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Emscripten: Turn wasm-eh on by default

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As specified by MCP:
https://github.com/rust-lang/compiler-team/issues/920
Resolves https://github.com/rust-lang/rust/issues/148309
This commit is contained in:
Hood Chatham 2025-10-01 15:13:38 +02:00
parent 646a3f8c15
commit f07a84fde8
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6 changed files with 15 additions and 14 deletions
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2
compiler/rustc_interface/src/tests.rs
View file

@ -798,7 +798,7 @@ fn test_unstable_options_tracking_hash() {
tracked!(embed_metadata, false);
tracked!(embed_source, true);
tracked!(emit_thin_lto, false);
tracked!(emscripten_wasm_eh, true);
tracked!(emscripten_wasm_eh, false);
tracked!(export_executable_symbols, true);
tracked!(fewer_names, Some(true));
tracked!(fixed_x18, true);

2
compiler/rustc_session/src/options.rs
View file

@ -2338,7 +2338,7 @@ options! {
"emit a section containing stack size metadata (default: no)"),
emit_thin_lto: bool = (true, parse_bool, [TRACKED],
"emit the bc module with thin LTO info (default: yes)"),
emscripten_wasm_eh: bool = (false, parse_bool, [TRACKED],
emscripten_wasm_eh: bool = (true, parse_bool, [TRACKED],
"Use WebAssembly error handling for wasm32-unknown-emscripten"),
enforce_type_length_limit: bool = (false, parse_bool, [TRACKED],
"enforce the type length limit when monomorphizing instances in codegen"),

15
src/doc/rustc/src/platform-support/wasm32-unknown-emscripten.md
View file

@ -95,10 +95,11 @@ This target can be cross-compiled from any host.
## Emscripten ABI Compatibility
The Emscripten compiler toolchain does not follow a semantic versioning scheme
that clearly indicates when breaking changes to the ABI can be made. Additionally,
Emscripten offers many different ABIs even for a single version of Emscripten
depending on the linker flags used, e.g. `-fexceptions` and `-sWASM_BIGINT`. If
the ABIs mismatch, your code may exhibit undefined behaviour.
that clearly indicates when breaking changes to the ABI can be made.
Additionally, Emscripten offers many different ABIs even for a single version of
Emscripten depending on the linker flags used, e.g. `-fwasm-exceptions` and
`-sWASM_BIGINT`. If the ABIs do not match, your code may exhibit undefined
behaviour.
To ensure that the ABIs of your Rust code, of the Rust standard library, and of
other code compiled for Emscripten all match, you should rebuild the Rust standard
@ -158,9 +159,9 @@ features can be disabled, and how Rust code can be conditionally compiled based
which features are enabled.
Note that Rust code compiled for `wasm32-unknown-emscripten` currently enables
`-fexceptions` (JS exceptions) by default unless the Rust code is compiled with
`-Cpanic=abort`. `-fwasm-exceptions` (WASM exceptions) is not yet currently supported,
see <https://github.com/rust-lang/rust/issues/112195>.
`-fwasm-exceptions` (legacy WASM exceptions) by default unless the Rust code is
compiled with `-Cpanic=abort`. It is possible to use JS exceptions by passing
the flag ``-Z emscripten-wasm-eh=false`` but this will be removed in the future.
Please refer to the [Emscripten ABI compatibility](#emscripten-abi-compatibility)
section to ensure that the features that are enabled do not cause an ABI mismatch

2
tests/codegen-llvm/emscripten-catch-unwind-js-eh.rs
View file

@ -1,4 +1,4 @@
//@ compile-flags: -Copt-level=3 --target wasm32-unknown-emscripten
//@ compile-flags: -Copt-level=3 --target wasm32-unknown-emscripten -Z emscripten-wasm-eh=false
//@ needs-llvm-components: webassembly
// Emscripten has its own unique implementation of catch_unwind (in `codegen_emcc_try`),

2
tests/ui/feature-gates/feature-gate-cfg-emscripten-wasm-eh.rs
View file

@ -1,4 +1,4 @@
//@ compile-flags: --check-cfg=cfg(emscripten_wasm_eh)
#[cfg(not(emscripten_wasm_eh))]
#[cfg(emscripten_wasm_eh)]
//~^ ERROR `cfg(emscripten_wasm_eh)` is experimental
fn main() {}

6
tests/ui/feature-gates/feature-gate-cfg-emscripten-wasm-eh.stderr
View file

@ -1,8 +1,8 @@
error[E0658]: `cfg(emscripten_wasm_eh)` is experimental and subject to change
--> $DIR/feature-gate-cfg-emscripten-wasm-eh.rs:2:11
--> $DIR/feature-gate-cfg-emscripten-wasm-eh.rs:2:7
|
LL | #[cfg(not(emscripten_wasm_eh))]
| ^^^^^^^^^^^^^^^^^^
LL | #[cfg(emscripten_wasm_eh)]
| ^^^^^^^^^^^^^^^^^^
|
= help: add `#![feature(cfg_emscripten_wasm_eh)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date