On Sat, Apr 16, 2011 at 5:54 PM, Chris Casinghino <chris.casinghino@gmail.com> wrote:

On Sat, Apr 16, 2011 at 10:45 AM, Greg Weber <greg@gregweber.info> wrote:
> Are you compiling with the development server or doing a cabal build/

I'm doing a cabal build. To reproduce this, I run (cabal configure &&
cabal build) from the command line in the project directory.

I can confirm that this happens. However, it *only* happens when building with cabal. When building with "ghc --make", using runghc or wai-handler-devel, everything works fine. So I tried compiling with "ghc --make -O", and sure enough the same bug appeared.

I don't think there's anything we can do in the libraries to avoid this, it looks like a bug in GHC. You can modify your ghc-options line in the cabal file to pass in "-O0" to disable optimizations, though this is obviously not optimal (bad pun intended). I think we need to report this to the GHC team.

I know virtually nothing about GHC internals, but in case this means something to someone else, here's some of the output from "ghc --make -O -v test.hs":

*** Simplify:

*** CorePrep:

*** ByteCodeGen:

*** Desugar:

Result size = 8699

*** Simplifier SimplMode {Phase = InitialPhase [Gentle],

no inline,

rules,

eta-expand,

no case-of-case} max-iterations=4:

Result size = 9841

Result size = 9797

*** Specialise:

Result size = 9797

*** Float out(FOS {Lam = Just 0, Consts = True, PAPs = False}):

Result size = 13259

*** Float inwards:

Result size = 13259

*** Simplifier SimplMode {Phase = 2 [main],

inline,

rules,

eta-expand,

case-of-case} max-iterations=4:

Result size = 677741

Result size = 850762

Result size = 1028928

*** Simplifier SimplMode {Phase = 1 [main],

inline,

rules,

eta-expand,

case-of-case} max-iterations=4:

Result size = 1026905

Result size = 1026876

*** Simplifier SimplMode {Phase = 0 [main],

inline,

rules,

eta-expand,

case-of-case} max-iterations=4:

Michael