Negative input vector with instantiated Graphics struct in code causes panic!

[Kiel97]

Hey! It is most likely more related to nightly's Rust build (rustc 1.90.0-nightly (11ad40bb8 2025-06-28)) than agb crate but at the moment this is a showstopper and you should be aware of it.

This happens when player presses either UP or LEFT buttons AND there is let mut gfx = gba.graphics.get(); in code. You don't have to show anything to make it panic. I found this bug today after updating Rust toolchain with rustup update command. Right now even Pong tutorial is crashing when pressing UP button.

Here's the stack

[ERROR] GBA Debug: [failed]
[INFO] GBA Debug: Stack trace: https://agbrs.dev/crash#5IBJDLJHD0Oe07005av1
[FATAL] GBA Debug: Error: panicked at /home/dyzio/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/agb-0.22.2/src/input.rs:38:18:
trying to construct an enum from an invalid value 0xffffffffffffffffffffffffffffffff

Here's the minimum example. Just clone agb's template and paste this code snippet.

#[agb::entry]
fn main(mut gba: agb::Gba) -> ! {
    let mut gfx = gba.graphics.get();

    let mut input = ButtonController::new();
    let mut v: Vector2D<i32> = vec2(16, 16);

    loop {
        input.update();

        // If `let mut gfx = gba.graphics.get();` is present in code, here program panics
        let dv = input.vector() as Vector2D<i32>;

        v += dv;

        // // This most likely doesn't have an impact on issue, that's why it's commented out
        // let mut frame = gfx.frame();
        // frame.commit();
        // agb::halt();
    }
}

[gwilymk]

Hi. Thanks for reporting! It looks like it's related to rust-lang/rust#141759, and seems like it's not handling negative numbers correctly.

0xffffffffffffffffffffffffffffffff is u128::MAX which is what -1 would be.

Full stack trace is this:

0:	__rustc::rust_begin_unwind <agb>/lib.rs:409
		let frames = backtrace::unwind_exception();
		             ^
1:	core::panicking::panic_nounwind_fmt::runtime <core>/panicking.rs:117
	(inlined into) core::panicking::panic_nounwind_fmt <core>/intrinsics/mod.rs:2340
		const_eval_select(($($val,)*), compiletime, runtime)
		^
2:	core::panicking::panic_invalid_enum_construction <core>/panicking.rs:327
3:	<agb::input::Tri as core::convert::From<(bool,bool)>>::from <agb>/input.rs:38
		unsafe { core::mem::transmute(b2 - b1) }
		         ^
	(inlined into) <T as core::convert::Into<U>>::into <core>/convert/mod.rs:768
		U::from(self)
		^
	(inlined into) agb::input::ButtonController::y_tri <agb>/input.rs:143
		(up, down).into()
		           ^
4:	agb::input::ButtonController::vector <agb>/input.rs:183
		(self.x_tri() as i32, self.y_tri() as i32).into()
		                           ^
	(inlined into) agb_template::_agb_main_func_13743959195958262542::inner <template>/main.rs:35
		let dv = input.vector() as Vector2D<i32>;
		               ^
5:	main <template>/main.rs:23
		#[agb::entry]
		^

Does show a gap in our test coverage though since we didn't spot this. Probably best to unblock you would be to fix to an older version of nightly for now, and we'll update our pinned issue with nightly issues until this is fixed :).

[gwilymk]

Actually, I'll just pin this issue for now until it's fixed.

The rust-toolchain.toml file you'll need to make this work is as follows:

[toolchain]
channel = "nightly-2025-06-27"
components = ["rust-src", "clippy", "rustfmt"]

[gwilymk]

I've created an issue against the rust compiler here: rust-lang/rust#143218

[Kiel97]

Actually, I'll just pin this issue for now until it's fixed.

The rust-toolchain.toml file you'll need to make this work is as follows:

[toolchain]
channel = "nightly-2025-06-27"
components = ["rust-src", "clippy", "rustfmt"]

Thanks! I confirm it works with 2025-06-27

[gwilymk]

Fixed, although now you also have to update to 0.22.3 because 0.22.2 doesn't compile on the first version where this bug was fixed 😂

[Kiel97]

Cool! Thanks! It's much appreciated 👍