Mangle personality symbol by Noratrieb · Pull Request #148413 · rust-lang/rust

Noratrieb · 2025-11-02T20:29:43Z

Previously, std-internal symbols (like __rust_alloc or rust_panic) were changed to now be mangled via a v0 scheme with the compiler version hash (_RNvCs4CIB29Id3dw_7___rustc10rust_panic) to make it possible to have multiple staticlibs (as long as they have different version hashes) in the same program without symbol conflicts. But the personality function remained unmangled, because LLVM hardcodes that name.

I made a change in LLVM llvm/llvm-project#166095 that makes LLVM now check the suffix instead of an exact match, so we can mangle the personality function with this scheme.

This removes the last completely unmangled symbol from Rust staticlibs! (though the mangling is still quite weak, so it's still not as nice as it would ideally be).

Before, on a trivial staticlib:

readelf -s liblib.a | rg GLOBAL | rg -v " UND | HIDDEN " | rg -v ' _ZN'
     8: 0000000000000000     5 FUNC    GLOBAL DEFAULT     3 _RNvCseCSg29WUqSe_7___rustc12___rust_alloc
    10: 0000000000000000     5 FUNC    GLOBAL DEFAULT     5 _RNvCseCSg29WUqSe_7___rustc14___rust_dealloc
    12: 0000000000000000     5 FUNC    GLOBAL DEFAULT     7 _RNvCseCSg29WUqSe_7___rustc14___rust_realloc
    14: 0000000000000000     5 FUNC    GLOBAL DEFAULT     9 _RNvCseCSg29WUqSe_7___rustc19___rust_alloc_zeroed
    16: 0000000000000000     3 FUNC    GLOBAL DEFAULT    11 _RNvCseCSg29WUqSe_7___rustc42___rust_alloc_error_handler_should_panic_v2
    17: 0000000000000000     1 FUNC    GLOBAL DEFAULT    12 _RNvCseCSg29WUqSe_7___rustc35___rust_no_alloc_shim_is_unstable_v2
  3383: 0000000000000000   111 FUNC    GLOBAL DEFAULT     5 _RNvCseCSg29WUqSe_7___rustc10rust_panic
  3387: 0000000000000000    93 FUNC    GLOBAL DEFAULT     7 _RNvCseCSg29WUqSe_7___rustc11___rdl_alloc
  3390: 0000000000000000    10 FUNC    GLOBAL DEFAULT     9 _RNvCseCSg29WUqSe_7___rustc12___rust_abort
  3391: 0000000000000000     6 FUNC    GLOBAL DEFAULT    11 _RNvCseCSg29WUqSe_7___rustc13___rdl_dealloc
  3393: 0000000000000000   167 FUNC    GLOBAL DEFAULT    13 _RNvCseCSg29WUqSe_7___rustc13___rdl_realloc
  3396: 0000000000000000   203 FUNC    GLOBAL DEFAULT    15 _RNvCseCSg29WUqSe_7___rustc17___rust_drop_panic
  3399: 0000000000000000    29 FUNC    GLOBAL DEFAULT    18 _RNvCseCSg29WUqSe_7___rustc17rust_begin_unwind
  3401: 0000000000000000   140 FUNC    GLOBAL DEFAULT    20 _RNvCseCSg29WUqSe_7___rustc18___rdl_alloc_zeroed
  3404: 0000000000000000   203 FUNC    GLOBAL DEFAULT    22 _RNvCseCSg29WUqSe_7___rustc24___rust_foreign_exception
  3405: 0000000000000000    19 FUNC    GLOBAL DEFAULT    25 _RNvCseCSg29WUqSe_7___rustc26___rust_alloc_error_handler
  4410: 0000000000000000  1471 FUNC    GLOBAL DEFAULT   2752 rust_eh_personality
    25: 0000000000000000   161 FUNC    GLOBAL DEFAULT     5 _RNvCseCSg29WUqSe_7___rustc18___rust_start_panic
    32: 0000000000000000    82 FUNC    GLOBAL DEFAULT     8 _RNvCseCSg29WUqSe_7___rustc20___rust_panic_cleanup
   249: 0000000000000000   182 FUNC    GLOBAL DEFAULT     5 _RNvCseCSg29WUqSe_7___rustc25___rdl_alloc_error_handler
     3: 0000000000000000    57 FUNC    GLOBAL DEFAULT     3 _RNvCseCSg29WUqSe_7___rustc17___rust_probestack

After:

     8: 0000000000000000     5 FUNC    GLOBAL DEFAULT     3 _RNvCs4CIB29Id3dw_7___rustc12___rust_alloc
    10: 0000000000000000     5 FUNC    GLOBAL DEFAULT     5 _RNvCs4CIB29Id3dw_7___rustc14___rust_dealloc
    12: 0000000000000000     5 FUNC    GLOBAL DEFAULT     7 _RNvCs4CIB29Id3dw_7___rustc14___rust_realloc
    14: 0000000000000000     5 FUNC    GLOBAL DEFAULT     9 _RNvCs4CIB29Id3dw_7___rustc19___rust_alloc_zeroed
    16: 0000000000000000     3 FUNC    GLOBAL DEFAULT    11 _RNvCs4CIB29Id3dw_7___rustc42___rust_alloc_error_handler_should_panic_v2
    17: 0000000000000000     1 FUNC    GLOBAL DEFAULT    12 _RNvCs4CIB29Id3dw_7___rustc35___rust_no_alloc_shim_is_unstable_v2
   422: 0000000000000000    19 FUNC    GLOBAL DEFAULT     5 _RNvCs4CIB29Id3dw_7___rustc26___rust_alloc_error_handler
   429: 0000000000000000   308 FUNC    GLOBAL DEFAULT     5 _RNvCs4CIB29Id3dw_7___rustc19rust_eh_personality
   349: 0000000000000000    10 FUNC    GLOBAL DEFAULT     5 _RNvCs4CIB29Id3dw_7___rustc12___rust_abort
   164: 0000000000000000    93 FUNC    GLOBAL DEFAULT     5 _RNvCs4CIB29Id3dw_7___rustc11___rdl_alloc
   167: 0000000000000000    11 FUNC    GLOBAL DEFAULT     7 _RNvCs4CIB29Id3dw_7___rustc13___rdl_dealloc
   169: 0000000000000000   167 FUNC    GLOBAL DEFAULT     9 _RNvCs4CIB29Id3dw_7___rustc13___rdl_realloc
   172: 0000000000000000   140 FUNC    GLOBAL DEFAULT    11 _RNvCs4CIB29Id3dw_7___rustc18___rdl_alloc_zeroed
   688: 0000000000000000   106 FUNC    GLOBAL DEFAULT     5 _RNvCs4CIB29Id3dw_7___rustc10rust_panic
   693: 0000000000000000   207 FUNC    GLOBAL DEFAULT     7 _RNvCs4CIB29Id3dw_7___rustc17___rust_drop_panic
   696: 0000000000000000    29 FUNC    GLOBAL DEFAULT    10 _RNvCs4CIB29Id3dw_7___rustc17rust_begin_unwind
   698: 0000000000000000   207 FUNC    GLOBAL DEFAULT    12 _RNvCs4CIB29Id3dw_7___rustc24___rust_foreign_exception
    26: 0000000000000000   161 FUNC    GLOBAL DEFAULT     5 _RNvCs4CIB29Id3dw_7___rustc18___rust_start_panic
    33: 0000000000000000    82 FUNC    GLOBAL DEFAULT     8 _RNvCs4CIB29Id3dw_7___rustc20___rust_panic_cleanup
    88: 0000000000000000   182 FUNC    GLOBAL DEFAULT     5 _RNvCs4CIB29Id3dw_7___rustc25___rdl_alloc_error_handler
     3: 0000000000000000    57 FUNC    GLOBAL DEFAULT     3 _RNvCs4CIB29Id3dw_7___rustc17___rust_probestack

r? bjorn3

rustbot · 2025-11-02T20:29:47Z

Some changes occurred in compiler/rustc_codegen_ssa

cc @WaffleLapkin

workingjubilee · 2025-11-03T07:59:36Z

re: LLVM version-detection, do you mean llvm_util::get_version() or?

LLVM needs to figure out the type of EH personality for various reasons. To do this, it currently matches against a hardcoded list of names. In Rust, we would like to mangle our personality function to better support linking multiple Rust standard libraries via staticlib. We have currently mangled all symbols except the personality, which remains unmangled because of this LLVM hardcoding. Instead, this now does a suffix match of the personality name, which will work with the mangling scheme used for these internal symbols (e.g. `_RNvCseCSg29WUqSe_7___rustc12___rust_alloc`). Companion Rust PR: rust-lang/rust#148413

…efix (#166095) LLVM needs to figure out the type of EH personality for various reasons. To do this, it currently matches against a hardcoded list of names. In Rust, we would like to mangle our personality function to better support linking multiple Rust standard libraries via staticlib. We have currently mangled all symbols except the personality, which remains unmangled because of this LLVM hardcoding. Instead, this now does a suffix match of the personality name, which will work with the mangling scheme used for these internal symbols (e.g. `_RNvCseCSg29WUqSe_7___rustc12___rust_alloc`). Companion Rust PR: rust-lang/rust#148413

rustbot · 2026-10-04T15:44:11Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

fee1-dead · 2026-10-04T19:09:03Z

This overall LGTM, however I cannot know of things that I should check or pay attention to (since it is not my expertise), so rerolling

@rustbot reroll

petrochenkov · 2026-10-14T15:44:36Z

Can this theoretically break some stable no_std code that previously used stable no_mangle to define a personality function, but now will have to use some other unstable attribute to do the same (similarly to the changes in tests)?
@rustbot author

bjorn3 · 2026-10-14T16:37:11Z

Yes it can. Such code has been using unstable implementation details either way. We would just start requiring that the no_std projects acknowledge this. In any case if you are compiling for a no_std target, then the standard library would already be compiled with panic=abort and no personality function would be needed unless you use extern "C-unwind" somewhere. So only no_std projects compiling for std targets are likely to break because of this change.

petrochenkov · 2026-10-15T10:59:23Z

@bors r+

rust-bors · 2026-10-15T10:59:26Z

📌 Commit 2233d39 has been approved by petrochenkov

It is now in the queue for this repository.

…uwer Rollup of 14 pull requests Successful merges: - #163132 (Test panics and wasm32-wasip3 in CI, not wasip1) - #164314 (Abby: use a smallvec for `And`/`Or` constraints) - #148413 (Mangle personality symbol) - #163688 (Add aarch64-unknown-qtee as a tier 3 target) - #164076 (Fix ICE when move expressions reference out-of-scope local bindings) - #164327 ([coff] Symbol renaming stored the original name, not the undecorated name) - #162432 (Improve diagnostics for non-well-formed associated items) - #164138 (cg_llvm: Use a callback to enforce scoped lifetimes in ModuleLlvm ) - #164210 (`incomplete` -> `unstable` for delegation feature) - #164225 (Point at assoc item for trait that needs to be implemented) - #164278 (Output remapped paths in rustdoc JSON with the `documentation` scope) - #164308 (format abby dsl errors better) - #164335 (expand and document tool attribute shadowing test) - #164342 (Use regular type parsing for argument-position const parameters)

Rollup merge of #148413 - Noratrieb:mangle-rust-eh-personality, r=petrochenkov Mangle personality symbol Previously, std-internal symbols (like `__rust_alloc` or `rust_panic`) were changed to now be mangled via a v0 scheme with the compiler version hash (`_RNvCs4CIB29Id3dw_7___rustc10rust_panic`) to make it possible to have multiple staticlibs (as long as they have different version hashes) in the same program without symbol conflicts. But the personality function remained unmangled, because LLVM hardcodes that name. I made a change in LLVM llvm/llvm-project#166095 that makes LLVM now check the suffix instead of an exact match, so we can mangle the personality function with this scheme. This removes the last completely unmangled symbol from Rust staticlibs! (though the mangling is still quite weak, so it's still not as nice as it would ideally be). Before, on a trivial staticlib: ``` readelf -s liblib.a | rg GLOBAL | rg -v " UND | HIDDEN " | rg -v ' _ZN' 8: 0000000000000000 5 FUNC GLOBAL DEFAULT 3 _RNvCseCSg29WUqSe_7___rustc12___rust_alloc 10: 0000000000000000 5 FUNC GLOBAL DEFAULT 5 _RNvCseCSg29WUqSe_7___rustc14___rust_dealloc 12: 0000000000000000 5 FUNC GLOBAL DEFAULT 7 _RNvCseCSg29WUqSe_7___rustc14___rust_realloc 14: 0000000000000000 5 FUNC GLOBAL DEFAULT 9 _RNvCseCSg29WUqSe_7___rustc19___rust_alloc_zeroed 16: 0000000000000000 3 FUNC GLOBAL DEFAULT 11 _RNvCseCSg29WUqSe_7___rustc42___rust_alloc_error_handler_should_panic_v2 17: 0000000000000000 1 FUNC GLOBAL DEFAULT 12 _RNvCseCSg29WUqSe_7___rustc35___rust_no_alloc_shim_is_unstable_v2 3383: 0000000000000000 111 FUNC GLOBAL DEFAULT 5 _RNvCseCSg29WUqSe_7___rustc10rust_panic 3387: 0000000000000000 93 FUNC GLOBAL DEFAULT 7 _RNvCseCSg29WUqSe_7___rustc11___rdl_alloc 3390: 0000000000000000 10 FUNC GLOBAL DEFAULT 9 _RNvCseCSg29WUqSe_7___rustc12___rust_abort 3391: 0000000000000000 6 FUNC GLOBAL DEFAULT 11 _RNvCseCSg29WUqSe_7___rustc13___rdl_dealloc 3393: 0000000000000000 167 FUNC GLOBAL DEFAULT 13 _RNvCseCSg29WUqSe_7___rustc13___rdl_realloc 3396: 0000000000000000 203 FUNC GLOBAL DEFAULT 15 _RNvCseCSg29WUqSe_7___rustc17___rust_drop_panic 3399: 0000000000000000 29 FUNC GLOBAL DEFAULT 18 _RNvCseCSg29WUqSe_7___rustc17rust_begin_unwind 3401: 0000000000000000 140 FUNC GLOBAL DEFAULT 20 _RNvCseCSg29WUqSe_7___rustc18___rdl_alloc_zeroed 3404: 0000000000000000 203 FUNC GLOBAL DEFAULT 22 _RNvCseCSg29WUqSe_7___rustc24___rust_foreign_exception 3405: 0000000000000000 19 FUNC GLOBAL DEFAULT 25 _RNvCseCSg29WUqSe_7___rustc26___rust_alloc_error_handler 4410: 0000000000000000 1471 FUNC GLOBAL DEFAULT 2752 rust_eh_personality 25: 0000000000000000 161 FUNC GLOBAL DEFAULT 5 _RNvCseCSg29WUqSe_7___rustc18___rust_start_panic 32: 0000000000000000 82 FUNC GLOBAL DEFAULT 8 _RNvCseCSg29WUqSe_7___rustc20___rust_panic_cleanup 249: 0000000000000000 182 FUNC GLOBAL DEFAULT 5 _RNvCseCSg29WUqSe_7___rustc25___rdl_alloc_error_handler 3: 0000000000000000 57 FUNC GLOBAL DEFAULT 3 _RNvCseCSg29WUqSe_7___rustc17___rust_probestack ``` After: ``` 8: 0000000000000000 5 FUNC GLOBAL DEFAULT 3 _RNvCs4CIB29Id3dw_7___rustc12___rust_alloc 10: 0000000000000000 5 FUNC GLOBAL DEFAULT 5 _RNvCs4CIB29Id3dw_7___rustc14___rust_dealloc 12: 0000000000000000 5 FUNC GLOBAL DEFAULT 7 _RNvCs4CIB29Id3dw_7___rustc14___rust_realloc 14: 0000000000000000 5 FUNC GLOBAL DEFAULT 9 _RNvCs4CIB29Id3dw_7___rustc19___rust_alloc_zeroed 16: 0000000000000000 3 FUNC GLOBAL DEFAULT 11 _RNvCs4CIB29Id3dw_7___rustc42___rust_alloc_error_handler_should_panic_v2 17: 0000000000000000 1 FUNC GLOBAL DEFAULT 12 _RNvCs4CIB29Id3dw_7___rustc35___rust_no_alloc_shim_is_unstable_v2 422: 0000000000000000 19 FUNC GLOBAL DEFAULT 5 _RNvCs4CIB29Id3dw_7___rustc26___rust_alloc_error_handler 429: 0000000000000000 308 FUNC GLOBAL DEFAULT 5 _RNvCs4CIB29Id3dw_7___rustc19rust_eh_personality 349: 0000000000000000 10 FUNC GLOBAL DEFAULT 5 _RNvCs4CIB29Id3dw_7___rustc12___rust_abort 164: 0000000000000000 93 FUNC GLOBAL DEFAULT 5 _RNvCs4CIB29Id3dw_7___rustc11___rdl_alloc 167: 0000000000000000 11 FUNC GLOBAL DEFAULT 7 _RNvCs4CIB29Id3dw_7___rustc13___rdl_dealloc 169: 0000000000000000 167 FUNC GLOBAL DEFAULT 9 _RNvCs4CIB29Id3dw_7___rustc13___rdl_realloc 172: 0000000000000000 140 FUNC GLOBAL DEFAULT 11 _RNvCs4CIB29Id3dw_7___rustc18___rdl_alloc_zeroed 688: 0000000000000000 106 FUNC GLOBAL DEFAULT 5 _RNvCs4CIB29Id3dw_7___rustc10rust_panic 693: 0000000000000000 207 FUNC GLOBAL DEFAULT 7 _RNvCs4CIB29Id3dw_7___rustc17___rust_drop_panic 696: 0000000000000000 29 FUNC GLOBAL DEFAULT 10 _RNvCs4CIB29Id3dw_7___rustc17rust_begin_unwind 698: 0000000000000000 207 FUNC GLOBAL DEFAULT 12 _RNvCs4CIB29Id3dw_7___rustc24___rust_foreign_exception 26: 0000000000000000 161 FUNC GLOBAL DEFAULT 5 _RNvCs4CIB29Id3dw_7___rustc18___rust_start_panic 33: 0000000000000000 82 FUNC GLOBAL DEFAULT 8 _RNvCs4CIB29Id3dw_7___rustc20___rust_panic_cleanup 88: 0000000000000000 182 FUNC GLOBAL DEFAULT 5 _RNvCs4CIB29Id3dw_7___rustc25___rdl_alloc_error_handler 3: 0000000000000000 57 FUNC GLOBAL DEFAULT 3 _RNvCs4CIB29Id3dw_7___rustc17___rust_probestack ``` r? bjorn3

Since rust-lang/rust#148413 (in nightly 2026-10-16) the compiler mangles the personality symbol like the other std-internal symbols, so the pre-built `core`/`alloc` now reference `__rustc::rust_eh_personality` and the `#[no_mangle] extern "C" fn rust_eh_personality()` in no_std_test no longer satisfies the linker: error: linking with `cc` failed = note: Undefined symbols for architecture arm64: "__RNvCs6EUDi8WbMwz_7___rustc19rust_eh_personality" Every NoStdBuild job has failed with this since that nightly, on every branch. Declare the function as `#[lang = "eh_personality"]` instead (with `#![feature(lang_items)]`), the shape rust-lang/rust's own no_std binary fixture (tests/run-make/no-alloc-shim/foo.rs) moved to in that PR. The compiler then emits the symbol under whatever name it expects, so this builds on the nightlies before and after the change. The routine is still never called: every profile sets `panic = "abort"`. Built with nightly 2026-10-16 (fails without this change) and nightly 2026-10-09 (builds either way), `--profile unix` and `--profile macos`.

…uwer Rollup of 14 pull requests Successful merges: - rust-lang/rust#163132 (Test panics and wasm32-wasip3 in CI, not wasip1) - rust-lang/rust#164314 (Abby: use a smallvec for `And`/`Or` constraints) - rust-lang/rust#148413 (Mangle personality symbol) - rust-lang/rust#163688 (Add aarch64-unknown-qtee as a tier 3 target) - rust-lang/rust#164076 (Fix ICE when move expressions reference out-of-scope local bindings) - rust-lang/rust#164327 ([coff] Symbol renaming stored the original name, not the undecorated name) - rust-lang/rust#162432 (Improve diagnostics for non-well-formed associated items) - rust-lang/rust#164138 (cg_llvm: Use a callback to enforce scoped lifetimes in ModuleLlvm ) - rust-lang/rust#164210 (`incomplete` -> `unstable` for delegation feature) - rust-lang/rust#164225 (Point at assoc item for trait that needs to be implemented) - rust-lang/rust#164278 (Output remapped paths in rustdoc JSON with the `documentation` scope) - rust-lang/rust#164308 (format abby dsl errors better) - rust-lang/rust#164335 (expand and document tool attribute shadowing test) - rust-lang/rust#164342 (Use regular type parsing for argument-position const parameters)

rustbot assigned bjorn3 Nov 2, 2025

Noratrieb marked this pull request as draft November 2, 2025 20:29

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 2, 2025

Noratrieb mentioned this pull request Nov 2, 2025

[llvm] Allow Rust personality name to contain arbitrary prefix llvm/llvm-project#166095

Merged