Nightly ICE regression

[ishitatsuyuki]

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.24.0-nightly (77efd6800 2017-12-15) running on x86_64-pc-windows-msvc

thread 'rustc' panicked at 'assertion failed: `(left == right)`
  left: `1`,
 right: `0`', src\librustc_trans\type_.rs:293:8
note: Run with `RUST_BACKTRACE=1` for a backtrace.

error: Could not compile `select`.

Backtrace

stack backtrace:
   0: <std::fs::DirBuilder as core::fmt::Debug>::fmt
   1: std::sync::condvar::Condvar::new
   2: std::panicking::Location::column
   3: std::panicking::Location::column
   4: std::panicking::rust_panic_with_hook
   5: std::panicking::begin_panic_fmt
   6: std::panicking::begin_panic_fmt
   7: rustc_trans::type_::Type::padding_filler
   8: <rustc_trans::mir::operand::OperandRef<'tcx> as core::fmt::Debug>::fmt
   9: <rustc::ty::layout::TyLayout<'tcx> as rustc_trans::type_of::LayoutLlvmExt<'tcx>>::llvm_type
  10: <rustc::ty::layout::TyLayout<'tcx> as rustc_trans::type_of::LayoutLlvmExt<'tcx>>::llvm_type
  11: <rustc_trans::abi::CastTarget as core::convert::From<rustc_trans::abi::Uniform>>::from
  12: <&'a rustc_trans::context::CrateContext<'a, 'tcx> as rustc::ty::layout::LayoutOf<&'tcx rustc::ty::TyS<'tcx>>>::layout_of
  13: rustc_trans::trans_item::predefine_fn
  14: rustc_trans::type_::Type::to_ref_slice
  15: rustc_trans::base::trans_crate
  16: rustc::ty::maps::<impl rustc::ty::maps::queries::compile_codegen_unit<'tcx>>::ensure
  17: rustc::dep_graph::graph::DepGraph::in_ignore
  18: rustc::ty::structural_impls::<impl rustc::ty::context::Lift<'tcx> for rustc::mir::Local>::lift_to_tcx
  19: <rustc::ty::_match::Match<'a, 'gcx, 'tcx> as rustc::ty::relate::TypeRelation<'a, 'gcx, 'tcx>>::tys
  20: rustc::ty::maps::<impl rustc::ty::maps::queries::compile_codegen_unit<'tcx>>::ensure
  21: rustc::ty::maps::<impl rustc::ty::maps::queries::compile_codegen_unit<'tcx>>::try_get
  22: rustc::ty::maps::TyCtxtAt::compile_codegen_unit
  23: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::compile_codegen_unit
  24: rustc_trans::base::trans_crate
  25: <rustc_trans::LlvmTransCrate as rustc_trans_utils::trans_crate::TransCrate>::trans_crate
  26: rustc_driver::driver::default_provide_extern
  27: <rustc_driver::derive_registrar::Finder as rustc::hir::itemlikevisit::ItemLikeVisitor<'v>>::visit_item
  28: <rustc_driver::derive_registrar::Finder as rustc::hir::itemlikevisit::ItemLikeVisitor<'v>>::visit_item
  29: <rustc_driver::derive_registrar::Finder as rustc::hir::itemlikevisit::ItemLikeVisitor<'v>>::visit_item
  30: <rustc_driver::Compilation as core::fmt::Debug>::fmt
  31: rustc_driver::driver::compile_input
  32: rustc_driver::run_compiler
  33: <rustc_driver::pretty::UserIdentifiedItem as core::fmt::Debug>::fmt
  34: _rust_maybe_catch_panic
  35: <rustc_driver::derive_registrar::Finder as rustc::hir::itemlikevisit::ItemLikeVisitor<'v>>::visit_item
  36: std::sync::condvar::Condvar::new
  37: std::sys::windows::thread::Thread::new
  38: BaseThreadInitThunk

Windows 10 (64-bit)

[arielb1]

@ishitatsuyuki

Which code had caused this assertion?

Details

Caused by this assertion:

rust/src/librustc_trans/type_.rs

Lines 289 to 295 in 1b1c792

	pub fn padding_filler(ccx: &CrateContext, size: Size, align: Align) -> Type {
	let unit = layout::Integer::approximate_abi_align(ccx, align);
	let size = size.bytes();
	let unit_size = unit.size().bytes();
	assert_eq!(size % unit_size, 0);
	Type::array(&Type::from_integer(ccx, unit), size / unit_size)
	}

Which was introduced in #46623, which is beta-nominated. cc @eddyb

[eddyb]

I'm glad I added that assertion! What it likely means is that size isn't a multiple of align.
I'd be quite surprised if #[repr(packed)] and/or #[repr(align(N))] weren't involved.

[rerz]

In my case this error is caused by the select crate. Simply including it in your cargo.toml and compiling crashes rustc.

Backtrace

stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::print
             at /checkout/src/libstd/sys_common/backtrace.rs:68
             at /checkout/src/libstd/sys_common/backtrace.rs:57
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/panicking.rs:381
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:391
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:577
   5: std::panicking::begin_panic
             at /checkout/src/libstd/panicking.rs:538
   6: std::panicking::begin_panic_fmt
             at /checkout/src/libstd/panicking.rs:522
   7: rustc_trans::type_::Type::padding_filler
   8: rustc_trans::type_of::struct_llfields
   9: <rustc::ty::layout::TyLayout<'tcx> as rustc_trans::type_of::LayoutLlvmExt<'tcx>>::llvm_type
  10: rustc_trans::abi::FnType::llvm_type
  11: rustc_trans::declare::declare_fn
  12: rustc_trans::trans_item::predefine_fn
  13: rustc_trans::trans_item::TransItemExt::predefine
  14: rustc_trans::base::compile_codegen_unit
  15: rustc::ty::maps::<impl rustc::ty::maps::queries::compile_codegen_unit<'tcx>>::compute_result
  16: rustc::dep_graph::graph::DepGraph::with_task_impl
  17: rustc_errors::Handler::track_diagnostics
  18: rustc::ty::maps::plumbing::<impl rustc::ty::context::TyCtxt<'a, 'gcx, 'tcx>>::cycle_check
  19: rustc::ty::maps::<impl rustc::ty::maps::queries::compile_codegen_unit<'tcx>>::force
  20: rustc::ty::maps::<impl rustc::ty::maps::queries::compile_codegen_unit<'tcx>>::try_get
  21: rustc::ty::maps::TyCtxtAt::compile_codegen_unit
  22: rustc::ty::maps::<impl rustc::ty::context::TyCtxt<'a, 'tcx, 'lcx>>::compile_codegen_unit
  23: rustc_trans::base::trans_crate
  24: <rustc_trans::LlvmTransCrate as rustc_trans_utils::trans_crate::TransCrate>::trans_crate
  25: rustc_driver::driver::phase_4_translate_to_llvm
  26: rustc_driver::driver::compile_input::{{closure}}
  27: <std::thread::local::LocalKey<T>>::with
  28: <std::thread::local::LocalKey<T>>::with
  29: rustc::ty::context::TyCtxt::create_and_enter
  30: rustc_driver::driver::compile_input
  31: rustc_driver::run_compiler

I'm on Arch running the latest nightly rustc.

[eddyb]

Looks like Option<(tendril::Tendril<tendril::fmt::UTF8>, bool)> triggers the assertion, and it has alignment 8 but size 17 (which is illegal), IIRC, tendril includes some types that are #[repr(packed)] (or at least in older versions this is indeed 0.3.1 which has a packed Tendril) and has caused issues in the past as well.

EDIT: minimal repro:

#[repr(packed)]
pub struct Packed(&'static (), usize);
pub fn make() -> Option<(Packed, bool)> { None }