Emscripten: Turn wasm-eh on by default by hoodmane · Pull Request #147224 · rust-lang/rust

hoodmane · 2025-10-01T13:17:26Z

As specified by MCP
Resolves #148309
Resolves #112195

rustbot · 2025-10-01T13:17:32Z

rustbot has assigned @lcnr.
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

lcnr · 2025-10-01T14:07:31Z

I think this is blocked on a team decision?

hoodmane · 2025-10-01T15:20:54Z

Indeed, waiting-on-MCP is the correct description. I turned it to a draft too, but I think it can merge as is once the MCP is approved.

hoodmane · 2025-10-01T15:21:52Z

Well I guess test_unstable_options_tracking_hash will need to be updated too.

rustbot · 2025-10-30T20:40:06Z

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

cc @Noratrieb

lcnr · 2025-11-26T11:52:13Z

r? @bjorn3 as the one who approved the MCP

As specified by MCP: rust-lang/compiler-team#920 Resolves rust-lang#148309

hoodmane · 2025-12-03T23:46:39Z

Okay CI looks green now

bjorn3 · 2025-12-04T09:11:37Z

@bors r+

bors · 2025-12-04T09:11:41Z

📌 Commit f07a84f has been approved by bjorn3

It is now in the queue for this repository.

Rollup of 9 pull requests Successful merges: - #147224 (Emscripten: Turn wasm-eh on by default) - #149405 (Recover on misspelled item keyword) - #149443 (Tidying up UI tests [6/N]) - #149524 (Move attribute safety checking to attribute parsing) - #149593 (powf, powi: point out SNaN non-determinism) - #149605 (Use branch name instead of HEAD when unshallowing) - #149612 (Apply the `bors` environment also to the `outcome` job) - #149623 (Don't require a normal tool build of clippy/rustfmt when running their test steps) - #149627 (Point to the item that is incorrectly annotated with `#[diagnostic::on_const]`) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #147224 - hoodmane:wasm-eh-default-on, r=bjorn3 Emscripten: Turn wasm-eh on by default As specified by [MCP](rust-lang/compiler-team#920) Resolves #148309 Resolves #112195

Rollup of 9 pull requests Successful merges: - rust-lang/rust#147224 (Emscripten: Turn wasm-eh on by default) - rust-lang/rust#149405 (Recover on misspelled item keyword) - rust-lang/rust#149443 (Tidying up UI tests [6/N]) - rust-lang/rust#149524 (Move attribute safety checking to attribute parsing) - rust-lang/rust#149593 (powf, powi: point out SNaN non-determinism) - rust-lang/rust#149605 (Use branch name instead of HEAD when unshallowing) - rust-lang/rust#149612 (Apply the `bors` environment also to the `outcome` job) - rust-lang/rust#149623 (Don't require a normal tool build of clippy/rustfmt when running their test steps) - rust-lang/rust#149627 (Point to the item that is incorrectly annotated with `#[diagnostic::on_const]`) r? `@ghost` `@rustbot` modify labels: rollup

hoodmane · 2025-12-05T17:25:04Z

Thanks @bjorn3!

Since this commit `-Z emscripten-wasm-eh` is the default for the Rust compiler: rust-lang/rust#147224 This switches to a recent Rust nightly which includes this change. This means we don't need a custom sysroot anymore.

Rust nightly 2025-12-05 enables Wasm EH by default, see: rust-lang/rust#147224 Compile with `-Zemscripten-wasm-eh=false` to ensure compat with Node.js 16.4.

Rollup of 9 pull requests Successful merges: - rust-lang/rust#147224 (Emscripten: Turn wasm-eh on by default) - rust-lang/rust#149405 (Recover on misspelled item keyword) - rust-lang/rust#149443 (Tidying up UI tests [6/N]) - rust-lang/rust#149524 (Move attribute safety checking to attribute parsing) - rust-lang/rust#149593 (powf, powi: point out SNaN non-determinism) - rust-lang/rust#149605 (Use branch name instead of HEAD when unshallowing) - rust-lang/rust#149612 (Apply the `bors` environment also to the `outcome` job) - rust-lang/rust#149623 (Don't require a normal tool build of clippy/rustfmt when running their test steps) - rust-lang/rust#149627 (Point to the item that is incorrectly annotated with `#[diagnostic::on_const]`) r? `@ghost` `@rustbot` modify labels: rollup

This MR contains the following updates: | Package | Update | Change | |---|---|---| | [rust](https://github.com/rust-lang/rust) | minor | `1.92.0` → `1.93.0` | MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot). **Proposed changes to behavior should be submitted there as MRs.** --- ### Release Notes <details> <summary>rust-lang/rust (rust)</summary> ### [`v1.93.0`](https://github.com/rust-lang/rust/blob/HEAD/RELEASES.md#Version-1930-2026-01-22) [Compare Source](rust-lang/rust@1.92.0...1.93.0) \========================== <a id="1.93.0-Language"></a> ## Language - [Stabilize several s390x `vector`-related target features and the `is_s390x_feature_detected!` macro](rust-lang/rust#145656) - [Stabilize declaration of C-style variadic functions for the `system` ABI](rust-lang/rust#145954) - [Emit error when using some keyword as a `cfg` predicate](rust-lang/rust#146978) - [Stabilize `asm_cfg`](rust-lang/rust#147736) - [During const-evaluation, support copying pointers byte-by-byte](rust-lang/rust#148259) - [LUB coercions now correctly handle function item types, and functions with differing safeties](rust-lang/rust#148602) - [Allow `const` items that contain mutable references to `static` (which is *very* unsafe, but not *always* UB)](rust-lang/rust#148746) - [Add warn-by-default `const_item_interior_mutations` lint to warn against calls which mutate interior mutable `const` items](rust-lang/rust#148407) - [Add warn-by-default `function_casts_as_integer` lint](rust-lang/rust#141470) <a id="1.93.0-Compiler"></a> ## Compiler - [Stabilize `-Cjump-tables=bool`](rust-lang/rust#145974). The flag was previously called `-Zno-jump-tables`. <a id="1.93.0-Platform-Support"></a> ## Platform Support - [Promote `riscv64a23-unknown-linux-gnu` to Tier 2 (without host tools)](rust-lang/rust#148435) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. [platform-support-doc]: https://doc.rust-lang.org/rustc/platform-support.html <a id="1.93.0-Libraries"></a> ## Libraries - [Stop internally using `specialization` on the `Copy` trait as it is unsound in the presence of lifetime dependent `Copy` implementations. This may result in some performance regressions as some standard library APIs may now call `Clone::clone` instead of performing bitwise copies](rust-lang/rust#135634) - [Allow the global allocator to use thread-local storage and `std::thread::current()`](rust-lang/rust#144465) - [Make `BTree::append` not update existing keys when appending an entry which already exists](rust-lang/rust#145628) - [Don't require `T: RefUnwindSafe` for `vec::IntoIter<T>: UnwindSafe`](rust-lang/rust#145665) <a id="1.93.0-Stabilized-APIs"></a> ## Stabilized APIs - [`<[MaybeUninit<T>]>::assume_init_drop`](https://doc.rust-lang.org/stable/core/primitive.slice.html#method.assume_init_drop) - [`<[MaybeUninit<T>]>::assume_init_ref`](https://doc.rust-lang.org/stable/core/primitive.slice.html#method.assume_init_ref) - [`<[MaybeUninit<T>]>::assume_init_mut`](https://doc.rust-lang.org/stable/core/primitive.slice.html#method.assume_init_mut) - [`<[MaybeUninit<T>]>::write_copy_of_slice`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.write_copy_of_slice) - [`<[MaybeUninit<T>]>::write_clone_of_slice`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.write_clone_of_slice) - [`String::into_raw_parts`](https://doc.rust-lang.org/stable/std/string/struct.String.html#method.into_raw_parts) - [`Vec::into_raw_parts`](https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.into_raw_parts) - [`<iN>::unchecked_neg`](https://doc.rust-lang.org/stable/std/primitive.isize.html#method.unchecked_neg) - [`<iN>::unchecked_shl`](https://doc.rust-lang.org/stable/std/primitive.isize.html#method.unchecked_shl) - [`<iN>::unchecked_shr`](https://doc.rust-lang.org/stable/std/primitive.isize.html#method.unchecked_shr) - [`<uN>::unchecked_shl`](https://doc.rust-lang.org/stable/std/primitive.usize.html#method.unchecked_shl) - [`<uN>::unchecked_shr`](https://doc.rust-lang.org/stable/std/primitive.usize.html#method.unchecked_shr) - [`<[T]>::as_array`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_array) - [`<[T]>::as_array_mut`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_mut_array) - [`<*const [T]>::as_array`](https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.as_array) - [`<*mut [T]>::as_array_mut`](https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.as_mut_array) - [`VecDeque::pop_front_if`](https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.pop_front_if) - [`VecDeque::pop_back_if`](https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.pop_back_if) - [`Duration::from_nanos_u128`](https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_nanos_u128) - [`char::MAX_LEN_UTF8`](https://doc.rust-lang.org/stable/std/primitive.char.html#associatedconstant.MAX_LEN_UTF8) - [`char::MAX_LEN_UTF16`](https://doc.rust-lang.org/stable/std/primitive.char.html#associatedconstant.MAX_LEN_UTF16) - [`std::fmt::from_fn`](https://doc.rust-lang.org/stable/std/fmt/fn.from_fn.html) - [`std::fmt::FromFn`](https://doc.rust-lang.org/stable/std/fmt/struct.FromFn.html) <a id="1.93.0-Cargo"></a> ## Cargo - [Enable CARGO\_CFG\_DEBUG\_ASSERTIONS in build scripts based on profile](rust-lang/cargo#16160) - [In `cargo tree`, support long forms for `--format` variables](rust-lang/cargo#16204) - [Add `--workspace` to `cargo clean`](rust-lang/cargo#16263) <a id="1.93.0-Rustdoc"></a> ## Rustdoc - [Remove `#![doc(document_private_items)]`](rust-lang/rust#146495) - [Include attribute and derive macros in search filters for "macros"](rust-lang/rust#148176) - [Include extern crates in search filters for `import`](rust-lang/rust#148301) - [Validate usage of crate-level doc attributes](rust-lang/rust#149197). This means if any of `html_favicon_url`, `html_logo_url`, `html_playground_url`, `issue_tracker_base_url`, or `html_no_source` either has a missing value, an unexpected value, or a value of the wrong type, rustdoc will emit the deny-by-default lint `rustdoc::invalid_doc_attributes`. <a id="1.93.0-Compatibility-Notes"></a> ## Compatibility Notes - [Introduce `pin_v2` into the builtin attributes namespace](rust-lang/rust#139751) - [Update bundled musl to 1.2.5](rust-lang/rust#142682) - [On Emscripten, the unwinding ABI used when compiling with `panic=unwind` was changed from the JS exception handling ABI to the wasm exception handling ABI.](rust-lang/rust#147224) If linking C/C++ object files with Rust objects, `-fwasm-exceptions` must be passed to the linker now. On nightly Rust, it is possible to get the old behavior with `-Zwasm-emscripten-eh=false -Zbuild-std`, but it will be removed in a future release. - The `#[test]` attribute, used to define tests, was previously ignored in various places where it had no meaning (e.g on trait methods or types). Putting the `#[test]` attribute in these places is no longer ignored, and will now result in an error; this may also result in errors when generating rustdoc. [Error when `test` attribute is applied to structs](rust-lang/rust#147841) - Cargo now sets the `CARGO_CFG_DEBUG_ASSERTIONS` environment variable in more situations. This will cause crates depending on `static-init` versions 1.0.1 to 1.0.3 to fail compilation with "failed to resolve: use of unresolved module or unlinked crate `parking_lot`". See [the linked issue](rust-lang/rust#150646 (comment)) for details. - [User written types in the `offset_of!` macro are now checked to be well formed.](rust-lang/rust#150465) - `cargo publish` no longer emits `.crate` files as a final artifact for user access when the `build.build-dir` config is unset - [Upgrade the `deref_nullptr` lint from warn-by-default to deny-by-default](rust-lang/rust#148122) - [Add future-incompatibility warning for `...` function parameters without a pattern outside of `extern` blocks](rust-lang/rust#143619) - [Introduce future-compatibility warning for `repr(C)` enums whose discriminant values do not fit into a `c_int` or `c_uint`](rust-lang/rust#147017) - [Introduce future-compatibility warning against ignoring `repr(C)` types as part of `repr(transparent)`](rust-lang/rust#147185) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever MR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this MR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this MR, check this box --- This MR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).

Pkgsrc changes: * Update version & checksums. * Adapt openssl-src patches to minor version update. Noteable failures at the time of commit: * The cross-build for sparc64 fails, not yet reported. Upstream changes relative to 1.92.0: Version 1.93 (2026-01-22) ========================== Language -------- - [Add warn-by-default `function_casts_as_integer` lint] (rust-lang/rust#141470) - [Add future-incompatibility warning for `...` function parameters without a pattern outside of `extern` blocks] (rust-lang/rust#143619) - [Stabilize several s390x `vector`-related target features and the `is_s390x_feature_detected!` macro] (rust-lang/rust#145656) - [Stabilize declaration of C-style variadic functions for the `system` ABI] (rust-lang/rust#145954) - [Emit error when using some keyword as a `cfg` predicate] (rust-lang/rust#146978) - [Introduce future-compatibility warning for `repr(C)` enums whose discriminant values do not fit into a `c_int` or `c_uint`] (rust-lang/rust#147017) - [Introduce future-compatibility warning against ignoring `repr(C)` types as part of `repr(transparent)`] (rust-lang/rust#147185) - [Stabilize `asm_cfg`] (rust-lang/rust#147736) - [Upgrade the `deref_nullptr` lint from warn-by-default to deny-by-default] (rust-lang/rust#148122) - [During const-evaluation, support copying pointers byte-by-byte] (rust-lang/rust#148259) - [Add warn-by-default `const_item_interior_mutations` lint to warn against calls which mutate interior mutable `const` items] (rust-lang/rust#148407) - [LUB coercions now correctly handle function item types, and functions with differing safeties] (rust-lang/rust#148602) - [Allow `const` items that contain mutable references to `static` (which is *very* unsafe, but not *always* UB)] (rust-lang/rust#148746) Compiler -------- - [Stabilize `-Cjump-tables=bool`] (rust-lang/rust#145974). The flag was previously called `-Zno-jump-tables`. - [Promote `riscv64a23-unknown-linux-gnu` to Tier 2 (without host tools)] (rust-lang/rust#148435) Platform Support ---------------- Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. [platform-support-doc]: https://doc.rust-lang.org/rustc/platform-support.html Libraries --------- - [Stop internally using `specialization` on the `Copy` trait as it is unsound in the presence of lifetime dependent `Copy` implementations. This may result in some performance regressions as some standard library APIs may now call `Clone::clone` instead of performing bitwise copies] (rust-lang/rust#135634) - [Allow the global allocator to use thread-local storage and `std::thread::current()`] (rust-lang/rust#144465) - [Make `BTree::append` not update existing keys when appending an entry which already exists] (rust-lang/rust#145628) - [Don't require `T: RefUnwindSafe` for `vec::IntoIter<T>: UnwindSafe`] (rust-lang/rust#145665) Stabilized APIs --------------- - [`<MaybeUninit<T>>::assume_init_drop`] (https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#method.assume_init_drop) - [`<MaybeUninit<T>>::assume_init_ref`] (https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#method.assume_init_ref) - [`<MaybeUninit<T>>::assume_init_mut`] (https://doc.rust-lang.org/stable/core/mem/union.MaybeUninit.html#method.assume_init_mut) - [`<[MaybeUninit<T>]>::write_copy_of_slice`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.write_copy_of_slice) - [`<[MaybeUninit<T>]>::write_clone_of_slice`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.write_clone_of_slice) - [`String::into_raw_parts`] (https://doc.rust-lang.org/stable/std/string/struct.String.html#method.into_raw_parts) - [`Vec::into_raw_parts`] (https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.into_raw_parts) - [`<iN>::unchecked_neg`] (https://doc.rust-lang.org/stable/std/primitive.isize.html#method.unchecked_neg) - [`<iN>::unchecked_shl`] (https://doc.rust-lang.org/stable/std/primitive.isize.html#method.unchecked_shl) - [`<iN>::unchecked_shr`] (https://doc.rust-lang.org/stable/std/primitive.isize.html#method.unchecked_shr) - [`<uN>::unchecked_shl`] (https://doc.rust-lang.org/stable/std/primitive.usize.html#method.unchecked_shl) - [`<uN>::unchecked_shr`] (https://doc.rust-lang.org/stable/std/primitive.usize.html#method.unchecked_shr) - [`<[T]>::as_array`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_array) - [`<[T]>::as_array_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_mut_array) - [`<*const [T]>::as_array`] (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.as_array) - [`<*mut [T]>::as_array_mut`] (https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.as_mut_array) - [`VecDeque::pop_front_if`] (https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.pop_front_if) - [`VecDeque::pop_back_if`] (https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.pop_back_if) - [`Duration::from_nanos_u128`] (https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_nanos_u128) - [`char::MAX_LEN_UTF8`] (https://doc.rust-lang.org/stable/std/primitive.char.html#associatedconstant.MAX_LEN_UTF8) - [`char::MAX_LEN_UTF16`] (https://doc.rust-lang.org/stable/std/primitive.char.html#associatedconstant.MAX_LEN_UTF16) - [`std::fmt::from_fn`] (https://doc.rust-lang.org/stable/std/fmt/fn.from_fn.html) - [`std::fmt::FromFn`] (https://doc.rust-lang.org/stable/std/fmt/struct.FromFn.html) Cargo ----- - [Enable CARGO_CFG_DEBUG_ASSERTIONS in build scripts based on profile] (rust-lang/cargo#16160) - [In `cargo tree`, support long forms for `--format` variables] (rust-lang/cargo#16204) - [Add `--workspace` to `cargo clean`] (rust-lang/cargo#16263) Rustdoc ----- - [Remove `#![doc(document_private_items)]`](rust-lang/rust#146495) - [Include attribute and derive macros in search filters for "macros"](rust-lang/rust#148176) - [Include extern crates in search filters for `import`](rust-lang/rust#148301) - [Validate usage of crate-level doc attributes](rust-lang/rust#149197). This means if any of `html_favicon_url`, `html_logo_url`, `html_playground_url`, `issue_tracker_base_url`, or `html_no_source` either has a missing value, an unexpected value, or a value of the wrong type, rustdoc will emit the deny-by-default lint `rustdoc::invalid_doc_attributes`. Compatibility Notes ------------------- - [Introduce `pin_v2` into the builtin attributes namespace] (rust-lang/rust#139751) - [Update bundled musl to 1.2.5] (rust-lang/rust#142682) - [On Emscripten, the unwinding ABI used when compiling with `panic=unwind` was changed from the JS exception handling ABI to the wasm exception handling ABI.] (rust-lang/rust#147224) If linking C/C++ object files with Rust objects, `-fwasm-exceptions` must be passed to the linker now. On nightly Rust, it is possible to get the old behavior with `-Zwasm-emscripten-eh=false -Zbuild-std`, but it will be removed in a future release. - The `#[test]` attribute, used to define tests, was previously ignored in various places where it had no meaning (e.g on trait methods or types). Putting the `#[test]` attribute in these places is no longer ignored, and will now result in an error; this may also result in errors when generating rustdoc. [Error when `test` attribute is applied to structs] (rust-lang/rust#147841) - Cargo now sets the `CARGO_CFG_DEBUG_ASSERTIONS` environment variable in more situations. This will cause crates depending on `static-init` versions 1.0.1 to 1.0.3 to fail compilation with "failed to resolve: use of unresolved module or unlinked crate `parking_lot`". See [the linked issue] (rust-lang/rust#150646 (comment)) for details. - [User written types in the `offset_of!` macro are now checked to be well formed.] (rust-lang/rust#150465) - `cargo publish` no longer emits `.crate` files as a final artifact for user access when the `build.build-dir` config is unset

The __cpp_exception Tag LinkError was never actually fixed by -Z emscripten-wasm-eh=false: rustc's own options.rs (rust-lang/rust#147224) shows that flag's default flipped false->true on 2025-12-05, and by the nightly this project had drifted to (2026-08-16) the flag was gone from rustc entirely -- confirmed by CI itself: `unknown unstable option: 'emscripten-wasm-eh'`, not just a changed default. There is currently no rustc flag, at any recency, that restores the legacy JS-based exception lowering Godot 4.7.1's official web templates expect. Pinning the toolchain to nightly-2025-11-15 (~3 weeks before the default flip) gets that ABI for free, with no flag needed at all. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

…flip instead 42c8c81's own nightly-2025-11-15 pin never got verified even at "does it compile": rustc's dated channel manifests (static.rust-lang.org) show the nightly version number bumps from 1.93 to 1.94 on 2025-12-06 -- the SAME day rust-lang/rust#147224 flipped emscripten_wasm_eh's default. godot 0.5.5's own MSRV is 1.94. There is no date where "before the flip" and "meets the MSRV" both hold; CI caught this immediately ("rustc 1.93.0-nightly is not supported by ... godot@0.5.5"), on the NATIVE build step, before the wasm step even got a chance to run. Separately, that commit also left the wasm build step invoking `cargo +nightly`, which never matched the pinned `nightly-2025-11-15` toolchain name at all -- a second bug that would have surfaced the moment the first one was fixed. Fix: pin nightly-2025-12-10 instead -- past the flip, so pass `-Z emscripten-wasm-eh=false` explicitly rather than relying on the old default -- and install it via dtolnay/rust-toolchain@master specifically so it does NOT become the rustup default (a plain `stable` toolchain is installed after it for that), since the native "Build the native core for the editor" step has no `+toolchain` of its own and needs the MSRV met. The wasm build step now says `cargo +nightly-2025-12-10` to match. Verified for real this time, not just green CI: installed a real emsdk 4.0.11 (matching EM_VERSION) locally and ran the complete build -- `cargo +nightly-2025-12-10 build --release --target wasm32-unknown-emscripten -Zbuild-std` -- through actual emcc linking. Also checked two more things by trying dates rather than assuming: nightly-2025-12-10 has cdylib support for this target (nightly-2026-02-01, picked first, silently dropped it -- "dropping unsupported crate type cdylib" -- an unrelated, independent regression on that specific nightly), and the `-Z emscripten-wasm-eh` flag itself is confirmed present in `rustc -Z help` output through at least 2026-05-01, gone by 2026-06-15, so 2025-12-10 has comfortable margin. Inspected the resulting angelbeach.wasm directly with wasm-objdump -x: memory import is `shared` (the threading requirement), and the import table has zero Tag[] entries and no __cpp_exception import anywhere -- only the legacy JS-based exception plumbing (env.invoke_*, env.__cxa_throw, env.__cxa_begin_catch/__cxa_end_catch) that Godot's official web templates were actually built against.

rustbot assigned lcnr Oct 1, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 1, 2025

hoodmane mentioned this pull request Oct 1, 2025

Turn emscripten-wasm-eh unwinding ABI on by default rust-lang/compiler-team#920

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