HWND address changes when used for a parameter from inside its windproc

Question

I was trying to make a function createscalingwindow that calls CreateWindowEx and writes the address's of the HWND used in CreateWindowEx to a vector, followed by it's initial size and position values.

Another function I made called scalewindowsize was supposed to take two given windows and scale the size of one window with the other, but at the moment I can't even match certain HWND's addresses because under certain conditions the address of an HWND passed to scalewindowsize will be entirely different from the address when initialized. This only happens when I call scalewindowsize from a window procedure using the same HWND in the window procedure's parameter as the HWND used in the parameter for scalewindowsize. Below is the relevant code:

#include <windows.h>
#include <stdio.h>
#include <winsock.h>
#include <vector>
#define ID_1 1000
#define ID_2 1001
#define ID_3 1002
HWND mainwin;  
HWND lobbywin;
int zero = 0;
char MENU1;
std::vector<intptr_t> sizevalues;
LRESULT CALLBACK mainproc (HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK lobbyproc (HWND, UINT, WPARAM, LPARAM);
char mainclassname[] = "main";
char lobbyclassname[] = "lobby";

void createscalingwindow(HWND &cswpara0,DWORD cswpara1,const CHAR* cswpara2,
const CHAR* cswpara3,DWORD cswpara4,int cswpara5,int cswpara6,int cswpara7,
int cswpara8,HWND cswpara9,HMENU cswpara10,HINSTANCE cswpara11,LPVOID cswpara12)
{
  cswpara0 = CreateWindowEx (cswpara1, cswpara2, cswpara3, cswpara4,cswpara5,
  cswpara6,cswpara7,cswpara8,cswpara9,cswpara10,cswpara11,cswpara12);
  char buffer[100];
  sizevalues.push_back((intptr_t)&cswpara0);
  snprintf (buffer, 20,"%d", sizevalues[zero]);
  MessageBox (NULL, buffer, "initialized", NULL);
  zero = (zero + 1);
  return;
}         

void scalewindowsize (HWND &ownerwin, const CHAR* tryz)
{
  char buffer[100];
  int checknumber = 0; 
  while (checknumber < sizevalues.size())
  {
    int compare = sizevalues[checknumber];
    if (sizevalues[checknumber] == (intptr_t)&ownerwin)
    {
      snprintf (buffer, 100,"%d", (intptr_t)&ownerwin);
      MessageBox (NULL, buffer, "value found", NULL);
      break;
    }
    else 
    {
      snprintf (buffer, 100,"%d", (intptr_t)&ownerwin);
      MessageBox (NULL, buffer, tryz, NULL);
      snprintf (buffer, 100,"%d", sizevalues[checknumber]);
      checknumber = (checknumber + 1);
      MessageBox (NULL, buffer, "fail currentcheck", NULL);
    }
  }
  return;
}

int WINAPI WinMain (HINSTANCE hThisInstance, HINSTANCE hPrevInstance,
LPSTR lpszArgument, int nCmdShow)
{
  MSG messages; 
  WNDCLASSEX mainwinclass;
  mainwinclass.hInstance = hThisInstance;
  mainwinclass.lpszClassName = mainclassname;
  mainwinclass.lpfnWndProc = mainproc;
  mainwinclass.style = CS_DBLCLKS;
  mainwinclass.cbSize = sizeof (WNDCLASSEX);
  mainwinclass.hIcon = LoadIcon (NULL, IDI_APPLICATION);
  mainwinclass.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
  mainwinclass.hCursor = LoadCursor (NULL, IDC_ARROW);
  mainwinclass.lpszMenuName = NULL;
  mainwinclass.cbClsExtra = 0;
  mainwinclass.cbWndExtra = 0;
  mainwinclass.hbrBackground = (HBRUSH) COLOR_BACKGROUND;
  if (!RegisterClassEx (&mainwinclass))
   return 0;

  WNDCLASSEX lobbywinclass;        
  lobbywinclass.hInstance = hThisInstance;
  lobbywinclass.lpszClassName = lobbyclassname;
  lobbywinclass.lpfnWndProc = lobbyproc;    
  lobbywinclass.style = CS_DBLCLKS;                
  lobbywinclass.cbSize = sizeof (WNDCLASSEX);
  lobbywinclass.hIcon = LoadIcon (NULL, IDI_APPLICATION);
  lobbywinclass.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
  lobbywinclass.hCursor = LoadCursor (NULL, IDC_ARROW);
  lobbywinclass.lpszMenuName = NULL;                 
  lobbywinclass.cbClsExtra = 0;                     
  lobbywinclass.cbWndExtra = 0;                      
  lobbywinclass.hbrBackground = (HBRUSH) COLOR_BACKGROUND;


  if (!RegisterClassEx (&lobbywinclass))
   return 0;
  HMENU playmenu = CreateMenu();
  HMENU playmenulist = CreatePopupMenu();
  HMENU helpmenulist = CreatePopupMenu();
  AppendMenu(playmenulist, MF_STRING, ID_1, "Join game");
  AppendMenu(playmenulist, MF_STRING, ID_3, "Host game");
  AppendMenu(playmenulist, MF_STRING, ID_2, "Quit");
  InsertMenu(playmenu, 1, MF_POPUP|MF_BYPOSITION, (UINT_PTR)playmenulist, "Play");

  createscalingwindow(mainwin, 0, mainclassname, "mainwindow",
  WS_OVERLAPPED|WS_CAPTION|WS_THICKFRAME|WS_MINIMIZEBOX|WS_MAXIMIZEBOX|WS_SYSMENU, 
  CW_USEDEFAULT, CW_USEDEFAULT, 544, 375, NULL, playmenu, hThisInstance, NULL);
  ShowWindow (mainwin, nCmdShow);

  createscalingwindow(lobbywin, 0, lobbyclassname, "Lobby", WS_OVERLAPPEDWINDOW,
  CW_USEDEFAULT, CW_USEDEFAULT, 600, 425, NULL, NULL, hThisInstance, NULL);

  while (GetMessage (&messages, NULL, 0, 0))
  {
    TranslateMessage(&messages);
    DispatchMessage(&messages);
  }
  return messages.wParam;
}

LRESULT CALLBACK mainproc(HWND mainwin, UINT message, WPARAM wParam, LPARAM lParam)
{
  switch (message)         
  {
    case WM_SIZE:
    {
      scalewindowsize (mainwin, "mainwin");
      scalewindowsize (lobbywin, "lobbywin");
      break;
    }
    case WM_DESTROY:
    PostQuitMessage(0);
    break;
  } 
  switch (wParam)
  {
    case ID_3:
    EnableWindow (mainwin, false);
    ShowWindow (mainwin, false);
    ShowWindow (lobbywin, true);              
    break;
    default:  
    return DefWindowProc (mainwin, message, wParam, lParam); 
    break;
  }  
  return 0;
}    
LRESULT CALLBACK lobbyproc(HWND lobbywin, UINT message, WPARAM wParam, LPARAM lParam)
{
  switch (message)
  {
    case WM_SIZE:
    {
      scalewindowsize (mainwin, "mainwin");
      scalewindowsize (lobbywin, "lobbywin");
      break;
    }
    break;
  }
  switch (wParam)
  {
    case SC_CLOSE:
    {
      EnableWindow (mainwin, true);
      ShowWindow (mainwin, true);
      ShowWindow (lobbywin, false);
      EnableWindow (lobbywin, false);
      break;
    }
    default:
    return DefWindowProc (lobbywin, message, wParam, lParam);
    break;
  }
}

If I run this program, click on host game, go back to the mainwindow and resize it slightly (setting off case WM_SIZE: in mainrpoc) then exit the program, I get the following messageboxes in chronological order:

1[title: Initialized |text: 4231184]
2[title: mainwin |text: 2292968]
3[title: fail currentcheck |text: 4231184]
4[title: lobbywin |text: 4231188]
5[title: fail currentcheck |text: 4231184]
6[title: initialized |text: 4231188] (no more boxes until I click on host game)
7[title: value found: |text: 4231184]
8[title: lobbywin |text: 2292676]
9[title: fail currentcheck |text: 4231184]
10[title: lobbywin |text: 2292676]
11[title: fail currentcheck |text: 4231188] (no more boxes until I go back to the mainwindow and resize it slightly)
12[title: mainwin |text: 2291164]
13[title: fail currentcheck |text: 4231184]
14[title: mainwin |text: 2291164]
15[title: fail currentcheck |text: 4231188]
16[title: lobbywin |text: 4231188]
17[title: fail currentcheck |text: 4231184]
18[title: value found |text: 4231188]

I'm very confused right now, I hope someone reading this can explain to me why the address is changing, thank you in advance for taking the time to read my question.

UPDATE: for anyone who's reading this I wanted to add in addition to whoz craigs answer that the way to call a global variable instead of a local in c++ is to add :: before the variable.

Answer 1

In both window procedures your sending the parameter HWND to scalewindow; not the global. Thus they're different addresses. Name resolution uses the "closest" variable, which in both cases is the HWND param, not the HWND global you're trying to use.

Example:

LRESULT CALLBACK mainproc(HWND mainwin, UINT message, WPARAM wParam, LPARAM lParam)
{
  switch (message)         
  {
    case WM_SIZE:
    {
      scalewindowsize (mainwin, "mainwin");   // passes parameter mainwin by reference
      scalewindowsize (lobbywin, "lobbywin"); // passes global lobbywin by reference
      break;
    }

Thus the references will have different address resolution. Another example:

LRESULT CALLBACK lobbyproc(HWND lobbywin, UINT message, WPARAM wParam, LPARAM lParam)
{
  switch (message)
  {
    case WM_SIZE:
    {
      scalewindowsize (mainwin, "mainwin");   // passes global mainwin by reference
      scalewindowsize (lobbywin, "lobbywin"); // passes parameter lobbywin by reference
      break;
    }
    break;

Answer 2

While WhozCraig already answered the question you asked, I'll explain how to get what you really wanted. It all boils down to your decision to store the address of a HWND being the wrong decision. Simply store the HWND - it is already pointer-sized so you're not wasting any space or performing costly copy operations.

Your container should be:

std::vector<HWND> sizevalues;

Change your createscalingwindow function to this (pseudo code):

void createscalingwindow( ... )
{
    cswpara0 = CreateWindowEx( .... );
    sizevalues.push_back(cswpara0);
    ...
}

And your scalewindowsize function should be modified as follows (again, pseudo code, with only the parts that require changes):

void scalewindowsize(HWND ownerwin, ...)
{
    char buffer[100];
    int checknumber = 0;
    while (checknumber < sizevalues.size())
    {
        if (sizevalues[checknumber] == ownerwin)
        {
            ...
        }
        else 
        {
            ...
        }
    }
}

This should fix your problems.