From 7362288acf6455a40bb5380bffe97fc052517a55 Mon Sep 17 00:00:00 2001
From: daxpedda <daxpedda@gmail.com>
Date: Sat, 9 Mar 2024 23:45:13 +0100
Subject: [PATCH] Make `catch` thread safe

---
 CHANGELOG.md |  5 +++++
 src/lib.rs   | 22 ++++++++++++----------
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index be9404e05f6e..580a0eed76e7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,11 @@
 * Copy port from headless test server when using `WASM_BINDGEN_TEST_ADDRESS`.
   [#3873](https://github.com/rustwasm/wasm-bindgen/pull/3873)
 
+* Fix `catch` not being thread-safe.
+  [#3879](https://github.com/rustwasm/wasm-bindgen/pull/3879)
+
+--------------------------------------------------------------------------------
+
 ## [0.2.92](https://github.com/rustwasm/wasm-bindgen/compare/0.2.91...0.2.92)
 
 Released 2024-03-04
diff --git a/src/lib.rs b/src/lib.rs
index 2f9e48e6d773..fdef0e8d39ab 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1687,26 +1687,28 @@ pub mod __rt {
         crate::externref::link_intrinsics();
     }
 
-    static mut GLOBAL_EXNDATA: [u32; 2] = [0; 2];
+    std::thread_local! {
+        static GLOBAL_EXNDATA: Cell<[u32; 2]> = Cell::new([0; 2]);
+    }
 
     #[no_mangle]
     pub unsafe extern "C" fn __wbindgen_exn_store(idx: u32) {
-        debug_assert_eq!(GLOBAL_EXNDATA[0], 0);
-        GLOBAL_EXNDATA[0] = 1;
-        GLOBAL_EXNDATA[1] = idx;
+        GLOBAL_EXNDATA.with(|data| {
+            debug_assert_eq!(data.get()[0], 0);
+            data.set([1, idx]);
+        });
     }
 
     pub fn take_last_exception() -> Result<(), super::JsValue> {
-        unsafe {
-            let ret = if GLOBAL_EXNDATA[0] == 1 {
-                Err(super::JsValue::_new(GLOBAL_EXNDATA[1]))
+        GLOBAL_EXNDATA.with(|data| {
+            let ret = if data.get()[0] == 1 {
+                Err(super::JsValue::_new(data.get()[1]))
             } else {
                 Ok(())
             };
-            GLOBAL_EXNDATA[0] = 0;
-            GLOBAL_EXNDATA[1] = 0;
+            data.set([0, 0]);
             ret
-        }
+        })
     }
 
     /// An internal helper trait for usage in `#[wasm_bindgen]` on `async`