量引起分段错误。变量 m 和 ma 不是 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？

函数代码在MQTTClient.c:

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;
}

这段代码来自Paho官方库： https://github.com/eclipse/paho.mqtt.c/blob/master/src/MQTTClient.c 以及为什么他们做出这样的分配： MQTTClients* m = handle;

Answer 1

How to know which exact variable raised the problem?

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。

哪个变量导致分段错误？

Which variable cause segmentation fault?

c

visual-c++

mqtt

paho