ICE: cannot read from extern static

[matthiaskrgr]

code from src/test/ui/consts/ice-zst-static-access.rs

// This is a regression test for ICEs from
// https://github.com/rust-lang/rust/issues/71612
// and
// https://github.com/rust-lang/rust/issues/71709

#[derive(Copy, Clone)]
pub struct Glfw;

static mut GLFW: Option<Glfw> = None;
pub fn new() -> Glfw {
    unsafe {
        if let Some(glfw) = GLFW {
            return glfw;
        } else {
            todo!()
        }
    };
}

extern "C" {
    static _dispatch_queue_attr_concurrent: [u8; 0];
}

static DISPATCH_QUEUE_CONCURRENT: &'static [u8; 0] =
    unsafe { &_dispatch_queue_attr_concurrent };

fn main() {
    *DISPATCH_QUEUE_CONCURRENT;
    new();
}

miri panics here:

warning: unused unary operation that must be used
  --> src/main.rs:28:5
   |
28 |     *DISPATCH_QUEUE_CONCURRENT;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ the unary operation produces a value
   |
   = note: `#[warn(unused_must_use)]` on by default
help: use `let _ = ...` to ignore the resulting value
   |
28 |     let _ = *DISPATCH_QUEUE_CONCURRENT;
   |     +++++++

thread 'rustc' panicked at 'Error should never be raised by Miri: cannot read from extern static (DefId(0:6 ~ mi[4f9b]::{extern#0}::_dispatch_queue_attr_concurrent))', src/tools/miri/src/diagnostics.rs:236:21
stack backtrace:
   0:     0x7fc6d669e21d - std::backtrace_rs::backtrace::libunwind::trace::h58f7ccf05e6e2202
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/../../backtrace/src/backtrace/libunwind.rs:93:5
   1:     0x7fc6d669e21d - std::backtrace_rs::backtrace::trace_unsynchronized::h6818d5037aac2151
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7fc6d669e21d - std::sys_common::backtrace::_print_fmt::h7e9e91520c325876
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/sys_common/backtrace.rs:66:5
   3:     0x7fc6d669e21d - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::hb3419ccbd7447054
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/sys_common/backtrace.rs:45:22
   4:     0x7fc6d66fa00c - core::fmt::write::hde8d85d5cf122740
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/core/src/fmt/mod.rs:1196:17
   5:     0x7fc6d668f911 - std::io::Write::write_fmt::h1a964cb20becd056
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/io/mod.rs:1654:15
   6:     0x7fc6d66a0ef5 - std::sys_common::backtrace::_print::h1e0d80c90ae8064d
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/sys_common/backtrace.rs:48:5
   7:     0x7fc6d66a0ef5 - std::sys_common::backtrace::print::h28b1535981317802
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/sys_common/backtrace.rs:35:9
   8:     0x7fc6d66a0ef5 - std::panicking::default_hook::{{closure}}::hd76d7ce191ece66f
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/panicking.rs:295:22
   9:     0x7fc6d66a0c16 - std::panicking::default_hook::h02e21fa5aac93eac
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/panicking.rs:314:9
  10:     0x7fc6d6efa041 - rustc_driver[84b62567f2ed5d49]::DEFAULT_HOOK::{closure#0}::{closure#0}
  11:     0x7fc6d66a15ca - std::panicking::rust_panic_with_hook::h2111e62403fb1455
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/panicking.rs:702:17
  12:     0x7fc6d66a1407 - std::panicking::begin_panic_handler::{{closure}}::ha3b53a10dc4480d8
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/panicking.rs:588:13
  13:     0x7fc6d669e6d4 - std::sys_common::backtrace::__rust_end_short_backtrace::h220589fe699b245e
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/sys_common/backtrace.rs:138:18
  14:     0x7fc6d66a1139 - rust_begin_unwind
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/panicking.rs:584:5
  15:     0x7fc6d6666343 - core::panicking::panic_fmt::hd5d5fec6a928eecd
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/core/src/panicking.rs:142:14
  16:     0x55d8cd1f7dd4 - miri[6fa434adb66cc6f5]::diagnostics::report_error
  17:     0x55d8cd0fcc65 - miri[6fa434adb66cc6f5]::eval::eval_entry
  18:     0x55d8cd068c7a - <rustc_interface[207a0d5049d4199e]::passes::QueryContext>::enter::<<miri[86decc69f57428a8]::MiriCompilerCalls as rustc_driver[84b62567f2ed5d49]::Callbacks>::after_analysis::{closure#0}, ()>
  19:     0x55d8cd06b75f - <miri[86decc69f57428a8]::MiriCompilerCalls as rustc_driver[84b62567f2ed5d49]::Callbacks>::after_analysis
  20:     0x7fc6d90a06cc - <rustc_interface[207a0d5049d4199e]::interface::Compiler>::enter::<rustc_driver[84b62567f2ed5d49]::run_compiler::{closure#1}::{closure#2}, core[be71da1b78cea8d]::result::Result<core[be71da1b78cea8d]::option::Option<rustc_interface[207a0d5049d4199e]::queries::Linker>, rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>>
  21:     0x7fc6d90c9d3f - rustc_span[45dafd7c97e42da1]::with_source_map::<core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>, rustc_interface[207a0d5049d4199e]::interface::create_compiler_and_run<core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>, rustc_driver[84b62567f2ed5d49]::run_compiler::{closure#1}>::{closure#1}>
  22:     0x7fc6d90a1542 - <scoped_tls[b8e034abe4adce2d]::ScopedKey<rustc_span[45dafd7c97e42da1]::SessionGlobals>>::set::<rustc_interface[207a0d5049d4199e]::interface::run_compiler<core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>, rustc_driver[84b62567f2ed5d49]::run_compiler::{closure#1}>::{closure#0}, core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>>
  23:     0x7fc6d90b6b7f - std[afa78adc105b1c86]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[207a0d5049d4199e]::util::run_in_thread_pool_with_globals<rustc_interface[207a0d5049d4199e]::interface::run_compiler<core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>, rustc_driver[84b62567f2ed5d49]::run_compiler::{closure#1}>::{closure#0}, core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>>::{closure#0}, core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>>
  24:     0x7fc6d90b6cd9 - <<std[afa78adc105b1c86]::thread::Builder>::spawn_unchecked_<rustc_interface[207a0d5049d4199e]::util::run_in_thread_pool_with_globals<rustc_interface[207a0d5049d4199e]::interface::run_compiler<core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>, rustc_driver[84b62567f2ed5d49]::run_compiler::{closure#1}>::{closure#0}, core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>>::{closure#0}, core[be71da1b78cea8d]::result::Result<(), rustc_errors[d790e5a717e9604b]::ErrorGuaranteed>>::{closure#1} as core[be71da1b78cea8d]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  25:     0x7fc6d66ab4f3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h689e1c39ea398210
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/alloc/src/boxed.rs:1951:9
  26:     0x7fc6d66ab4f3 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h6aea3b7ce18650de
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/alloc/src/boxed.rs:1951:9
  27:     0x7fc6d66ab4f3 - std::sys::unix::thread::Thread::new::thread_start::h2e612d703ca53c2a
                               at /rustc/ca122c7ebb3ab50149c9d3d24ddb59c252b32272/library/std/src/sys/unix/thread.rs:108:17
  28:     0x7fc6d639854d - <unknown>
  29:     0x7fc6d641db14 - clone
  30:                0x0 - <unknown>

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.63.0-nightly (ca122c7eb 2022-06-13) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental -C target-cpu=native

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
warning: 1 warning emitted

[oli-obk]

MVP

extern "C" {
    static x: [u8; 0];
}

static X: &'static [u8; 0] = unsafe { &x };

fn main() {
    *X;
}

[RalfJung]

This is very strange, so somehow the error from CTFE is propagated to runtime Miri diagnostic handling?

It should behave like this.

[RalfJung]

Ah, I got it. Will need a rustc change though: rust-lang/rust#98099