Panics when "focused_window" is the only block configured

[ammgws]

As per title.

config.toml contents

theme = "solarized-dark"
icons = "awesome"

[[block]]
block = "focused_window"

stdout at time of panic:

{"version": 1, "click_events": true}
[[],
thread 'main' panicked at 'overflow when adding duration to instant', src/libcore/option.rs:1185:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

backtrace:

{"version": 1, "click_events": true}
[[],
thread 'main' panicked at 'overflow when adding duration to instant', src/libcore/option.rs:1185:5
stack backtrace:
   0:     0x557fb6fcace4 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h4c5e39dd6bf38933
   1:     0x557fb6fedc8c - core::fmt::write::h94b22f3cbda6422c
   2:     0x557fb6fc79a7 - std::io::Write::write_fmt::he7e02466cb3dc860
   3:     0x557fb6fcd38e - std::panicking::default_hook::{{closure}}::h077f2d0f0f4550db
   4:     0x557fb6fcd081 - std::panicking::default_hook::hcc1ceebfaf9d0a58
   5:     0x557fb6fcda8b - std::panicking::rust_panic_with_hook::h328d8e7ed959397b
   6:     0x557fb6fcd62e - std::panicking::continue_panic_fmt::h745b12464b662c8f
   7:     0x557fb6fcd516 - rust_begin_unwind
   8:     0x557fb6fe9ace - core::panicking::panic_fmt::hdb91b8826feb6fc9
   9:     0x557fb6fe9b37 - core::option::expect_failed::h02ca44b00cc41c7f
  10:     0x557fb6fca879 - <std::time::SystemTime as core::ops::arith::Add<core::time::Duration>>::add::h93fc4eab81208764
  11:     0x557fb6dad0b3 - crossbeam_channel::flavors::after::Channel::new::h7cf3b0b56e89f831
                               at /home/ammgws/.cargo/registry/src/github.com-1ecc6299db9ec823/crossbeam-channel-0.4.0/src/flavors/after.rs:31
  12:     0x557fb6dad020 - crossbeam_channel::channel::after::h5ed64f402a86cc04
                               at /home/ammgws/.cargo/registry/src/github.com-1ecc6299db9ec823/crossbeam-channel-0.4.0/src/channel.rs:177
  13:     0x557fb6889d46 - i3status_rs::run::ha9322434272d2061
                               at src/main.rs:243
  14:     0x557fb688557d - i3status_rs::main::hc785fa21c69d20b9
                               at src/main.rs:87
  15:     0x557fb68f12b0 - std::rt::lang_start::{{closure}}::h4fad3d60d7e957f2
                               at /build/rust/src/rustc-1.40.0-src/src/libstd/rt.rs:61
  16:     0x557fb6fcd4b3 - std::panicking::try::do_call::h81508b6a18a6e157
  17:     0x557fb6fd57ba - __rust_maybe_catch_panic
  18:     0x557fb6fce02d - std::rt::lang_start_internal::hfccf8c6e859ea61a
  19:     0x557fb68f1289 - std::rt::lang_start::h9a863fff0d11033c
                               at /build/rust/src/rustc-1.40.0-src/src/libstd/rt.rs:61
  20:     0x557fb688b5aa - main
  21:     0x7f9203c39153 - __libc_start_main
  22:     0x557fb67a00de - _start
  23:                0x0 - <unknown>

This is what I think is happening:

• focused_window block only sends updates (tx.send(...)) when it receives an update on the IPC channel
• main thread expects update_time to have been set by a block, otherwise it sets the timeout to std::u64::MAX which instantly causes the overflow panic to occur

Further investigation:

I changed the above std::u64::MAX to 10 seconds. As long as you keep changing the window focus within 10 seconds, i3status-rs works fine. But if you leave it for 10 seconds you will get the panic below which now points to the scheduler:

backtrace when timeout is set to 10s

{"version": 1, "click_events": true}
[[],
[{"background":null,"color":"#002b36","full_text":"","markup":"pango","separator":false,"separator_block_width":0},{"background":"#002b36","color":"#93a1a1","full_text":" /tmp | fish ","separator":false,"separator_block_width":0}],
[{"background":"#000000","color":"#dc322f","full_text":" Internal error in context 'scheduler': schedule is empty ","separator":false,"separator_block_width":0}]


Internal error in context 'scheduler': schedule is empty
thread '<unnamed>' panicked at 'called `Result::unwrap()` on an `Err` value: "SendError(..)"', src/libcore/result.rs:1165:5
stack backtrace:
   0:     0x55c0da414ce4 - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h4c5e39dd6bf38933
   1:     0x55c0da437c8c - core::fmt::write::h94b22f3cbda6422c
   2:     0x55c0da4119a7 - std::io::Write::write_fmt::he7e02466cb3dc860
   3:     0x55c0da41738e - std::panicking::default_hook::{{closure}}::h077f2d0f0f4550db
   4:     0x55c0da417081 - std::panicking::default_hook::hcc1ceebfaf9d0a58
   5:     0x55c0da417a8b - std::panicking::rust_panic_with_hook::h328d8e7ed959397b
   6:     0x55c0da41762e - std::panicking::continue_panic_fmt::h745b12464b662c8f
   7:     0x55c0da417516 - rust_begin_unwind
   8:     0x55c0da433ace - core::panicking::panic_fmt::hdb91b8826feb6fc9
   9:     0x55c0da433bc7 - core::result::unwrap_failed::haba3c6d5a6de1991
  10:     0x55c0d9c3fdfc - core::result::Result<T,E>::unwrap::h62c1cc4849b4e08a
                               at /build/rust/src/rustc-1.40.0-src/src/libcore/result.rs:933
  11:     0x55c0d9e9a283 - <i3status_rs::blocks::focused_window::FocusedWindow as i3status_rs::blocks::ConfigBlock>::new::{{closure}}::hca064e0f0147e248
                               at src/blocks/focused_window.rs:69
  12:     0x55c0d9ee2000 - std::sys_common::backtrace::__rust_begin_short_backtrace::h49fe9e8f6df29001
                               at /build/rust/src/rustc-1.40.0-src/src/libstd/sys_common/backtrace.rs:129
  13:     0x55c0d9e057d2 - std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}}::hbcaf183d72c49056
                               at /build/rust/src/rustc-1.40.0-src/src/libstd/thread/mod.rs:469
  14:     0x55c0d9dd8822 - <std::panic::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once::h861413b3c039f0f8
                               at /build/rust/src/rustc-1.40.0-src/src/libstd/panic.rs:317
  15:     0x55c0d9caa4dc - std::panicking::try::do_call::hf8e4ef7e39c8ba81
                               at /build/rust/src/rustc-1.40.0-src/src/libstd/panicking.rs:287
  16:     0x55c0da41f7ba - __rust_maybe_catch_panic
  17:     0x55c0d9ca8c7e - std::panicking::try::h94b234fb9e84ef30
                               at /build/rust/src/rustc-1.40.0-src/src/libstd/panicking.rs:265
  18:     0x55c0d9dd8b42 - std::panic::catch_unwind::h7bd6e96b94b73647
                               at /build/rust/src/rustc-1.40.0-src/src/libstd/panic.rs:396
  19:     0x55c0d9e02ace - std::thread::Builder::spawn_unchecked::{{closure}}::h2c494a8806a81a27
                               at /build/rust/src/rustc-1.40.0-src/src/libstd/thread/mod.rs:468
  20:     0x55c0d9c77dd3 - core::ops::function::FnOnce::call_once{{vtable.shim}}::hb00a27c0d6380e5b
                               at /build/rust/src/rustc-1.40.0-src/src/libcore/ops/function.rs:227
  21:     0x55c0da40a13f - <alloc::boxed::Box<F> as core::ops::function::FnOnce<A>>::call_once::h9c0116b07c5d124e
  22:     0x55c0da41ec60 - std::sys::unix::thread::Thread::new::thread_start::h20a61bfd6b1bfdd0
  23:     0x7faa5ba484cf - start_thread
  24:     0x7faa5b95b2d3 - clone
  25:                0x0 - <unknown>

Takeaways:

1. Should we really be using std::u64::MAX here?

2. This project seems dependent on each block to be sending updates, so this issue is probably just due to the focused_window block not following the correct pattern.

3. Note that this panic doesn't occur if you define another block or more alongside focused_window as those block will provide the updates to keep the code in main.rs/scheduler.rs happy.

[ammgws]

So apparently this was actually a bug with crossbeam_channel: crossbeam-rs/crossbeam#798