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repr(transparent) wrapper with uninhabited ZST has different return ABI than wrapped field. #135802

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#136985
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repr(transparent) wrapper with uninhabited ZST has different return ABI than wrapped field.#135802
#136985
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A-ABIArea: Concerning the application binary interface (ABI)A-miriArea: The miri toolA-reprArea: the `#[repr(stuff)]` attributeC-bugCategory: This is a bug.I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.T-langRelevant to the language team
@zachs18

Description

@zachs18
zachs18
opened on Jan 21, 2025

This code ICEs Miri, the normal compiler compiles this without complaint, but might be miscompiling it1, though a const version using -Zunleash-the-miri-inside-of-you does ICE the compiler.

Code

type Field = u8; // any non-1ZST probably #[repr(transparent)] struct Foo { _zst: std::convert::Infallible, _field: Field, } fn foo() -> Foo { panic!() } fn main() { let f: fn() -> Foo = foo; let f: fn() -> Field = unsafe { std::mem::transmute(f) }; f(); } 
cargo +nightly miri run
modified version using `-Zunleash-the-miri-inside-of-you` that ICEs rustc 
type Field = u8; // any non-1ZST probably #[repr(transparent)] struct Foo { _zst: std::convert::Infallible, _field: Field, } const fn foo() -> Foo { panic!() } fn main() { const { let f: fn() -> Foo = foo; let f: fn() -> Field = unsafe { std::mem::transmute(f) }; f(); } }
RUSTFLAGS="-Zunleash-the-miri-inside-of-you" cargo +nightly run

Backtrace:

thread 'rustc' panicked at compiler/rustc_const_eval/src/interpret/call.rs:253:13: assertion failed: caller_abi.eq_abi(callee_abi) stack backtrace: 0: 0x7e3cb9b652a5 - std::backtrace::Backtrace::create::h8985a2f6ef2eb84f 1: 0x7e3cb80e39f5 - std::backtrace::Backtrace::force_capture::h9a611efb2a942dc9 2: 0x7e3cb725a4e0 - std[4faddc71fb6fa0e5]::panicking::update_hook::<alloc[c55780341d73682]::boxed::Box<rustc_driver_impl[80a9ca323d3e3890]::install_ice_hook::{closure#1}>>::{closure#0} 3: 0x7e3cb80fc333 - std::panicking::rust_panic_with_hook::hf47d9e178e038701 4: 0x7e3cb80fbff6 - std::panicking::begin_panic_handler::{{closure}}::hd9b9f2d3dd54e86c 5: 0x7e3cb80f99e9 - std::sys::backtrace::__rust_end_short_backtrace::h342bb668fc58e319 6: 0x7e3cb80fbced - rust_begin_unwind 7: 0x7e3cb4da8db0 - core::panicking::panic_fmt::hb3cd74fdfc019257 8: 0x7e3cb5897b9c - core::panicking::panic::h92e08174b9fe42d1 9: 0x7e3cb92c11bb - <rustc_const_eval[e3d2a21e14ef9d90]::interpret::eval_context::InterpCx<rustc_const_eval[e3d2a21e14ef9d90]::const_eval::machine::CompileTimeMachine>>::init_stack_frame 10: 0x7e3cb92bde11 - <rustc_const_eval[e3d2a21e14ef9d90]::interpret::eval_context::InterpCx<rustc_const_eval[e3d2a21e14ef9d90]::const_eval::machine::CompileTimeMachine>>::init_fn_call 11: 0x7e3cb6314e8f - rustc_const_eval[e3d2a21e14ef9d90]::const_eval::eval_queries::eval_to_allocation_raw_provider 12: 0x7e3cb9041f5c - rustc_query_impl[283282ac12660651]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[283282ac12660651]::query_impl::eval_to_allocation_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[d099a8b084c78b18]::query::erase::Erased<[u8; 24usize]>> 13: 0x7e3cb9041fb7 - <rustc_query_impl[283282ac12660651]::query_impl::eval_to_allocation_raw::dynamic_query::{closure#2} as core[b8d8efd06dd057cd]::ops::function::FnOnce<(rustc_middle[d099a8b084c78b18]::ty::context::TyCtxt, rustc_middle[d099a8b084c78b18]::ty::PseudoCanonicalInput<rustc_middle[d099a8b084c78b18]::mir::interpret::GlobalId>)>>::call_once 14: 0x7e3cb90406be - rustc_query_system[57efd1c10fae1b2]::query::plumbing::try_execute_query::<rustc_query_impl[283282ac12660651]::DynamicConfig<rustc_query_system[57efd1c10fae1b2]::query::caches::DefaultCache<rustc_middle[d099a8b084c78b18]::ty::PseudoCanonicalInput<rustc_middle[d099a8b084c78b18]::mir::interpret::GlobalId>, rustc_middle[d099a8b084c78b18]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[283282ac12660651]::plumbing::QueryCtxt, true> 15: 0x7e3cb903fffd - rustc_query_impl[283282ac12660651]::query_impl::eval_to_allocation_raw::get_query_incr::__rust_end_short_backtrace 16: 0x7e3cb904475f - rustc_const_eval[e3d2a21e14ef9d90]::const_eval::eval_queries::eval_to_const_value_raw_provider 17: 0x7e3cb9044554 - rustc_query_impl[283282ac12660651]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[283282ac12660651]::query_impl::eval_to_const_value_raw::dynamic_query::{closure#2}::{closure#0}, rustc_middle[d099a8b084c78b18]::query::erase::Erased<[u8; 24usize]>> 18: 0x7e3cb904450d - <rustc_query_impl[283282ac12660651]::query_impl::eval_to_const_value_raw::dynamic_query::{closure#2} as core[b8d8efd06dd057cd]::ops::function::FnOnce<(rustc_middle[d099a8b084c78b18]::ty::context::TyCtxt, rustc_middle[d099a8b084c78b18]::ty::PseudoCanonicalInput<rustc_middle[d099a8b084c78b18]::mir::interpret::GlobalId>)>>::call_once 19: 0x7e3cb903f2e6 - rustc_query_system[57efd1c10fae1b2]::query::plumbing::try_execute_query::<rustc_query_impl[283282ac12660651]::DynamicConfig<rustc_query_system[57efd1c10fae1b2]::query::caches::DefaultCache<rustc_middle[d099a8b084c78b18]::ty::PseudoCanonicalInput<rustc_middle[d099a8b084c78b18]::mir::interpret::GlobalId>, rustc_middle[d099a8b084c78b18]::query::erase::Erased<[u8; 24usize]>>, false, true, false>, rustc_query_impl[283282ac12660651]::plumbing::QueryCtxt, true> 20: 0x7e3cb903ebc7 - rustc_query_impl[283282ac12660651]::query_impl::eval_to_const_value_raw::get_query_incr::__rust_end_short_backtrace 21: 0x7e3cb95e110b - <rustc_middle[d099a8b084c78b18]::ty::context::TyCtxt>::const_eval_resolve 22: 0x7e3cb5825b39 - <rustc_mir_transform[e7af90bdb15a3f20]::known_panics_lint::ConstPropagator as rustc_middle[d099a8b084c78b18]::mir::visit::Visitor>::visit_operand 23: 0x7e3cb5829080 - <rustc_mir_transform[e7af90bdb15a3f20]::known_panics_lint::ConstPropagator as rustc_middle[d099a8b084c78b18]::mir::visit::Visitor>::visit_assign 24: 0x7e3cb582799b - <rustc_mir_transform[e7af90bdb15a3f20]::known_panics_lint::ConstPropagator as rustc_middle[d099a8b084c78b18]::mir::visit::Visitor>::visit_body 25: 0x7e3cb95f79f9 - <rustc_mir_transform[e7af90bdb15a3f20]::known_panics_lint::KnownPanicsLint as rustc_mir_transform[e7af90bdb15a3f20]::pass_manager::MirLint>::run_lint 26: 0x7e3cb880b6f3 - rustc_mir_transform[e7af90bdb15a3f20]::run_analysis_to_runtime_passes 27: 0x7e3cb8c28174 - rustc_mir_transform[e7af90bdb15a3f20]::mir_drops_elaborated_and_const_checked 28: 0x7e3cb8c27da5 - rustc_query_impl[283282ac12660651]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[283282ac12660651]::query_impl::mir_drops_elaborated_and_const_checked::dynamic_query::{closure#2}::{closure#0}, rustc_middle[d099a8b084c78b18]::query::erase::Erased<[u8; 8usize]>> 29: 0x7e3cb8c2bcd9 - rustc_query_system[57efd1c10fae1b2]::query::plumbing::try_execute_query::<rustc_query_impl[283282ac12660651]::DynamicConfig<rustc_data_structures[ff6b6eb237e26604]::vec_cache::VecCache<rustc_span[6fdbe82b95f770dc]::def_id::LocalDefId, rustc_middle[d099a8b084c78b18]::query::erase::Erased<[u8; 8usize]>, rustc_query_system[57efd1c10fae1b2]::dep_graph::graph::DepNodeIndex>, false, false, false>, rustc_query_impl[283282ac12660651]::plumbing::QueryCtxt, true> 30: 0x7e3cb8c24dae - rustc_query_impl[283282ac12660651]::query_impl::mir_drops_elaborated_and_const_checked::get_query_incr::__rust_end_short_backtrace 31: 0x7e3cb8c248f3 - <rustc_middle[d099a8b084c78b18]::hir::map::Map>::par_body_owners::<rustc_interface[5facaafd3cd44e6f]::passes::run_required_analyses::{closure#3}::{closure#0}>::{closure#0} 32: 0x7e3cb8c21df4 - rustc_interface[5facaafd3cd44e6f]::passes::run_required_analyses 33: 0x7e3cb976ca9e - rustc_interface[5facaafd3cd44e6f]::passes::analysis 34: 0x7e3cb976ca6f - rustc_query_impl[283282ac12660651]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[283282ac12660651]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[d099a8b084c78b18]::query::erase::Erased<[u8; 0usize]>> 35: 0x7e3cb97683cf - rustc_query_system[57efd1c10fae1b2]::query::plumbing::try_execute_query::<rustc_query_impl[283282ac12660651]::DynamicConfig<rustc_query_system[57efd1c10fae1b2]::query::caches::SingleCache<rustc_middle[d099a8b084c78b18]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[283282ac12660651]::plumbing::QueryCtxt, true> 36: 0x7e3cb9767d47 - rustc_query_impl[283282ac12660651]::query_impl::analysis::get_query_incr::__rust_end_short_backtrace 37: 0x7e3cb9820669 - rustc_interface[5facaafd3cd44e6f]::passes::create_and_enter_global_ctxt::<core[b8d8efd06dd057cd]::option::Option<rustc_interface[5facaafd3cd44e6f]::queries::Linker>, rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0} 38: 0x7e3cb9813896 - rustc_interface[5facaafd3cd44e6f]::interface::run_compiler::<(), rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}>::{closure#1} 39: 0x7e3cb9670807 - std[4faddc71fb6fa0e5]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_with_globals<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_pool_with_globals<rustc_interface[5facaafd3cd44e6f]::interface::run_compiler<(), rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()> 40: 0x7e3cb96704d9 - <<std[4faddc71fb6fa0e5]::thread::Builder>::spawn_unchecked_<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_with_globals<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_pool_with_globals<rustc_interface[5facaafd3cd44e6f]::interface::run_compiler<(), rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[b8d8efd06dd057cd]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 41: 0x7e3cb966fc6b - std::sys::pal::unix::thread::Thread::new::thread_start::h07063fc11dcd9adf 42: 0x7e3cb389ca94 - start_thread at ./nptl/pthread_create.c:447:8 43: 0x7e3cb3929c3c - clone3 at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:78:0 44: 0x0 - <unknown> rustc version: 1.86.0-nightly (9a1d156f3 2025-01-19) platform: x86_64-unknown-linux-gnu query stack during panic: #0 [eval_to_allocation_raw] const-evaluating + checking `main::{constant#0}` #1 [eval_to_const_value_raw] simplifying constant for the type system `main::{constant#0}` #2 [mir_drops_elaborated_and_const_checked] elaborating drops for `main` #3 [analysis] running analysis passes on this crate end of query stack

Meta

rustc --version --verbose:

rustc 1.86.0-nightly (9a1d156f3 2025-01-19) binary: rustc commit-hash: 9a1d156f38c51441ee51e5a068f1d0caf4bb0f27 commit-date: 2025-01-19 host: x86_64-unknown-linux-gnu release: 1.86.0-nightly LLVM version: 19.1.7

Error output

Error output 
thread 'rustc' panicked at /rustc/9a1d156f38c51441ee51e5a068f1d0caf4bb0f27/compiler/rustc_const_eval/src/interpret/call.rs:253:13: assertion failed: caller_abi.eq_abi(callee_abi) stack backtrace: 0: 0x78aed8af951a - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h70d5098cfd90b01a 1: 0x78aed9212da6 - core::fmt::write::h854c563aac02d08a 2: 0x78aeda171291 - std::io::Write::write_fmt::hac4174e389a0e8e6 3: 0x78aed8af9372 - std::sys::backtrace::BacktraceLock::print::hc6aba0d6b3a91e1f 4: 0x78aed8afb7f2 - std::panicking::default_hook::{{closure}}::h9628a97795328020 5: 0x78aed8afb67a - std::panicking::default_hook::h0dc7e102448ae736 6: 0x78aed7c59eeb - std[4faddc71fb6fa0e5]::panicking::update_hook::<alloc[c55780341d73682]::boxed::Box<rustc_driver_impl[80a9ca323d3e3890]::install_ice_hook::{closure#1}>>::{closure#0} 7: 0x78aed8afc333 - std::panicking::rust_panic_with_hook::hf47d9e178e038701 8: 0x78aed8afbff6 - std::panicking::begin_panic_handler::{{closure}}::hd9b9f2d3dd54e86c 9: 0x78aed8af99e9 - std::sys::backtrace::__rust_end_short_backtrace::h342bb668fc58e319 10: 0x78aed8afbced - rust_begin_unwind 11: 0x78aed57a8db0 - core::panicking::panic_fmt::hb3cd74fdfc019257 12: 0x78aed6297b9c - core::panicking::panic::h92e08174b9fe42d1 13: 0x592a4689f7ae - <rustc_const_eval[e3d2a21e14ef9d90]::interpret::eval_context::InterpCx<miri[d18ac4a41561b88d]::machine::MiriMachine>>::check_argument_compat 14: 0x592a4689ec5a - <rustc_const_eval[e3d2a21e14ef9d90]::interpret::eval_context::InterpCx<miri[d18ac4a41561b88d]::machine::MiriMachine>>::init_stack_frame 15: 0x592a4689c98b - <rustc_const_eval[e3d2a21e14ef9d90]::interpret::eval_context::InterpCx<miri[d18ac4a41561b88d]::machine::MiriMachine>>::init_fn_call 16: 0x592a46915db4 - miri[d18ac4a41561b88d]::eval::eval_entry::{closure#0} 17: 0x592a46911e9b - miri[d18ac4a41561b88d]::eval::eval_entry 18: 0x592a467c4226 - <miri[e9b5d2e94aebaf6c]::MiriCompilerCalls as rustc_driver_impl[80a9ca323d3e3890]::Callbacks>::after_analysis 19: 0x78aeda220676 - rustc_interface[5facaafd3cd44e6f]::passes::create_and_enter_global_ctxt::<core[b8d8efd06dd057cd]::option::Option<rustc_interface[5facaafd3cd44e6f]::queries::Linker>, rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0} 20: 0x78aeda213896 - rustc_interface[5facaafd3cd44e6f]::interface::run_compiler::<(), rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}>::{closure#1} 21: 0x78aeda070807 - std[4faddc71fb6fa0e5]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_with_globals<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_pool_with_globals<rustc_interface[5facaafd3cd44e6f]::interface::run_compiler<(), rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()> 22: 0x78aeda0704d9 - <<std[4faddc71fb6fa0e5]::thread::Builder>::spawn_unchecked_<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_with_globals<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_pool_with_globals<rustc_interface[5facaafd3cd44e6f]::interface::run_compiler<(), rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[b8d8efd06dd057cd]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 23: 0x78aeda06fc6b - std::sys::pal::unix::thread::Thread::new::thread_start::h07063fc11dcd9adf 24: 0x78aed429ca94 - start_thread at ./nptl/pthread_create.c:447:8 25: 0x78aed4329c3c - clone3 at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:78:0 26: 0x0 - <unknown> error: the compiler unexpectedly panicked. this is a bug. note: we would appreciate a bug report: https://github.com/rust-lang/miri/issues/new note: please make sure that you have updated to the latest nightly note: please attach the file at `/tmp/sadkjlhfsakdf/rustc-ice-2025-01-21T00_17_45-3693735.txt` to your bug report note: compiler flags: --crate-type bin -C embed-bitcode=no -C debuginfo=2 -C incremental=[REDACTED] note: some of the compiler flags provided by cargo are hidden query stack during panic: end of query stack Miri caused an ICE during evaluation. Here's the interpreter backtrace at the time of the panic: note: the place in the program where the ICE was triggered --> src/main.rs:7:5 | 7 | panic!() | ^^^^^^^^ | = note: BACKTRACE: = note: inside `foo` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panic.rs:90:9: 90:30 note: inside `main` --> src/main.rs:12:5 | 12 | f(); | ^^^ = note: inside `<fn() as std::ops::FnOnce<()>>::call_once - shim(fn())` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5: 250:71 = note: inside `std::sys::backtrace::__rust_begin_short_backtrace::<fn(), ()>` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:152:18: 152:21 = note: inside closure at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:194:18: 194:75 = note: inside `std::ops::function::impls::<impl std::ops::FnOnce<()> for &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>::call_once` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:284:13: 284:31 = note: inside `std::panicking::r#try::do_call::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:587:40: 587:43 = note: inside `std::panicking::r#try::<i32, &dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe>` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:550:19: 550:88 = note: inside `std::panic::catch_unwind::<&dyn std::ops::Fn() -> i32 + std::marker::Sync + std::panic::RefUnwindSafe, i32>` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:358:14: 358:33 = note: inside closure at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:163:24: 163:49 = note: inside `std::panicking::r#try::do_call::<{closure@std::rt::lang_start_internal::{closure#0}}, isize>` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:587:40: 587:43 = note: inside `std::panicking::r#try::<isize, {closure@std::rt::lang_start_internal::{closure#0}}>` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:550:19: 550:88 = note: inside `std::panic::catch_unwind::<{closure@std::rt::lang_start_internal::{closure#0}}, isize>` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:358:14: 358:33 = note: inside `std::rt::lang_start_internal` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:159:5: 181:7 = note: inside `std::rt::lang_start::<()>` at /home/zachary/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/rt.rs:193:5: 198:6 = note: this note originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
ICE file 

thread 'rustc' panicked at /rustc/9a1d156f38c51441ee51e5a068f1d0caf4bb0f27/compiler/rustc_const_eval/src/interpret/call.rs:253:13: assertion failed: caller_abi.eq_abi(callee_abi) stack backtrace: 0: 0x78aeda5652a5 - std::backtrace::Backtrace::create::h8985a2f6ef2eb84f 1: 0x78aed8ae39f5 - std::backtrace::Backtrace::force_capture::h9a611efb2a942dc9 2: 0x78aed7c5a4e0 - std[4faddc71fb6fa0e5]::panicking::update_hook::<alloc[c55780341d73682]::boxed::Box<rustc_driver_impl[80a9ca323d3e3890]::install_ice_hook::{closure#1}>>::{closure#0} 3: 0x78aed8afc333 - std::panicking::rust_panic_with_hook::hf47d9e178e038701 4: 0x78aed8afbff6 - std::panicking::begin_panic_handler::{{closure}}::hd9b9f2d3dd54e86c 5: 0x78aed8af99e9 - std::sys::backtrace::__rust_end_short_backtrace::h342bb668fc58e319 6: 0x78aed8afbced - rust_begin_unwind 7: 0x78aed57a8db0 - core::panicking::panic_fmt::hb3cd74fdfc019257 8: 0x78aed6297b9c - core::panicking::panic::h92e08174b9fe42d1 9: 0x592a4689f7ae - <rustc_const_eval[e3d2a21e14ef9d90]::interpret::eval_context::InterpCx<miri[d18ac4a41561b88d]::machine::MiriMachine>>::check_argument_compat 10: 0x592a4689ec5a - <rustc_const_eval[e3d2a21e14ef9d90]::interpret::eval_context::InterpCx<miri[d18ac4a41561b88d]::machine::MiriMachine>>::init_stack_frame 11: 0x592a4689c98b - <rustc_const_eval[e3d2a21e14ef9d90]::interpret::eval_context::InterpCx<miri[d18ac4a41561b88d]::machine::MiriMachine>>::init_fn_call 12: 0x592a46915db4 - miri[d18ac4a41561b88d]::eval::eval_entry::{closure#0} 13: 0x592a46911e9b - miri[d18ac4a41561b88d]::eval::eval_entry 14: 0x592a467c4226 - <miri[e9b5d2e94aebaf6c]::MiriCompilerCalls as rustc_driver_impl[80a9ca323d3e3890]::Callbacks>::after_analysis 15: 0x78aeda220676 - rustc_interface[5facaafd3cd44e6f]::passes::create_and_enter_global_ctxt::<core[b8d8efd06dd057cd]::option::Option<rustc_interface[5facaafd3cd44e6f]::queries::Linker>, rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}::{closure#2}>::{closure#2}::{closure#0} 16: 0x78aeda213896 - rustc_interface[5facaafd3cd44e6f]::interface::run_compiler::<(), rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}>::{closure#1} 17: 0x78aeda070807 - std[4faddc71fb6fa0e5]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_with_globals<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_pool_with_globals<rustc_interface[5facaafd3cd44e6f]::interface::run_compiler<(), rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()> 18: 0x78aeda0704d9 - <<std[4faddc71fb6fa0e5]::thread::Builder>::spawn_unchecked_<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_with_globals<rustc_interface[5facaafd3cd44e6f]::util::run_in_thread_pool_with_globals<rustc_interface[5facaafd3cd44e6f]::interface::run_compiler<(), rustc_driver_impl[80a9ca323d3e3890]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[b8d8efd06dd057cd]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} 19: 0x78aeda06fc6b - std::sys::pal::unix::thread::Thread::new::thread_start::h07063fc11dcd9adf 20: 0x78aed429ca94 - start_thread at ./nptl/pthread_create.c:447:8 21: 0x78aed4329c3c - clone3 at ./misc/../sysdeps/unix/sysv/linux/x86_64/clone3.S:78:0 22: 0x0 - <unknown> rustc version: 1.86.0-nightly (9a1d156f3 2025-01-19) platform: x86_64-unknown-linux-gnu query stack during panic: end of query stack

@rustbot label +A-miri +A-ABI

This shouldn't ICE regardless, but whether there is a miscompilation depends on if the original code is sound:

CC rust-lang/unsafe-code-guidelines#485

Possible Miscompilation

Does #[repr(transparent)]s ABI-compatility guarantee apply in the prescence of uninhabited 1-ZST fields?

A #[repr(transparent)] wrapper that contains an uninhabited 1-ZST field gets Uninhabited ABI IIUC, which may contradict the guarantees about #[repr(transparent)] wrappers being ABI-compatible.

Consider Foo from above:

type Field = u8; // any non-1ZST probably #[repr(transparent)] struct Foo { _zst: std::convert::Infallible, _field: Field, }

If #[repr(transparent)]'s ABI-compatility guarantees do apply, then the above code should be sound:

  1. If a function returns Foo, it must diverge (e.g. by panicking).
  2. If Foo is ABI-compatible with Field, then it should be sound to transmute a function pointer to a diverging fn() -> Foo into a fn() -> Field that also diverges.
rustc_layout(debug)

Using #![feature(rustc_attrs)] and #[rustc_layout(debug)] we see that the ABI it has is

error: layout_of(Foo) = Layout { // snip abi: Uninhabited, // snip }

whereas Field has

error: layout_of(u8) = Layout { // snip abi: Scalar( Initialized { value: Int( I8, false, ), valid_range: 0..=255, }, ), // snip }

Possible Miscompilation

Assuming this is supposed to be sound, then there is an observable miscompilation here too. Where Field is returned by invisible reference, fn(u32) -> Foo does not return Foo by invisible reference, so transmuting fn(u32) -> Foo into fn(u32) -> Field will pass a different number of arguments.

Specifically on x86_64-unknown-linux-gnu: If Field is returned on the stack, then fn(..) -> Foo does not reserve stack space or pass a hidden reference parameter, but fn(..) -> Field does. This can be made into an observable miscompilation if the function takes parameters: (playground link, IIUC: the invisible reference is being passed, but the callee isn't expecting it, so it thinks it's the first "real" parameter instead (caller: ret by-ref in rdi, x in rsi; callee: ret uninhabited, x in rdi)).

Footnotes

  1. see "Possible Miscompilation" section ↩

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    A-ABIArea: Concerning the application binary interface (ABI)A-miriArea: The miri toolA-reprArea: the `#[repr(stuff)]` attributeC-bugCategory: This is a bug.I-ICEIssue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.T-langRelevant to the language team

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