rust-lang / rust-lang/rust

[ICE]: `InterpErrorInfo(InterpErrorInfoInner { kind: UndefinedBehavior(ValidationError` `encountered 0, but expected something greater or equal to 1`

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C-bug I-ICE needs-triage T-compiler
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Rust
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Description

Code
//@ compile-flags -Zmir-opt-level=3  -Clink-dead-code -Zvalidate-mir -Zextra-const-ub-checks  --emit=mir
use std::mem::ManuallyDrop;
use std::ptr;
struct BitVec<T> {
    pointer: ptr::NonNull<T>,
    capacity: usize,
}
impl<T> BitVec<T> {
    fn with_vec<F, R>(self, func: F) -> R
    where
        F: FnOnce(&ManuallyDrop<Vec<T>>) -> R,
    {
        let cap = self.capacity;
        let elts = 0;
        let vec = ManuallyDrop::new(unsafe { Vec::from_raw_parts(ptr::null_mut(), elts, cap) });
        let out = func(&vec);
        out
    }
}

fn main() {}
Meta

rustc --version --verbose:

rustc 1.97.0-nightly (36ba2c771 2026-04-23)
binary: rustc
commit-hash: 36ba2c7712052d731a7082d0eba5ed3d9d56c133
commit-date: 2026-04-23
host: x86_64-unknown-linux-gnu
release: 1.97.0-nightly
LLVM version: 22.1.2
Error output
<output>
Backtrace 

warning: struct `BitVec` is never constructed
 --> code.rs:3:8
  |
3 | struct BitVec<T> {
  |        ^^^^^^
  |
  = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default

warning: method `with_vec` is never used
 --> code.rs:8:8
  |
7 | impl<T> BitVec<T> {
  | ----------------- method in this implementation
8 |     fn with_vec<F, R>(self, func: F) -> R
  |        ^^^^^^^^


thread 'rustc' (971639) panicked at /rustc-dev/36ba2c7712052d731a7082d0eba5ed3d9d56c133/compiler/rustc_const_eval/src/util/check_validity_requirement.rs:201:41:
called `Result::unwrap()` on an `Err` value: InterpErrorInfo(InterpErrorInfoInner { kind: UndefinedBehavior(ValidationError { orig_ty: pattern_type!(*const u8 is !null), path: None, msg: "encountered 0, but expected something greater or equal to 1", ptr_bytes_warning: false }), backtrace: InterpErrorBacktrace { backtrace: None } })
stack backtrace:
   0:     0x7f639141e9db - <<std[75ea15d2214b0ed8]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[2481842aaaac4afd]::fmt::Display>::fmt
   1:     0x7f6391a2d408 - core[2481842aaaac4afd]::fmt::write
   2:     0x7f6391435986 - <std[75ea15d2214b0ed8]::sys::stdio::unix::Stderr as std[75ea15d2214b0ed8]::io::Write>::write_fmt
   3:     0x7f63913f4c58 - std[75ea15d2214b0ed8]::panicking::default_hook::{closure#0}
   4:     0x7f6391412043 - std[75ea15d2214b0ed8]::panicking::default_hook
   5:     0x7f63903d301c - std[75ea15d2214b0ed8]::panicking::update_hook::<alloc[38765da0c132a06f]::boxed::Box<rustc_driver_impl[7a2168e1d29e28dc]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f6391412322 - std[75ea15d2214b0ed8]::panicking::panic_with_hook
   7:     0x7f63913f4d18 - std[75ea15d2214b0ed8]::panicking::panic_handler::{closure#0}
   8:     0x7f63913eba59 - std[75ea15d2214b0ed8]::sys::backtrace::__rust_end_short_backtrace::<std[75ea15d2214b0ed8]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f63913f677d - __rustc[8f3dd88aee2b0d44]::rust_begin_unwind
  10:     0x7f638e02569c - core[2481842aaaac4afd]::panicking::panic_fmt
  11:     0x7f638db5ee02 - core[2481842aaaac4afd]::result::unwrap_failed
  12:     0x7f6390350e71 - rustc_const_eval[b6a1f833c92620e1]::util::check_validity_requirement::validate_scalar_in_layout
  13:     0x7f6390865296 - <rustc_const_eval[b6a1f833c92620e1]::provide::{closure#3} as core[2481842aaaac4afd]::ops::function::FnOnce<(rustc_middle[c570919ef227af48]::ty::context::TyCtxt, rustc_middle[c570919ef227af48]::ty::consts::int::ScalarInt, rustc_middle[c570919ef227af48]::ty::Ty)>>::call_once
  14:     0x7f6390aa48b3 - <rustc_middle[c570919ef227af48]::ty::print::pretty::FmtPrinter as rustc_middle[c570919ef227af48]::ty::print::pretty::PrettyPrinter>::pretty_print_const_scalar_int
  15:     0x7f6392e913a6 - rustc_middle[c570919ef227af48]::mir::pretty::pretty_print_const_value_tcx
  16:     0x7f6392e91b8d - rustc_middle[c570919ef227af48]::mir::pretty::pretty_print_const_value_tcx
  17:     0x7f6392e90e00 - <rustc_middle[c570919ef227af48]::mir::consts::Const as core[2481842aaaac4afd]::fmt::Display>::fmt
  18:     0x7f6391a2d408 - core[2481842aaaac4afd]::fmt::write
  19:     0x7f6390a62b57 - <&alloc[38765da0c132a06f]::boxed::Box<rustc_middle[c570919ef227af48]::mir::syntax::ConstOperand> as core[2481842aaaac4afd]::fmt::Debug>::fmt
  20:     0x7f6391a2d408 - core[2481842aaaac4afd]::fmt::write
  21:     0x7f6390a9087e - <rustc_middle[c570919ef227af48]::mir::syntax::Operand as core[2481842aaaac4afd]::fmt::Debug>::fmt
  22:     0x7f638fc7e3cc - <core[2481842aaaac4afd]::fmt::builders::DebugStruct>::field
  23:     0x7f63909fc4c2 - rustc_middle[c570919ef227af48]::ty::context::tls::with::<<rustc_middle[c570919ef227af48]::mir::syntax::Rvalue as core[2481842aaaac4afd]::fmt::Debug>::fmt::{closure#3}, core[2481842aaaac4afd]::result::Result<(), core[2481842aaaac4afd]::fmt::Error>>
  24:     0x7f6390a8e316 - <rustc_middle[c570919ef227af48]::mir::syntax::Rvalue as core[2481842aaaac4afd]::fmt::Debug>::fmt
  25:     0x7f6391a2d408 - core[2481842aaaac4afd]::fmt::write
  26:     0x7f6390a777ed - <rustc_middle[c570919ef227af48]::mir::syntax::StatementKind as core[2481842aaaac4afd]::fmt::Debug>::fmt
  27:     0x7f6391a2d408 - core[2481842aaaac4afd]::fmt::write
  28:     0x7f6391a2d2d5 - alloc[38765da0c132a06f]::fmt::format::format_inner
  29:     0x7f6390a20840 - <rustc_middle[c570919ef227af48]::mir::pretty::MirWriter>::write_mir_fn
  30:     0x7f6390a0d09b - rustc_middle[c570919ef227af48]::mir::pretty::write_mir_pretty::{closure#0}
  31:     0x7f6390a423d9 - rustc_middle[c570919ef227af48]::mir::pretty::write_mir_pretty
  32:     0x7f638f704c94 - rustc_mir_transform[117acae470dacc9e]::dump_mir::emit_mir
  33:     0x7f6392b5c716 - rustc_interface[27fd4870d2d649e5]::interface::run_compiler::<(), rustc_driver_impl[7a2168e1d29e28dc]::run_compiler::{closure#0}>::{closure#1}
  34:     0x7f6392b2c004 - std[75ea15d2214b0ed8]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[27fd4870d2d649e5]::util::run_in_thread_with_globals<rustc_interface[27fd4870d2d649e5]::util::run_in_thread_pool_with_globals<rustc_interface[27fd4870d2d649e5]::interface::run_compiler<(), rustc_driver_impl[7a2168e1d29e28dc]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  35:     0x7f6392b2c6ed - <std[75ea15d2214b0ed8]::thread::lifecycle::spawn_unchecked<rustc_interface[27fd4870d2d649e5]::util::run_in_thread_with_globals<rustc_interface[27fd4870d2d649e5]::util::run_in_thread_pool_with_globals<rustc_interface[27fd4870d2d649e5]::interface::run_compiler<(), rustc_driver_impl[7a2168e1d29e28dc]::run_compiler::{closure#0}>::{closure#1}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[2481842aaaac4afd]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  36:     0x7f6392b2d56c - <std[75ea15d2214b0ed8]::sys::thread::unix::Thread>::new::thread_start
  37:     0x7f638c6a597a - <unknown>
  38:     0x7f638c7292bc - <unknown>
  39:                0x0 - <unknown>

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 `/home/matthias/vcs/github/CRED/rustc-ice-2026-04-24T20_15_57-971629.txt` to your bug report

note: rustc 1.97.0-nightly (36ba2c771 2026-04-23) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z mir-opt-level=3 -C link-dead-code -Z validate-mir -Z extra-const-ub-checks

query stack during panic:
end of query stack

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  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 with the provided example and the listed MIR, validation, and const-UB-check flags. Start at rustc_const_eval/src/util/check_validity_requirement.rs:201 and trace the MIR pretty-printing path shown in the backtrace. Done means the example no longer panics while emitting MIR or reports the issue through a normal compiler diagnostic.

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
Quiet
Clarity
Mostly clear
Newbie friendliness
45/100

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