Programming Windows Compiler Link Error - unresolved external

Question

I am new to Windows Programming.

I created a win32 console project (without preCompiled header) with VS2005. And the code as below.

// HelloWin.cpp : Defines the entry point for the console application.
//
#include <windows.h>
#include "stdafx.h"

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int _tmain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("HelloWin");
    HWND        hwnd;
    MSG         msg;
    WNDCLASS    wndclass;

    wndclass.style          = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc    = WndProc;
    wndclass.cbClsExtra     = 0;
    wndclass.cbWndExtra     = 0;
    wndclass.hInstance      = hInstance;
    wndclass.hIcon          = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor        = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground  = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName   = NULL;
    wndclass.lpszClassName  = szAppName;

    if(!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("This Program requires Windows NT!"), szAppName, MB_ICONERROR);
        return 0;

    }

    hwnd = CreateWindow(szAppName,                  // window class name
                        TEXT("The Hello Program"),  // window caption
                        WS_OVERLAPPEDWINDOW,        // window style
                        CW_USEDEFAULT,              // initial x position
                        CW_USEDEFAULT,              // initial y position
                        CW_USEDEFAULT,              // initial x size
                        CW_USEDEFAULT,              // initial y size
                        NULL,                       // parent window handle
                        NULL,                       // window menu handle
                        hInstance,                  // program instance handle
                        NULL);                      // creation parameters

    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);

    while(GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    HDC         hdc;
    PAINTSTRUCT ps;
    RECT        rect;

    switch(message)
    {
    case WM_CREATE:
        PlaySound(TEXT("hellowin.wav"), NULL, SND_FILENAME | SND_ASYNC);
        return 0;

    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);

        GetClientRect(hwnd, &rect);

        DrawText(hdc, TEXT("Hello Windows XP"), -1, &rect, 
                 DT_SINGLELINE | DT_CENTER | DT_VCENTER);
        EndPaint(hwnd, &ps);
        return 0;

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }   
    return DefWindowProc(hwnd, message, wParam, lParam);
}

And now there is two Link Errors as this, Could anybody help me to fix this errors.

Does it caused by there is no hellowin.wav file in my local harddisk? If it does. What directory can I place a simular WAV file to?

Thanks.

1>Linking... 1>HelloWin.obj :

error LNK2019: unresolved external symbol imp__PlaySoundW@12 referenced in function "long __stdcall WndProc(struct HWND *,unsigned int,unsigned int,long)" (?WndProc@@YGJPAUHWND__@@IIJ@Z) 1>D:\learning\windows\ProgrammingWindows(5thEdition)\HelloWin\Debug\HelloWin.exe :

fatal error LNK1120: 1 unresolved externals 1>Build log was saved at

"file://d:\learning\windows\ProgrammingWindows(5thEdition)\HelloWin\HelloWin\Debug\BuildLog> .htm" 1>HelloWin - 2 error(s), 1 warning(s) ========== Rebuild All: 0 succeeded, 1 failed, 0 skipped ==========

Mike Kwan Mike Kwan · Accepted Answer · 2011-09-05T10:22:00

You have several problems here. Firstly you say that your application is a console app. If it is, then you are using the wrong main. Your subsystem is probably WINDOWS in which case your main should be this instead:

int CALLBACK _tWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR szCmdLine, int iCmdShow)

You also say you're not using precompiled headers but you have an include for stdafx.h. Your problems can be fixed by changing your main and also changing your includes to look like this:

#include <windows.h>
#include <tchar.h>
#pragma comment(lib, "Winmm.lib")

This allows the linker to look for the library file we tell it to. I also got rid of your precompiled header and replaced it with tchar.h since that is your only other dependency so far.

The fact hellowin.wav is not present at compilation time is irrelevant. The program only looks for it at runtime.

Programming Windows Compiler Link Error - unresolved external

1 Answers