- Glasgow-haskell-users

big FFI bug in x86_64
by John Meacham 22 Apr '05

22 Apr '05

ghc 6.4 x86_64 appears to be interpreting foreign import "&foo" as importing the value of foo rather than the address of foo. I wrote a test case that demonstrates this problem here http://repetae.net/john/ghc-bug.tar.gz correct output: ;./foo () 0x080774f0 0x080774f4 0xdeadbeef incorrect output: ;./foo () 0x00000000deadbeef 0xffffffffdeadbeef zsh: segmentation fault (core dumped) ./foo This is a pretty major bug. I don't know how the libraries are even working. John -- John Meacham - ⑆repetae.net⑆john⑈

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building guide
by Bulat Ziganshin 21 Apr '05

21 Apr '05

Hello GHC, where i can find building guide in the html/pdf/... any other form readable by windows/IE? -- Best regards, Bulat mailto:bulatz@HotPOP.com

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limited-scope retry?
by Abraham Egnor 21 Apr '05

21 Apr '05

Suppose that a program using the Control.Concurrent.STM module had a producer/consumer setup - one thread writing to a channel, the other thread reading from the channel. It seems natural to want a function that the producer can call that will block until the consumer has finished consuming everything currently in the channel. The way I first tried implementing this was: -- types simplified for this example flush :: TChan () -> STM () flush chan = do e <- isEmptyTChan if not e then retry else return () Used in isolation, i.e. atomically $ writeTChan chan () atomically $ flush chan it works fine. However, when composed (atomically $ writeTChan chan () >> flush chan), it causes a race condition, usually resulting in deadlock, as the "retry" in flush replays the call to writeTChan as well. This situation begs for a way to limit the scope of "retry", in which case flush would be: flush chan = limitRetry $ do e <- isEmptyTChan if not e then retry else return () Abe

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RE: ghc for hp-ux 10.20 or 11
by Simon Marlow 21 Apr '05

21 Apr '05

On 21 April 2005 11:56, Benjamin Franksen wrote: > On Thursday 21 April 2005 11:38, Benjamin Franksen wrote: >> Has anyone ever succeeded in porting ghc to HP-UX 10.20 or later? > > Sidenote: The background is that I want to persuade people at work to > switch from CVS to darcs. It would be a lot easier to do so if I could > get darcs to compile under (at least) HP-UX 11. There are binaries for 4.08.2 that work on HP-UX (not sure which version, though). It's a 2-step bootstrap from 4.08.2: build 5.04.3, then use that to build 6.4. There are more recent binaries for Debian on HPPA, if that's any use. Cheers, Simon

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ghc for hp-ux 10.20 or 11
by Benjamin Franksen 21 Apr '05

21 Apr '05

Has anyone ever succeeded in porting ghc to HP-UX 10.20 or later? Ben

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wx library trouble
by Patrick Scheibe 21 Apr '05

21 Apr '05

Hi, I compiled successful the wxHaskell lib. But when I want to start ghci -package wx following error occurs: Loading package concurrent-1.0 ... linking ... done. Loading package wxcore-0.9 ... linking ... ghc-6.4.20050320: /home/izbifs/scheibe/built/lib/wxcore2.o: unknown symbol `wxcWakeUpIdle' *** Deleting temp files Deleting: ghc-6.4.20050320: unable to load package `wxcore-0.9' I have a running wxHaskell home. Same configuration... wxGtk version, wxhaskell version, same config options except of the prefix. In university it is installed local but I set the LD_LIBRARY_PATH. How can I figure out what's wrong? Can find out where and why the function `wxcWakeUpIdle' is available home and where are the differences? Has anybody a good hint where to start or what to check? Any help is welcome Cheers Patrick PS: Additional informations.. i386 GNU/Linux Fedora gtk+-1.2.10-33 gtk+-devel-1.2.10-33 wxGTK-2.4.2 wxHaskell 0.9 ghc version 6.4.20050320

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existential & GADT & escape
by Jim Apple 20 Apr '05

20 Apr '05

> data Z > data S a > > data L a n where > Nil :: L a Z > Con :: a -> L a b -> L a (S b) > > data LL a = forall n . LL (L a n) > > class Append p q r where > nappend' :: L a p -> L a q -> L a r > > instance Append Z q q where > nappend' _ y = y > > instance (Append p q r) => Append (S p) q (S r) where > nappend' (Con x y) z = Con x (nappend' y z) > > nappend (LL x) (LL y) = LL (nappend' x y) No instance for (Append n n1 r) arising from use of `nappend'' at NList.lhs: :29-36 Probable fix: add (Append n n1 r) to the existential context for `LL' In the first argument of `LL', namely `(nappend' x y)' In the definition of `nappend': nappend (LL x) (LL y) = LL (nappend' x y) Clearly I can write nappend like: nappend :: LL a -> LL a -> LL a nappend (LL Nil) y = y nappend (LL (Con x Nil)) (LL z) = LL (Con x z) nappend (LL (Con x y)) (LL z) = nappend (LL (Con x Nil)) (nappend (LL y) (LL z)) but I'd rather keep the nice guarentee from nappend'. Any ideas? Jim

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RE: Porting the GHC to GNU/Hurd
by Simon Marlow 20 Apr '05

20 Apr '05

On 10 April 2005 14:20, Thomas Schwinge wrote: > [ Grrr. Why do I have to subscribe just to post this message? ] Sorry for the inconvenience, it's because I don't have time to wade through all the spam. > Is someone aware of any efforts to port the GHC to GNU/Hurd? > If not, I'd like to give that a try. No, and good luck! Cheers, Simon

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RE: garbage collection
by Simon Marlow 20 Apr '05

20 Apr '05

On 12 April 2005 15:59, Bulat Ziganshin wrote: > Hello glasgow-haskell-users, > > 1) can you add disableGC and enableGC procedures? this can > significantly improve performance in some cases Sure. I imagine you want to do this to avoid a major collection right at the peak of a residency spike. You probably only want to disable major collections though: it's safe for minor collections to happen. You might be better off using System.Mem.performGC just before the residency spike. This doesn't have the pitfalls of enable/disableGC, but it might entail doing more GC than necessary. > 2) if, for example, program's data before GC is 80 mb and after GC is > 60 mb then the program will occupy after GC the whole 140 mb and ALL > this space will be marked by OS as used! if there's a memory shortage, > old program data even can be swapped to disk despite the fact that we > absolutely don't need them! that behaviour significantly enlarge > memory needs of GHC-compiled programs > > if this unused memory will be returned to OS or marked as unneeded > after GC then will problem will go on. preferably this must be done > during the time of GC, on each page which contents has been already > compacted. in this case such program will never use more than 80mb of > real memory (+ 1 page + memory for GC) I guess you're proposing using madvise(M_FREE) (or whatever the equivalent is on your favourite OS). This would certainly be a good idea if the program is swapping, but might impose an overhead when running in memory. I don't know, I haven't tried. Also, you might be better off using +RTS -c or +RTS -M<size> to avoid swapping in the first place. Cheers, Simon

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RE: Why this happens?
by Simon Marlow 20 Apr '05

20 Apr '05

On 19 April 2005 15:37, Santoemma Enrico wrote: > I've always thought that compilers for functional languages were able > to recognize tail recursion and to transform it into a loop. So, why > this line eats all my machine's memory (and then runs out of stack > space)? > > sum [1..10000000] -- ten millions Without optimisation, or in GHCi, you get the overloaded version of sum: sum :: (Num a) => [a] -> a the compiler therefore cannot assume that (+) is strict. If you compile with optimisation, you'll get sum specialised to Int or Integer, which will use the strict definition. Cheers, Simon

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