Unable to natively compile as target-cpu=native on aarch64 ( AWS c6g )

[ribasushi]

Hi!

According to the history and the library CI aarch64 should be fully supported. Yet:

~$ uname -a
Linux ip-172-31-25-117 5.4.0-1018-aws #18-Ubuntu SMP Wed Jun 24 01:14:47 UTC 2020 aarch64 aarch64 aarch64 GNU/Linux

~$ rustc --version
rustc 1.46.0-nightly (f844ea1e5 2020-07-03)

~$ RUSTFLAGS="-C target-cpu=native -g" make ...

...

   Compiling bitintr v0.3.0
error[E0658]: use of unstable library feature 'stdsimd'
  --> {{redacted}}/.cargo/registry/src/github.com-1ecc6299db9ec823/bitintr-0.3.0/src/lib.rs:28:13
   |
28 |     pub use core::arch::aarch64::*;
   |             ^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #27731 <https://github.com/rust-lang/rust/issues/27731> for more information

error: aborting due to previous error

What am I missing / doing wrong?

[ribasushi]

The offending code is here: https://github.com/gnzlbg/bitintr/blob/6c49e0139280/src/lib.rs#L12-L29

• line 13 pulls in stdsimd
• line 28 bombs with "I don't have that"

Google does not turn up anything even remotely relevant. Worse: the tests for this very crate seem to work on aarch64: https://github.com/gnzlbg/bitintr/blob/6c49e0139280/.travis.yml#L19

Clearly something subtle-yet-dumb...

[ribasushi]

Apologies for the noise: the culprit was a build system explicitly ignoring the default toolchain for a portion of the compilation. This library kept being ran against stable i stead of nightly.