Assertion failure only when compiling with -O #2989
Description
The assert in this crate (which is derived from std::bitv) passes when compiled without -O and fails when compiled with -O:
use std;
fn some_unused_fn() { fail }
trait methods {
fn to_bytes() -> ~[u8];
}
impl of methods for () {
fn to_bytes() -> ~[u8] {
vec::from_elem(42, 0)
}
}
// the position of this function is significant! - if it comes before methods
// then it works, if it comes after it then it doesnt!
fn to_bools(bitv: {storage: ~[u64], nbits: uint}) -> ~[bool] {
vec::from_fn(bitv.nbits, |i| {
let w = i / 64;
let b = i % 64;
let x = 1u64 & (bitv.storage[w] >> b);
x == 1u64
})
}
fn main() {
let bools = ~[false, false, true, false, false, true, true, false];
let bitv = {storage: ~[0b01100100], nbits: 8};
assert to_bools(bitv) == bools;
}
As mentioned in a comment in the code the position of the items in the crate also seem to be significant. Removing some_unused_fn and/or methods also makes the code work as expected.
This bug is blocking #2964 and possibly #2341.
I found this bug on a 64 bit Ubuntu system.