ICE with aligned enum #92464

MiSawa · 2021-12-31T22:12:07Z

Code

#[allow(dead_code)]
#[repr(align(8))]
enum Aligned {
    Zero = 0,
    One = 1,
}

fn main() {
    let aligned = Aligned::Zero;
    println!("{}", aligned as u8);
}

Error output

error: internal compiler error: /rustc/b60e32c82864d841e87359333af1e6d1f9cff9ee/compiler/rustc_const_eval/src/interpret/operand.rs:324:13: primitive read failed for type: Aligned
  --> ./ice.rs:10:14
   |
10 |     println!("{}", aligned as u8);
   |              ^^^^

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/b60e32c82864d841e87359333af1e6d1f9cff9ee/compiler/rustc_errors/src/lib.rs:1115:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

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 1.59.0-nightly (b60e32c82 2021-12-30) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [optimized_mir] optimizing MIR for `main`
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: aborting due to previous error

Backtrace

error: internal compiler error: /rustc/b60e32c82864d841e87359333af1e6d1f9cff9ee/compiler/rustc_const_eval/src/interpret/operand.rs:324:13: primitive read failed for type: Aligned
  --> ./ice.rs:10:14
   |
10 |     println!("{}", aligned as u8);
   |              ^^^^

thread 'rustc' panicked at 'Box<dyn Any>', /rustc/b60e32c82864d841e87359333af1e6d1f9cff9ee/compiler/rustc_errors/src/lib.rs:1115:9
stack backtrace:
   0: std::panicking::begin_panic::<rustc_errors::ExplicitBug>
   1: std::panic::panic_any::<rustc_errors::ExplicitBug>
   2: <rustc_errors::HandlerInner>::span_bug::<rustc_span::span_encoding::Span>
   3: <rustc_errors::Handler>::span_bug::<rustc_span::span_encoding::Span>
   4: rustc_middle::ty::context::tls::with_opt::<rustc_middle::util::bug::opt_span_bug_fmt<rustc_span::span_encoding::Span>::{closure#0}, ()>
   5: rustc_middle::util::bug::opt_span_bug_fmt::<rustc_span::span_encoding::Span>
   6: rustc_middle::util::bug::span_bug_fmt::<rustc_span::span_encoding::Span>
   7: <rustc_const_eval::interpret::eval_context::InterpCx<rustc_mir_transform::const_prop::ConstPropMachine>>::eval_rvalue_into_place
   8: <rustc_mir_transform::const_prop::ConstPropagator as rustc_middle::mir::visit::MutVisitor>::visit_body
   9: <rustc_mir_transform::const_prop::ConstProp as rustc_middle::mir::MirPass>::run_pass
  10: rustc_mir_transform::pass_manager::run_passes
  11: rustc_mir_transform::optimized_mir
  12: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<rustc_span::def_id::DefId, &rustc_middle::mir::Body>>
  13: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::optimized_mir
  14: <rustc_middle::ty::context::TyCtxt>::instance_mir
  15: rustc_monomorphize::collector::collect_neighbours
  16: rustc_monomorphize::collector::collect_items_rec
  17: <rustc_session::session::Session>::time::<(), rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}>
  18: rustc_monomorphize::collector::collect_crate_mono_items
  19: rustc_monomorphize::partitioning::collect_and_partition_mono_items
  20: rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::plumbing::QueryCtxt, rustc_query_system::query::caches::DefaultCache<(), (&std::collections::hash::set::HashSet<rustc_span::def_id::DefId, core::hash::BuildHasherDefault<rustc_hash::FxHasher>>, &[rustc_middle::mir::mono::CodegenUnit])>>
  21: rustc_query_system::query::plumbing::get_query::<rustc_query_impl::queries::collect_and_partition_mono_items, rustc_query_impl::plumbing::QueryCtxt>
  22: <rustc_query_impl::Queries as rustc_middle::ty::query::QueryEngine>::collect_and_partition_mono_items
  23: <rustc_codegen_llvm::LlvmCodegenBackend as rustc_codegen_ssa::traits::backend::CodegenBackend>::codegen_crate
  24: <rustc_session::session::Session>::time::<alloc::boxed::Box<dyn core::any::Any>, rustc_interface::passes::start_codegen::{closure#0}>
  25: <rustc_interface::queries::Queries>::ongoing_codegen
  26: <rustc_interface::interface::Compiler>::enter::<rustc_driver::run_compiler::{closure#1}::{closure#2}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_errors::ErrorReported>>
  27: rustc_span::with_source_map::<core::result::Result<(), rustc_errors::ErrorReported>, rustc_interface::interface::create_compiler_and_run<core::result::Result<(), rustc_errors::ErrorReported>, rustc_driver::run_compiler::{closure#1}>::{closure#1}>
  28: rustc_interface::interface::create_compiler_and_run::<core::result::Result<(), rustc_errors::ErrorReported>, rustc_driver::run_compiler::{closure#1}>
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

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 1.59.0-nightly (b60e32c82 2021-12-30) running on x86_64-unknown-linux-gnu

query stack during panic:
#0 [optimized_mir] optimizing MIR for `main`
#1 [collect_and_partition_mono_items] collect_and_partition_mono_items
end of query stack
error: aborting due to previous error

The text was updated successfully, but these errors were encountered:

MiSawa · 2021-12-31T22:18:45Z

FYI, also fails in stable rustc 1.57.0 (f1edd0429 2021-11-29). https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=72d716ba5a7f274d8c518b82236688b8

bugadani · 2022-01-01T19:40:46Z

Slightly different example, different error message, probably the same cause:

#[repr(align(2))] // 2, 4, 8 crashes, 1 compiles
enum Aligned {
    Zero = 0,
    One = 1,
}

pub fn main() {
    println!("{}", tou8(Aligned::Zero))
}

fn tou8(al: Aligned) -> u8 {
    al as u8
}

error: internal compiler error: /rustc/b60e32c82864d841e87359333af1e6d1f9cff9ee/compiler/rustc_codegen_ssa/src/mir/operand.rs:118:18: not immediate: OperandRef(Ref((%Aligned*:  %2 = alloca %Aligned, align 2), None, Align { pow2: 1 }) @ TyAndLayout { ty: Aligned, layout: Layout { fields: Arbitrary { offsets: [Size { raw: 0 }], memory_index: [0] }, variants: Multiple { tag: Scalar { value: Int(I8, false), valid_range: 0..=1 }, tag_encoding: Direct, tag_field: 0, variants: [Layout { fields: Arbitrary { offsets: [], memory_index: [] }, variants: Single { index: 0 }, abi: Aggregate { sized: true }, largest_niche: None, align: AbiAndPrefAlign { abi: Align { pow2: 1 }, pref: Align { pow2: 3 } }, size: Size { raw: 2 } }, Layout { fields: Arbitrary { offsets: [], memory_index: [] }, variants: Single { index: 1 }, abi: Aggregate { sized: true }, largest_niche: None, align: AbiAndPrefAlign { abi: Align { pow2: 1 }, pref: Align { pow2: 3 } }, size: Size { raw: 2 } }] }, abi: Aggregate { sized: true }, largest_niche: Some(Niche { offset: Size { raw: 0 }, scalar: Scalar { value: Int(I8, false), valid_range: 0..=1 } }), align: AbiAndPrefAlign { abi: Align { pow2: 1 }, pref: Align { pow2: 3 } }, size: Size { raw: 2 } } })

RalfJung · 2022-01-03T09:52:02Z

So looks like we have that same problem both in the CTFE engine and in the codegen backend. Fun. At least we are consistent. ;)

Temporary fix for the layout of aligned enums Fix for the issue rust-lang#92464 ~~I was after this issue for quite some time now, I have a temporary fix for it. I think the current problem is [here](https://github.com/ouz-a/rust/blob/e75f96763f99d56d03ada939fe05cbeb2254888d/compiler/rustc_middle/src/ty/layout.rs#L1305-L1310) created `tag` value might be wrong, because when I checked `min` and `max` values it's always between 0..1, which results in wrong size comparison in a few lines down below. I think `min` and `max` values don't take `#[repr(aligned(8))]` into consideration and just act from base values assigned inside the enum. If what I am saying is true, aligned enums were created with the wrong layout for some time.~~ ~~As stated in the title this is only a temporary fix and I think this needs further investigation, if someone wants to mentor it I would like to work on that too.~~ 😸 **Edit: Weird some tests fail now going to close this for now...** **Edit2: I made it work again.** I think I figured out the main problem of the issue, layout types of aligned enums with custom discriminant types were not handled, which resulted in confusing(such as this issue) behavior down the line, this is a kinda hacky fix for the issue.

JohnTitor · 2022-02-05T06:26:22Z

Fixed by #92932, closing.

Fix repr(align) enum handling `enum`, for better or worse, supports `repr(align)`. That has already caused a bug in rust-lang#92464, which was "fixed" in rust-lang#92932, but it turns out that that fix is wrong and caused rust-lang#96185. So this reverts rust-lang#92932 (which fixes rust-lang#96185), and attempts another strategy for fixing rust-lang#92464: special-case enums when doing a cast, re-using the code to load the discriminant rather than assuming that the enum has scalar layout. This works fine for the interpreter. However, rust-lang#92464 contained another testcase that was previously not in the test suite -- and after adding it, it ICEs again. This is not surprising; codegen needs the same patch that I did in the interpreter. Probably this has to happen [around here](https://github.com/rust-lang/rust/blob/d32ce37a171663048a4c4a536803434e40f52bd6/compiler/rustc_codegen_ssa/src/mir/rvalue.rs#L276). Unfortunately I don't know how to do that -- the interpreter can load a discriminant from an operand, but codegen can only do that from a place. `@oli-obk` `@eddyb` `@bjorn3` any idea?

MiSawa added C-bug Category: This is a bug. I-ICE Issue: The compiler panicked, giving an Internal Compilation Error (ICE) ❄️ T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Dec 31, 2021

RalfJung added A-codegen Area: Code generation A-const-eval Area: Constant evaluation, covers all const contexts (static, const fn, ...) labels Jan 3, 2022

rust-lang-glacier-bot added the glacier ICE tracked in rust-lang/glacier. label Jan 5, 2022

ouz-a mentioned this issue Jan 15, 2022

Temporary fix for the layout of aligned enums #92932

Merged

github-actions bot mentioned this issue Feb 4, 2022

ices/92464.rs: fixed with no errors rust-lang/glacier#1106

Merged

JohnTitor closed this as completed Feb 5, 2022

This was referenced May 7, 2022

enums with repr(align) generate Scalar layout with padding (ICE: miri: field access on non aggregate <uninitialized> ) #96185

Closed

Fix repr(align) enum handling #96814

Merged

Change enum->int casts to not go through MIR casts. #96862

Merged

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ICE with aligned enum #92464

ICE with aligned enum #92464

MiSawa commented Dec 31, 2021

MiSawa commented Dec 31, 2021

bugadani commented Jan 1, 2022 •

edited

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RalfJung commented Jan 3, 2022

JohnTitor commented Feb 5, 2022

ICE with aligned enum #92464

ICE with aligned enum #92464

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MiSawa commented Dec 31, 2021

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Error output

MiSawa commented Dec 31, 2021

bugadani commented Jan 1, 2022 • edited Loading

RalfJung commented Jan 3, 2022

JohnTitor commented Feb 5, 2022

bugadani commented Jan 1, 2022 •

edited

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