Question

my project contains a few classes (1 of them is Point3D) & a cpp (CreatePoint.cpp) & a header file (CreatePoint.h).

my stdafx.h file is

// stdafx.h : include file for standard system include files,
// or project specific include files that are used frequently, but
// are changed infrequently
//

#pragma once

#include "targetver.h"

#include <stdio.h>
#include <tchar.h>


// TODO: reference additional headers your program requires here

#include "CreatePoint.h"
#include "Point3D.h"
#include "Vector3D.h"
#include "Sys.h"

my CreatePoint.h file is

#include "stdafx.h"
#pragma once
#include "Point3D.h"


//*******************************************************************
void initialise();

//*******************************************************************
Point3D *get_point(int);

//*******************************************************************
int get_index(Point3D *);

//*******************************************************************
Point3D *create_point();

//*******************************************************************
void del_point(Point3D *);

//*******************************************************************
void destruct_point();

my CreatePoint.cpp file is

#include "stdafx.h"
#include "CreatePoint.h"

int counter;
int size = 50;
Point3D *point[];
//*******************************************************************
void initialise()//run this func each time point[] is created
{
    counter = 0;
    for(int i = 0; i<size; i++)
    {
    point[i] = '\0';
}
}

//*******************************************************************
Point3D *get_point(int index)
{
    return point[index];
}

//*******************************************************************
int get_index(Point3D *p)
{
    for(int i = 0; i<size; i++)
{
    if(point[i] == p)
        return i;
}
}

//*******************************************************************
Point3D *create_point()
{
point[counter] = new Point3D;
counter++;
return point[counter];
}

//*******************************************************************
void del_point(Point3D *p)
{
int d = get_index(p);
delete point[d];
}

//*******************************************************************
void destruct_point()
{
delete [] point;
}

i am getting a run time error :

CreatePoint.obj : error LNK2001: unresolved external symbol "class Point3D * * point" (?point@@3PAPAVPoint3D@@A)
1>C:\Documents and Settings\my documents\visual studio 2010\Projects\Maths\Debug\Maths.exe : fatal error LNK1120: 1 unresolved externals

i have searched the web & mostly the reason for such a failure is not including stdafx.h in 1st line of each file… but i have already included it.
i am also gettting some warning for the last function destruct_point() ->

\maths\maths\createpoint.cpp(51): warning C4154: deletion of an array expression; conversion to pointer supplied

Answer 1

LNK2001 is a linker error, not a runtime error.

Point3D *point[]; seems to be a declaration, but not an instantiation. That is, this line tells the compiler that this variable will exist somewhere later. Because arrays must have a size to be instantiated. (I hadn’t even known [] without a size was allowed in that scope)

Change this to Point3D *point[size]; and it will actually create the array. Also, size will have to be a const int.

[Edit]
destruct_point() attempts to delete the entire array of points. Since the array is statically allocated, that’s not allowed. Since you already have a function to delete individual points, I can’t imagine why this function exists. Since the array was not declared with new[], you should NOT use delete[] on it.