What do these errors mean??

[VisuAlly]

I'm writing this program for a class. This is the second part of a three part program, so it's not supposed to actually work, it's just supposed to compile.

It won't though.
The errors i get look like this:

/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/rt1.o(.debug_info):relocation 20 has invalid symbol index 19

it shows up with about 20 or so of those. What does that mean? How do I fix it?

  #include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>

#include "sketch.h"

#include <string>
#include <iostream>
#include <fstream>
#include <cmath>
using namespace std;

#define PI 3.1415926536

#define WIDTH    	700
#define HEIGHT   	600

#define MENUWIDTH 	100
#define BOXHEIGHT	(HEIGHT/NCOLORS)

#define DSLEFT    	MENUWIDTH
#define DSRIGHT  	WIDTH
#define DSBOTTOM  	0
#define DSTOP     	HEIGHT

#define NCOLORS 	8

#define RGBRED 		1, 0, 0
#define	RGBGREEN	0, 1, 0
#define RGBBLUE		0, 0, 1
#define RGBYELLOW	1, 1, 0
#define RGBMAGENTA	1, 0, 1
#define RGBCYAN		0, 1, 1
#define RGBBLACK	0, 0, 0
#define RGBWHITE	1, 1, 1

#define R		0
#define G		1
#define B		2

static float colormenu[8][3] = {{RGBRED}, {RGBGREEN}, {RGBBLUE}, {RGBYELLOW}, {RGBMAGENTA}, {RGBCYAN}, {RGBWHITE}, {RGBBLACK}};

//Line
void Sketch::CreateObject(int c, int t, int x1, int y1)
{
	objects[n].colortype=c;
	objects[n].tooltype=t;
	objects[n].tool.endpoints.pt1.x=x1;
	objects[n].tool.endpoints.pt1.y=y1;
	objects[n].tool.endpoints.pt2.x=x1;
	objects[n].tool.endpoints.pt2.y=y1;
	n++;
}

//Rectangle
void Sketch::CreateObject(int c, int t, int x1, int y1, int x2, int y2)
{
	objects[n].colortype=c;
	objects[n].tooltype=t;
	objects[n].tool.endpoints.pt1.x=x1;
	objects[n].tool.endpoints.pt1.y=y1;
	objects[n].tool.endpoints.pt2.x=x2;
	objects[n].tool.endpoints.pt2.y=y2;
	n++;
}

//Circle
void Sketch::CreateObject(int c, int t, int r, int x1, int y1)
{
	objects[n].colortype=c;
	objects[n].tooltype=t;
	objects[n].tool.circle.radius=r;
	objects[n].tool.circle.center.x=x1;
	objects[n].tool.circle.center.y=y1;
	n++;
}

void Sketch::UpdateObject(int _x, int _y)
{
	switch(objects[n-1].tooltype)
	{
		case 0:
		case 1:
		case 2:
		case 3:
		{
			int x1;
			{x1 = objects[n-1].tool.circle.center.x;}
			int y1;
			{y1 = objects[n-1].tool.circle.center.y;}
			int x2;
			{x2 = _x;}
			int y2;
			{y2 = _y;}
			int r = sqrt(pow(x2-x1,2)+pow(y2-y1,2));
			objects[n-1].tool.circle.radius=r;
			break;
		}
		case 4:
		{
			objects[n-1].tool.endpoints.pt2.x=_x;
			objects[n-1].tool.endpoints.pt2.y=_y;
			break;	
		}		
	}
}

void Sketch::Load()
{
	string filename;
	ifstream fin;
	cout<<"Load: ";
	cin>>filename;
	fin.open(filename.c_str());
	if (fin.is_open())
	{		
		while (fin.good())
		{
			fin>>n;
			for(int i=0; i<n; i++)
			{
				fin>>objects[i].colortype;
				fin>>objects[i].tooltype;
				if(objects[i].tooltype==2 || objects[i].tooltype==3)
				{
				  fin>>objects[i].tool.circle.center.x;
				  fin>>objects[i].tool.circle.center.y;
				  fin>>objects[i].tool.circle.radius;
				}
				else
				{
				  fin>>objects[i].tool.endpoints.pt1.x;
				  fin>>objects[i].tool.endpoints.pt1.y;
				  fin>>objects[i].tool.endpoints.pt2.x;
				  fin>>objects[i].tool.endpoints.pt2.y;
				}
			}
		}
	}
	else{cout<<"Load failed";}
}

void Sketch::Save()
{
	string filename;
	ofstream fout;
	cout<<"Save as: ";
	cin>>filename;
	fout.open(filename.c_str());
	if(fout.is_open())
	{
		fout<<n<<" ";
		for(int i=0; i<n; i++)
		{
			fout<<objects[i].colortype<<" "<<objects[i].tooltype<<" ";
			if(objects[i].tooltype==2 || objects[i].tooltype==3)
			{
				fout<<objects[i].tool.circle.center.x<<" ";
				fout<<objects[i].tool.circle.center.y<<" ";
				fout<<objects[i].tool.circle.radius<<" ";
			}
			else
			{
				fout<<objects[i].tool.endpoints.pt1.x<<" ";
				fout<<objects[i].tool.endpoints.pt1.y<<" ";
				fout<<objects[i].tool.endpoints.pt2.x<<" ";
				fout<<objects[i].tool.endpoints.pt2.y<<" ";
			}
		fout<<endl;
		}
	}
	
}

void Sketch::Clear()
{
	n=0; 
	glutPostRedisplay();
}

void Sketch::drawRectangle(int index, GLint type)
{
	int c = objects[index].colortype;
	int x1 = objects[index].tool.endpoints.pt1.x;
	int y1 = objects[index].tool.endpoints.pt1.y;
	int x2 = objects[index].tool.endpoints.pt2.x;
	int y2 = objects[index].tool.endpoints.pt2.y;

	glColor3f(colormenu[c][R], colormenu[c][G], colormenu[c][B]);

	glBegin(type);
		glVertex2i(x1,y1);
		glVertex2i(x1,y2);
		glVertex2i(x2,y2);
		glVertex2i(x2,y1);
	glEnd();
}


void Circle(GLint type)
{
	int i=36;                 
  	float angle;
  	float anglecounter= 2*PI/i; 
        
   	glBegin(type);
    	for(int k=0; k<i; k++)
	{
      		angle = k*anglecounter;
      		glVertex2f(cos(angle),sin(angle));
    	}
  	glEnd(); 
}

void Sketch::drawCircle(int index, GLint type)
{
	int c=objects[index].colortype;
	int x=objects[index].tool.circle.center.x;
	int y=objects[index].tool.circle.center.y;
	float r=objects[index].tool.circle.radius;

	glColor3f(colormenu[c][R], colormenu[c][G], colormenu[c][B]);

	glPushMatrix();
		glTranslatef(x,y,0);
		glScalef(r,r,1);
		Circle(type);
	glPopMatrix();
}

void Sketch::drawLine(int index)
{
	int c=objects[index].colortype;
	int x1=objects[index].tool.endpoints.pt1.x;
	int y1=objects[index].tool.endpoints.pt1.y;
	int x2=objects[index].tool.endpoints.pt2.x;
	int y2=objects[index].tool.endpoints.pt2.y;

	glColor3f(colormenu[c][R], colormenu[c][G], colormenu[c][B]);

	glBegin(GL_LINE_LOOP);
		glVertex2i(x1,y1);
		glVertex2i(x2,y2);
	glEnd();	
}

void Sketch::draw()
{
	for(int i=0; i<n; i++)
	{
		switch(objects[i].tooltype)
		{
			case 0: drawRectangle(i, GL_LINE_LOOP);
				break;

			case 1: drawRectangle(i, GL_POLYGON);
				break;

			case 2: drawCircle(i, GL_LINE_LOOP);
				break;

			case 3: drawCircle(i, GL_POLYGON);
				break;

			case 4: drawLine(i);
				break;

			case 5: drawLine(i);
				break;
		}
	}
	glutPostRedisplay();
}

This program must be compiled along with this

#  include <GL/gl.h>
#  include <GL/glu.h>
#  include <GL/glut.h>

struct Point
{
	int x,y;
};

struct EndPoint
{
	Point pt1, pt2;
};
	
struct Circle
{
	Point center;
	int radius;
};

union Tool
{
	EndPoint endpoints;
	Circle circle;
};

struct Object
{
	short int colortype;
	short int tooltype;
	Tool tool;
};

class Sketch
{
	Object objects[10000];
	static int n;

		public:
		void CreateObject(int, int, int, int);
		void CreateObject(int, int, int, int, int);
		void CreateObject(int, int, int, int, int, int);
		void UpdateObject(int, int);
		void Save();
		void Load();
		void Clear();
		void drawRectangle(int, GLint);
		void drawCircle(int, GLint);
		void drawLine(int);
		void draw();	
};

int Sketch::n=0;