Add emscripten_wasm_eh cfg flag and use it to adjust the libraries

Author: hoodmane

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -2468,7 +2468,7 @@ fn add_order_independent_options(
     if sess.target.os == "emscripten" {
         cmd.cc_arg(if sess.panic_strategy() == PanicStrategy::Abort {
             "-sDISABLE_EXCEPTION_CATCHING=1"
-        } else if (sess.unstable_options.emscripten_wasm_eh) {
+        } else if sess.opts.unstable_opts.emscripten_wasm_eh {
             "-fwasm-exceptions"
         } else {
             "-sDISABLE_EXCEPTION_CATCHING=0"

compiler/rustc_codegen_ssa/src/base.rs

@@ -389,7 +389,7 @@ pub(crate) fn build_shift_expr_rhs<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 // us
 pub fn wants_wasm_eh(sess: &Session) -> bool {
     sess.target.is_like_wasm
-        && (sess.target.os != "emscripten" || sess.unstable_options.emscripten_wasm_eh)
+        && (sess.target.os != "emscripten" || sess.opts.unstable_opts.emscripten_wasm_eh)
 }
 
 /// Returns `true` if this session's target will use SEH-based unwinding.

compiler/rustc_passes/src/weak_lang_items.rs

@@ -28,7 +28,7 @@ pub(crate) fn check_crate(
     }
     if tcx.sess.target.os == "emscripten"
         && items.eh_catch_typeinfo().is_none()
-        && !tcx.sess.unstable_options.emscripten_wasm_eh
+        && !tcx.sess.opts.unstable_opts.emscripten_wasm_eh
     {
         items.missing.push(LangItem::EhCatchTypeinfo);
     }

compiler/rustc_session/src/config/cfg.rs

@@ -143,6 +143,7 @@ pub(crate) fn disallow_cfgs(sess: &Session, user_cfgs: &Cfg) {
             | (sym::target_has_atomic_load_store, Some(_))
             | (sym::target_thread_local, None) => disallow(cfg, "--target"),
             (sym::fmt_debug, None | Some(_)) => disallow(cfg, "-Z fmt-debug"),
+            (sym::emscripten_wasm_eh, None | Some(_)) => disallow(cfg, "-Z emscripten_wasm_eh"),
             _ => {}
         }
     }
@@ -295,6 +296,9 @@ pub(crate) fn default_configuration(sess: &Session) -> Cfg {
         ins_none!(sym::ub_checks);
     }
 
+    if sess.opts.unstable_opts.emscripten_wasm_eh {
+        ins_none!(sym::emscripten_wasm_eh);
+    }
     ret
 }
 
@@ -350,6 +354,7 @@ impl CheckCfg {
         ins!(sym::clippy, no_values);
         ins!(sym::doc, no_values);
         ins!(sym::doctest, no_values);
+        ins!(sym::emscripten_wasm_eh, no_values);
         ins!(sym::miri, no_values);
         ins!(sym::rustfmt, no_values);
 

compiler/rustc_span/src/symbol.rs

@@ -823,6 +823,7 @@ symbols! {
         emit_enum_variant_arg,
         emit_struct,
         emit_struct_field,
+        emscripten_wasm_eh,
         enable,
         encode,
         end,

library/panic_unwind/src/lib.rs

@@ -25,13 +25,17 @@
 // `real_imp` is unused with Miri, so silence warnings.
 #![cfg_attr(miri, allow(dead_code))]
 #![allow(internal_features)]
+#![cfg_attr(bootstrap, allow(unexpected_cfgs))]
 
 use alloc::boxed::Box;
 use core::any::Any;
 use core::panic::PanicPayload;
 
 cfg_if::cfg_if! {
-    if #[cfg(target_os = "hermit")] {
+    if #[cfg(all(target_os = "emscripten", not(emscripten_wasm_eh)))] {
+        #[path = "emcc.rs"]
+        mod imp;
+    } else if #[cfg(target_os = "hermit")] {
         #[path = "hermit.rs"]
         mod imp;
     } else if #[cfg(target_os = "l4re")] {

library/unwind/src/lib.rs

@@ -3,7 +3,11 @@
 #![feature(link_cfg)]
 #![feature(staged_api)]
 #![cfg_attr(not(target_env = "msvc"), feature(libc))]
-#![cfg_attr(all(target_family = "wasm"), feature(simd_wasm64, wasm_exception_handling_intrinsics))]
+#![cfg_attr(bootstrap, allow(unexpected_cfgs))]
+#![cfg_attr(
+    all(target_family = "wasm", any(not(target_os = "emscripten"), emscripten_wasm_eh)),
+    feature(simd_wasm64, wasm_exception_handling_intrinsics)
+)]
 #![allow(internal_features)]
 
 // Force libc to be included even if unused. This is required by many platforms.