Rust no_std static lib panic_handler

Question

I want to build a no_std static library with rust. I got the following:

[package]
name = "nostdlb"
version = "0.1.0"
edition = "2021"

[lib]
crate-type = ["staticlib"]

[profile.dev]
panic = "abort"

[profile.release]
panic = "abort"

lib.rs:

#![no_std]

pub fn add(left: usize, right: usize) -> usize {
    left + right
}

Despite setting the panic behaviour for both dev and release to abort cargo gives the following error:

error: `#[panic_handler]` function required, but not found

error: could not compile `nostdlb` due to previous error

I thought the panic handler is only required when there is no stack unwinding provided by std?

The panic handler is also responsible for printing the panic message, which the default handler won't be able to do without std. — Colonel Thirty Two, Feb 01 '23 at 13:30

score 4 · Accepted Answer · answered Feb 01 '23 at 13:41

4

No, you need to write your own one. If you need just aborting, consider using the following one:

#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {
    loop {}
}

I also highly recommend to unmangle the function and use C calling convention if you’re going to use this symbol somewhere (not import it the library as a crate, but link it manually):

#[no_mangle]
extern fn add(right: usize, left: usize) -> usize {
   right + left
}

answered Feb 01 '23 at 13:41

Miiao

751
1
8

Thanks for the explanation! btw. One also has to add the `eh_personality` language item. – Curunir Feb 02 '23 at 08:20
@curunir, it's not supposed to require an `eh_personality` of your target or cargo.toml declare aborting on panic. You can make a dummy function though ``` #[lang = "eh_personality"] fn ep() {} ``` This will generate one or two dummy symbols in binary. Not the best option, but definitely not the worst. – Miiao Feb 02 '23 at 18:12
Strangely enough I had panic = "abort" on both the release and dev profile but it kept complaining. – Curunir Feb 03 '23 at 07:47

Rust no_std static lib panic_handler

1 Answers1