ICE when rustc asked to -o /dev/null on OSX

[gilescope]

Ok, so rustc outputting to /dev/null is a bit pathelogical but it used to not ICE the compiler.

If you checkout

https://github.com/jethrogb/rust-reduce/tree/master/tests/suite/futures_core

and from dir tests/suite/futures_core run:

rustc --crate-type lib -o /dev/null input.rs

Then rustc is vexed:

error: failed to write bytecode to /dev/null.input.3a1fbbbh-cgu.3.rcgu.bc.z: Permission denied (os error 13)

error: failed to write bytecode to /dev/null.input.3a1fbbbh-cgu.0.rcgu.bc.z: Permission denied (os error 13)

error: failed to write bytecode to /dev/null.input.3a1fbbbh-cgu.4.rcgu.bc.z: Permission denied (os error 13)

error: failed to write bytecode to /dev/null.input.3a1fbbbh-cgu.7.rcgu.bc.z: Permission denied (os error 13)

thread '<unnamed>' panicked at 'src/librustc_codegen_ssa/back/write.rs:1544: worker thread panicked', src/librustc/util/bug.rs:37:26
stack backtrace:
   0: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
   1: core::fmt::write
   2: std::io::Write::write_fmt
   3: std::panicking::default_hook::{{closure}}
   4: std::panicking::default_hook
   5: rustc_driver::report_ice
   6: std::panicking::rust_panic_with_hook
   7: std::panicking::begin_panic
   8: rustc::util::bug::opt_span_bug_fmt::{{closure}}
   9: rustc::ty::context::tls::with_opt::{{closure}}
  10: rustc::ty::context::tls::with_context_opt
  11: rustc::ty::context::tls::with_opt
  12: rustc::util::bug::opt_span_bug_fmt
  13: rustc::util::bug::bug_fmt
  14: rustc_codegen_ssa::back::write::start_executing_work::{{closure}}
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

error: internal compiler error: unexpected panic

(ICEs on stable and nightly)

The irony is that this is in the test suite of a rust code minimisation project.... 🤣 🤣 🤣

Let me minimise the reproduction of the problem...

[gilescope]

Thanks to rust-reduce I managed to get the repro down to:

#![cfg_attr(not(feature = "std"), no_std)]
pub mod task {
    pub mod __internal {
        use crate::task::Waker;
    }
    pub use core::task::Waker;
}

Interestingly it doesn't ICE on playground - I'm guessing playground is on linux?

[bjorn3]

I'm guessing playground is on linux?

Indeed

[pnkfelix]

triage: P-medium, removing nomination tag, assigning self.

[pnkfelix]

Thanks to rust-reduce I managed to get the repro down to:

#![cfg_attr(not(feature = "std"), no_std)]
pub mod task {
    pub mod __internal {
        use crate::task::Waker;
    }
    pub use core::task::Waker;
}

Interestingly it doesn't ICE on playground - I'm guessing playground is on linux?

hmm. I nonetheless see an ICE on my own Linux machine.

(There is probably some other reason the ICE does not replicate on the playpen.)