Question

my code is:

#pragma once
#include "stdafx.h"
#include <vector>
#include "field.h"

class output
{
    void putAtLocation(COORD, char chIcon); //currently this outputs to console

    static std::vector<COORD> m_vsOutputBuffer;
public:
    output(void);

    static void addToken(COORD);
    void drawTokens();

    ~output(void);
};

and the linker error is:

output.obj : error LNK2001: unresolved external symbol "private: static class std::vector<struct _COORD,class std::allocator<struct _COORD> > output::m_vsOutputBuffer" (?m_vsOutputBuffer@output@@0V?$vector@U_COORD@@V?$allocator@U_COORD@@@std@@@std@@A)

this must be the problem line:

static std::vector<COORD> m_vsOutputBuffer;

I’ve been at this for hours stuck. I finally noticed that changing COORD to int causes the linker error to go away. I’ve read that it’s(linker errors) are usually caused by dependency issues. But here it just changing a TYPE. I’ve also read it can be caused by using a function in a way it wasn’t supposed to be. I figure it has to be the way is handling COORDs; or something about COORDS is forward declared, or referenced in output.cpp properly.

Edit:
all changing to int did was make compiler errors that caused it never to hit the linker. now I am back to nothing

and the cpp file:

#include "stdafx.h"
#include "output.h"
#include <vector>

static std::vector<int> m_vsOutputBuffer;

output::output(void)
{
}
void output::addToken(COORD sCoordinate) //mark a coord in the buffer as needing refreshed
{
    m_vsOutputBuffer.push_back(sCoordinate);
}

void output::drawTokens() //release the outputbuffer the the output window
{
    for (unsigned int iii = 0; iii < m_vsOutputBuffer.size(); iii++)
    {
        putAtLocation(m_vsOutputBuffer[iii], field::checkHit( m_vsOutputBuffer[iii] ) );
    }
}

void output::putAtLocation(COORD sCoordinate, char chIcon) //outputs a single character to the console
{
    DWORD dwNumWritten = 0;
    LPDWORD lpdNumWritten = &dwNumWritten;

    WriteConsoleOutputCharacter(
    GetStdHandle( STD_OUTPUT_HANDLE ), //***repeatedly getting this handle may end up a bottleneck
    LPCTSTR(&chIcon),
    1,
    sCoordinate,
    lpdNumWritten
    );
}

output::~output(void)
{
}

also I found this: http://www.cplusplus.com/forum/general/6111/

so I tried moving the static statement to the cpp file and it compiled and ran. but not its not a member variable. So I Need to somehow forward declare the vector.(before the declaration was also creating the static object in the header file.

Answer 1

you need this line in your .cpp file:

std::vector<COORD> output::m_vsOutputBuffer;

(Note the absence of static and the scope output::)

This is the actual definition of the member variable. What you have in the class (.h) is only the declaration.

Without this the static variable output:m_vsOutputBuffer does not exist and the linker rightfully complains that it can’t find it.