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rustc_symbol_mangling: use core's disambiguator for internal symbols #164693

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rustc_symbol_mangling: use core's disambiguator for internal symbols #164693

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2543dc0
use core's disambiguator for internal symbols
Darksonn Oct 21, 2026
de147c9
simplify logic by skipping disambiguator if there's no Sized trait
Darksonn Oct 21, 2026
9a95360
Unwrap if the Sized trait is missing
Darksonn Oct 21, 2026
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26 changes: 13 additions & 13 deletions compiler/rustc_symbol_mangling/src/v0.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
use std::fmt::Write;
use std::hash::Hasher;
use std::iter;
use std::ops::Range;

Expand All @@ -8,8 +7,6 @@ use rustc_data_structures::base_n::ToBaseN;
use rustc_data_structures::either::Either;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::intern::Interned;
use rustc_data_structures::stable_hash::StableHasher;
use rustc_hashes::Hash64;
use rustc_hir as hir;
use rustc_hir::def::CtorKind;
use rustc_hir::def_id::{CrateNum, DefId};
Expand Down Expand Up @@ -154,16 +151,19 @@ pub fn mangle_internal_symbol<'tcx>(tcx: TyCtxt<'tcx>, item_name: &str) -> Strin
|p| {
p.push("C");
p.push_disambiguator({
let mut hasher = StableHasher::new();
// Incorporate the rustc version to ensure #[rustc_std_internal_symbol] functions
// get a different symbol name depending on the rustc version.
//
// RUSTC_FORCE_RUSTC_VERSION is ignored here as otherwise different we would get an
// abi incompatibility with the standard library.
hasher.write(tcx.sess.cfg_version.as_bytes());

let hash: Hash64 = hasher.finish();
hash.as_u64()
let core = tcx
.lang_items()
.sized_trait()
// The Sized trait is guaranteed to exist at this point. If you try to define
// any function or static without defining the Sized trait you will get an error
// during type checking.
.expect("#[rustc_std_internal_symbol] requires the Sized trait to be defined")
.krate;

// Use the same disambiguator as 'core' to ensure #[rustc_std_internal_symbol]
// functions get a different symbol name depending on the rustc version and
// -Cmetadata flags.
tcx.stable_crate_id(core).as_u64()
});
p.push_ident("__rustc");
Ok(())
Expand Down
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