fix(ios): fix Hermes startup race in ExpoBridgeModule (patch) (#10672)

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-01 17:56:34 +03:00
parent 9e275d3898
commit 601dae0cda
3 changed files with 63 additions and 4 deletions
@@ -13,3 +13,39 @@ index 47c4d15f6b10bbd77858cfff425cda9a618735b9..afe138d22d566244482498a7be0e14b8
   // Check for Content-Type
   val skipContentTypes = listOf(
     "text/event-stream", // Server Sent Events
+diff --git a/ios/Core/ExpoBridgeModule.mm b/ios/Core/ExpoBridgeModule.mm
+index 2ed1c00f47406e109750cc27ace7e0d88e42c00e..99d0d140eddf95a8db7beb57c61dfcb12c1424b4 100644
+--- a/ios/Core/ExpoBridgeModule.mm
+++ b/ios/Core/ExpoBridgeModule.mm
+@@ -7,6 +7,9 @@
+ // The runtime executor is included as of React Native 0.74 in bridgeless mode.
+ #if __has_include(<ReactCommon/RCTRuntimeExecutor.h>)
+ #import <ReactCommon/RCTRuntimeExecutor.h>
+#else // React Native <0.74
+// dispatchBlock:queue: is declared in RCTBridge+Private.h, not the public header.
+#import <React/RCTBridge+Private.h>
+ #endif // React Native >=0.74
+ 
+ @implementation ExpoBridgeModule
+@@ -46,7 +49,20 @@ - (void)setBridge:(RCTBridge *)bridge
+   _appContext.reactBridge = bridge;
+ 
+ #if !__has_include(<ReactCommon/RCTRuntimeExecutor.h>)
+-  _appContext._runtime = [EXJavaScriptRuntimeManager runtimeFromBridge:bridge];
+  // Hop the runtime install (and the prepareRuntime() chain it triggers via
+  // _runtime.didSet) onto RCTJSThread. The original line ran synchronously
+  // on whatever thread called setBridge: - typically the main thread - and
+  // raced JSIExecutor::initializeRuntime() on the JS thread, corrupting
+  // Hermes' Hades GC (HadesGC::writeBarrierSlow EXC_BAD_ACCESS).
+  __weak EXAppContext *weakAppContext = _appContext;
+  __weak RCTBridge *weakBridge = bridge;
+  [bridge dispatchBlock:^{
+    EXAppContext *strongAppContext = weakAppContext;
+    RCTBridge *strongBridge = weakBridge;
+    if (strongAppContext != nil && strongBridge != nil && strongAppContext._runtime == nil) {
+      strongAppContext._runtime = [EXJavaScriptRuntimeManager runtimeFromBridge:strongBridge];
+    }
+  } queue:RCTJSThread];
+ #endif // React Native <0.74
+ }
+ 
@@ -1,3 +1,26 @@
 ## expo-modules-core Patch

-This patch fixes an issue where bitdrift's API stream gets blocked by the Expo interceptor used to power the devtools
+This patch contains two unrelated fixes:
+
+### Android: bitdrift interceptor
+
+Fixes an issue where bitdrift's API stream gets blocked by the Expo interceptor used to power the devtools.
+
+### iOS: Hermes startup race in `ExpoBridgeModule.setBridge:`
+
+On the legacy bridge (old architecture, where `RCTRuntimeExecutor.h` is
+absent), `setBridge:` installed the Expo runtime synchronously on whatever
+thread called it - typically the main thread, since RN's lazy module-load
+path ignores `+requiresMainQueueSetup`. The `_runtime.didSet` then ran
+`prepareRuntime()` (JSI mutations) on the main thread while the JS thread was
+concurrently inside `JSIExecutor::initializeRuntime()`. Two threads mutating
+the same Hermes runtime corrupted Hades GC, producing intermittent
+`EXC_BAD_ACCESS` launch crashes (e.g. `HadesGC::writeBarrierSlow`,
+`prepareRuntime` / `bindNativePerformanceNow`).
+
+The fix hops the runtime install onto `RCTJSThread` so all JSI mutation is
+serialized on the JS thread. This backports the upstream fix discussed in
+expo/expo#45374; the racy `ExpoBridgeModule` is removed entirely in SDK 55+
+(expo/expo#44351), so this patch can be dropped on that upgrade.
+
+Refs: expo/expo#43003, expo/expo#45374, expo/expo#44351