GitLab

The following code prints "Main: Why?" when compiled with ghc -O1. With -fno-state-hack it works fine.

data X = X ()

{-# NOINLINE newX #-}
newX :: () -> IO X
newX n = do
    let {-# NOINLINE value #-}
        value = n
    return (X value)

main = do
    x <- newX (error "Why?")
    case x of
        X _ -> return ()

Both pragmas are needed to exhibit the bug.

(In my actual code, value is an unsafePerformIO -- this was the motivation for adding the pragmas.)

Trac metadata

Trac field	Value
Version	6.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture