ice `Can't change TLS data object to normal or in the opposite way`

[matthiaskrgr]

#![feature(thread_local)]
#[no_mangle]
static EXPORTED: u64 = 0;
extern "C" {
    #[thread_local]
    #[link_name = "EXPORTED"]
    static C: u64;
}
fn thread_local_ptr<T>(key: &'static std::thread::LocalKey<T>) -> *const T {
    key.with(|local| core::ptr::from_ref(local))
}
fn main() {
    unsafe { C };
}

warning: function `thread_local_ptr` is never used
 --> a.rs:9:4
  |
9 | fn thread_local_ptr<T>(key: &'static std::thread::LocalKey<T>) -> *const T {
  |    ^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` (part of `#[warn(unused)]`) on by default


thread 'rustc' (1825008) panicked at /rust/deps/cranelift-module-0.134.0/src/module.rs:411:9:
assertion `left == right` failed: Can't change TLS data object to normal or in the opposite way
  left: false
 right: true
stack backtrace:
   0:     0x7f25e6492846 - <<std[5a41d20a063701f0]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[cb6dd95fb6db39b2]::fmt::Display>::fmt
   1:     0x7f25e6a0ad23 - core[cb6dd95fb6db39b2]::fmt::write
   2:     0x7f25e64a7ccc - <std[5a41d20a063701f0]::sys::stdio::unix::Stderr as core[cb6dd95fb6db39b2]::io::write::Write>::write_fmt
   3:     0x7f25e6465c9a - std[5a41d20a063701f0]::panicking::default_hook::{closure#0}
   4:     0x7f25e6486af3 - std[5a41d20a063701f0]::panicking::default_hook
   5:     0x7f25e54085da - std[5a41d20a063701f0]::panicking::update_hook::<alloc[7eac85f6001fa66c]::boxed::Box<rustc_driver_impl[be15a1de4f8adf7c]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f25e6486f92 - std[5a41d20a063701f0]::panicking::panic_with_hook
   7:     0x7f25e6465d52 - std[5a41d20a063701f0]::panicking::panic_handler::{closure#0}
   8:     0x7f25e645cc39 - std[5a41d20a063701f0]::sys::backtrace::__rust_end_short_backtrace::<std[5a41d20a063701f0]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f25e646775d - __rustc[d7d9a081177ff67c]::rust_begin_unwind
  10:     0x7f25e316f23c - core[cb6dd95fb6db39b2]::panicking::panic_fmt
  11:     0x7f25e4d8f703 - core[cb6dd95fb6db39b2]::panicking::assert_failed_inner
  12:     0x7f25d357bde9 - core[cb6dd95fb6db39b2]::panicking::assert_failed::<bool, bool>
  13:     0x7f25d357d2b8 - <cranelift_module[2eb1bc0d7108a86c]::module::ModuleDeclarations>::declare_data
  14:     0x7f25d353ac23 - <cranelift_object[bb96b36a0857ccef]::backend::ObjectModule as cranelift_module[2eb1bc0d7108a86c]::module::Module>::declare_data
  15:     0x7f25d34ecee9 - rustc_codegen_cranelift[24e9fc91d79ce9ea]::constant::data_id_for_static
  16:     0x7f25d34df2f2 - rustc_codegen_cranelift[24e9fc91d79ce9ea]::base::codegen_fn_body
  17:     0x7f25d350627c - rustc_codegen_cranelift[24e9fc91d79ce9ea]::driver::aot::codegen_cgu
  18:     0x7f25d34aa42e - <rustc_codegen_cranelift[24e9fc91d79ce9ea]::driver::aot::AotDriver as rustc_codegen_ssa[a93c6d9b7850f4fb]::traits::backend::ExtraBackendMethods>::compile_codegen_unit::{closure#0}
  19:     0x7f25d35143fe - <rustc_codegen_cranelift[24e9fc91d79ce9ea]::driver::aot::AotDriver as rustc_codegen_ssa[a93c6d9b7850f4fb]::traits::backend::ExtraBackendMethods>::compile_codegen_unit
  20:     0x7f25d3479882 - rustc_codegen_ssa[a93c6d9b7850f4fb]::base::codegen_crate::<rustc_codegen_cranelift[24e9fc91d79ce9ea]::driver::aot::AotDriver, rustc_codegen_cranelift[24e9fc91d79ce9ea]::driver::aot::AotModule>
  21:     0x7f25d35233cf - <rustc_codegen_cranelift[24e9fc91d79ce9ea]::CraneliftCodegenBackend as rustc_codegen_ssa[a93c6d9b7850f4fb]::traits::backend::CodegenBackend>::codegen_crate
  22:     0x7f25e7c879cc - <rustc_interface[727e6560ae5ab0f8]::queries::Linker>::codegen_and_build_linker
  23:     0x7f25e7c7f395 - rustc_interface[727e6560ae5ab0f8]::interface::run_compiler::<(), rustc_driver_impl[be15a1de4f8adf7c]::run_compiler::{closure#0}>::{closure#2}
  24:     0x7f25e7cae7a4 - std[5a41d20a063701f0]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[727e6560ae5ab0f8]::util::run_in_thread_with_globals<rustc_interface[727e6560ae5ab0f8]::util::run_in_thread_pool_with_globals<rustc_interface[727e6560ae5ab0f8]::interface::run_compiler<(), rustc_driver_impl[be15a1de4f8adf7c]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  25:     0x7f25e7cae56d - <std[5a41d20a063701f0]::thread::lifecycle::spawn_unchecked<rustc_interface[727e6560ae5ab0f8]::util::run_in_thread_with_globals<rustc_interface[727e6560ae5ab0f8]::util::run_in_thread_pool_with_globals<rustc_interface[727e6560ae5ab0f8]::interface::run_compiler<(), rustc_driver_impl[be15a1de4f8adf7c]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[cb6dd95fb6db39b2]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  26:     0x7f25e7cab807 - <std[5a41d20a063701f0]::sys::thread::unix::Thread>::new::thread_start
  27:     0x7f25e1297739 - <unknown>
  28:     0x7f25e131bedc - <unknown>
  29:                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 `/tmp/cr/rustc-ice-2026-08-15T09_56_24-1824987.txt` to your bug report

note: rustc 1.99.0-nightly (d453bdd8f 2026-08-14) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z codegen-backend=cranelift

query stack during panic:
end of query stack
stmt _1 = &/*tls*/ C
fn main() -> () {
    let mut _0: ();
    let mut _1: *const u64;
    let mut _2: *const ();
    let mut _3: usize;
    let mut _4: usize;
    let mut _5: usize;
    let mut _6: bool;
    let mut _7: *const ();
    let mut _8: usize;
    let mut _9: bool;
    let mut _10: bool;
    let mut _11: bool;
    let mut _12: bool;

    bb0: {
        _1 = &/*tls*/ C;
        _2 = copy _1 as *const () (PtrToPtr);
        _3 = copy _2 as usize (Transmute);
        _4 = Sub(const <u64 as std::mem::SizedTypeProperties>::ALIGN, const 1_usize);
        _5 = BitAnd(copy _3, copy _4);
        _6 = Eq(copy _5, const 0_usize);
        assert(copy _6, "misaligned pointer dereference: address must be a multiple of {} but is {}", const <u64 as std::mem::SizedTypeProperties>::ALIGN, copy _3) -> [success: bb1, unwind unreachable];
    }

    bb1: {
        _7 = copy _1 as *const () (PtrToPtr);
        _8 = copy _7 as usize (Transmute);
        _9 = Ne(const <u64 as std::mem::SizedTypeProperties>::SIZE, const 0_usize);
        _10 = Eq(copy _8, const 0_usize);
        _11 = BitAnd(copy _10, copy _9);
        _12 = Not(copy _11);
        assert(copy _12, "null pointer dereference occurred") -> [success: bb2, unwind unreachable];
    }

    bb2: {
        return;
    }
}

warning: 1 warning emitted

rustc 1.99.0-nightly (d453bdd8f 2026-08-14)
binary: rustc
commit-hash: d453bdd8f092d099bc336f0bda4163f809ad18e0
commit-date: 2026-08-14
host: x86_64-unknown-linux-gnu
release: 1.99.0-nightly
LLVM version: 23.1.0