stack overflow when using rand and lazy_static about may

[Xudong-Huang]

rand is using a big stack size in it's implementation.
for debug version stack usage

coroutine name = None, stack size = 40959,  used size = 9205

for release version

coroutine name = None, stack size = 40959,  used size = 2740

here is the modified test

#[macro_use]
extern crate lazy_static;
#[macro_use]
extern crate may;
extern crate rand;

use std::io::Read;
use std::collections::HashMap;

// the ThreadRng is using a big stack!
lazy_static! {
    static ref DATA: Vec<u8> = vec![rand::random::<u8>()];
}

// the OsRng is not using a big stack, you can safely use it in coroutine context
/*
lazy_static! {
    static ref DATA: Vec<u8> = {
        use rand::Rng;
        let mut rand = rand::OsRng::new().unwrap();
        vec![rand.gen()]
    };
}
*/
fn main() {
    may::config().set_stack_size(4096*10 - 1);
    let mut entries: HashMap<usize, Vec<u8>> = HashMap::new();

    // force init DATA in the main thread
    // let _ = DATA[0];

    let task = go!(move || {
        entries.insert(0, DATA.clone());
    });

    task.join().unwrap();
    std::io::stdin().read(&mut [0]).ok();
}

the solution is init the DATA in main thread (not in the coroutine context, just like what you did to pass the test), or use the os rand interface which doesn't use a huge stack.

[alanhoff]

Now it makes perfect sense. Static values declared with lazy_static! only get evaluated once the value is used, that's why lazy (d'oh), and if it's being used inside the coroutine context it also affect's it's stack. I'm such a noob.

Thanks for your time and patience!