Two 2d-arrays defined in main function make C program do nothing

Question

I either found a very weird bug, or I am doing something wrong.

I am using Visual Studio Code v1.62.3 with CMakeTools v1.9.2

Here's my project structure:

clab
│   CMakeLists.txt
│
└───src
        not_a_test.c

And contents of CMakeLists.txt:

cmake_minimum_required(VERSION 3.15)
project(clab)

add_executable(not_a_test src/not_a_test.c)

The kit I'm using is

So here's the strange part. If the contents of not_a_test.c are

#include <stdio.h> 

#define MAX_ARR_SIZE 500

int main(void) {
    int mat[MAX_ARR_SIZE][MAX_ARR_SIZE];

    printf("Hello!\n");

    return 0;
}

It runs absolutely normally.

But if I add one line

#include <stdio.h> 

#define MAX_ARR_SIZE 500

int main(void) {
    int mat[MAX_ARR_SIZE][MAX_ARR_SIZE];
    int mat2[MAX_ARR_SIZE][MAX_ARR_SIZE]; // this one

    printf("Hello!\n");

    return 0;
}

It suddenly stops working at all

Also, when compiled via ideone / GCC v8.3 it works fine again: https://ideone.com/Vvrnnn

So, what do you think happens here?