ICE when running tests in a no_std lib crate

[saethlin]

This crate comes with a aarch64-skyline-switch.json file, I feel like there's some sort of target mismatch when I blindly run cargo miri test on it. So on the one hand I'm not actually expecting tests to run or pass, but also we probably shouldn't ICE in std::rt?

https://crates.io/crates/nnsdk/0.3.0

thread 'rustc' panicked at 'failed to find required Rust item: ["libc", "_SC_PAGESIZE"]', src/tools/miri/src/helpers.rs:156:32

note: the place in the program where the ICE was triggered
   --> /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/unix/os.rs:593:14
    |
593 |     unsafe { libc::sysconf(libc::_SC_PAGESIZE) as usize }
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: inside `std::sys::unix::os::page_size` at /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/unix/os.rs:593:14: 593:47
    = note: inside `std::sys::unix::thread::guard::init` at /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/unix/thread.rs:782:25: 782:40
    = note: inside `std::rt::init` at /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:99:26: 99:52
    = note: inside closure at /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:147:42: 147:67
    = note: inside `std::panicking::r#try::do_call::<[closure@std::rt::lang_start_internal::{closure#1}], ()>` at /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:500:40: 500:43
    = note: inside `std::panicking::r#try::<(), [closure@std::rt::lang_start_internal::{closure#1}]>` at /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:464:19: 464:81
    = note: inside `std::panic::catch_unwind::<[closure@std::rt::lang_start_internal::{closure#1}], ()>` at /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:142:14: 142:33
    = note: inside `std::rt::lang_start_internal` at /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:147:5: 147:70
    = note: inside `std::rt::lang_start::<()>` at /home/ben/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:165:17: 170:6

[RalfJung]

Are the crate sources on github somewhere or so?

cargo miri test without --target should ignore that target file. So somehow it looks like libc is missing? Is this a no_std situation?

[saethlin]

The crate doesn't have a repo link and I can't find it on @jam1garner's GitHub page. I downloaded the sources from crates.io, for example using https://github.com/saethlin/miri-tools/blob/50412bc80fd5966e53e103bde987bad7107bebc9/cargo-download/src/main.rs

[jam1garner]

Don't have to time to look at this rn in case I have other insight but here's the repo link: https://github.com/ultimate-research/nnsdk-rs

[saethlin]

Ah, perfect. I wasn't expecting any help from you, I think this is almost certainly just a Miri issue.

[RalfJung]

Ah it is no_std indeed. Our sysconf shim doesn't really work in that case.

Fixing the ICE is fairly easy by being less panic-y around here. Actually making it work is harder though. Judging from the backtrace there actually is a std linked into the test care... I don't quite understand how no_std and unit tests interact.

[bjorn3]

#![no_std] in unit tests will still inject extern crate test;, which in turn pulls in libstd as dependency, but it won't make it available as std::* I think.