wrapping_rem called with a value of zero

[michael-temp]

Seems to occur here https://github.com/yoshuawuyts/futures-concurrency/blob/a2a7f6a17ada682e01a0096e0b2a223c886eba39/src/utils/indexer.rs#L20C41-L20C53

attempt to calculate the remainder with a divisor of zero

   0:     0x56172194545c - std::backtrace_rs::backtrace::libunwind::trace::h0533452212810ad0
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x56172194545c - std::backtrace_rs::backtrace::trace_unsynchronized::heac64938397c8c70
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x56172194545c - std::sys_common::backtrace::_print_fmt::hb23dc0a3b2464f20
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/sys_common/backtrace.rs:67:5
   3:     0x56172194545c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h019008fb57527154
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x56172196edcc - core::fmt::rt::Argument::fmt::hf0ca3042505afdbe
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/core/src/fmt/rt.rs:138:9
   5:     0x56172196edcc - core::fmt::write::h64998bddcdaf5f5a
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/core/src/fmt/mod.rs:1094:21
   6:     0x56172194248e - std::io::Write::write_fmt::hf94b1afaea4dfb0e
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/io/mod.rs:1714:15
   7:     0x561721945244 - std::sys_common::backtrace::_print::hf32e9b06ae985cc8
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x561721945244 - std::sys_common::backtrace::print::h17d3f51425764561
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x561721946ada - std::panicking::panic_hook_with_disk_dump::{{closure}}::hbbc54c0cbf946921
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/panicking.rs:280:22
  10:     0x5617219467d5 - std::panicking::panic_hook_with_disk_dump::h55dfddf51ab4cb86
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/panicking.rs:314:9
  11:     0x5617219470e7 - std::panicking::default_hook::hfb6cc71965100937
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/panicking.rs:239:5
  12:     0x5617219470e7 - std::panicking::rust_panic_with_hook::h0f54142a4d88dc09
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/panicking.rs:753:13
  13:     0x561721946f96 - std::panicking::begin_panic_handler::{{closure}}::ha6353fe00a1ee230
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/panicking.rs:623:13
  14:     0x561721945986 - std::sys_common::backtrace::__rust_end_short_backtrace::h14b2a5ee3b4ff34e
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/sys_common/backtrace.rs:170:18
  15:     0x561721946d22 - rust_begin_unwind
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/std/src/panicking.rs:619:5
  16:     0x56172130f2a5 - core::panicking::panic_fmt::had794612bbf3a65e
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/core/src/panicking.rs:72:14
  17:     0x56172130f343 - core::panicking::panic::h130bbbcc8243c26e
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/core/src/panicking.rs:127:5
  18:     0x56172174f867 - core::num::<impl usize>::wrapping_rem::hfea8ea753c74a507
                               at /rustc/58e967a9cc3bd39122e8cb728e8cec6e3a4eeef2/library/core/src/num/mod.rs:1267:5
  19:     0x56172174f867 - futures_concurrency::utils::indexer::Indexer::iter::h355ba57a82748b72
                               at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-concurrency-7.4.2/src/utils/indexer.rs:20:41
  20:     0x56172148fd53 - <futures_concurrency::future::race::vec::Race<Fut> as core::future::future::Future>::poll::h3f8741cf78a1a619
                               at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-concurrency-7.4.2/src/future/race/vec.rs:51:22
  21:     0x56172148fd53 - <futures_time::future::timeout::Timeout<F,D> as core::future::future::Future>::poll::h44e3139b74cfd46f
                               at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/futures-time-3.0.0/src/future/timeout.rs:46:15

Will add more details shortly

[michael-temp]

My code looks like:

            if let Ok((i, Ok(..))) = notifiers
                .iter_mut()
                .enumerate()
                .map(|(i, notifier)| async move { (i, notifier.receiver.recv().await) })
                .collect_vec()
                .race()
                .timeout(Duration::from_millis(500))
                .await
            {
                has_update[i] = true;
            }

[michael-temp]

I suspect its an empty vec issue like #153 :)

[michael-temp]

In case it helps

    #[tokio::test]
    // #[ignore]
    async fn test_race_empty_vec() -> Result<()> {
        // https://github.com/yoshuawuyts/futures-concurrency/issues/156

        _ = Vec::<AbortOnDrop<()>>::new().race().timeout(DurationF::from_millis(500)).await;

        Ok(())
    }

[yoshuawuyts]

Thanks for reporting this! I wasn't aware of this behavior. I've filed a bug against rustc to document that this method may in fact panic here: rust-lang/rust#116063. I'll work on a fix in our code here for this next.