state hack causes unneeded value to be evaluated
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 |