Bug 234 - Interlocked.Exchange<T>(...) crashes the App and throws System.ExecutionEngineException in debug
Summary: Interlocked.Exchange<T>(...) crashes the App and throws System.ExecutionEngin...
Alias: None
Product: iOS
Classification: Xamarin
Component: XI runtime ()
Version: 4.x
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2011-08-08 17:40 UTC by zelyony
Modified: 2011-08-09 13:54 UTC (History)
6 users (show)

Tags: Interlocked.Exchange
Is this bug a regression?: ---
Last known good build:

log (32.91 KB, text/plain)
2011-08-08 17:40 UTC, zelyony

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Description zelyony 2011-08-08 17:40:03 UTC
Created attachment 91 [details]

Interlocked.Exchange<T> crashes app on device (I have iPod4)
others Interlocked.XXX worked

- create windows-based app for iPhone
- add variables to AppDelegate 
    string str = null;
- insert first line of code in AppDelegate.FinishedLaunching
    Interlocked.Exchange( ref str, "one" );
Comment 1 Sebastien Pouliot 2011-08-08 20:13:09 UTC
Confirmed. It happens with, or without, the linker being enabled.

Not sure why the AOT compiler is not able to detect and compile a string version of this call.

Reducing the severity to Normal since you can use the non-generic overload that accept System.Object to pass string instances as a workaround.
Comment 2 Sebastien Pouliot 2011-08-08 20:20:49 UTC
That same issue has hit other people (before
Comment 3 Sebastien Pouliot 2011-08-09 08:33:16 UTC
It looks like AOT is well aware of the generic type to use:

imac:Keychain sebastienpouliot$ MONO_PATH=/Users/sebastienpouliot/git/monotouch-samples/Keychain/Keychain/bin/iPhone/Debug/Keychain.app /Developer/MonoTouch/usr/bin/arm-darwin-mono --debug --aot=full,static,asmonly,soft-debug,iphone-abi,outfile=Keychain.exe.6.s -v -v "/Users/sebastienpouliot/git/monotouch-samples/Keychain/Keychain/bin/iPhone/Debug/Keychain.app/Keychain.exe" | grep Interlock
	 call R202 <- [System.Threading.Interlocked:Exchange<string> (string&,string)] [arm_r0 <- R203] [arm_r1 <- R204] [arm_v5 <- R201] clobbers: c

So I wonder if this could be a (undocumented) AOT (or full-AOT) restriction wrt internal calls:

		[ComVisible (false)]
		[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
		public extern static T Exchange<T> (ref T location1, T value) where T:class;

c.c. Rodrigo
Comment 4 Zoltan Varga 2011-08-09 13:16:43 UTC
Fixed by 79b99d358b1321759ea3a42f22eaf141aecf0e79 on the mono 2.10 branch.
Comment 5 Sebastien Pouliot 2011-08-09 13:29:24 UTC
Thanks Zoltan! I'll test the fix and include it into monotouch.
Comment 6 Sebastien Pouliot 2011-08-09 13:54:43 UTC
Thanks for the test case!