Skip to content

Comments

For panic=unwind on Wasm targets, define __cpp_exception tag#152241

Merged
rust-bors[bot] merged 1 commit intorust-lang:mainfrom
hoodmane:wasm-unwind-link-cpp-exception
Feb 21, 2026
Merged

For panic=unwind on Wasm targets, define __cpp_exception tag#152241
rust-bors[bot] merged 1 commit intorust-lang:mainfrom
hoodmane:wasm-unwind-link-cpp-exception

Conversation

@hoodmane
Copy link
Contributor

@hoodmane hoodmane commented Feb 6, 2026 •
edited
Loading

Since llvm/llvm-project#159143, llvm no longer weak links the __cpp_exception tag into each object that uses it. They are now defined in compiler-rt. Rust doesn't seem to get them from compiler-rt so llvm decides they need to be imported. This adds them to libunwind.

Same changes applied to compiler-builtins: rust-lang/compiler-builtins#1077

See wasm-bindgen/wasm-bindgen#4938 for a downstream workaround.

cc @sbc100

@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 6, 2026
@rustbot
Copy link
Collaborator

rustbot commented Feb 6, 2026

r? @Mark-Simulacrum

rustbot has assigned @Mark-Simulacrum.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

  • Fallback group: @Mark-Simulacrum, @jieyouxu
  • @Mark-Simulacrum, @jieyouxu expanded to Mark-Simulacrum, jieyouxu
  • Random selection from Mark-Simulacrum, jieyouxu

sbc100
sbc100 reviewed Feb 6, 2026
View reviewed changes
@hoodmane hoodmane force-pushed the wasm-unwind-link-cpp-exception branch from bef9d13 to 82fbfa6 Compare February 6, 2026 21:39
@rustbot
Copy link
Collaborator

rustbot commented Feb 6, 2026

Some changes occurred in src/tools/compiletest

cc @jieyouxu

compiler-builtins is developed in its own repository. If possible, consider making this change to rust-lang/compiler-builtins instead.

cc @tgross35

@rustbot rustbot added A-compiler-builtins Area: compiler-builtins (https://github.com/rust-lang/compiler-builtins) A-compiletest Area: The compiletest test runner A-run-make Area: port run-make Makefiles to rmake.rs A-testsuite Area: The testsuite used to check the correctness of rustc T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Feb 6, 2026
@tgross35
Copy link
Contributor

tgross35 commented Feb 6, 2026

compiler-builtins is developed in its own repository. If possible, consider making this change to rust-lang/compiler-builtins instead.

cc @tgross35

Since this is a nontrivial change, please do file it to the compiler-builtins repo

@hoodmane
Copy link
Contributor Author

hoodmane commented Feb 6, 2026 •
edited
Loading

Do I make it in both places? It's not clear if the test would work in compiler-builtins.

@hoodmane hoodmane mentioned this pull request Feb 6, 2026
Closed
@hoodmane
Copy link
Contributor Author

hoodmane commented Feb 6, 2026

Opened rust-lang/compiler-builtins#1077.

@hoodmane hoodmane force-pushed the wasm-unwind-link-cpp-exception branch from 82fbfa6 to 160ebdb Compare February 6, 2026 23:06
@Mark-Simulacrum
Copy link
Member

Mark-Simulacrum commented Feb 8, 2026

r? @tgross35

But I suspect this should be closed in favor of the compiler-builtins PR.

@rustbot rustbot assigned tgross35 and unassigned Mark-Simulacrum Feb 8, 2026
@rustbot
Copy link
Collaborator

rustbot commented Feb 8, 2026

tgross35 is currently at their maximum review capacity.
They may take a while to respond.

@hoodmane
Copy link
Contributor Author

hoodmane commented Feb 8, 2026

Seems like over there @alexcrichton is saying I should move this back to libunwind like what I had before so it seems that the compiler-builtins pr is going to be closed in favor of a modified version of this one.

@tgross35
Copy link
Contributor

tgross35 commented Feb 9, 2026

Do I make it in both places? It's not clear if the test would work in compiler-builtins.

Sorry, missed this bit - c-b changes go through that repo and only need to be made there, then they get synced back to this repo. Then this PR would just add the test.

(The reason to prefer doing things in the c-b repo is because CI there does a lot more)

@hoodmane hoodmane force-pushed the wasm-unwind-link-cpp-exception branch 2 times, most recently from 010353f to 3e57ee9 Compare February 9, 2026 16:50
alexcrichton
alexcrichton reviewed Feb 9, 2026
View reviewed changes
@alexcrichton
Copy link
Member

alexcrichton commented Feb 9, 2026

@hoodmane would you also be up for extending the target-specific documentation to discuss this ABI detail? Doesn't need to be too in-depth necessarily but at least mentioning it and saying how it relates to WASI/Emscripten I think could be valuable

@hoodmane
For panic=unwind on Wasm targets, define __cpp_exception tag
1cd345b 
Since llvm/llvm-project 159143, llvm no longer weak links the __cpp_exception tag into
each object that uses it. They are now defined in compiler-rt. Rust doesn't seem to
get them from compiler-rt so llvm decides they need to be imported. This adds them to
libunwind.
@hoodmane
Copy link
Contributor Author

hoodmane commented Feb 19, 2026

Okay @alexcrichton I applied those changes.

@hoodmane hoodmane force-pushed the wasm-unwind-link-cpp-exception branch from 3e57ee9 to 1cd345b Compare February 19, 2026 10:39
@rustbot
Copy link
Collaborator

rustbot commented Feb 19, 2026

Some changes occurred in src/doc/rustc/src/platform-support

cc @Noratrieb

@alexcrichton
Copy link
Member

alexcrichton commented Feb 20, 2026

@bors r+

@rust-bors
Copy link
Contributor

rust-bors bot commented Feb 20, 2026

📌 Commit 1cd345b has been approved by alexcrichton

It is now in the queue for this repository.

@rust-bors rust-bors bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 20, 2026
@JonathanBrouwer JonathanBrouwer mentioned this pull request Feb 20, 2026
Merged
@tgross35 tgross35 assigned alexcrichton and unassigned tgross35 Feb 20, 2026
rust-bors bot pushed a commit that referenced this pull request Feb 21, 2026
@bors
Auto merge of #152924 - JonathanBrouwer:rollup-vnwkCh0, r=JonathanBro…
1c00e98 
…uwer

Rollup of 9 pull requests

Successful merges:

 - #146832 (Not linting irrefutable_let_patterns on let chains)
 - #146972 (Support importing path-segment keyword with renaming)
 - #152241 (For panic=unwind on Wasm targets, define __cpp_exception tag)
 - #152527 (Remove -Zemit-thin-lto flag)
 - #152769 (Do not cancel try builds after first job failure)
 - #152907 (Add tests for delegation generics)
 - #152455 (Remove the translation `-Z` options and the `Translator` type. )
 - #152813 (Skip the `use_existential_projection_new_instead` field in the `Debug` impl)
 - #152912 (Expose Span for all DefIds in rustc_public)
@rust-bors rust-bors bot merged commit 1706756 into rust-lang:main Feb 21, 2026
11 checks passed
@rustbot rustbot added this to the 1.95.0 milestone Feb 21, 2026
rust-timer added a commit that referenced this pull request Feb 21, 2026
@rust-timer
Unrolled build for #152241
6526668 
Rollup merge of #152241 - hoodmane:wasm-unwind-link-cpp-exception, r=alexcrichton

For panic=unwind on Wasm targets, define __cpp_exception tag

Since llvm/llvm-project#159143, llvm no longer weak links the __cpp_exception tag into each object that uses it. They are now defined in compiler-rt. Rust doesn't seem to get them from compiler-rt so llvm decides they need to be imported. This adds them to libunwind.

Same changes applied to compiler-builtins: rust-lang/compiler-builtins#1077

See wasm-bindgen/wasm-bindgen#4938 for a downstream workaround.

cc @sbc100
github-actions bot pushed a commit to rust-lang/miri that referenced this pull request Feb 22, 2026
@bors
Auto merge of #152924 - JonathanBrouwer:rollup-vnwkCh0, r=JonathanBro…
1df0436 
…uwer

Rollup of 9 pull requests

Successful merges:

 - rust-lang/rust#146832 (Not linting irrefutable_let_patterns on let chains)
 - rust-lang/rust#146972 (Support importing path-segment keyword with renaming)
 - rust-lang/rust#152241 (For panic=unwind on Wasm targets, define __cpp_exception tag)
 - rust-lang/rust#152527 (Remove -Zemit-thin-lto flag)
 - rust-lang/rust#152769 (Do not cancel try builds after first job failure)
 - rust-lang/rust#152907 (Add tests for delegation generics)
 - rust-lang/rust#152455 (Remove the translation `-Z` options and the `Translator` type. )
 - rust-lang/rust#152813 (Skip the `use_existential_projection_new_instead` field in the `Debug` impl)
 - rust-lang/rust#152912 (Expose Span for all DefIds in rustc_public)
github-actions bot pushed a commit to rust-lang/rustc-dev-guide that referenced this pull request Feb 23, 2026
@bors
Auto merge of #152924 - JonathanBrouwer:rollup-vnwkCh0, r=JonathanBro…
ec1b20b 
…uwer

Rollup of 9 pull requests

Successful merges:

 - rust-lang/rust#146832 (Not linting irrefutable_let_patterns on let chains)
 - rust-lang/rust#146972 (Support importing path-segment keyword with renaming)
 - rust-lang/rust#152241 (For panic=unwind on Wasm targets, define __cpp_exception tag)
 - rust-lang/rust#152527 (Remove -Zemit-thin-lto flag)
 - rust-lang/rust#152769 (Do not cancel try builds after first job failure)
 - rust-lang/rust#152907 (Add tests for delegation generics)
 - rust-lang/rust#152455 (Remove the translation `-Z` options and the `Translator` type. )
 - rust-lang/rust#152813 (Skip the `use_existential_projection_new_instead` field in the `Debug` impl)
 - rust-lang/rust#152912 (Expose Span for all DefIds in rustc_public)
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@alexcrichton alexcrichton Awaiting requested review from alexcrichton

1 more reviewer

@sbc100 sbc100 sbc100 left review comments

Reviewers whose approvals may not affect merge requirements

Assignees

@alexcrichton alexcrichton

Labels

A-compiler-builtins Area: compiler-builtins (https://github.com/rust-lang/compiler-builtins) A-compiletest Area: The compiletest test runner A-run-make Area: port run-make Makefiles to rmake.rs A-testsuite Area: The testsuite used to check the correctness of rustc S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue.

Projects

None yet

Milestone

1.95.0

Development

Successfully merging this pull request may close these issues.

6 participants

@hoodmane @rustbot @tgross35 @Mark-Simulacrum @alexcrichton @sbc100