LLVM ERROR: Too many bits for int64_t

Code

#![feature(repr128)]
#[derive(PartialEq, Debug)]
#[repr(i128)]
enum Test {
    A(Box<u64>) = 0,
    B(usize) = u64::MAX as i128 + 1,
}

fn main() {
    assert_ne!(Test::A(Box::new(2)), Test::B(0));
    // This previously caused a segfault.
    //
    // See https://github.com/rust-lang/rust/issues/70509#issuecomment-620654186
    // for a detailed explanation.
}

Error output

warning: the feature `repr128` is incomplete and may not be safe to use and/or cause compiler crashes
 --> 100612.rs:1:12
  |
1 | #![feature(repr128)]
  |            ^^^^^^^
  |
  = note: see issue #56071 <https://github.com/rust-lang/rust/issues/56071> for more information
  = note: `#[warn(incomplete_features)]` on by default

Backtrace

rustc: /home/matthias/vcs/github/rust_debug_assertions/src/llvm-project/llvm/include/llvm/ADT/APInt.h:1519: int64_t llvm::APInt::getSExtValue() const: Assertion `getSignificantBits() <= 64 && "Too many bits for int64_t"' failed.
[2]    32637 IOT instruction  RUST_BACKTRACE=full ~/.rustup/toolchains/local-debug-assertions/bin/rustc

What platform are you running this on? I can't repro this with a custom-built LLVM with debug assertions enabled on x86_64-unknown-linux-gnu.

You need -Cdebuginfo=2 to reproduce.

This is the same as #100612, except it's now failing the assertion in LLVM instead of rustc.

#![feature(repr128)]

#[repr(u128)]
pub enum NotTrunctable {
    A = 0,
    B([u8; 1024]) = 1,
    C([u8; 4096]) = 0x10000000000000001,
}

pub fn trunc() {
  let mut a = NotTrunctable::A;
  a = NotTrunctable::B([0; 1024]);
}

pub fn main() {
  trunc();
}

warning: the feature `repr128` is incomplete and may not be safe to use and/or cause compiler crashes
 --> 52F3D9FC05D68B335092D7DEFC92AEAF218938602BBDEF4528FC527AB879E042.rs:1:12
  |
1 | #![feature(repr128)]
  |            ^^^^^^^
  |
  = note: see issue #56071 <https://github.com/rust-lang/rust/issues/56071> for more information
  = note: `#[warn(incomplete_features)]` on by default

warning: variable `a` is assigned to, but never used
  --> 52F3D9FC05D68B335092D7DEFC92AEAF218938602BBDEF4528FC527AB879E042.rs:11:11
   |
11 |   let mut a = NotTrunctable::A;
   |           ^
   |
   = note: consider using `_a` instead
   = note: `#[warn(unused_variables)]` on by default

warning: value assigned to `a` is never read
  --> 52F3D9FC05D68B335092D7DEFC92AEAF218938602BBDEF4528FC527AB879E042.rs:12:3
   |
12 |   a = NotTrunctable::B([0; 1024]);
   |   ^
   |
   = help: maybe it is overwritten before being read?
   = note: `#[warn(unused_assignments)]` on by default

rustc: /home/matthias/vcs/github/rust_debug_assertions/src/llvm-project/llvm/include/llvm/ADT/APInt.h:1497: uint64_t llvm::APInt::getZExtValue() const: Assertion `getActiveBits() <= 64 && "Too many bits for uint64_t"' failed.
[1]    1502395 IOT instruction  ~/.rustup/toolchains/local-debug-assertions/bin/rustc  -Cdebuginfo=2

Cannot reproduce this with 1.75.0-nightly.

nightly doesn't have debug assertions, see the corresponding label

nightly doesn't have debug assertions, see the corresponding label

Eh, I thought -Cdebuginfo=2 would suffice... oh well.

This is the same as #100612, except it's now failing the assertion in LLVM instead of rustc.

Triage: Let's close this as duplicate then.

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LLVM ERROR: `Too many bits for int64_t` #112770

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LLVM ERROR: Too many bits for int64_t #112770

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compiler-errors commented on Jun 18, 2023

lukas-code commented on Jun 18, 2023

matthiaskrgr commented on Jul 19, 2023

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Enselic commented on Oct 24, 2025

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LLVM ERROR: `Too many bits for int64_t` #112770