Compile error on linux arm64.

[tubzby]

error[E0119]: conflicting implementations of trait `std::convert::TryFrom<&[u8]>` for type `MacAddr6`
   --> /home/nv/.cargo/registry/src/rsproxy.cn-8f6827c7555bfaf8/advmac-1.0.3/src/lib.rs:247:9
    |
239 |         impl TryFrom<&[u8]> for $nm {
    |         --------------------------- first implementation here
...
247 |         impl TryFrom<&[core::ffi::c_char]> for $nm {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MacAddr6`
...
309 | mac_impl!(MacAddr6, 6, 12);
    | -------------------------- in this macro invocation
    |
    = note: this error originates in the macro `mac_impl` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0119]: conflicting implementations of trait `std::convert::TryFrom<&[u8]>` for type `MacAddr8`
   --> /home/nv/.cargo/registry/src/rsproxy.cn-8f6827c7555bfaf8/advmac-1.0.3/src/lib.rs:247:9
    |
239 |         impl TryFrom<&[u8]> for $nm {
    |         --------------------------- first implementation here
...
247 |         impl TryFrom<&[core::ffi::c_char]> for $nm {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MacAddr8`
...
310 | mac_impl!(MacAddr8, 8, 16);
    | -------------------------- in this macro invocation
    |
    = note: this error originates in the macro `mac_impl` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0119`.

[GamePad64]

What Rust version are you trying to compile against?

[bcecchinato]

@GamePad64 I'm also having this issue on nightly-2023-02-23. This is because core::ffi::c_char and u8 are identical on armhf target.

The c_char element is defined as this :

mod c_char_definition {
    cfg_if! {
        // These are the targets on which c_char is unsigned.
        if #[cfg(any(
            all(
                target_os = "linux",
                any(
                    target_arch = "aarch64",
                    target_arch = "arm",
                    target_arch = "hexagon",
                    target_arch = "powerpc",
                    target_arch = "powerpc64",
                    target_arch = "s390x",
                    target_arch = "riscv64",
                    target_arch = "riscv32"
                )
            ),
            all(target_os = "android", any(target_arch = "aarch64", target_arch = "arm")),
            all(target_os = "l4re", target_arch = "x86_64"),
            all(
                any(target_os = "freebsd", target_os = "openbsd"),
                any(
                    target_arch = "aarch64",
                    target_arch = "arm",
                    target_arch = "powerpc",
                    target_arch = "powerpc64",
                    target_arch = "riscv64"
                )
            ),
            all(
                target_os = "netbsd",
                any(target_arch = "aarch64", target_arch = "arm", target_arch = "powerpc")
            ),
            all(
                target_os = "vxworks",
                any(
                    target_arch = "aarch64",
                    target_arch = "arm",
                    target_arch = "powerpc64",
                    target_arch = "powerpc"
                )
            ),
            all(target_os = "fuchsia", target_arch = "aarch64"),
            target_os = "horizon"
        ))] {
            pub type c_char = u8;
            pub type NonZero_c_char = crate::num::NonZeroU8;
        } else {
            // On every other target, c_char is signed.
            pub type c_char = i8;
            pub type NonZero_c_char = crate::num::NonZeroI8;
        }
    }
}

The solution would be to exclude the TryFrom ffi function when c_cach == u8.

[bcecchinato]

And a quick and dirty solution would be to add a "feature" to enable/disable ffi parsing if you don't want to bother with managing all different platforms.