attempt to copy from a singular iterator

[bhatiaharsh]

Hi,

I have the following lines in the constructor of a class:

cout<<"1\n";
contourPoint s(v);
cout<<"2\n";
seed = contourPoint(v);
cout<<"3\n";

where, contourPoint is a structure I defined (contains a valid copy constructor as well). the program runs just fine in release mode, but in the debug mode, I get the following error

1
2
/usr/include/c++/4.2.1/debug/safe_iterator.h:164:error: attempt to copy 
    from a singular iterator.

Objects involved in the operation:
iterator "this" @ 0x0x7fff5fbfdb28 {
type = N11__gnu_debug14_Safe_iteratorISt23_Rb_tree_const_iteratorISt4pairIiiEENSt7__debug3setIS3_St4lessIS3_ESaIS3_EEEEE (mutable iterator);
  state = singular;
}
iterator "other" @ 0x0x7fff5fbfda58 {
type = N11__gnu_debug14_Safe_iteratorISt23_Rb_tree_const_iteratorISt4pairIiiEENSt7__debug3setIS3_St4lessIS3_ESaIS3_EEEEE (mutable iterator);
  state = singular;
}
Abort

It doesnt even give me the line number, so I printed 1,2,3 to see what line it breaks only on the commandline.

Any ideas as to how to fix this ? Googling didnt help me much here.

Thanks

[yUq2Nwbp]

and what type has your seed??

[onur]

Could you list your class contourPoint? It seems to happen in one of its members, probably the red-black tree.

Btw. if you use cerr instead of cout you get unbuffered output so it will be displayed "immediately". Alternatively you can an endl or flush.

cout<<"1\n";
cerr<<"1\n";
// or
cout<<"1" << endl;
// or
cout<<"1\n" << flush;

(see also: http://www.cplusplus.com/reference/iostream/ )

[bhatiaharsh]

seed is the member variable of the class whose constructor is being called. it is of 'contourPoint' class.

[bhatiaharsh]

here is the contour point class

//================================================================
// a point on the contour : can only exist on a vertex or an edge
class contourPoint{

	bool isVertex;

	int V;

	set<Edge>::const_iterator edge;
	double alpha;

public:
	contourPoint(){
		V = -1;
		isVertex = true;
	}
	contourPoint(int v_){
		V = v_;
		isVertex = true;
	}
    contourPoint::contourPoint(const contourPoint& p) {
        V = p.get_V();
        isVertex = p.is_onVertex();
    }
	contourPoint(set<Edge>::const_iterator ed, double alp){
		V = -1;
		isVertex = false;
		edge = ed;
		alpha = alp;
	}

could it be that the second constructor does not initialize the iterator edge which creates a problem ? I dont want to use the iterator if I call the second constructor. Is there a default/null value I can assign to the iterator ?

[onur]

/usr/include/c++/4.2.1/debug/safe_iterator.h:164:error: attempt to copy from a singular iterator.

This line says that you try to do something like this:

set<Edge>::const_iterator someUninitializedIterator;

contourPoint cp (someUninitializedIterator, 1.0); // here you pass uninitalized iterator 

Could you post the lines where you create the contourPoint?

You could also refactor the constructor:

class contourPoint{

//...
	contourPoint(set<Edge>::const_iterator ed, double alp)
        : V(-1)
        , isVertex(false)   
        , edge(ed)
        , alpha(alp)
       {}

Because in your version there is first an uninitalized iterator created which is later assigned a valid iterator. Maybe your compiler complains about this.