Panic broken on Windows XP

[arcnmx]

On Windows XP, the program fn main() { panic!() } will fail to run with the following:

thread panicked while processing panic. aborting.

I understand that XP isn't necessarily supported by the standard library, and certain sync implementations are stubbed out (probably the root cause of this issue?), but panicking seems like an operation that should really work if at all possible...

Tested with i686-pc-windows-gnu target and mingw-w64 on:

rustc 1.11.0-nightly (ad7fe6521 2016-06-23)
binary: rustc
commit-hash: ad7fe6521b8a59d84102113ad660edb21de2cba6
commit-date: 2016-06-23
host: x86_64-unknown-linux-gnu
release: 1.11.0-nightly

[alexcrichton]

Indeed this should definitely work! Would you be able to debug a bit and explore why the double panic is happening? (e.g. the panic messages that were printed or the stack traces)

[alexcrichton]

I'm also not sure I've ever heard of pc-windows-gnu working on XP, so MSVC may work better. Even then though we don't regularly test so it may still have regressed.

[arcnmx]

@alexcrichton

Hm, I can try to see if I can install a debugger and get more info, but I did find notify-rs/notify#79 (comment) which seems to include a stack trace of the same issue happening with a double panic.

I'm also not sure I've ever heard of pc-windows-gnu working on XP, so MSVC may work better

It seems to work well enough here, besides the aforementioned issue. If I don't trigger a panic most basic functionality seems fine! I don't have a MSVC Rust dev setup, but if anyone wants to compile the minimal test program and attach an exe I can try running it!

[alexcrichton]

Aha, that'd do it. When a thread panics it attempts to run its panic hook, but that panic hook is protected by an RwLock which is in turn not implemented on XP. That means that when panicking you'll panic immediately as you attempt to acquire an rwlock.

We could change this to use a mutex somehow perhaps which I believe is implemented on XP at least.

[retep998]

Alternatively all of Rust's synchronization primitives could be replaced by versions from parking_lot which works on XP (and is faster). cc @Amanieu

[steveklabnik]

Triage: no changes I'm aware of

[mbilker]

I found that this happens to me too. I may go and modify the panic handler to use a Mutex rather than an RWLock so I can find out why this program I am writing is panic-ing on Windows XP Embedded.

[mbilker]

Would there be too much of a performance hit if RWLock checks for SRW lock support at runtime like Mutex? Could always implement it and do a crater run to find out myself.

Mutexes work on XP since it falls back to using CriticalSection* functions.

[jonas-schievink]

Triage: #56410 will switch libstd to use parking_lot, but it's still got a long way to go

[mbilker]

I've been using the changes from #56410 in a small program running on Windows XP Embedded machines for a few months now with working panic messages.