unsafe causes bug, news @ 11

I know there has been plenty of levity here lately but here goes :)

I didn't expect ‘isUndefined’ to be safe but this may be interesting to the devs (I am obedient and report it thusly and hereby-ly per GHC's request)

% ghci -ignore-dot-ghci
GHCi, version 8.1.20160117: http://www.haskell.org/ghc/  :? for help
Prelude> import Control.Exception
Prelude Control.Exception> import System.IO.Unsafe
Prelude Control.Exception System.IO.Unsafe> import Unsafe.Coerce
Prelude Control.Exception System.IO.Unsafe Unsafe.Coerce> isUndefined x = unsafePerformIO $ catch ((unsafeCoerce x :: IO ()) >> return False) (const $ return True :: SomeException -> IO Bool)
Prelude Control.Exception System.IO.Unsafe Unsafe.Coerce> isUndefined (succ True)
True
Prelude Control.Exception System.IO.Unsafe Unsafe.Coerce> isUndefined (succ False)
<interactive>: internal error: stg_ap_v_ret
    (GHC version 8.1.20160117 for x86_64_unknown_linux)
    Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
Aborted (core dumped)
%

Trac metadata

Trac field	Value
Version	7.10.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 5

added Tbug Trac import labels

Well, unsafeCoerce can certainly cause seg-faults. Is there more to it than that?

closed

Indeed, I'm going to chalk this up as not-a-bug unless there's compelling reason to believe otherwise.

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedInvalid

mentioned in issue #16302 (closed)

added Pnormal label