Cortex-M build is failing: 0 vs 3

[dtolnay]

     Running `qemu-system-arm -cpu cortex-m3 -machine lm3s6965evb -nographic -semihosting-config enable=on,target=native -kernel /home/runner/work/linkme/linkme/target/thumbv7m-none-eabi/release/cortex-m-linkme-test`
panicked at 'assertion failed: `(left == right)`
  left: `0`,
 right: `3`', tests/cortex/src/main.rs:25:5

This appears to be a regression from nightly-2021-08-21 to nightly-2021-08-22. A couple older nightlies I spot checked all work, whereas 2021-08-22 fails consistently.

[dtolnay]

Per cargo-bisect-rustc --start 2021-08-21 --end 2021-08-22 --target thumbv7m-none-eabi -- run --release, this bisects to rust-lang/rust#87570.

[yfblock]

I used #[used(linker)] instead of #[used] in the linkme and passed the cortex test. But #![feature(used with arg)] needs to be added to the crate using distributed_slice. I don't know if it is a efficient way.

[dtolnay]

It didn't work when I tried it. The Cortex-M job fails the same way with #[used(linker)] as it does with just #[used]. See #55. @yfblock could you make a PR showing exactly what change you made to make the cortex test succeed?

[yfblock]

@dtolnay Very strange. I can't reproduce it anywhere else, not just my computer or github CodeSpace. It only seems to happen on github ci.

https://github.com/yfblock/linkme/tree/temp

What I did was modify the "memory.x" file according to your pr #55.

[yfblock]

I try to remove linkme related code from cortex test. But still got errors when pushing.