Windows XP doesn't have ConditionVariables, which notify requires via mpsc channels

[bbigras]

I'm not sure if I should report this here or not. I don't know what's the status of xp support with Rust. A simple 'hello world' works but the sample code from README.md results in a 'thread panicked while processing panic. aborting.'.

rustc 1.9.0 (e4e8b6668 2016-05-18)
notify = "2.6.1"

[passcod]

Is there any more than that message, by some chance? Sounds pretty hard to debug if not.

[passcod]

Tagging with help-wanted because there's no label for "I have no idea."

[passcod]

CCing @retep998 and @maurizi as the usual Windows suspects.

[retep998]

Windows XP support is super shady. While libstd does not link to any functions that are unavailable on Windows XP (hence "Hello world!" works), certain std functionality does load those functions at runtime and will panic if they don't exist. It's quite likely that somewhere rsnotify depends on some functionality that requires an API that isn't available on Windows XP.

[passcod]

So, probably want to close that as wontfix?

[maurizi]

@BrunoQC maybe if you run the sample program with RUST_BACKTRACE=1 to get a backtrace that would help determine if the problem is with Rust in general or something specific to rsnotify?

[bbigras]

F:\Dev\rust\test_notify\target\release>set RUST_BACKTRACE=1

F:\Dev\rust\test_notify\target\release>test_notify.exe
thread panicked while processing panic. aborting.

[retep998]

What happens if you do fn main(){panic!()}? Does that panic while panicking?

[bbigras]

F:\Dev\rust\test_panic\target\debug>test_panic.exe
thread panicked while processing panic. aborting.

[retep998]

Yep, so Rust is currently just broken on Windows XP when it comes to panicking. So you'll just have to get a debugger that works on Windows XP and use that to get a backtrace instead.

[bbigras]

Like this?

F:\Dev\rust\test_notify\target\debug>gdb test_notify.exe
GNU gdb (GDB) 7.6.1
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "mingw32".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from F:\Dev\rust\test_notify\target\debug\test_notify.exe...done.
(gdb) run
Starting program: F:\Dev\rust\test_notify\target\debug/test_notify.exe
[New Thread 944.0xb0]
[New Thread 944.0x69c]
thread panicked while processing panic. aborting.

Program received signal SIGILL, Illegal instruction.
0x00489b50 in std::sys_common::unwind::begin_unwind_inner::h39d40f52add53ef7 ()
(gdb) bt
#0  0x00489b50 in std::sys_common::unwind::begin_unwind_inner::h39d40f52add53ef7 ()
#1  0x00489ac3 in std::sys_common::unwind::begin_unwind::hd78480d5ec5c51b2 ()
#2  0x004bba57 in std::sys::c::AcquireSRWLockShared::fallback::h9437df0460b592c9 ()
#3  0x00489bce in std::sys_common::unwind::begin_unwind_inner::h39d40f52add53ef7 ()
#4  0x00489ac3 in std::sys_common::unwind::begin_unwind::hd78480d5ec5c51b2 ()
#5  0x004bba57 in std::sys::c::AcquireSRWLockShared::fallback::h9437df0460b592c9 ()
#6  0x00489bce in std::sys_common::unwind::begin_unwind_inner::h39d40f52add53ef7 ()
#7  0x00489ac3 in std::sys_common::unwind::begin_unwind::hd78480d5ec5c51b2 ()
#8  0x004bb937 in std::sys::c::SleepConditionVariableSRW::fallback::h3ba0cdf394e650a8 ()
#9  0x00488b5d in std::thread::park::h0427818cd37b30b3 ()
#10 0x004b0c60 in std::sync::mpsc::blocking::WaitToken::wait::h021a385a9b027589 ()
#11 0x0045fb35 in notify::sync::mpsc::oneshot::{{impl}}::recv (self=0x244d38) at ../src/libstd\sync\mpsc/oneshot.rs:148
#12 0x0045f141 in notify::sync::mpsc::{{impl}}::recv (self=0x22fd3c) at ../src/libstd\sync\mpsc/mod.rs:841
#13 0x0045bd0e in notify::windows::{{impl}}::send_action_require_ack (self=0x22fd30, action=..., pb=0x22fb08)
    at C:\Users\bbigras\.cargo\registry\src\github.aaakk.us.kg-48ad6e4054423464\notify-2.6.1\src/windows.rs:381
#14 0x00416188 in test_notify::windows::{{impl}}::watch<&str> (self=0x22fd30, path=...)
    at C:\Users\bbigras\.cargo\registry\src\github.aaakk.us.kg-48ad6e4054423464\notify-2.6.1\src/windows.rs:420
#15 0x004018f4 in test_notify::watch () at src/main.rs:18
#16 0x0041b771 in test_notify::main () at src/main.rs:34
#17 0x004c3dae in std::sys_common::unwind::try::try_fn::h09ba69fd13531e58 ()
#18 0x004b825b in __rust_try ()
#19 0x004b81cc in std::sys_common::unwind::inner_try::h9eebd8dc83f388a6 ()
#20 0x004c3c1a in std::rt::lang_start::h5b0863080165c75e ()
#21 0x0041b943 in main ()
(gdb)

[passcod]

Ah, XP doesn't have ConditionVariables, and the mpsc channels use that.

[retep998]

Perhaps one day someone can replace the mutexes and condvars and such in Rust's std with https://github.com/Amanieu/parking_lot. Then it would work on Windows XP (and be faster too!).

[passcod]

We could also bypass that process and use nonstd concurrency in notify directly, but that's a bit of a bigger project.

[passcod]

Possibly maybe could be solved by not using mpsc at all i.e. the v5 design. To be tested.

[passcod]

v5 will not solve this, as futures use condition variables internally. Truly an upstream issue.

[bbigras]

Btw I don't need XP support anymore. Maybe someone else do.

[passcod]

I'll close this, then.