SDL2 C++ Unhandled Exception

Question

First and foremost, I'm in the process of learning C++ & SDL2 coming from a C# background. I'm getting an unhandled exception which should be contained within a try/catch but the line of code should from other examples should execute successfully. The exception is happening at the SDL_RenderCopy() function.

Any help/direction would be most appreciated in my long journey of C++!

Gameboard.h

#ifndef GAMEBOARD_H
#define GAMEBOARD_H

#include "GenericEntity.h"
#include "GameboardParameters.h"
#include "Piece.h"
#include <iostream>

// Board witdh & height in pieces
#define BOARD_WIDTH 6
#define BOARD_HEIGHT 11

// Piece width & height in pixels
#define PIECE_WIDTH 32
#define PIECE_HEIGHT 32

// Define next pieces buffer 
#define NEXT_PIECES 255

class Gameboard : public GenericEntity {

public:
    Gameboard(SDL_Renderer *renderer, GameboardParameters parms);
    ~Gameboard();
    void Render(float delta);
    void Update(float delta);
    void CreateLevel();

public:
    float FALL_SPEED = 50;
    Piece p1_pieces[BOARD_WIDTH][BOARD_HEIGHT];
    Piece next_pieces[NEXT_PIECES];

private:
    SDL_Texture *sdlTextureBackground;
    SDL_Texture *sdlTextureBackgroundGrid;
    SDL_Texture *texTarget;

};

#endif //GAMEBOARD_H

Gameboard.cpp

Gameboard::Gameboard(SDL_Renderer *renderer, GameboardParameters parms) : GenericEntity(renderer) {
     SDL_Surface *sdlSurfaceBackground = IMG_Load("resources/backgrounds/SC_S_01.BMP");
     sdlTextureBackground = SDL_CreateTextureFromSurface(renderer, sdlSurfaceBackground);
     SDL_FreeSurface(sdlSurfaceBackground);

     SDL_Surface *sdlSurfaceBackgroundGrid = IMG_Load("resources/backgrounds/GRID-768X1408.PNG");
     sdlTextureBackgroundGrid = SDL_CreateTextureFromSurface(renderer, sdlSurfaceBackgroundGrid);
     SDL_FreeSurface(sdlSurfaceBackgroundGrid);
}

...

void Gameboard::Render(float delta) {

     // Clear screen
     SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
     SDL_RenderClear(renderer);
     SDL_RenderPresent(renderer);

     // Render background
     SDL_RenderCopy(renderer, sdlTextureBackground, NULL, NULL);
}

`SDL_CreateTextureFromSurface` can return `NULL`, ensure that `sdlTextureBackground` isn't null before passing it to `SDL_RenderCopy` — kmdreko, Apr 25 '18 at 01:10
There was an error with that particular file and the variable. I don't know exactly but I believe it was the order of functions which freed the texture before copying it, is my understanding of it atleast. Ultimately, this tutorial helped understand the SDL draw process more clearly http://www.willusher.io/sdl2%20tutorials/2013/08/17/lesson-1-hello-world — tkrn, Apr 25 '18 at 13:17

Johannes · Accepted Answer · 2018-04-25T06:57:41.990

There is likely an error in one of the initialisations. In general you have to assume that resource initialization can fail so you will need to check those errors. SDL offers methods to check for errors.

The documentation for IMG_Load states that NULL is returned on error. That may be an error source. You should check for null and use IMG_GetError to gain some more insights.

More Tips for your journey:

You can not catch all exceptions using try/catch. Here is a jump off point for that information.

In C++ you want to use the RAII Idiom for acquisition.

You should also consider using std::unique_ptr (or the shared variant in some cases) to handle your raw pointers. This also works for C-Style APIs like SDL.

For SDL I would also supplement your studies with Lazy Foos tutorials.

Good Luck.

Thank you for the direction and I will certainly be following up with these links. I've been following the Lazy Foo tutorials for the SDL functionality but also learning the C++ language is some of the curve (syntactically) mixed in there. Thanks! — tkrn, Apr 25 '18 at 13:19

SDL2 C++ Unhandled Exception

1 Answers1