rust-lang / rust-lang/rust

ICE: `builtin derive created an unaligned reference`

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A-proc-macros A-repr-packed C-bug I-ICE T-compiler
Dominant language
Rust
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Description

I'm developing a toy kernel and created a proc-macro for annotation packed structs. Using the macro along with #[derive(Debug)] causes an ice.

Code

src/main.rs

extern crate packed_macro;
use packed_macro::{packed, Packed};

pub trait _Packed_: Sized {}

pub trait FromBytes: _Packed_ {}

#[derive(Debug)]
#[packed]
pub struct Struct {
    x: u32,
}

fn main() {}

proc-macro crate:

#[proc_macro_attribute]
pub fn packed(_attr: TokenStream, item: TokenStream) -> TokenStream {
    let input = parse_macro_input!(item as ItemStruct);

    let vis = &input.vis;
    let name = &input.ident;
    let fields = &input.fields;

    let expanded = quote! {
        #[repr(C, packed)]
        #[derive(Packed, Clone, Copy)]
        #vis struct #name #fields
    };

    TokenStream::from(expanded)
}

#[proc_macro_derive(Packed)]
pub fn derive_packed(input: TokenStream) -> TokenStream {
    let name = &parse_macro_input!(input as DeriveInput).ident;

    TokenStream::from(quote! {
        impl crate::_Packed_ for #name {}
    })
}
Meta

rustc --version --verbose:

rustc 1.81.0-nightly (c6727fc9b 2024-07-12)
binary: rustc
commit-hash: c6727fc9b5c64cefa7263486497ee95e529bd0f8
commit-date: 2024-07-12
host: x86_64-unknown-linux-gnu
release: 1.81.0-nightly
LLVM version: 18.1.7
Error output
error: internal compiler error: compiler/rustc_mir_transform/src/check_packed_ref.rs:50:21: builtin derive created an unaligned reference
  --> src/main.rs:11:5
   |
8  | #[derive(Debug)]
   |          ----- in this derive macro expansion
...
11 |     x: u32,
   |     ^^^^^^
   |
   = note: this error: internal compiler error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
Backtrace 

thread 'rustc' panicked at compiler/rustc_mir_transform/src/check_packed_ref.rs:50:21:
Box<dyn Any>
stack backtrace:
   0:     0x7f05ae7459e5 - std::backtrace_rs::backtrace::libunwind::trace::h90ef53671b8f35e2
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:     0x7f05ae7459e5 - std::backtrace_rs::backtrace::trace_unsynchronized::hd3a497571d63ea87
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f05ae7459e5 - std::backtrace::Backtrace::create::h8bff861c2af14d3f
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/backtrace.rs:331:13
   3:     0x7f05ae745935 - std::backtrace::Backtrace::force_capture::h84acf91f68ab21d6
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/backtrace.rs:312:9
   4:     0x7f05b1c0b9ff - std[85c3ca4c170da0bb]::panicking::update_hook::<alloc[d335478de6b4a53f]::boxed::Box<rustc_driver_impl[dc4b00a9cfefcaac]::install_ice_hook::{closure#0}>>::{closure#0}
   5:     0x7f05ae760aff - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hbe29137bf798c82c
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/alloc/src/boxed.rs:2078:9
   6:     0x7f05ae760aff - std::panicking::rust_panic_with_hook::h869b30cecbb157c4
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/panicking.rs:804:13
   7:     0x7f05b1c46151 - std[85c3ca4c170da0bb]::panicking::begin_panic::<rustc_errors[24d2db88e61fdfbe]::ExplicitBug>::{closure#0}
   8:     0x7f05b1c39106 - std[85c3ca4c170da0bb]::sys::backtrace::__rust_end_short_backtrace::<std[85c3ca4c170da0bb]::panicking::begin_panic<rustc_errors[24d2db88e61fdfbe]::ExplicitBug>::{closure#0}, !>
   9:     0x7f05b1c390b6 - std[85c3ca4c170da0bb]::panicking::begin_panic::<rustc_errors[24d2db88e61fdfbe]::ExplicitBug>
  10:     0x7f05b1c4f391 - <rustc_errors[24d2db88e61fdfbe]::diagnostic::BugAbort as rustc_errors[24d2db88e61fdfbe]::diagnostic::EmissionGuarantee>::emit_producing_guarantee
  11:     0x7f05b235dd0d - <rustc_errors[24d2db88e61fdfbe]::DiagCtxtHandle>::span_bug::<rustc_span[67819806738ee56d]::span_encoding::Span, alloc[d335478de6b4a53f]::string::String>
  12:     0x7f05b23905d8 - rustc_middle[aeeec62211ae3a75]::util::bug::opt_span_bug_fmt::<rustc_span[67819806738ee56d]::span_encoding::Span>::{closure#0}
  13:     0x7f05b239060a - rustc_middle[aeeec62211ae3a75]::ty::context::tls::with_opt::<rustc_middle[aeeec62211ae3a75]::util::bug::opt_span_bug_fmt<rustc_span[67819806738ee56d]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  14:     0x7f05b237c83b - rustc_middle[aeeec62211ae3a75]::ty::context::tls::with_context_opt::<rustc_middle[aeeec62211ae3a75]::ty::context::tls::with_opt<rustc_middle[aeeec62211ae3a75]::util::bug::opt_span_bug_fmt<rustc_span[67819806738ee56d]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  15:     0x7f05b237bbb7 - rustc_middle[aeeec62211ae3a75]::util::bug::span_bug_fmt::<rustc_span[67819806738ee56d]::span_encoding::Span>
  16:     0x7f05b323fdba - <rustc_mir_transform[e83149d28cb0f37b]::pass_manager::Lint<rustc_mir_transform[e83149d28cb0f37b]::check_packed_ref::CheckPackedRef> as rustc_middle[aeeec62211ae3a75]::mir::MirPass>::run_pass
  17:     0x7f05b3201cbb - rustc_mir_transform[e83149d28cb0f37b]::pass_manager::run_passes_inner
  18:     0x7f05b36d526c - rustc_query_impl[1a70eeac4d27cd99]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[1a70eeac4d27cd99]::query_impl::mir_built::dynamic_query::{closure#2}::{closure#0}, rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 8usize]>>
  19:     0x7f05b358c038 - rustc_query_system[a1535082eb398a6e]::query::plumbing::try_execute_query::<rustc_query_impl[1a70eeac4d27cd99]::DynamicConfig<rustc_query_system[a1535082eb398a6e]::query::caches::VecCache<rustc_span[67819806738ee56d]::def_id::LocalDefId, rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 8usize]>>, false, false, false>, rustc_query_impl[1a70eeac4d27cd99]::plumbing::QueryCtxt, true>
  20:     0x7f05b359579c - rustc_query_impl[1a70eeac4d27cd99]::query_impl::mir_built::get_query_incr::__rust_end_short_backtrace
  21:     0x7f05b36ce63e - rustc_mir_build[ef33ca6215fc9157]::check_unsafety::check_unsafety
  22:     0x7f05b36ce3dd - rustc_query_impl[1a70eeac4d27cd99]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[1a70eeac4d27cd99]::query_impl::check_unsafety::dynamic_query::{closure#2}::{closure#0}, rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 0usize]>>
  23:     0x7f05b359362e - rustc_query_system[a1535082eb398a6e]::query::plumbing::try_execute_query::<rustc_query_impl[1a70eeac4d27cd99]::DynamicConfig<rustc_query_system[a1535082eb398a6e]::query::caches::VecCache<rustc_span[67819806738ee56d]::def_id::LocalDefId, rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 0usize]>>, false, false, false>, rustc_query_impl[1a70eeac4d27cd99]::plumbing::QueryCtxt, true>
  24:     0x7f05b3593141 - rustc_query_impl[1a70eeac4d27cd99]::query_impl::check_unsafety::get_query_incr::__rust_end_short_backtrace
  25:     0x7f05b357cdb8 - rustc_interface[a6452cf60fc426fe]::passes::analysis
  26:     0x7f05b357bf07 - rustc_query_impl[1a70eeac4d27cd99]::plumbing::__rust_begin_short_backtrace::<rustc_query_impl[1a70eeac4d27cd99]::query_impl::analysis::dynamic_query::{closure#2}::{closure#0}, rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 1usize]>>
  27:     0x7f05b40ac804 - rustc_query_system[a1535082eb398a6e]::query::plumbing::try_execute_query::<rustc_query_impl[1a70eeac4d27cd99]::DynamicConfig<rustc_query_system[a1535082eb398a6e]::query::caches::SingleCache<rustc_middle[aeeec62211ae3a75]::query::erase::Erased<[u8; 1usize]>>, false, false, false>, rustc_query_impl[1a70eeac4d27cd99]::plumbing::QueryCtxt, true>
  28:     0x7f05b40ac4ba - rustc_query_impl[1a70eeac4d27cd99]::query_impl::analysis::get_query_incr::__rust_end_short_backtrace
  29:     0x7f05b3fc2745 - rustc_interface[a6452cf60fc426fe]::interface::run_compiler::<core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>, rustc_driver_impl[dc4b00a9cfefcaac]::run_compiler::{closure#0}>::{closure#1}
  30:     0x7f05b3f8f589 - std[85c3ca4c170da0bb]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[a6452cf60fc426fe]::util::run_in_thread_with_globals<rustc_interface[a6452cf60fc426fe]::util::run_in_thread_pool_with_globals<rustc_interface[a6452cf60fc426fe]::interface::run_compiler<core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>, rustc_driver_impl[dc4b00a9cfefcaac]::run_compiler::{closure#0}>::{closure#1}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#0}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>
  31:     0x7f05b3f8f33a - <<std[85c3ca4c170da0bb]::thread::Builder>::spawn_unchecked_<rustc_interface[a6452cf60fc426fe]::util::run_in_thread_with_globals<rustc_interface[a6452cf60fc426fe]::util::run_in_thread_pool_with_globals<rustc_interface[a6452cf60fc426fe]::interface::run_compiler<core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>, rustc_driver_impl[dc4b00a9cfefcaac]::run_compiler::{closure#0}>::{closure#1}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#0}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[2213ecb858fb81d5]::result::Result<(), rustc_span[67819806738ee56d]::ErrorGuaranteed>>::{closure#2} as core[2213ecb858fb81d5]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  32:     0x7f05ae76a95b - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h7aa527871fe5008e
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/alloc/src/boxed.rs:2064:9
  33:     0x7f05ae76a95b - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h661f413d6ffad84b
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/alloc/src/boxed.rs:2064:9
  34:     0x7f05ae76a95b - std::sys::pal::unix::thread::Thread::new::thread_start::h77623da8b368e6ce
                               at /rustc/c6727fc9b5c64cefa7263486497ee95e529bd0f8/library/std/src/sys/pal/unix/thread.rs:108:17
  35:     0x7f05ae53ca42 - start_thread
  36:     0x7f05ae5bc05c - clone3
  37:                0x0 - <unknown>


rustc version: 1.81.0-nightly (c6727fc9b 2024-07-12)
platform: x86_64-unknown-linux-gnu

query stack during panic:
#0 [mir_built] building MIR for `<impl at src/main.rs:8:10: 8:15>::fmt`
#1 [check_unsafety] unsafety-checking `<impl at src/main.rs:8:10: 8:15>::fmt`
#2 [analysis] running analysis passes on this crate
end of query stack

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the ICE from the src/main.rs example, then inspect compiler/rustc_mir_transform/src/check_packed_ref.rs and the MIR for the generated Debug implementation. Start with the CheckPackedRef pass and the backtrace's mir_built entry point. Done means this packed-struct derive case no longer triggers an internal compiler error.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
35/100

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