Bug 7449 - Variable is still assigned to even if expression throws exception
Summary: Variable is still assigned to even if expression throws exception
Alias: None
Product: iOS
Classification: Xamarin
Component: General ()
Version: 6.0.x
Hardware: PC Mac OS
: --- major
Target Milestone: Untriaged
Assignee: Zoltan Varga
Depends on:
Reported: 2012-09-25 12:30 UTC by jesse.attas
Modified: 2012-10-04 07:06 UTC (History)
5 users (show)

Is this bug a regression?: ---
Last known good build:

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Description jesse.attas 2012-09-25 12:30:59 UTC
The code snippet below behaves incorrectly. The value of "result" at the end of the program should be -1 because the expression that assigns it throws an exception. Instead it's garbage data like 2.69291027116829E-308. This bug only occurs in release mode with "Use LLVM optimizing compiler" turned on.

    public class ClassWithBug : UIViewController
        public override void ViewDidLoad()
            OtherClass c = new OtherClass();
            bool hitException = false;
            double result = -1;
                Console.WriteLine("Before calling: {0}", result);
                result = c.PropertyThatThrowsException;            // THIS LINE SHOULD NOT AFFECT "result" BECAUSE IT THROWS
                Console.WriteLine("Shouldn't hit: {0}", result);
            catch(Exception e)
                hitException = true;
                Console.WriteLine("Hit Exception {1}: {0}", result, e);
            Console.WriteLine("hitException:{1} result:{0}", result, hitException);            
    public class OtherClass
        public OtherClass()
        private double _backingStore;
        public double PropertyThatThrowsException
                if (FunctionThatReturnsFalse())
                    return _backingStore;
                    Console.WriteLine("In other class, value is {0}", _backingStore);
                    throw new ArgumentException("Property not supported");
                _backingStore = value;
        private bool FunctionThatReturnsFalse()
            Random r = new Random();
            return r.NextDouble() < 0;
Comment 1 jesse.attas 2012-09-25 12:31:36 UTC
Version info:

	Mono 2.10.9 (tarball)
	GTK 2.24.10
	GTK# (
	Package version: 210090011
Apple Developer Tools:
	 Xcode 4.5 (1839)
	 Build 4G182
Monotouch: 6.0.0
Comment 2 Sebastien Pouliot 2012-09-25 14:38:07 UTC
>  This bug only occurs in release mode with "Use LLVM optimizing compiler" turned on.

Zoltan, that looks like your area :)
Comment 3 Rolf Bjarne Kvinge [MSFT] 2012-09-26 16:34:26 UTC
This might be related to bug #6650.
Comment 4 Zoltan Varga 2012-10-04 07:06:57 UTC
Fixed in mobile-master/monotouch-6.0-series.