Bug 12799 - Incorrect exception handling with async methods
Summary: Incorrect exception handling with async methods
Status: RESOLVED FIXED
Alias: None
Product: Compilers
Classification: Mono
Component: C# ()
Version: unspecified
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: ---
Assignee: Marek Safar
URL:
Depends on:
Blocks:
 
Reported: 2013-06-20 16:04 UTC by Greg Shackles
Modified: 2013-06-26 09:33 UTC (History)
3 users (show)

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

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Status:
RESOLVED FIXED

Description Greg Shackles 2013-06-20 16:04:16 UTC
Given the following method:

async Task foo<TException>() where TException : Exception, new()
{
	try
	{
		throw new TException();
	}
	catch (TException)
	{
		Console.WriteLine ("caught in correct block");
	}
	catch (Exception ex)
	{
		Console.WriteLine ("caught in generic block");
		Console.WriteLine("type: " + ex.GetType());
	}
}

Called like: foo<InvalidOperationException>().Wait();

In .NET, "caught in correct block" is the output, as expected. When I run that same code with Mono, it outputs "caught in generic block", but does actually display "System.InvalidOperationException" as the type. This was tested with Mono 3.0.12, and was also reproducible in Xamarin.iOS 6.3.6.77
Comment 1 Zoltan Varga 2013-06-22 09:23:50 UTC
This looks like an mcs problem, a csc compiled exe runs fine on mono.
Testcase:
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
using System;
using System.Threading.Tasks;

public class Application {

	static async Task foo<TException>() where TException : Exception, new()
{
    try
    {
        throw new TException();
    }
    catch (TException)
    {
        Console.WriteLine ("caught in correct block");
    }
    catch (Exception ex)
    {
        Console.WriteLine ("caught in generic block");
        Console.WriteLine("type: " + ex.GetType());
    }
}

    static void Main (string[] args)
    {
		foo<InvalidOperationException>().Wait();
    }
}
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

csc generates the following code:
    .try
    {
...
    }  // end .try
    catch !TException 
while mcs generates:
 .try
  {
....
  }  // end .try
  catch !!0
Comment 2 Marek Safar 2013-06-26 09:33:29 UTC
Fixed in master