SDL program immediately quitting after being started. What did I do wrong?

Question

I am trying to write a simple program with the help of SDL. This program loads in an SDL_Texture, and renders it to the window. However, upon starting my program it immediately quits. I am using VS Express 2013 with SDL2 and SDL2_image libraries added to the project. What can be the problem? Thanks in advance!

#include "SDL.h"
#include "SDL_image.h"
#include <iostream>
#include <string>

const int SCREEN_WIDTH = 640;
const int SCREEN_HEIGHT = 480;

bool init();
bool loadMedia();
void close();
// Loads individual image as texture
SDL_Texture* loadTexture(std::string);

SDL_Event event;
SDL_Window* gWindow = NULL;
// The window renderes
SDL_Renderer* gRenderer = NULL;
// Current displayed texture
SDL_Texture* gTexture = NULL;

int main(int argc, char* args[])
{
    if (!init())
    {
        std::cout << "An error has occured while initializing the window: " << SDL_GetError();
        return 1;
    }

    if (loadMedia())
    {
        std::cout << "Could not load media!";
        return 1;
    }

    bool quit = false;
    // main game loop
    while (!quit)
    {
        while (SDL_PollEvent(&event))
        {
            switch (event.type)
            {
            case SDL_QUIT:
                quit = true;
                break;      
            }
        }

        // Clear screen
        SDL_RenderClear(gRenderer);

        // Render texture to screen
        SDL_RenderCopy(gRenderer, gTexture, NULL, NULL);

        SDL_RenderPresent(gRenderer);
    }

    close();
    return 0;
}

bool init()
{
    //initialize SDL
    if (SDL_Init(SDL_INIT_VIDEO) == -1)
    {
        std::cout << "SDL could not initialize! Error: " << SDL_GetError();
        return false;
    }

    // Set texture filtering to linear
    if (!SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "1"))
        std::cout << "Warning: Linear texture filtering not enabled!";

    //create window
    gWindow = SDL_CreateWindow("Hello World", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);

    if (gWindow == NULL)
        return false;

    // Hardware accelerated renderer
    gRenderer = SDL_CreateRenderer(gWindow, -1, SDL_RENDERER_ACCELERATED);

    if (gRenderer == NULL)
        return false;

    // Initialize renderer color
    SDL_SetRenderDrawColor(gRenderer, 0xFF, 0xFF, 0xFF, 0xFF);

    //Initialize PNG loading 
    int imgFlags = IMG_INIT_PNG; 
    if(!(IMG_Init(imgFlags ) & imgFlags))
    { 
        std::cout << "SDL_image could not initialize! SDL_image Error: " << IMG_GetError();
        return false;
    }

    return true;
}

bool loadMedia()
{
    gTexture = loadTexture("texture.png");

    if (gTexture == NULL)
    {   
        std::cout << "Failed to load texture image!!";
        return false;
    }

    return true;
}

SDL_Texture* loadTexture(std::string path)
{
    SDL_Texture* newTexture = NULL;

    // Load an image from a specific path
    SDL_Surface* loadedSurface = IMG_Load(path.c_str());

    if (loadedSurface == NULL)
    {
        std::cout << "Error while loading surface: " << IMG_GetError();
        return newTexture;
    }

    newTexture = SDL_CreateTextureFromSurface(gRenderer, loadedSurface);

    SDL_FreeSurface(loadedSurface);
    loadedSurface = NULL;

    return newTexture;
}

void close()
{
    SDL_DestroyTexture(gTexture);
    SDL_DestroyWindow(gWindow);
    IMG_Quit();
    SDL_Quit();
}

Answer 1

Your code is fine having tested it on my system. I suspect it is one of the following:

1. The texture you are trying to load is not in the correct directory. This would cause the application to fail when trying to load the texture. The texture, according to your code, should reside in the same folder as your VC++ Project file. You can put it in other directories, you just need to specify a path when loading it.

2. You don't have the SDL and SDL_image DLL files in the same directory as your executable. This will cause the application to fail during the initialisation calls for SDL and SDL_image. These are the DLL's which I had in in the directory (I tend to include all the image type libs but if you are only ever use one image format you can just have that one):

   • libjpeg-9.dll
   • libpng16-16.dll
   • libtiff-5.dll
   • libwebp-4.dll
   • SDL2.dll
   • SDL2_image.dll

It should be easy to find where it is failing by stepping through the code one line at a time.

The only other comment I would make is that loadmedia() returns a bool so you should probably change if (loadMedia() == NULL) to just if (!loadMedia())

Answer 2

Adding one more point - in some Windows platforms libpng16-16.dll needs zlib1.dll to be added explicitly in the folder location as libpng16-16.dll .

You can find the precompiled zlib1.dll from http://www.zlib.net/

Answer 3

Works fine for me.

Try to replace returns inside main() with while(1). Maybe you're getting error messages and application closes instantly?