C-unwind and Rust 1.71.0

[herabit]

Rust 1.71.0 stabilizes (at least partially) C-unwinding. However, due to issues with the feature attribute's usage on stable, one is unable to utilize C-unwind on Rust 1.71.0+, despite it being available, when on stable.

There should be some kind of additional conditional compilation code to handle these versions, while still maintaining the current MSRV of 0.60.0. I'm trying to figure out how myself rn, hence my fork.

[madsmtm]

If we just remove the #![feature(c_unwind)], then it should compile on stable, no?

[madsmtm]

Though actually making extern "C-unwind" sound will take more effort, since Rust panics and Objective-C exceptions are not compatible.

[herabit]

Yeah this is kind of annoying when I'm trying to make Rust cocoa wrappers that, are Rusty, and, safe. I wonder if there's any way to bridge this incompatibility...

[madsmtm]

Given that rust-lang/rust#115285 is FCP, this is now becoming a bit more important.

Unfortunately, I can't really raise the MSRV for objc2 to 1.71.0 yet, as Winit's MSRV is still at 1.70.0 :/

[herabit]

It could, at least in the short term be an opt-in feature, or perhaps enabled only on newer rust versions with a crate such as rustversion, which, well allows conditional compilation based upon whatever version of rustc you're compiling for. It may be worth taking a look at, though, in the short term it may complicate maintainability, and anger some folk due to the additional dependency. A build script may be able to provide similar functionality, though, again with potential issues pertaining to maintainability, as managing a lot of conditional compilation can, really be a pain in the ass.

[madsmtm]

Yeah. I think the easier solution might be to allow a bump to Winit's Rust version on macOS only.

[madsmtm]

In bbf81ac and fc7e6e2 I've improved upon this by making the (still unstable) feature available in block2, and by removing #![feature(c_unwind)].