Using Classes and Structs

I am confused on using Classes and Structs.
Can anyone shed light on what MS has changed about them

example this code generates a ton of weird errors

#include <windows.h>
class CIGECORE
{
public:
    LPSTR sAppTitle;
    int iPosX;
    int iPosY;
    int iWidth;
    int iHeight;
};

Answer this question

Using Classes and Structs

DaveJohnson

ok I did that, and I tried using a pragma to include the user32lib but still getting link errors:

Windows.cpp

#pragma lib("user32.lib")

#define WIN32_LEAN_AND_MEAN // DO NOT USE MFC

#include <windows.h>
#include <windowsx.h>
#include "IGE.h"
#include "main.h"

#define WINDOWSCLASS "WINCLASS1" // DECLARE WINCLASS CONSTANT

CIGECORE            IGECORE;

LRESULT CALLBACK WindowProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
// EVENT HANDELER/////////////////////////////////////////////////////////////
{
    PAINTSTRUCT ps;
    HDC            hdc;

    switch(msg)
    {
    case WM_CREATE:
        {
            // WINDOW CREATION CODE
            return(0);
        }break;
    case WM_PAINT:
        {
            hdc = BeginPaint(hwnd,&ps);
            EndPaint(hwnd,&ps);
            return(0);
        }break;
    case WM_DESTROY:
        {
            PostQuitMessage(0);
            return(0);
        }break;
    default:break;
    }
    return(DefWindowProc(hwnd,msg,wparam,lparam));
}

int WINAPI WinMain(HINSTANCE hinstance, HINSTANCE hprevinstance,
                   LPSTR lpcmdline, int ncmdshow)
// WIN MAIN /////////////////////////////////////////////////////////////
{
    WNDCLASSEX winclass;
    HWND hwnd;
    MSG msg;

    winclass.cbSize = sizeof(WNDCLASSEX);
    winclass.style = CS_DBLCLKS | CS_OWNDC | CS_HREDRAW | CS_HREDRAW;
    winclass.lpfnWndProc = WindowProc;
    winclass.cbClsExtra = 0;
    winclass.cbWndExtra = 0;
    winclass.hInstance = hinstance;
    winclass.hIcon = LoadIcon(NULL,IDI_APPLICATION);
    winclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    winclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
    winclass.lpszMenuName = NULL;
    winclass.lpszClassName = WINDOWSCLASS;
    winclass.hIconSm = LoadIcon(NULL,IDI_APPLICATION);

    if(!RegisterClassEx(&winclass)){
        return(0);
    }

    if(!(hwnd = CreateWindowEx(NULL,WINDOWSCLASS,IGECORE.sAppTitle,WS_OVERLAPPEDWINDOW | WS_VISIBLE,
        IGECORE.iPosX,IGECORE.iPosY,IGECORE.iWidth,IGECORE.iHeight,NULL,NULL,hinstance,NULL)))
    {
        return(0);
    }

    while(TRUE)
    {
        if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
        {
            if(msg.message == WM_QUIT)
            {
                break;
            }
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        IGERUNTIME();
    }
}

------ Build started: Project: Insane Game Engine, Configuration: Debug Win32 ------
Compiling...
Windows.cpp
.\Windows.cpp(7) : warning C4068: unknown pragma
c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\windows.cpp(93) : warning C4715: 'WinMain' : not all control paths return a value
Linking...
Windows.obj : error LNK2019: unresolved external symbol __imp__PostQuitMessage@4 referenced in function "long __stdcall WindowProc(struct HWND__ *,unsigned int,unsigned int,long)" ( WindowProc@@YGJPAUHWND__@@IIJ@Z)
Windows.obj : error LNK2019: unresolved external symbol __imp__EndPaint@8 referenced in function "long __stdcall WindowProc(struct HWND__ *,unsigned int,unsigned int,long)" ( WindowProc@@YGJPAUHWND__@@IIJ@Z)
Windows.obj : error LNK2019: unresolved external symbol __imp__BeginPaint@8 referenced in function "long __stdcall WindowProc(struct HWND__ *,unsigned int,unsigned int,long)" ( WindowProc@@YGJPAUHWND__@@IIJ@Z)
Windows.obj : error LNK2019: unresolved external symbol __imp__DefWindowProcA@16 referenced in function "long __stdcall WindowProc(struct HWND__ *,unsigned int,unsigned int,long)" ( WindowProc@@YGJPAUHWND__@@IIJ@Z)
Windows.obj : error LNK2019: unresolved external symbol __imp__DispatchMessageA@4 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__TranslateMessage@4 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__PeekMessageA@20 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__CreateWindowExA@48 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__RegisterClassExA@4 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__GetStockObject@4 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__LoadCursorA@8 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__LoadIconA@8 referenced in function _WinMain@16
C:\Documents and Settings\Owner\My Documents\Visual Studio\Projects\Insane Game Engine\Debug\Insane Game Engine.exe : fatal error LNK1120: 12 unresolved externals
Build log was saved at "file://c:\Documents and Settings\Owner\My Documents\Visual Studio\Projects\Insane Game Engine\Insane Game Engine\Debug\BuildLog.htm"
Insane Game Engine - 13 error(s), 2 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Irfan Habib

It has WinMain for an entry point.

windows.cpp

#define WIN32_LEAN_AND_MEAN // DO NOT USE MFC

#include <windows.h> // WINDOWS HEADER FILES
#include <windowsx.h> // EXTRA DEFINES MACROS ETC
#include "IGE.h"
#include "IGE2D.h"
#include "IGE3D.h"
#include "IGENETWORK.h"
#include "IGEPHYSICS.h"
#include "main.cpp"

#define WINDOWSCLASS "WINCLASS1" // DECLARE WINCLASS CONSTANT

LRESULT CALLBACK WindowProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
// EVENT HANDELER/////////////////////////////////////////////////////////////
{
    PAINTSTRUCT ps;
    HDC            hdc;

    switch(msg)
    {
    case: WM_CREATE:
        {
            // WINDOW CREATION CODE
            CIGECORE            IGECORE;
            CIGE2D                IGE2D;
            CIGE3D                IGE3D;
            CIGENETWORK            IGENETWORK;
            CIGEPHYSICS            IGEPHYSICS;
            return(0);
        }break;
    case:WM_PAINT
        {
            hdc = BeginPaint(hwnd,&ps);
            EndPaint(hwnd,&ps);
            return(0);
        }break;
        case WMDESTROY
        {
            PostQuitMessage(0);
            return(0);
        }break;
    default:break;
    }
    return(DefWindowProc(hwnd,msg.wparam,lparam));
}

int WINAPI WinMain(HINSTANCE hinstance, HINSTANCE hprevinstance,
                   LPSTR lpcmdline, int ncmdshow)
// WIN MAIN /////////////////////////////////////////////////////////////
{
    WNDCLASSEX winclass;
    HWND hwnd;
    MSG msg;

    winclass.cbSize = sizeof(WNDCLASSEX);
    winclass.style = CS_DBLCLKS | CS_OWNDC | CS_HREDRAW | CS_HREDRAW;
    winclass.lpfnWndProc = WindowProc;
    winclass.cbClsExtra = 0;
    winclass.cbWndExtra = 0;
    winclass.hInstance = hinstance;
    winclass.hIcon = LoadIcon(NULL,IDI_APPLICATION);
    winclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    winclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
    winclass.lpszMenuName = NULL;
    winclass.lpszClassName = WINDOWSCLASS;
    winclass.hIconSm = LoadIcon(NULL,IDI_APPLICATION);

    if(!RegisterClassEx(&winclass)){
        return(0);
    }

    if(!(hwnd = CreateWindowEx(NULL,WINDOWSCLASS,IGECORE.sAppTitle,WS_OVERLAPPEDWINDOW | WS_VISIBLE,
        IGECORE.iPosX,IGECORE.iPosY,IGECORE.iWidth,IGECORE.iHeight,NULL,NULL,hinstance,NULL)))
    {
        return(0);
    }

    while(TRUE)
    {
        if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
        {
            if(msg.message == WM_QUIT)
            {
                break;
            }
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        IGERUNTIME();
    }
}

spuckupine

A struct is just a class whose members default to public access ( for a class, it's private ). I doubt very much that Microsoft have changed anything to do with classes and structs.

A .NET class and a .NET struct is a very different beast, and if you're using C++/CLI, you may have to do some reading there, but in straight C++, the difference is trivial.
DataBound
eh I see

Now only these 2.

Compiling...
Windows.cpp
c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\windows.cpp(91) : warning C4715: 'WinMain' : not all control paths return a value
Linking...
Windows.obj : error LNK2019: unresolved external symbol __imp__GetStockObject@4 referenced in function _WinMain@16
C:\Documents and Settings\Owner\My Documents\Visual Studio\Projects\Insane Game Engine\Debug\Insane Game Engine.exe : fatal error LNK1120: 1 unresolved externals
Build log was saved at "file://c:\Documents and Settings\Owner\My Documents\Visual Studio\Projects\Insane Game Engine\Insane Game Engine\Debug\BuildLog.htm"
Insane Game Engine - 2 error(s), 1 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
rishi bajaj
Heh well thats quite embarassing.
Anyway, made those changes.

Now I got 12 linker errors :x

------ Build started: Project: Insane Game Engine, Configuration: Debug Win32 ------
Compiling...
Windows.cpp
c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\windows.cpp(91) : warning C4715: 'WinMain' : not all control paths return a value
Linking...
Windows.obj : error LNK2005: "void __cdecl IGERUNTIME(void)" ( IGERUNTIME@@YAXXZ) already defined in main.obj
Windows.obj : error LNK2019: unresolved external symbol __imp__PostQuitMessage@4 referenced in function "long __stdcall WindowProc(struct HWND__ *,unsigned int,unsigned int,long)" ( WindowProc@@YGJPAUHWND__@@IIJ@Z)
Windows.obj : error LNK2019: unresolved external symbol __imp__EndPaint@8 referenced in function "long __stdcall WindowProc(struct HWND__ *,unsigned int,unsigned int,long)" ( WindowProc@@YGJPAUHWND__@@IIJ@Z)
Windows.obj : error LNK2019: unresolved external symbol __imp__BeginPaint@8 referenced in function "long __stdcall WindowProc(struct HWND__ *,unsigned int,unsigned int,long)" ( WindowProc@@YGJPAUHWND__@@IIJ@Z)
Windows.obj : error LNK2019: unresolved external symbol __imp__DefWindowProcA@16 referenced in function "long __stdcall WindowProc(struct HWND__ *,unsigned int,unsigned int,long)" ( WindowProc@@YGJPAUHWND__@@IIJ@Z)
Windows.obj : error LNK2019: unresolved external symbol __imp__DispatchMessageA@4 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__TranslateMessage@4 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__PeekMessageA@20 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__CreateWindowExA@48 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__RegisterClassExA@4 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__GetStockObject@4 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__LoadCursorA@8 referenced in function _WinMain@16
Windows.obj : error LNK2019: unresolved external symbol __imp__LoadIconA@8 referenced in function _WinMain@16
C:\Documents and Settings\Owner\My Documents\Visual Studio\Projects\Insane Game Engine\Debug\Insane Game Engine.exe : fatal error LNK1120: 12 unresolved externals
Build log was saved at "file://c:\Documents and Settings\Owner\My Documents\Visual Studio\Projects\Insane Game Engine\Insane Game Engine\Debug\BuildLog.htm"
Insane Game Engine - 14 error(s), 1 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
RichardAB
OK, in that case, at least one of your errors is caused by your class being included more than once, you don't have an inclusion guard in there ( the #ifndef blah stuff at the top of most Windows classes ). Also, I notice you're including windows.h in your other class, as well as here - why Are you not using precompiled headers

Why does windows.cpp #include main.cpp
kadonk
Then the pragma doesn't work. I never do it that way, I add the library to the link settings of the project file.
Andre Da Costa

I tried the sample you provided and it compiled with no errors. What kind of errors you are seeing

Thanks,
Ayman Shoukry
VC++ Team
Leijtens
This code is riddled with errors

case: WM_CREATE

For a case statement, the : comes at the end, not the middle

case WMDESTROY

it's WM_DESTROY

IGECORE.iPosX,IGECORE.iPosY,IGECORE.iWidth,IGECORE.iHeight

case WM_CREATE:

{

// WINDOW CREATION CODE

CIGECORE IGECORE;

return(0);

}break;

The {} define a scope. Your CIGECORE instance exists for but a moment. I also don't see anywhere that you initialise it's values. It certainly does not exist when you're trying to use it.

return(DefWindowProc(hwnd,msg.wparam,lparam));

msg.wparam should be msg, wparam.

In other words, Microsoft have made no changes to how structs and classes work, but your code is completely riddled with errors.
flape
Your project needs to link against User32.lib, at least. Then add a file called main.h., which looks like this:

void IGERUNTIME();

and add #include "main.h" at the top of main.cpp. Then change your #include in windows.cpp to be main.h.

Joe McCollough

Ok here is my entire project at the moment, ive made a few changes.

Windows.cpp this is the windows code, I basically need all the functions and classes in the headers to be able to be used in Windows.cpp.

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <windowsx.h>
#include "IGE.h"
#include "main.cpp"

#define WINDOWSCLASS "WINCLASS1"

LRESULT CALLBACK WindowProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)

{
    PAINTSTRUCT ps;
    HDC            hdc;

    switch(msg)
    {
    case: WM_CREATE
        {
            CIGECORE            IGECORE;
            return(0);
        }break;
    case:WM_PAINT
        {
            hdc = BeginPaint(hwnd,&ps);
            EndPaint(hwnd,&ps);
            return(0);
        }break;
        case WMDESTROY
        {
            PostQuitMessage(0);
            return(0);
        }break;
    default:break;
    }
    return(DefWindowProc(hwnd,msg.wparam,lparam));
}

int WINAPI WinMain(HINSTANCE hinstance, HINSTANCE hprevinstance,
                   LPSTR lpcmdline, int ncmdshow)
{
    WNDCLASSEX winclass;
    HWND hwnd;
    MSG msg;

    winclass.cbSize = sizeof(WNDCLASSEX);
    winclass.style = CS_DBLCLKS | CS_OWNDC | CS_HREDRAW | CS_HREDRAW;
    winclass.lpfnWndProc = WindowProc;
    winclass.cbClsExtra = 0;
    winclass.cbWndExtra = 0;
    winclass.hInstance = hinstance;
    winclass.hIcon = LoadIcon(NULL,IDI_APPLICATION);
    winclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    winclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
    winclass.lpszMenuName = NULL;
    winclass.lpszClassName = WINDOWSCLASS;
    winclass.hIconSm = LoadIcon(NULL,IDI_APPLICATION);

    if(!RegisterClassEx(&winclass)){
        return(0);
    }

    if(!(hwnd = CreateWindowEx(NULL,WINDOWSCLASS,IGECORE.sAppTitle,WS_OVERLAPPEDWINDOW | WS_VISIBLE,
        IGECORE.iPosX,IGECORE.iPosY,IGECORE.iWidth,IGECORE.iHeight,NULL,NULL,hinstance,NULL)))
    {
        return(0);
    }

    while(TRUE)
    {
        if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
        {
            if(msg.message == WM_QUIT)
            {
                break;
            }
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
        IGERUNTIME();
    }
}

Here is IGE.h this contains the CIGECORE class.

class CIGECORE
{
public:
    LPSTR sAppTitle;
    int iPosX;
    int iPosY;
    int iWidth;
    int iHeight;
};

Here is main.cpp this contains the function that executes the game code. All the code the user types with be put into main.cpp into the function IGERUNTIME.

void IGERUNTIME(){

}

------ Build started: Project: Insane Game Engine, Configuration: Debug Win32 ------
Compiling...
Windows.cpp
.\Windows.cpp(24) : error C2059: syntax error : ':'
.\Windows.cpp(25) : error C2143: syntax error : missing ';' before '{'
.\Windows.cpp(30) : error C2059: syntax error : ':'
.\Windows.cpp(31) : error C2143: syntax error : missing ';' before '{'
.\Windows.cpp(37) : error C2065: 'WMDESTROY' : undeclared identifier
.\Windows.cpp(37) : error C2143: syntax error : missing ':' before '{'
.\Windows.cpp(37) : error C2051: case expression not constant
.\Windows.cpp(43) : error C2228: left of '.wparam' must have class/struct/union
        type is 'UINT'
.\Windows.cpp(43) : error C2660: 'DefWindowProcA' : function does not take 3 arguments
.\Windows.cpp(71) : error C2065: 'IGECORE' : undeclared identifier
.\Windows.cpp(71) : error C2228: left of '.sAppTitle' must have class/struct/union
        type is ''unknown-type''
.\Windows.cpp(72) : error C2228: left of '.iPosX' must have class/struct/union
        type is ''unknown-type''
.\Windows.cpp(72) : error C2228: left of '.iPosY' must have class/struct/union
        type is ''unknown-type''
.\Windows.cpp(72) : error C2228: left of '.iWidth' must have class/struct/union
        type is ''unknown-type''
.\Windows.cpp(72) : error C2228: left of '.iHeight' must have class/struct/union
        type is ''unknown-type''
main.cpp
Generating Code...
Build log was saved at "file://c:\Documents and Settings\Owner\My Documents\Visual Studio\Projects\Insane Game Engine\Insane Game Engine\Debug\BuildLog.htm"
Insane Game Engine - 15 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

j104
So your project does not contain an int main() Perhaps you should start again with a project that contains an entry point If the code you posted is your entire project, I'm not surprised that things have gone awry.
slifinger
That would be Gdi32.lib. FWIW, I just googled GetStockObject, the first link is MSDN, and the MSDN page at the bottom tells you what to link to ( if you ever have these sort of troubles again ). I tried a couple from your longer list, and they were all user32 ( to be honest, I expected you to need gdi32.lib, but the ones I tried and thought may be in there, were not ).
Ralf Boeck
Here are the errors im getting with this code.

c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\IGE.h(11) : error C2143: syntax error : missing ';' before '<class-head>'
c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\IGE.h(11) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\IGE.h(11) : error C2011: 'CIGECORE' : 'class' type redefinition
c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\IGE.h(11) : see declaration of 'CIGECORE'
c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\IGE.h(18) : fatal error C1903: unable to recover from previous error(s); stopping compilation
main.cpp
c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\IGE.h(11) : error C2143: syntax error : missing ';' before '<class-head>'
c:\documents and settings\owner\my documents\visual studio\projects\insane game engine\insane game engine\IGE.h(11) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int

I started a blank project.
Using Classes and Structs

Answer this question

Using Classes and Structs

Hot Topic

VS Express Editions

Using Classes and Structs

Using Classes and Structs

DaveJohnson

Irfan Habib

spuckupine

DataBound

rishi bajaj

RichardAB

kadonk

Andre Da Costa

Leijtens

flape

Joe McCollough

j104

slifinger

Ralf Boeck