`Cargo.toml` should document MSRV

[riptl]

error: could not compile `mdbx-sys` (lib) due to 121 previous errors
warning: build failed, waiting for other jobs to finish...
error: failed to compile `nimiq-client v1.0.6 (/home/nimiq/core-rs/client)`, intermediate artifacts can be found at `/home/nimiq/core-rs/target`.

Possibly a MSRV issue

I tried to compile with cargo-1.79.0-2.el9.x86_64

build.log

[Eligioo]

The MSRV is of the nimiq-client is 1.82.0.

1.82.0 introduces unsafe extern blocks (RFC3484) which are used by libmdbx 0.5.3.

[riptl]

Thank you, @Eligioo. I suggest adding rust-version to Cargo.toml. This would turn such confusing build error spam into a more human-readable error.

[riptl]

On second thought, it would make more sense to add it to mdbx-sys instead.
Looks like the rust-version attribute was recently removed 🤔 vorot93/libmdbx-rs@5132006

[riptl]

@Eligioo Ok, hmm, I think the flaw lies in bindgen 0.71.0.

In Rust 2021, using C FFI extern blocks without unsafe does not fail the build.
In Rust 2024, unsafe extern blocks become mandatory.

The Rust maintainers seem to encourage early adoption in Rust 2021 via code warnings.

Writing an extern block without the unsafe keyword is provided for compatibility only, and will eventually generate a warning.

Therefore, bindgen introduced a change that tries to guess whether the compiler supports. If it fails detection, then it seems to assumes unsafe extern is supported (rust-lang/rust-bindgen#3052 (comment)).
When used in build.rs it causes non-deterministic code generation.

IMHO the root cause is bindgen introducing breaking changes due to broken compiler feature detection in a minor release.

I don't think the MSRV needs to be quite as high. If we can lower it (by fixing bindgen's unsafe extern detection), this allows people to build Nimiq with the Rust toolchain from the operating system's package manager.

[hrxi]

rust-version should probably be added for better error messages.

[hrxi]

If we can lower it (by fixing bindgen's unsafe extern detection), this allows people to build Nimiq with the Rust toolchain from the operating system's package manager.

Which Linux distro do you use?

[riptl]

Which Linux distro do you use?

@hrxi Rocky Linux 9.5 (which is like RHEL 9)