SDL2 Segmentation fault when trying to Poll Event - c++

Question

I want to create a little program, which should draw some Math Functions.
At first a just wrote the code, that should create a little Window, that should just be visisble until I hit the X at the window.
#include <iostream>
#include <SDL2/SDL.h>
SDL_Window* window;
SDL_Renderer* renderer;
bool running = true;
bool init() {
if(SDL_Init(SDL_INIT_EVERYTHING) < 0) return false;
window = SDL_CreateWindow("Visual Functions", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 100, 200, SDL_WINDOW_SHOWN);
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
if(window == NULL) return false;
if(renderer == NULL) return false;
std::cout << "App and SDL init success" << std::endl;
return true;
}
void onEvent(SDL_Event* event) {
switch (event->type)
{
case SDL_QUIT:
running = false;
break;
default:
break;
}
}
void loop() {
SDL_Event* event;
while(SDL_PollEvent(event)) onEvent(event);
}
void cleanUp() {
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
}
int main(int, char**) {
if(!init()) {
std::cout << "SDL or/and App init failed" << std::endl;
exit(-1);
}
while(running) loop();
cleanUp();
}
But the window pops so fast up and again down, that I couldn't even see it and in the command is at first App and SDL init success but then there stands Segmentation fault.
In a other code, which has the same Initialization and Loop code runs very well and everything is displayed displayed normally (at least for the SDL part).
I found out with some debug messages, that the loop comes not to the Event Function, but also not to the end of the Loop Function, so the problem is SDL_PollEvent(event), but what is the prolem and how to I fix it ?

Answer 1

You never create the SDL_Event struct that you are using:
void loop() {
SDL_Event* event;
while(SDL_PollEvent(event)) onEvent(event);
}
should be this
void loop() {
SDL_Event event;
while(SDL_PollEvent(&event)) onEvent(&event);
}