SDL 表面返回空值

我遇到了分割错误，我已经将其跟踪到我的表面，这是空的(但就地检查不会触发(。

不确定我是否正确创建了表面。在创建 Surface 时，我需要添加一些我错过的东西吗？

bool init()
{
    //Initialize SDL
    if( SDL_Init( SDL_INIT_VIDEO ) < 0 )
    {
        printf( "SDL could not initialize! SDL Error: %sn", SDL_GetError() );
        return false;
    }
    else
    {
        //Set texture filtering to linear
        if( !SDL_SetHint( SDL_HINT_RENDER_SCALE_QUALITY, "1" ) )
        {
            printf( "Warning: Linear texture filtering not enabled!" );
            return false;
        }
        else
        {
            //Create window
            gWindow = SDL_CreateWindow( "kPaint", 575, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN );
            GUI = SDL_CreateWindow( "GUI", 0, SDL_WINDOWPOS_UNDEFINED, 573, 542, SDL_WINDOW_SHOWN );
            if( gWindow == NULL || GUI == NULL )
            {
                printf( "Window could not be created! SDL Error: %sn", SDL_GetError() );
                return false;
            }
            else
            {
                //Create renderer for window
                gRenderer = SDL_CreateRenderer( gWindow, -1, SDL_RENDERER_ACCELERATED );
                if( gRenderer == NULL )
                {
                    printf( "Renderer could not be created! SDL Error: %sn", SDL_GetError() );
                    return false;
                }
                surface = SDL_GetWindowSurface( gWindow );
                GUIsurface = SDL_GetWindowSurface( GUI );
                if( surface == NULL )
                {
                    printf( "surface could not be created!" );
                    return false;
                }
                SDL_FillRect(surface, NULL, SDL_MapRGB(surface->format, 255,255,255));
                //Initialize PNG loading
                int imgFlags = IMG_INIT_PNG;
                if( !( IMG_Init( imgFlags ) && imgFlags ) )
                {
                    printf( "SDL_image could not initialize! SDL_image Error: %sn", IMG_GetError() );
                    return false;
                }
            }
        }
    }
    return true;
}