Add cfg_emscripten_wasm_eh feature

Author: hoodmane

compiler/rustc_feature/src/builtin_attrs.rs

@@ -37,6 +37,7 @@ const GATED_CFGS: &[GatedCfg] = &[
     (sym::sanitizer_cfi_normalize_integers, sym::cfg_sanitizer_cfi, Features::cfg_sanitizer_cfi),
     // this is consistent with naming of the compiler flag it's for
     (sym::fmt_debug, sym::fmt_debug, Features::fmt_debug),
+    (sym::emscripten_wasm_eh, sym::cfg_emscripten_wasm_eh, Features::cfg_emscripten_wasm_eh),
 ];
 
 /// Find a gated cfg determined by the `pred`icate which is given the cfg's name.

compiler/rustc_feature/src/unstable.rs

@@ -202,6 +202,8 @@ declare_features! (
     (internal, allow_internal_unstable, "1.0.0", None),
     /// Allows using anonymous lifetimes in argument-position impl-trait.
     (unstable, anonymous_lifetime_in_impl_trait, "1.63.0", None),
+    /// Allows access to the emscripten_wasm_eh config, used by panic_unwind and unwind
+    (internal, cfg_emscripten_wasm_eh, "CURRENT_RUSTC_VERSION", None),
     /// Allows identifying the `compiler_builtins` crate.
     (internal, compiler_builtins, "1.13.0", None),
     /// Allows writing custom MIR

compiler/rustc_span/src/symbol.rs

@@ -570,6 +570,7 @@ symbols! {
         cfg_autodiff_fallback,
         cfg_boolean_literals,
         cfg_doctest,
+        cfg_emscripten_wasm_eh,
         cfg_eval,
         cfg_fmt_debug,
         cfg_hide,

library/panic_unwind/src/lib.rs

@@ -25,6 +25,7 @@
 // `real_imp` is unused with Miri, so silence warnings.
 #![cfg_attr(miri, allow(dead_code))]
 #![allow(internal_features)]
+#![cfg_attr(not(bootstrap), feature(cfg_emscripten_wasm_eh))]
 
 use alloc::boxed::Box;
 use core::any::Any;

library/unwind/src/lib.rs

@@ -8,6 +8,7 @@
     feature(simd_wasm64, wasm_exception_handling_intrinsics)
 )]
 #![allow(internal_features)]
+#![cfg_attr(not(bootstrap), feature(cfg_emscripten_wasm_eh))]
 
 // Force libc to be included even if unused. This is required by many platforms.
 #[cfg(not(all(windows, target_env = "msvc")))]

tests/ui/cfg/disallowed-cli-cfgs.rs

@@ -7,6 +7,7 @@
 //@ revisions: target_has_atomic_equal_alignment_ target_has_atomic_load_store_
 //@ revisions: target_thread_local_ relocation_model_
 //@ revisions: fmt_debug_
+//@ revisions: emscripten_wasm_eh_
 
 //@ [overflow_checks_]compile-flags: --cfg overflow_checks
 //@ [debug_assertions_]compile-flags: --cfg debug_assertions

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

@@ -0,0 +1,4 @@
+//@ compile-flags: --check-cfg=cfg(emscripten_wasm_eh)
+#[cfg(not(emscripten_wasm_eh))]
+//~^ `cfg(emscripten_wasm_eh)` is experimental
+fn main() {}

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

@@ -0,0 +1,12 @@
+error[E0658]: `cfg(emscripten_wasm_eh)` is experimental and subject to change
+  --> $DIR/feature-gate-cfg-emscripten-wasm-eh.rs:2:11
+   |
+LL | #[cfg(not(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
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0658`.