SDL crashes when any standard variable is declared - c

Question

This SDL program works fine (displays a windows and a draws a bitmap onto it), however, if I declare any variables in my program (such as int, long, etc), the windows freezes and is white instead of black and nothing draws. What could possibly cause this?
#include <stdio.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
int main(int argc, char* argv[]) {
// line below will cause SDL crash
// int blabla = 640;
SDL_Window *window;
SDL_Init(SDL_INIT_VIDEO);
window = SDL_CreateWindow(
"A rather exceptional SDL window",
SDL_WINDOWPOS_UNDEFINED,
SDL_WINDOWPOS_UNDEFINED,
640,
480,
SDL_WINDOW_OPENGL
);
if (window == NULL) {
printf("Could not create window: %s\n", SDL_GetError());
return 1;
}
SDL_Renderer *renderer;
SDL_Texture *texture;
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
SDL_Surface *brush;
brush = IMG_Load("brush2.png");
texture = SDL_CreateTextureFromSurface(renderer, brush);
SDL_RenderClear(renderer);
SDL_Rect *sRect, *dRect;
sRect->w = 10;
sRect->h = 4;
sRect->x = 0;
sRect->y = 0;
dRect->w = 10;
dRect->h = 4;
dRect->x = 10;
dRect->y = 10;
SDL_RenderCopy(renderer, texture, sRect, dRect);
SDL_RenderPresent(renderer);
SDL_Delay(1000);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}

Answer 1

You are writing unallocated memory.
SDL_Rect *sRect, *dRect;
sRect->w = 10; /* w doesn't exist. Writing is undefined behaviour. */
sRect and dRect are only pointers. They need to point to valid memory before struct members are accessed.
You could declare them in stack instead:
SDL_Rect sRect, dRect;
sRect.w = 10;
sRect.h = 4;
...
SDL_RenderCopy(renderer, texture, &sRect, &dRect);
You should also check return values of SDL_-functions. If those fail, and you continue execution regardless, you may experience weird behaviour or crashes.