Modifying pointer leads to SIGSEGV signal - c++

Question

this is my first experience,so don't be picky.
It's SIGSEGV problem, and it appears only in class linking.
The problem within "SDL_surface *ScreenSurface" pointer.
Here goes the code...
Screen header
class screen
{
public:
screen();
SDLclass_Window *MainWindow=NULL;
SDL_Surface *ScreenSurface=NULL; //this is the problem pointer to the struct that cause error
//Those pointer are't NULL, see below
virtual ~screen();
protected:
private:
const int SCREEN_WIDTH = 1280;
const int SCREEN_HEIGHT = 726;
bool init();
};
Screen code
screen::screen()
{
if(!init())
{
std::cout<<"ERROR at INIT";
SDL_Delay( 4000 );
}
else
{
bool quit=0;
SDL_Event e;
while (!quit)
{
SDL_UpdateWindowSurface(MainWindow);
//Looking for events
while( SDL_PollEvent( &e ) != 0 )
{
//User requests quit
if( e.type == SDL_QUIT )
{
quit = true;
}
}
}
}
this->~screen();
}
bool screen::init() //Initialization
{
bool succses=1;
if (SDL_Init( SDL_INIT_VIDEO ) < 0 )
{
std::cout<< "SDL could not initialize! SDL_Error:"<< SDL_GetError()<<std::endl;
succses=0;
return succses;
}
MainWindow= SDL_CreateWindow( "Arachy: WIP Version", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN ); //Setting parameters to SDL_window
if (MainWindow==NULL)
{
std::cout<<"can't create window"<<SDL_GetError()<<std::endl;
succses=0;
return succses;
}
else
{
//Get window surface
ScreenSurface = SDL_GetWindowSurface( MainWindow );// telling ScreenSurface that it our main screen surface
}
return succses;
}
screen::~screen()
{
SDL_Quit();
}
Activity header
(another class that uses SDL_Surface which defined above in class Screen)
class activity
{
public:
activity();
virtual ~activity();
protected:
private:
screen mainScreen;
void load();
};
Activity code (I'm trying to modify SDL_Surface with SDL_FillRect() after that i got SIGSEGV signal during debug
activity::activity()
{
SDL_FillRect(mainScreen.ScreenSurface,NULL,SDL_MapRGB(mainScreen.ScreenSurface->format,255,000000,255));
}
Please , help me to find out...
Thank you

Answer 1

The problem is twofold:
A) It's likely that the destructor of screen is called twice, causing SDL_DestroyWindow() and SDL_FreeSurface() to be called on invalid, non-NULL pointers.
If you absolutely, positively want to call your destructor twice, you should at least reset these pointers to NULL after destroying the objects they point to.
But in most cases you should simply, you know, not explicitly call the destructor...
B) As set now, activity's constructor body will never be called until the main event loop is over.