metaObject() function retrieves exception

[ClintEastwood]

Hello all:

I have defined a new class which inherits from QObject but when I try to invoke the QObject::metaObject() function from an instance of this object I get an access violation exception. Does anyone know why I cannot call the QObject::metaObject() function???

This is the call to the function from the object pointer pendingMsgs which generates the exception:

PendingList *pendingMsgs = new PendingList(this, settings->value("GENERAL/CheckTimeoutInterval").toInt());
const QMetaObject *meta = pendingMsgs->metaObject();

PendingList *pendingMsgs = new PendingList(this, settings->value("GENERAL/CheckTimeoutInterval").toInt());
const QMetaObject *meta = pendingMsgs->metaObject();

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And this is the class that I have defined (PendingList):

#include "MM.h"
#include "Message.h"
#include <QTimer>
 
struct PendingMsg
{
	Message request; //message pending to receive a response
	CMD cmd; // type of the pending response {ACK or ORD_RESP}
	int timeout; // Time that can be stored the message before emitting a timeout signal
 
	PendingMsg(Message m, CMD c, int t)
	{
		request = m;
		cmd = c; 
		timeout = t;
	};
 
	QString display() const
	{
		//return "[" + cmdTags[cmd] + " (" + cmdTags[request.getCmd()] + "), " + stateNames[newState] + "]";
		return "[" + cmdTags[cmd] + " (" + cmdTags[request.getCmd()] + ")]";
	};
};
 
class PendingList : public QObject
{
 
	Q_OBJECT
 
public:
	PendingList(QObject* parent, int time);
	~PendingList(void);
 
	bool add(System sys, Message req, CMD cmd, int time);
	bool remove(System sys, CMD cmd);
 
	void setCheckTimeInterval(int t) { checkTimeInterval = t;};
 
	int size() const;
	void display() const;
 
private:
 
	int checkTimeInterval;
	QTimer timer;
 
	QList<PendingMsg> list[MAX_CLIENTS];
 
	// finds the position of the command cmd inside list[sys]
	int match(System sys, CMD cmd) const;
 
	bool startIfEmpty();
	bool stopIfEmpty();
 
	// Reports that the system 'sys' has not sent a message of type 'cmd1' as answer of the message 'req'
	void emitTimeout(System sys, CMD cmd, Message req);
 
	void emitMatch(System sys, CMD cmd, Message req);
 
private slots:
 
	void checkTimeouts();
 
signals:
 
	void timeout_ack_insp_mis(System);
	void timeout_ack_pause(System);
	void timeout_ack_abort(System);
	void timeout_ack_resume(System);
	void timeout_ack_mosaic(System);
	void timeout_ack_weed_map(System);
	void timeout_ack_tre_mis(System);
	void timeout_resp_insp_mis(System);
	void timeout_resp_pause(System);
	void timeout_resp_abort(System);
	void timeout_resp_resume(System);
	void timeout_resp_mosaic(System);
	void timeout_resp_weed_map(System);
	void timeout_resp_tre_mis(System);
 
	void ack_insp_mis(System);
	void ack_mosaic(System);
	void ack_weed_map(System);
	void ack_tre_mis(System);
	void ack_unit_ctrl(System);
	void ack_abort(System);
	void ack_resume(System);
	void ack_pause(System);
	void resp_insp_mis(System);
	void resp_mosaic(System);
	void resp_weed_map(System);
	void resp_tre_mis(System);
	void resp_abort(System);
	void resp_resume(System);
	void resp_pause(System);
};

#include "MM.h"
#include "Message.h"
#include <QTimer>

struct PendingMsg
{
	Message request; //message pending to receive a response
	CMD cmd; // type of the pending response {ACK or ORD_RESP}
	int timeout; // Time that can be stored the message before emitting a timeout signal
	
	PendingMsg(Message m, CMD c, int t)
	{
		request = m;
		cmd = c; 
		timeout = t;
	};
	
	QString display() const
	{
		//return "[" + cmdTags[cmd] + " (" + cmdTags[request.getCmd()] + "), " + stateNames[newState] + "]";
		return "[" + cmdTags[cmd] + " (" + cmdTags[request.getCmd()] + ")]";
	};
};

class PendingList : public QObject
{

	Q_OBJECT

public:
	PendingList(QObject* parent, int time);
	~PendingList(void);

	bool add(System sys, Message req, CMD cmd, int time);
	bool remove(System sys, CMD cmd);

	void setCheckTimeInterval(int t) { checkTimeInterval = t;};

	int size() const;
	void display() const;

private:

	int checkTimeInterval;
	QTimer timer;

	QList<PendingMsg> list[MAX_CLIENTS];

	// finds the position of the command cmd inside list[sys]
	int match(System sys, CMD cmd) const;

	bool startIfEmpty();
	bool stopIfEmpty();

	// Reports that the system 'sys' has not sent a message of type 'cmd1' as answer of the message 'req'
	void emitTimeout(System sys, CMD cmd, Message req);

	void emitMatch(System sys, CMD cmd, Message req);

private slots:

	void checkTimeouts();

signals:
		 
	void timeout_ack_insp_mis(System);
	void timeout_ack_pause(System);
	void timeout_ack_abort(System);
	void timeout_ack_resume(System);
	void timeout_ack_mosaic(System);
	void timeout_ack_weed_map(System);
	void timeout_ack_tre_mis(System);
	void timeout_resp_insp_mis(System);
	void timeout_resp_pause(System);
	void timeout_resp_abort(System);
	void timeout_resp_resume(System);
	void timeout_resp_mosaic(System);
	void timeout_resp_weed_map(System);
	void timeout_resp_tre_mis(System);

	void ack_insp_mis(System);
	void ack_mosaic(System);
	void ack_weed_map(System);
	void ack_tre_mis(System);
	void ack_unit_ctrl(System);
	void ack_abort(System);
	void ack_resume(System);
	void ack_pause(System);
	void resp_insp_mis(System);
	void resp_mosaic(System);
	void resp_weed_map(System);
	void resp_tre_mis(System);
	void resp_abort(System);
	void resp_resume(System);
	void resp_pause(System);
};

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[Santosh Reddy]

This is the call to the function from the object pointer pendingMsgs which generates the exception:

What is the exception?

[ClintEastwood]

Sorry, I have found the problem. I was not executing the above first 2 instructions in the order I thought. I was calling the metaobject() function from a non initialized pointer... My apologies for the inconveniences caused.