Example to reproduce stackoverflow error

output.txt

thread '
thread 'outer-thread-0' has overflowed its stack
fatal runtime error: stack overflow
outer-thread-1' has overflowed its stack
fatal runtime error: stack overflow
Aborted (core dumped)

rayon_demo2.rs

use rayon;
use rayon::prelude::*;

fn main() {
    let pool_outer = rayon::ThreadPoolBuilder::new()
        .num_threads(2)
        .thread_name(|i| format!("outer-thread-{}", i))
        .build()
        .unwrap();
    let pool_inner = rayon::ThreadPoolBuilder::new()
        .num_threads(2)
        .thread_name(|i| format!("inner-thread-{}", i))
        .build()
        .unwrap();

    pool_outer.scope(|_| {
        (0..90000000).into_par_iter().for_each(|out_i| {
            pool_inner.scope(|_| {
                // rayon::scope(|_| {      // rayon::scope doesn't cause stack overflow
                let sum: i32 = (0..2000).into_par_iter().map(|i| i + 1).sum();
                if out_i == 1 {
                    println!("sum = {:?}, out_i = {}", sum, out_i);
                }
            })
        });
    })
}