No_std compile error

[karv1c]

There is an compilation error without std feature:

error: #[panic_handler] function required, but not found
error: unwinding panics are not supported without std

Adding flags like panic=abort doesn't make any sense.

Seems like the problem is in crate-type = ["cdylib", "rlib"]. Removing this block makes hifitime compile with no_std.

Rust 1.82, Ubuntu

[ephraim71]

Adding flags like panic=abort doesn't make any sense.

Why not? Isn't that whats usually done for no_std?

[ephraim71]

If we don't need cdylib in no_std, then can do this :

[lib]
crate-type = ["rlib"]
name = "hifitime"

[target.'cfg(feature = "std")'.lib]
crate-type = ["cdylib", "rlib"]

[ChristopherRabotin]

@ephraim71 that's an interesting idea I hadn't thought of! Could you see if it works in CI? There's a test that runs with no-std already, and I don't remember being able to reproduce the bug. The cdynlib is only required for the Python builds IIRC.

[ephraim71]

@ChristopherRabotin
Ah, what failed for me for locally was cargo build --no-default-features (And I assume that is what @karv1c was using).
CI uses this : cargo build --no-default-features --target=aarch64-unknown-none -Z build-std=core, taking a closer look.

[ephraim71]

Okay, checked out master and tried building no_std with aarch64-unknown-none, thumbv6m-none-eabi and x86_64-unknown-linux-gnu (3rd one is just my development laptop)

The first two work with this warning, this is also whats in CI:
warning: dropping unsupported crate type cdylib for target aarch64-unknown-none
cargo build --target aarch64-unknown-none --no-default-features
cargo build --target thumbv6m-none-eabi --no-default-features

The third one fails with the error
error: unwinding panics are not supported without std
cargo build --target x86_64-unknown-linux-gnu --no-default-features

As x86_64-unknown-linux-gnu supports dynamic linking, it included cdylib and then failed. The other two just dropped cdylib themselves.

So to always enforce no cdylib when no_std and to try no_std without having to cross compile, this would help : #408