Remove calls to JSGlobalContextSetIncludesNativeCallStackWhenReportingExceptions()

[appden]

It gets called inside RealmRPC.mm and RealmReactTests.m to prevent crashes. The issue is that calls to JSObjectCallAsFunction (and others) that result in an exception will in turn make JavaScriptCore want to create a stack trace that includes native functions.

My current theory is that JavaScriptCore doesn't correctly handle C++ lambdas (and might be fixed in the RPC server by switching to regular functions when migrating to pure C++ – see #72), though it may instead be caused by something else pertaining to how we link together our framework.

[bdash]

Do you have the crash report / stack trace of the crash you see without the call to JSGlobalContextSetIncludesNativeCallStackWhenReportingExceptions?

[appden]

Sure. It crashes at dladdr. JavaScriptCore is passing a function pointer it got from calling backtrace.

[bdash]

Thanks. I'm not sure it's inherently related to C++ lambdas. On OS X 10.11.1, a test program that uses backtrace, dladdr, and abi::__cxa_demangle in a similar manner to JavaScriptCore's appendAPIBacktrace has no problem. You can see the code I tested with at https://gist.github.com/bdash/906bddc3d5ece607b4af.

[appden]

@bdash you're right. It's actually crashing on the last element of the trace, which is the return address for main it looks like. I'm not quite sure why. If I artificially make the stack trace deeper (with a little recursive function), then it no longer crashes. 😄

[appden]

Just an update: [NSThread callStackSymbols] also causes it to crash the same way (it does essentially the same thing). We are doing this inside a dispatch_sync(dispatch_get_main_queue(), ^{...}), which might part of the issue.

[appden]

It's definitely fixed if I run everything inside my own thread, which will be fine for this purpose, but I'd still really like to understand what the issue is with main.

[appden]

Update: since upgrading to Xcode 7.1, this crash no longer seems to happen on the main thread in the iOS 9.1 simulator (thanks @bdash). However, I have seen this crash occur on other threads unrelated to JavaScriptCore, such as when RCTLog attempts to create a backtrace with backtrace_symbols.

I need to test this on a device running 9.0.x (not 9.1) to see if it's an issue there before deciding to remove calls to JSGlobalContextSetIncludesNativeCallStackWhenReportingExceptions().