Nice work tracking this down! :)

Seems this is the same as in #1289 from TFS that was later rolled back?

dotnet-bot@838b043
dotnet-bot@0aef784

Yeah, looks like it. Why did it get rolled back?

@masonwheeler Not quite sure, but here it is again :)

Maybe we could ask @sivarv? :)

Should we include the regression test here or in a followup PR?

@mmdriley I've managed to narrow down a regression test, I'll have that included in the merge tomorrow morning :)

Wow you guys still haven't figured out why the bug is there, and why the fix was rolled back previously...?
This is really worrying.

@danielgindi it looks like @sivarv wanted to fix dotnet/fsharp#536 (comment), but it wasn't the correct fix for that so I assume he rolled it back.

@forki Thanks for your response :-)

Btw, I love it that Microsoft has moved to Git!

Thanks!

I was just thinking, how come this didn't show up in the tests? It seems like this would blow up everywhere.

Nope. This blows up in production environment only, and only where there are function call which are the last statement in a function, and only when the optimizer decides to...

This would imply the tests are either not run in "production environment" (meaning "Release" mode with "Optimize code" enabled) or there is no such test that would trigger the tail call opt.

Or this case is such an edge case that one of the test just doesn't trigger it. They probably have added a test case now to their internal tests that hits this edge case. (Atleast I hope so ;))

Hey all, sorry for the delay in response. I have added the test case along with the fix.

The reason that the original fix was backed was for a few reasons:

1. We wanted to check the fix directly into github rather than having it go across the mirror for visibility reasons
2. We wanted to evaluate the fix further to see what kind of security impact it might have.

@richlander has posted a nice blog about the issue over at the MSDN dotnet blog: http://blogs.msdn.com/b/dotnet/archive/2015/07/28/ryujit-bug-advisory-in-the-net-framework-4-6.aspx

Thank you @mmitche.