ICE: Cannot Eq compare incompatible types *mut T/#0 and *const T/#0

[chenzhuoyu]

Compiling the following code with rustc -C opt-level=3 -o main main.rs results in ICE.

Strangely, this code compiles fine without -C opt-level=3. Replace std::ptr::eq with plain == comparison also works.

Code

main.rs:

#![feature(strict_provenance)]

struct Foo<T>(std::marker::PhantomData<T>);

impl<T> Foo<T> {
    const SENTINEL: *mut T = std::ptr::dangling_mut();

    fn cmp_ptr(a: *mut T) -> bool {
        std::ptr::eq(a, Self::SENTINEL)
    }
}

pub fn main() {
    Foo::<u8>::cmp_ptr(std::ptr::dangling_mut());
}

Meta

rustc --version --verbose:

rustc 1.81.0-nightly (9c3bc805d 2024-06-27)
binary: rustc
commit-hash: 9c3bc805dd9cb84019c124b9a50fdff1e62a7ec9
commit-date: 2024-06-27
host: aarch64-apple-darwin
release: 1.81.0-nightly
LLVM version: 18.1.7

Error output

thread 'rustc' panicked at compiler/rustc_mir_transform/src/validate.rs:94:25:
broken MIR in Item(DefId(0:10 ~ main[a0a6]::{impl#0}::cmp_ptr)) (after phase change to runtime-optimized) at bb0[2]:
Cannot Eq compare incompatible types *mut T/#0 and *const T/#0

Backtrace

thread 'rustc' panicked at compiler/rustc_mir_transform/src/validate.rs:94:25:
broken MIR in Item(DefId(0:10 ~ main[0f07]::{impl#0}::cmp_ptr)) (after phase change to runtime-optimized) at bb0[2]:
Cannot Eq compare incompatible types *mut T/#0 and *const T/#0
stack backtrace:
   0:        0x10166abb0 - <std::sys::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::he3d597287e17a7dd
   1:        0x1016ae128 - core::fmt::write::h03b4629f44ceab5b
   2:        0x101660d0c - std::io::Write::write_fmt::h87342a3edd7134e6
   3:        0x10166aa08 - std::sys::backtrace::print::ha920eaaf60abc78c
   4:        0x10166d018 - std::panicking::default_hook::{{closure}}::h7ad69dc6a5c53104
   5:        0x10166cce4 - std::panicking::default_hook::h9d08a9b346efd6d1
   6:        0x10b484d30 - std[76b399b4b9fa005f]::panicking::update_hook::<alloc[53949c4a0a9a41eb]::boxed::Box<rustc_driver_impl[e337739a2a22afd0]::install_ice_hook::{closure#0}>>::{closure#0}
   7:        0x10166db64 - std::panicking::rust_panic_with_hook::h84287953c8418b94
   8:        0x10166d474 - std::panicking::begin_panic_handler::{{closure}}::h398278ce2f98270b
   9:        0x10166b03c - std::sys::backtrace::__rust_end_short_backtrace::h999c20c26585ce7f
  10:        0x10166d180 - _rust_begin_unwind
  11:        0x1016c8940 - core::panicking::panic_fmt::h18805dc216586a3b
  12:        0x10c485220 - <rustc_mir_transform[a22c9e098425d728]::validate::CfgChecker>::fail::<alloc[53949c4a0a9a41eb]::string::String>
  13:        0x10c484a04 - <rustc_mir_transform[a22c9e098425d728]::validate::Validator as rustc_middle[a37ff32571d5c1a9]::mir::MirPass>::run_pass
  14:        0x10c47d0cc - rustc_mir_transform[a22c9e098425d728]::pass_manager::run_passes_inner
  15:        0x10c3431f8 - rustc_mir_transform[a22c9e098425d728]::optimized_mir
  16:        0x10c953634 - rustc_query_impl[a9de1c92a9de04a0]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a9de1c92a9de04a0]::query_impl::optimized_mir::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 8usize]>>
  17:        0x10cb02cf0 - <rustc_query_impl[a9de1c92a9de04a0]::query_impl::optimized_mir::dynamic_query::{closure#2} as core[d0cf843891889b67]::ops::function::FnOnce<(rustc_middle[a37ff32571d5c1a9]::ty::context::TyCtxt, rustc_span[19473d8b3fea81af]::def_id::DefId)>>::call_once
  18:        0x10c86bfe0 - rustc_query_system[e2da81a1c072113]::query::plumbing::try_execute_query::<rustc_query_impl[a9de1c92a9de04a0]::DynamicConfig<rustc_query_system[e2da81a1c072113]::query::caches::DefIdCache<rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a9de1c92a9de04a0]::plumbing::QueryCtxt, false>
  19:        0x10cb10ea0 - rustc_query_impl[a9de1c92a9de04a0]::query_impl::optimized_mir::get_query_non_incr::__rust_end_short_backtrace
  20:        0x10c4746b8 - rustc_middle[a37ff32571d5c1a9]::query::plumbing::query_get_at::<rustc_query_system[e2da81a1c072113]::query::caches::DefIdCache<rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 8usize]>>>
  21:        0x10c47eda4 - rustc_mir_transform[a22c9e098425d728]::cross_crate_inline::cross_crate_inlinable
  22:        0x10c957818 - rustc_query_impl[a9de1c92a9de04a0]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a9de1c92a9de04a0]::query_impl::cross_crate_inlinable::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 1usize]>>
  23:        0x10c9b6acc - <rustc_query_impl[a9de1c92a9de04a0]::query_impl::cross_crate_inlinable::dynamic_query::{closure#2} as core[d0cf843891889b67]::ops::function::FnOnce<(rustc_middle[a37ff32571d5c1a9]::ty::context::TyCtxt, rustc_span[19473d8b3fea81af]::def_id::DefId)>>::call_once
  24:        0x10c860ae8 - rustc_query_system[e2da81a1c072113]::query::plumbing::try_execute_query::<rustc_query_impl[a9de1c92a9de04a0]::DynamicConfig<rustc_query_system[e2da81a1c072113]::query::caches::DefIdCache<rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[a9de1c92a9de04a0]::plumbing::QueryCtxt, false>
  25:        0x10cb39148 - rustc_query_impl[a9de1c92a9de04a0]::query_impl::cross_crate_inlinable::get_query_non_incr::__rust_end_short_backtrace
  26:        0x10c32c7f0 - rustc_middle[a37ff32571d5c1a9]::query::plumbing::query_get_at::<rustc_query_system[e2da81a1c072113]::query::caches::DefIdCache<rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 1usize]>>>
  27:        0x10c336090 - <rustc_mir_transform[a22c9e098425d728]::inline::Inliner>::try_inlining
  28:        0x10c335378 - <rustc_mir_transform[a22c9e098425d728]::inline::Inliner>::process_blocks
  29:        0x10c334da4 - <rustc_mir_transform[a22c9e098425d728]::inline::Inline as rustc_middle[a37ff32571d5c1a9]::mir::MirPass>::run_pass
  30:        0x10c47cbb4 - rustc_mir_transform[a22c9e098425d728]::pass_manager::run_passes_inner
  31:        0x10c3431f8 - rustc_mir_transform[a22c9e098425d728]::optimized_mir
  32:        0x10c953634 - rustc_query_impl[a9de1c92a9de04a0]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a9de1c92a9de04a0]::query_impl::optimized_mir::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 8usize]>>
  33:        0x10cb02cf0 - <rustc_query_impl[a9de1c92a9de04a0]::query_impl::optimized_mir::dynamic_query::{closure#2} as core[d0cf843891889b67]::ops::function::FnOnce<(rustc_middle[a37ff32571d5c1a9]::ty::context::TyCtxt, rustc_span[19473d8b3fea81af]::def_id::DefId)>>::call_once
  34:        0x10c86bfe0 - rustc_query_system[e2da81a1c072113]::query::plumbing::try_execute_query::<rustc_query_impl[a9de1c92a9de04a0]::DynamicConfig<rustc_query_system[e2da81a1c072113]::query::caches::DefIdCache<rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[a9de1c92a9de04a0]::plumbing::QueryCtxt, false>
  35:        0x10cb10ea0 - rustc_query_impl[a9de1c92a9de04a0]::query_impl::optimized_mir::get_query_non_incr::__rust_end_short_backtrace
  36:        0x10c052394 - rustc_middle[a37ff32571d5c1a9]::query::plumbing::query_get_at::<rustc_query_system[e2da81a1c072113]::query::caches::DefIdCache<rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 8usize]>>>
  37:        0x10c0599b0 - <rustc_middle[a37ff32571d5c1a9]::ty::context::TyCtxt>::instance_mir
  38:        0x10c507700 - rustc_monomorphize[148aaa952e24e330]::collector::collect_items_of_instance
  39:        0x10c5067f0 - rustc_monomorphize[148aaa952e24e330]::collector::collect_items_rec
  40:        0x10c5456fc - std[76b399b4b9fa005f]::panicking::try::<(), core[d0cf843891889b67]::panic::unwind_safe::AssertUnwindSafe<rustc_data_structures[b2b8ae2df7595792]::sync::parallel::enabled::par_for_each_in<rustc_middle[a37ff32571d5c1a9]::mir::mono::MonoItem, alloc[53949c4a0a9a41eb]::vec::Vec<rustc_middle[a37ff32571d5c1a9]::mir::mono::MonoItem>, rustc_monomorphize[148aaa952e24e330]::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}::{closure#0}>>
  41:        0x10c53432c - <rustc_data_structures[b2b8ae2df7595792]::sync::parallel::ParallelGuard>::run::<(), rustc_data_structures[b2b8ae2df7595792]::sync::parallel::enabled::par_for_each_in<rustc_middle[a37ff32571d5c1a9]::mir::mono::MonoItem, alloc[53949c4a0a9a41eb]::vec::Vec<rustc_middle[a37ff32571d5c1a9]::mir::mono::MonoItem>, rustc_monomorphize[148aaa952e24e330]::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#1}::{closure#0}>
  42:        0x10c5452a0 - <rustc_session[4e5213968b08c628]::session::Session>::time::<(), rustc_monomorphize[148aaa952e24e330]::collector::collect_crate_mono_items::{closure#1}>
  43:        0x10c508f74 - rustc_monomorphize[148aaa952e24e330]::collector::collect_crate_mono_items
  44:        0x10c512d34 - rustc_monomorphize[148aaa952e24e330]::partitioning::collect_and_partition_mono_items
  45:        0x10c95a1cc - rustc_query_impl[a9de1c92a9de04a0]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[a9de1c92a9de04a0]::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 24usize]>>
  46:        0x10ca6c160 - <rustc_query_impl[a9de1c92a9de04a0]::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2} as core[d0cf843891889b67]::ops::function::FnOnce<(rustc_middle[a37ff32571d5c1a9]::ty::context::TyCtxt, ())>>::call_once
  47:        0x10c873b14 - rustc_query_system[e2da81a1c072113]::query::plumbing::try_execute_query::<rustc_query_impl[a9de1c92a9de04a0]::DynamicConfig<rustc_query_system[e2da81a1c072113]::query::caches::SingleCache<rustc_middle[a37ff32571d5c1a9]::query::erase::Erased<[u8; 24usize]>>, false, false, false>, rustc_query_impl[a9de1c92a9de04a0]::plumbing::QueryCtxt, false>
  48:        0x10cb3259c - rustc_query_impl[a9de1c92a9de04a0]::query_impl::collect_and_partition_mono_items::get_query_non_incr::__rust_end_short_backtrace
  49:        0x10b105728 - rustc_codegen_ssa[e3e96a407e96fbaf]::base::codegen_crate::<rustc_codegen_llvm[eac619daf28d4c]::LlvmCodegenBackend>
  50:        0x10b1c4100 - <rustc_codegen_llvm[eac619daf28d4c]::LlvmCodegenBackend as rustc_codegen_ssa[e3e96a407e96fbaf]::traits::backend::CodegenBackend>::codegen_crate
  51:        0x10bcf39cc - <rustc_session[4e5213968b08c628]::session::Session>::time::<alloc[53949c4a0a9a41eb]::boxed::Box<dyn core[d0cf843891889b67]::any::Any>, rustc_interface[859372deaefb7862]::passes::start_codegen::{closure#0}>
  52:        0x10bdb824c - rustc_interface[859372deaefb7862]::passes::start_codegen
  53:        0x10bd1be88 - <rustc_interface[859372deaefb7862]::queries::Queries>::codegen_and_build_linker
  54:        0x10b436298 - <rustc_interface[859372deaefb7862]::interface::Compiler>::enter::<rustc_driver_impl[e337739a2a22afd0]::run_compiler::{closure#0}::{closure#1}, core[d0cf843891889b67]::result::Result<core[d0cf843891889b67]::option::Option<rustc_interface[859372deaefb7862]::queries::Linker>, rustc_span[19473d8b3fea81af]::ErrorGuaranteed>>
  55:        0x10b49ac6c - rustc_span[19473d8b3fea81af]::create_session_globals_then::<core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>, rustc_interface[859372deaefb7862]::util::run_in_thread_with_globals<rustc_interface[859372deaefb7862]::util::run_in_thread_pool_with_globals<rustc_interface[859372deaefb7862]::interface::run_compiler<core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>, rustc_driver_impl[e337739a2a22afd0]::run_compiler::{closure#0}>::{closure#1}, core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>>::{closure#0}, core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}>
  56:        0x10b468a4c - std[76b399b4b9fa005f]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[859372deaefb7862]::util::run_in_thread_with_globals<rustc_interface[859372deaefb7862]::util::run_in_thread_pool_with_globals<rustc_interface[859372deaefb7862]::interface::run_compiler<core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>, rustc_driver_impl[e337739a2a22afd0]::run_compiler::{closure#0}>::{closure#1}, core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>>::{closure#0}, core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>>
  57:        0x10b42ebbc - <<std[76b399b4b9fa005f]::thread::Builder>::spawn_unchecked_<rustc_interface[859372deaefb7862]::util::run_in_thread_with_globals<rustc_interface[859372deaefb7862]::util::run_in_thread_pool_with_globals<rustc_interface[859372deaefb7862]::interface::run_compiler<core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>, rustc_driver_impl[e337739a2a22afd0]::run_compiler::{closure#0}>::{closure#1}, core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>>::{closure#0}, core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[d0cf843891889b67]::result::Result<(), rustc_span[19473d8b3fea81af]::ErrorGuaranteed>>::{closure#2} as core[d0cf843891889b67]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  58:        0x1016760b4 - std::sys::pal::unix::thread::Thread::new::thread_start::hd57c46075faf34b9
  59:        0x1917a2f94 - __pthread_joiner_wake

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: please make sure that you have updated to the latest nightly

note: please attach the file at `/tmp/rustc-ice-2024-06-28T16_06_04-34433.txt` to your bug report

note: compiler flags: -C opt-level=3

query stack during panic:
#0 [optimized_mir] optimizing MIR for `<impl at main.rs:5:1: 5:15>::cmp_ptr`
#1 [cross_crate_inlinable] whether the item should be made inlinable across crates
end of query stack

rustc-ice-2024-06-28T16_06_04-34433.txt

[lqd]

This seems to bisect to #126844 cc @scottmcm

[scottmcm]

Thanks for the ping! I'll take a look.

I thought I'd checked for this with https://github.com/rust-lang/rust/pull/126844/files#diff-6202eda9e5f3c8b8a291cf165920ea8484c372002e485eafa920b319f7cb4dd3R1072, but clearly I missed something.