libsecp256k1_bug.rs

use libsecp256k1::curve::Scalar;

fn main() {
    let limbs: [u32; 8] = [23, 4, 55, 6, 7, 2, 4, 1];

    let (mut b, ptr) = {
        let a = Scalar(limbs);
        println!("Creation Address: {:?}", a.0.as_ptr());
        (a, a.0.as_ptr()) // a gets copied and returned 
    };

    println!("Value before dropping: {:?}", b.0);
    b.clear();  

    let val_at_returned_memory = unsafe {
        core::slice::from_raw_parts(b.0.as_ptr(), 8)
    };
    println!("Value at Returned Address: {:?}", val_at_returned_memory); // Zeroed

    let val_at_dropped_memory = unsafe {
        core::slice::from_raw_parts(ptr, 8)
    };
    println!("Value at Creation Address: {:?}", val_at_dropped_memory); // value still in memory
}