App Crashes on Exception on Non-critical Path (C++ Exception)

Description

Soft exception thrown in callbacks, e.g., setTimeout incurs a crash. In the reported core dump the signature is "C++ Exception".

Scope:

• Uncontrolled exception in callbacks passed in to setTimeout, <Pressable>, etc;
• Above crashes exist also in less defensive 3rd party libs (extended scope);
• Incidents are also found in ReactFabric::extractEvents.

Steps to reproduce

Code below crashes app 10 secs after bootstrap:

setTimeout(() => {throw new Error('SWW')}, 10000);

Comparable throws in a <Pressable>, etc., can easily reproduce.

React Native Version

0.77.2, 0.79.2

Affected Platforms

Runtime - iOS

Output of npx @react-native-community/cli info

System:
  OS: macOS 15.4
  CPU: (8) arm64 Apple M1 Pro
  Memory: 135.81 MB / 16.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 20.19.1
    path: ~/.nvm/versions/node/v20.19.1/bin/node
  Yarn:
    version: 1.22.19
    path: /opt/homebrew/bin/yarn
  npm:
    version: 10.8.2
    path: ~/.nvm/versions/node/v20.19.1/bin/npm
  Watchman:
    version: 2025.04.28.00
    path: /opt/homebrew/bin/watchman
Managers:
  CocoaPods:
    version: 1.15.2
    path: /Users/holmes/.rvm/gems/ruby-3.2.0/bin/pod
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 24.4
      - iOS 18.4
      - macOS 15.4
      - tvOS 18.4
      - visionOS 2.4
      - watchOS 11.4
  Android SDK: Not Found
IDEs:
  Android Studio: 2024.2 AI-242.23726.103.2422.12816248
  Xcode:
    version: 16.3/16E140
    path: /usr/bin/xcodebuild
Languages:
  Java:
    version: 17.0.14
    path: /usr/bin/javac
  Ruby:
    version: 3.2.0
    path: /Users/holmes/.rvm/rubies/ruby-3.2.0/bin/ruby
npmPackages:
  "@react-native-community/cli":
    installed: 18.0.0
    wanted: 18.0.0
  react:
    installed: 19.0.0
    wanted: 19.0.0
  react-native:
    installed: 0.79.2
    wanted: 0.79.2
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Stacktrace or Logs

terminating due to uncaught exception of type facebook::jsi::JSError: ExceptionsManager.reportException raised an exception: Unhandled JS Exception: Error: SWW, js engine: hermes, stack:
anonymous@49376:19
Error: ExceptionsManager.reportException raised an exception: Unhandled JS Exception: Error: SWW, js engine: hermes, stack:
anonymous@49376:19
CoreSimulator 1010.10 - Device: iPhone 16 Pro (A124ADE1-D75C-4F48-A913-0C72B0BC212A) - Runtime: iOS 18.0 (22A3351) - DeviceType: iPhone 16 Pro

MANDATORY Reproducer

https://github.com/ehsemloh/crash-cpp-excetpion

Screenshots and Videos

https://drive.google.com/file/d/1fyPmGmg6MdMOXZHYrm0voWaMNtnmlUOZ/view?usp=sharing

Start by running the mandatory reproducer and tracing the callback path from setTimeout or Pressable through ExceptionsManager.reportException. Compare that path with the incidents mentioned in ReactFabric::extractEvents; done means the reproducer no longer terminates the iOS app on an exception from a non-critical callback.