Нужно вывести в окно текст, который подали, как параметр командной строки

#include <windows.h>
#include <string.h>
#include <assert.h>
#include <stdio.h>
#define SECTOR_SIZE 14
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM);
char* readStringFromFile(char*);
 
int WINAPI WinMain (HINSTANCE hlnstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int iCmdShow)
{
    static char szAppName[] = "HelloWin";
    HWND hwnd;
    MSG msg;
    WNDCLASSEX wndclass;
    wndclass.cbSize = sizeof(wndclass);
    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hlnstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;
    wndclass.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
    RegisterClassEx(&wndclass);
    hwnd = CreateWindow(szAppName,//window class name
        "Misus application 12.09.10",//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
        hlnstance,//program instance handle
        lpCmdLine);//creation parameters
    ShowWindow(hwnd, iCmdShow);//display window but not client region
    UpdateWindow(hwnd);//display client region of the window
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
{
    static char *cpPrintString = NULL;
    HDC hdc;
    PAINTSTRUCT ps;
    RECT rect;
    static LPRECT lpRect = (LPRECT)malloc(sizeof(lpRect));
    static LOGFONT lf;
    switch(iMsg)
    {
    case WM_CREATE:
        GetObject(GetStockObject(ANSI_FIXED_FONT), sizeof(LOGFONT), &lf);
        GetWindowRect(hwnd, lpRect);
        assert((LPCREATESTRUCT)lParam != NULL);
        cpPrintString = readStringFromFile((char*)(((LPCREATESTRUCT)lParam) -> lpCreateParams));
        return 0;
    case WM_PAINT: 
        hdc = BeginPaint(hwnd, &ps);
        GetClientRect(hwnd, &rect);
        if (cpPrintString)
        {
            TextOut(hdc, 0, 0, cpPrintString, strlen(cpPrintString));//-1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
            free(cpPrintString);
        }
        else 
        {
            DrawTextA(hdc, "No such file!", -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
        }
        EndPaint(hwnd, &ps);
        return 0;
    case WM_DESTROY:
        //free
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, iMsg, wParam, lParam);
}
 
char* readStringFromFile(char* cpFileName)    
{
    FILE *file;
    char * expr, * temp;
    int sectorsCount = 1, exprLength = 0, symbol;
    expr = malloc (sectorsCount * SECTOR_SIZE  * sizeof(char));   
    file = fopen(cpFileName, "r");
    if (!file)
    {
        free(expr);
        return NULL;
    }
    do                     
    {
      symbol = getc (file);       
      if (symbol == EOF)           
      {
        if (feof(file))          
        {        
          expr[exprLength] = '\0';
          fclose(file);
          return expr;
        }
        else
        {
          free (expr);          
          return NULL;
        }
      }
      else        
      {
        if (exprLength > (sectorsCount * SECTOR_SIZE - 3))           
        {
          sectorsCount++;
          temp = realloc (expr, sectorsCount * SECTOR_SIZE);      
          if (!temp)        
          {
                return NULL;
          }
          expr = temp;
        }
        expr[exprLength] = (char) symbol;      
        exprLength++;
      }
    } while (1);
    return NULL;
}