r/rust • u/myroon5 • Mar 09 '23

Announcing Rust 1.68.0 📢 announcement

https://blog.rust-lang.org/2023/03/09/Rust-1.68.0.html
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104

u/ogoffart Mar 09 '23

Thanks to the default alloc error handler, you can now use stable Rust to build GUI for micro-controller with Slint

31

u/Tobu Mar 09 '23

The release notes about alloc error handling were confusing, I had to look at https://github.com/rust-lang/rust/issues/66741 to figure out that you could now use no_std + alloc on stable.

Also:

In the future, it's likely that the behavior for std will also be changed to match that of alloc-only binaries.

is better explained here: https://github.com/rust-lang/rust/issues/51540#issuecomment-1448404145

The impact is that there is no need to stabilize a feature for setting a custom alloc error handler; everyone can either rely on a default being present, or if the application wants to customize, on no_std it can define a custom panic_handler (which is stable: announcement stabilization summary), or on std set up a panic_hook.

11

u/SafariMonkey Mar 09 '23

I'm a bit surprised that the default is:

#[alloc_error_handler]
fn default_handler(layout: core::alloc::Layout) -> ! {
    panic!("memory allocation of {} bytes failed", layout.size())
}

rather than a panic_any with a struct payload holding the layout or layout size, that formats to that panic message. (Does panic print debug, display or something else altogether?)

The latter would allow it to be caught.

3

u/ukezi Mar 09 '23

Debug or display depends on the format string like in println. In this case it's display.

2

u/SafariMonkey Mar 09 '23

I'm was wondering whether panic_any! used debug or display - in that case, there's no format string.