ICE: extern type field offset

[matthiaskrgr]

from rustc: ./tests/ui/extern/extern-types-field-offset.rs

auto-reduced (treereduce-rust):

#![feature(extern_types)]

extern "C" {
    type Opaque;
}

struct Newtype(Opaque);

struct S {
    i: i32,
    j: i32,
    a: Newtype,
}

fn main() {
    let buf = [0i32; 4];

    let x: &S = unsafe { &*(&buf as *const _ as *const S) };

    let _field = &x.a;
}

original:

#![feature(extern_types)]

extern "C" {
    type Opaque;
}

struct Newtype(Opaque);

struct S {
    i: i32,
    j: i32,
    a: Newtype,
}

fn main() {
    let buf = [0i32; 4];

    let x: &Newtype = unsafe { &*(&buf as *const _ as *const Newtype) };
    // Projecting to the newtype works, because it is always at offset 0.
    let _field = &x.0;

    let x: &S = unsafe { &*(&buf as *const _ as *const S) };
    // Accessing sized fields is perfectly fine, even at non-zero offsets.
    let _field = &x.i;
    let _field = &x.j;
    // This needs to compute the field offset, but we don't know the type's alignment,
    // so this panics.
    let _field = &x.a; //~ERROR: does not have a known offset
}

Version information

rustc 1.76.0-nightly (77d169975 2023-12-13)
binary: rustc
commit-hash: 77d16997566dfb2384bcbc504e2579c7ae973666
commit-date: 2023-12-13
host: x86_64-unknown-linux-gnu
release: 1.76.0-nightly
LLVM version: 17.0.5

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zcodegen-backend=cranelift

Program output

warning: fields `i` and `j` are never read
  --> /tmp/icemaker_global_tempdir.PxgKg5hoooyA/rustc_testrunner_tmpdir_reporting.4ri42q0caYiT/mvce.rs:10:5
   |
9  | struct S {
   |        - fields in this struct
10 |     i: i32,
   |     ^
11 |     j: i32,
   |     ^
   |
   = note: `#[warn(dead_code)]` on by default

thread 'rustc' panicked at src/value_and_place.rs:739:61:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x7f3e2d98b45c - std::backtrace_rs::backtrace::libunwind::trace::h8eaf990e4a504b86
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/../../backtrace/src/backtrace/libunwind.rs:104:5
   1:     0x7f3e2d98b45c - std::backtrace_rs::backtrace::trace_unsynchronized::hbc236c387b7f1e2f
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f3e2d98b45c - std::sys_common::backtrace::_print_fmt::h854fa9a625b79fe7
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/sys_common/backtrace.rs:68:5
   3:     0x7f3e2d98b45c - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h367ac729761cc34a
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/sys_common/backtrace.rs:44:22
   4:     0x7f3e2d9de510 - core::fmt::rt::Argument::fmt::hc045d8fab7f11469
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/core/src/fmt/rt.rs:142:9
   5:     0x7f3e2d9de510 - core::fmt::write::h5adaab5759d35e9c
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/core/src/fmt/mod.rs:1120:17
   6:     0x7f3e2d97f34f - std::io::Write::write_fmt::hdf01958bd3129cc1
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/io/mod.rs:1810:15
   7:     0x7f3e2d98b244 - std::sys_common::backtrace::_print::hef493aa049da10fb
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/sys_common/backtrace.rs:47:5
   8:     0x7f3e2d98b244 - std::sys_common::backtrace::print::hceb63a7aa0b95526
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/sys_common/backtrace.rs:34:9
   9:     0x7f3e2d98df47 - std::panicking::default_hook::{{closure}}::h379064c2e91c2583
  10:     0x7f3e2d98dcaf - std::panicking::default_hook::h74d2197136da14a8
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/panicking.rs:292:9
  11:     0x7f3e30735c30 - std[5e29b6ead2e77b88]::panicking::update_hook::<alloc[57adf5c47884753f]::boxed::Box<rustc_driver_impl[143a96d1e9339ddc]::install_ice_hook::{closure#0}>>::{closure#0}
  12:     0x7f3e2d98e688 - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::he81fb398d05e4b0f
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/alloc/src/boxed.rs:2029:9
  13:     0x7f3e2d98e688 - std::panicking::rust_panic_with_hook::h2b6da4caf2f04b60
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/panicking.rs:783:13
  14:     0x7f3e2d98e3a9 - std::panicking::begin_panic_handler::{{closure}}::h830b6617ba119779
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/panicking.rs:649:13
  15:     0x7f3e2d98b926 - std::sys_common::backtrace::__rust_end_short_backtrace::h55a117102e902ec7
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/sys_common/backtrace.rs:171:18
  16:     0x7f3e2d98e142 - rust_begin_unwind
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/panicking.rs:645:5
  17:     0x7f3e2d9dabd5 - core::panicking::panic_fmt::hf8c847bebf55f403
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/core/src/panicking.rs:72:14
  18:     0x7f3e2d9dac93 - core::panicking::panic::hed6e296997f82f3a
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/core/src/panicking.rs:144:5
  19:     0x7f3e24059957 - <rustc_codegen_cranelift[871d4eb929383ae1]::value_and_place::CPlace>::place_field
  20:     0x7f3e240113cc - rustc_codegen_cranelift[871d4eb929383ae1]::base::codegen_place
  21:     0x7f3e24008258 - rustc_codegen_cranelift[871d4eb929383ae1]::base::codegen_fn_body
  22:     0x7f3e24023417 - rustc_codegen_cranelift[871d4eb929383ae1]::driver::aot::module_codegen::{closure#0}
  23:     0x7f3e24020685 - rustc_codegen_cranelift[871d4eb929383ae1]::driver::aot::module_codegen
  24:     0x7f3e2402cd2c - rustc_codegen_cranelift[871d4eb929383ae1]::driver::aot::run_aot
  25:     0x7f3e2405bd6a - <rustc_codegen_cranelift[871d4eb929383ae1]::CraneliftCodegenBackend as rustc_codegen_ssa[8440f8116a4e2fa3]::traits::backend::CodegenBackend>::codegen_crate
  26:     0x7f3e32783dc5 - rustc_interface[1010bb494e88232]::passes::start_codegen
  27:     0x7f3e3278352e - <rustc_interface[1010bb494e88232]::queries::Queries>::codegen_and_build_linker
  28:     0x7f3e32a3afad - rustc_interface[1010bb494e88232]::interface::run_compiler::<core[52cdeeaf75e7a502]::result::Result<(), rustc_span[80493f288ab27be]::ErrorGuaranteed>, rustc_driver_impl[143a96d1e9339ddc]::run_compiler::{closure#0}>::{closure#0}
  29:     0x7f3e329af54a - std[5e29b6ead2e77b88]::sys_common::backtrace::__rust_begin_short_backtrace::<rustc_interface[1010bb494e88232]::util::run_in_thread_with_globals<rustc_interface[1010bb494e88232]::util::run_in_thread_pool_with_globals<rustc_interface[1010bb494e88232]::interface::run_compiler<core[52cdeeaf75e7a502]::result::Result<(), rustc_span[80493f288ab27be]::ErrorGuaranteed>, rustc_driver_impl[143a96d1e9339ddc]::run_compiler::{closure#0}>::{closure#0}, core[52cdeeaf75e7a502]::result::Result<(), rustc_span[80493f288ab27be]::ErrorGuaranteed>>::{closure#0}, core[52cdeeaf75e7a502]::result::Result<(), rustc_span[80493f288ab27be]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[52cdeeaf75e7a502]::result::Result<(), rustc_span[80493f288ab27be]::ErrorGuaranteed>>
  30:     0x7f3e329af373 - <<std[5e29b6ead2e77b88]::thread::Builder>::spawn_unchecked_<rustc_interface[1010bb494e88232]::util::run_in_thread_with_globals<rustc_interface[1010bb494e88232]::util::run_in_thread_pool_with_globals<rustc_interface[1010bb494e88232]::interface::run_compiler<core[52cdeeaf75e7a502]::result::Result<(), rustc_span[80493f288ab27be]::ErrorGuaranteed>, rustc_driver_impl[143a96d1e9339ddc]::run_compiler::{closure#0}>::{closure#0}, core[52cdeeaf75e7a502]::result::Result<(), rustc_span[80493f288ab27be]::ErrorGuaranteed>>::{closure#0}, core[52cdeeaf75e7a502]::result::Result<(), rustc_span[80493f288ab27be]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[52cdeeaf75e7a502]::result::Result<(), rustc_span[80493f288ab27be]::ErrorGuaranteed>>::{closure#1} as core[52cdeeaf75e7a502]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  31:     0x7f3e2d998515 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::ha17502cbcaf4d2cc
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/alloc/src/boxed.rs:2015:9
  32:     0x7f3e2d998515 - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h928bfdaf626c1d3d
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/alloc/src/boxed.rs:2015:9
  33:     0x7f3e2d998515 - std::sys::unix::thread::Thread::new::thread_start::he4ab37baefb01514
                               at /rustc/77d16997566dfb2384bcbc504e2579c7ae973666/library/std/src/sys/unix/thread.rs:108:17
  34:     0x7f3e2d7799eb - <unknown>
  35:     0x7f3e2d7fd7cc - <unknown>
  36:                0x0 - <unknown>

error: 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 1.76.0-nightly (77d169975 2023-12-13) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z codegen-backend=cranelift -Z dump-mir-dir=dir

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

[bjorn3]

Fixed by fdcf56c