id,summary,reporter,owner,description,type,status,priority,milestone,component,version,resolution,keywords,cc,os,architecture,failure,difficulty,testcase,blockedby,blocking,related
3049,STM with data invariants crashes GHC,simonpj,,"Ben Franksen writes: my ghc(i) crashes when using STM data invariants. This little piece of code demonstrates the problem:
{{{
module Bug where

import Control.Concurrent.STM

test = do
  x <- atomically $ do
    v <- newTVar 0
    always $ return True -- remove this line and all is fine
    return v
  atomically (readTVar x) >>= print
}}}
This is what ghci makes of it:
{{{
ben@sarun> ghci Bug.hs
GHCi, version 6.10.1: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer ... linking ... done.
Loading package base ... linking ... done.
[1 of 1] Compiling Bug              ( Bug.hs, interpreted )
Ok, modules loaded: Bug.
*Bug> test
Loading package syb ... linking ... done.
Loading package array-0.2.0.0 ... linking ... done.
Loading package stm-2.1.1.2 ... linking ... done.
zsh: segmentation fault  ghci Bug.hs
}}}
I am using ghc-6.10.1 freshly installed from source with just a 'cabal
install stm' thrown after it.

BTW, the documentation for `Control.Concurrent.STM.TVar` lists... nothing.
Similar with `Control.Monad.STM`. Well, at least the source link works, so
one isn't completely lost... :-)

",bug,closed,normal,6.12.1,Runtime System,6.10.1,fixed,,ben.franksen@… nicolas.pouillard@… int-e@… dbueno@…,Unknown/Multiple,Unknown/Multiple,,Unknown,,,,