Thread: double free or corruption (fasttop) help

I am sure the operator= isn't overloaded correctly but how can I fix this? My friend looked at this and also helped me on the overload operators and we have identical operators to help debug. Did I type something wrong?

Code:

*** glibc detected *** queue: double free or corruption (fasttop): 0x0907e008 ***
======= Backtrace: =========
/lib/libc.so.6[0x48c268c9]
queue[0x804922b]
queue[0x8048ef5]
queue[0x8048c51]
queue[0x80489cc]
queue[0x8049714]
/lib/libc.so.6(__libc_start_main+0xf5)[0x48bca635]
queue[0x8048881]
======= Memory map: ========
08048000-0804b000 r-xp 00000000 09:03 3663402    
0804b000-0804c000 rw-p 00002000 09:03 3663402    
0907e000-0909f000 rw-p 00000000 00:00 0          [heap]
48b8e000-48bad000 r-xp 00000000 68:05 483370     /usr/lib/ld-2.15.so
48bad000-48bae000 r--p 0001e000 68:05 483370     /usr/lib/ld-2.15.so
48bae000-48baf000 rw-p 0001f000 68:05 483370     /usr/lib/ld-2.15.so
48bb1000-48d5c000 r-xp 00000000 68:05 483373     /usr/lib/libc-2.15.so
48d5c000-48d5d000 ---p 001ab000 68:05 483373     /usr/lib/libc-2.15.so
48d5d000-48d5f000 r--p 001ab000 68:05 483373     /usr/lib/libc-2.15.so
48d5f000-48d60000 rw-p 001ad000 68:05 483373     /usr/lib/libc-2.15.so
48d60000-48d63000 rw-p 00000000 00:00 0
48d81000-48daa000 r-xp 00000000 68:05 483865     /usr/lib/libm-2.15.so
48daa000-48dab000 r--p 00029000 68:05 483865     /usr/lib/libm-2.15.so
48dab000-48dac000 rw-p 0002a000 68:05 483865     /usr/lib/libm-2.15.so
48f41000-48f5d000 r-xp 00000000 68:05 483949     /usr/lib/libgcc_s-4.7.2-20120921.so.1
48f5d000-48f5e000 rw-p 0001b000 68:05 483949     /usr/lib/libgcc_s-4.7.2-20120921.so.1
4930f000-493ef000 r-xp 00000000 68:05 484683     /usr/lib/libstdc++.so.6.0.17
493ef000-493f3000 r--p 000e0000 68:05 484683     /usr/lib/libstdc++.so.6.0.17
493f3000-493f4000 rw-p 000e4000 68:05 484683     /usr/lib/libstdc++.so.6.0.17
493f4000-493fb000 rw-p 00000000 00:00 0
b77c3000-b77c6000 rw-p 00000000 00:00 0
b77dc000-b77e0000 rw-p 00000000 00:00 0
b77e0000-b77e1000 r-xp 00000000 00:00 0          [vdso]
bfccf000-bfcf0000 rw-p 00000000 00:00 0          [stack]
Abort

Code:

Queue :: Queue(int size)
{       size=0;
        count=0;
        MaxElements=256;        }


Queue :: ~Queue()
{       clear();                }


Queue :: Queue(const Queue& other)
{       InitFromCopy(other);    }


Queue Queue :: operator= (const Queue& other)
{
        //clear();
        InitFromCopy(other);
        return *this;
}


bool Queue :: operator== (const Queue& other) const
{
        for(int i=0; i<count; i++)
        {
                if(qa.get(i) != other.qa.get(i))
                {       return false;           }
        }
        return true;
}


bool Queue :: operator!= (const Queue& other) const
{
        if((*this)==other)
                return false;
        return true;
}


ostream& operator << (ostream& s, const Queue& q)
{
        s << q.front() << "\t<-- front" << endl;


        for(int i=1; i<q.size(); i++)
                s << q.qa.get(i) << endl;

Aren't you in the wrong forum?

Bye, Andreas

Sorry guys was busy. Will post up initfromcopy code up. It should be there tho

Code:

Queue :: Queue(int size)
{	size=0;
	count=0;
	MaxElements=256;	}


Queue :: ~Queue()
{	clear();		}


Queue :: Queue(const Queue& other)
{	InitFromCopy(other);	}


Queue Queue :: operator= (const Queue& other)
{
	//clear();
	InitFromCopy(other);
	return *this;
}


bool Queue :: operator== (const Queue& other) const
{
	for(int i=0; i<count; i++)
	{
		if(qa.get(i) != other.qa.get(i))
		{	return false;		}
	}	
	return true;
}


bool Queue :: operator!= (const Queue& other) const
{
	if((*this)==other)
		return false;
	return true;
}


ostream& operator << (ostream& s, const Queue& q)
{
	s << q.front() << "\t<-- front" << endl;


	for(int i=1; i<q.size(); i++)
		s << q.qa.get(i) << endl;


	return s;


}


// Accessors
int Queue :: size() const
{	return count;	}


bool Queue :: isempty() const
{
	if(count)
		return false;
	return true;
}


bool Queue :: isfull() const
{
	if(count==MaxElements)
		return true;
	return false;
}


Entry Queue :: front() const
{	return qa.get(0);	}




// Mutators
void Queue :: clear()
{
	qa.clear();
	count = 0;
}


void Queue :: push(Entry x)
{	
	if(isfull())
		cout << "Queue is full!" << endl;
	else
	{
		qa.insert(x);
		count++;
	}
}


Entry Queue :: pop(void)
{	
	if(isempty())
		cout << "The Queue is empty!" << endl;
	else
	{
		count--;
		return qa.remove(0);
	}
}


Entry Queue :: front(void)
{
	return qa.get(0);
}


// Private
void Queue :: InitFromCopy(const Queue& other)
{
//	qa = other.qa;
//	MaxElements = other.MaxElements;
//	count = other.count;


	qa = other.qa;
	MaxElements = other.MaxElements;


	for(int i=0; i<size(); i++)
		qa.insert(other.qa.get(i));
}

You will notice there are functions called "Entry" there is no code for those so they are working fine. I have posted everything that should relate to the error. I will be at relay for life today so I won't get on the computer much for the rest of the day but will try to check back later tonight.

So in Entry:

Code:

typedef char Entry;

Definition of Queue:

Code:

const int MaxQueueSize = 100;




class Queue
{   public:


	Container qa;
	
	Queue(int size = MaxQueueSize);
	Queue(const Queue& other);
	~Queue();


	Queue operator= (const Queue& other);
	bool operator== (const Queue& other) const;
	bool operator!= (const Queue& other) const;
	friend ostream& operator<< (ostream& s, const Queue& qa);


	int size() const;
	bool isempty() const;
	bool isfull() const;
	Entry front() const;
	


	void clear();
	void push(Entry x);
	Entry pop(void);
	Entry front(void);




   private:
	int MaxElements;
	Container a;
	int count;
	void InitFromCopy(const Queue& other);
};

Originally Posted by Salem

No idea, but if you compile your code with the -g flag, like

g++ -g prog.cpp

Then
queue[0x804922b]
queue[0x8048ef5]
queue[0x8048c51]
queue[0x80489cc]
queue[0x8049714]
Will be replaced with actual function names within your code, so you can more easily trace what is going on.

Can you show me how to put it in a makefile? I have been trying but I have no luck.