- Glasgow-haskell-users

fun with sockets (ghc-5.04.1)
by Peter Thiemann 09 Mar '03

09 Mar '03

Hi, I'm running into a problem using server code (running on a UNIX domain socket) that I basically snatched from Simon Marlow's web server: ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ mainLoop sock defUser getMs = do putStrLn "Accepting connections..." installHandler sigPIPE Ignore Nothing loop (0::Int) where loop n = do (connection, peerAddress) <- accept sock h <- socketToHandle connection ReadWriteMode forkIO ( (talk n getMs defUser h `finally` goodBye n h) `Exception.catch` (\e -> putStrLn ("Exception: " ++ show e)) ) loop (n+1) goodBye n h = do putStrLn (show n ++ ": finished") hClose h ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ After processing a random number of connections, the server dies with Fail: invalid argument Action: accept Reason: Invalid argument after finishing the last connection. For the record, here is the code that is executed for each connection: ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ talk n getMs user h = do hSetBuffering h LineBuffering putStrLn (show n ++ ": ") str <- hGetLine h lstr <- hGetLine h putStrLn ("...: " ++ lstr) -- last output before core dump let msglength = read (takeWhile isDigit (drop 1 lstr)) rawmsg <- hGetContents h putStrLn ("Got " ++ show (length msg) ++ " characters") ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ The machine is Linux kailua 2.4.18-4GB #1 Wed Mar 27 13:57:05 UTC 2002 i686 unknown The problem seems to go away if I switch to INET sockets, so I'm also including my initialization code: ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ withSocketsDo $ do sock <- socket AF_UNIX Stream 0 bindSocket sock (SockAddrUnix path) listen sock maxListenQueue getMs <- initializeAll mainLoop sock defUser getMs ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ -Peter

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RE: Stack profiling
by Simon Marlow 06 Mar '03

06 Mar '03

> > In the CVS version there's a -xt RTS flag that enables inclusion of > > thread stacks in a heap profile. It's crude, because thread stacks > > grow > > by doubling their size every time they run out of space, > but it should > > be enough to show the difference between O(n) stack usage and O(1). > > Hmm. That sounds like what I need, I think. Is it in HEAD or in the > 5.04 (now 5.04.3?) branch? It's only in the HEAD. Cheers, Simon

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RE: Stack profiling
by Simon Marlow 06 Mar '03

06 Mar '03

> | > Stephen Pitts <smpitts(a)ou.edu> wrote: > | >> Is there an easy way to profile stack usage without > rebuilding with > | >> ticky-ticky profiling? I have two implementations of an > algorithm; > | >> the one with straight lists seems to use constant stack, > while the > | >> one with a JoinList is eating up stack at an O(n) rate. > > I don't think there is right now. What sort of profile would you like > to see in an ideal world? What sort of profile would still be useful, > even if not ideal? Remember that GHC is a concurrent system, so there > may be many threads running, each with its own stack. > > Even with ticky-ticky, I'm not sure if we capture maximum > stack depth at > the moment. But I agree that something along those lines > sounds useful. > > Anyone feel like helping implement it, if we could agree a spec? In the CVS version there's a -xt RTS flag that enables inclusion of thread stacks in a heap profile. It's crude, because thread stacks grow by doubling their size every time they run out of space, but it should be enough to show the difference between O(n) stack usage and O(1). Cheers, Simon

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How Make a executable file in Glasgow
by jmario＠uniquindio.edu.co 06 Mar '03

06 Mar '03

Hello, i am beginner in Glasgow and Haskell, And I would like to know How I do to create a executable file in Glasgow (*.exe) thanks! Mario

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GHC's readLitChar does not conform to 98
by Akim Demaille 05 Mar '03

05 Mar '03

Hi! I believe the implementation of readLitChar (and lexLitChar) does not conform to the documentation, and this results in GHC and Hugs disagreeing on the following code: ---------------------------------------- module Main (main) where import IO (stderr, hPutStrLn) import Char (digitToInt, lexLitChar, readLitChar) main :: IO () main = do hPutStrLn stderr (show $ readLitChar "A") hPutStrLn stderr (show $ readLitChar "'A'") ---------------------------------------- ghc says: /tmp % ghc --version nostromo 14:45 The Glorious Glasgow Haskell Compilation System, version 5.04.2 /tmp % /tmp/a.out nostromo 14:46 [] [('A',"")] and Hugs says: /tmp % runhugs Main.hs nostromo Err 1 [('A',"")] [('\'',"A'")] The doc seems to agree with Hugs (thanks to sebc for the pointer): <http://www.haskell.org/onlinereport/char.html> > The function showLitChar converts a character to a string using only > printable characters, using Haskell source-language escape > conventions. The function lexLitChar does the reverse, returning the > sequence of characters that encode the character. The function > readLitChar does the same, but in addition converts the to the > character that it encodes. For example: > > showLitChar '\n' s = "\\n" ++ s > lexLitChar "\\nHello" = [("\\n", "Hello")] > readLitChar "\\nHello" = [('\n', "Hello")]

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RE: Stack profiling
by Simon Peyton-Jones 05 Mar '03

05 Mar '03

| > Stephen Pitts <smpitts(a)ou.edu> wrote: | >> Is there an easy way to profile stack usage without rebuilding with | >> ticky-ticky profiling? I have two implementations of an algorithm; | >> the one with straight lists seems to use constant stack, while the | >> one with a JoinList is eating up stack at an O(n) rate. I don't think there is right now. What sort of profile would you like to see in an ideal world? What sort of profile would still be useful, even if not ideal? Remember that GHC is a concurrent system, so there may be many threads running, each with its own stack. Even with ticky-ticky, I'm not sure if we capture maximum stack depth at the moment. But I agree that something along those lines sounds useful. Anyone feel like helping implement it, if we could agree a spec? Simon

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Re: Stack profiling
by Wolfgang Thaller 04 Mar '03

04 Mar '03

I had wanted to CC this to the list, but of course I forgot: > Stephen Pitts <smpitts(a)ou.edu> wrote: >> Is there an easy way to profile stack usage without rebuilding with >> ticky-ticky profiling? I have two implementations of an algorithm; >> the one with straight lists seems to use constant stack, while the >> one with a JoinList is eating up stack at an O(n) rate. > > No idea. I haven't used all features of the profiler yet. I'm taking > the liberty of CCing the glasgow-haskell-users(a)haskell.org mailing > list, I hope somebody else can provide an answer. > >> If not, could I have your build script to generate a MacOS X package >> for a rebuilt GHC with ticky-ticky libraries? No matter what I do, >> all roads lead to rebuilding from source ;-). > > There's no build script for making Mac OS X packages - I need to use > Apple's GUI tools to create the package, and the rest is a relatively > simple matter of configure and make. > You'd have to download the source, create a build.mk file saying that > you want ticky-ticky profiling, and then configure, make and make > install... > > Cheers, > > Wolfgang >

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Effect of large binaries on garbage collection
by Adrian Hey 04 Mar '03

04 Mar '03

Hello, I'm writing a library which will require many blocks of binary data of various sizes (some very large) to be stored in the heap. I'm a little worried about the effect this will have on the efficiency of garbage collection. I'm not sure how ghc gc works these days, but I seem to remember it's a copying collector by default. If so it seems a pity to waste time copying 10's of MBytes of binaries at each collection. The options I'm considering are.. (1) Use Haskell heap space Pros: Easy for me Cons: May slow down gc AFAICS I can't use anything like realloc Current FFI proposals seem to prevent me from directly accessing Haskell heap objects from C land (or have I misunderstood?). (2) Use C heap space Pros: Easy(ish) to use from C and Haskell ffi Cons: Unless C heaps have improved a lot since I last looked (which I doubt), it seems likely I will suffer from slow allocation and fragmentation problems. (3) Write my own "sliding" heap manager and use finalisers for garbage collection. Pros: Can tailor it to work exactly the way I want. Cons: More work for me, especially if I want the result to be portable across OS's. Might be a complete waste of time if my worries about ghc heap management are groundless :-) Any advice? Thanks -- Adrian Hey

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Network on Win98: failed - socket - no error ??
by Claus Reinke 04 Mar '03

04 Mar '03

I'm playing with the Network library (the recommended portable way?) and have a surprising problem with a simple client/server example. As the same program works fine on Solaris and Win2k, I suspect its a standard "feature" and someone here with more network programming experience might be able to enlighten me? - Server: listenOn port, then accept handle and enter loop, echoing from handle to stdout - Client: connectTo "localhost" port, then enter loop echoing from stdin to handle Both programs work on Solaris and Win2k, but fail on Win98, with: Fail: failed Action: socket Reason: No error which would be merely amusing, I guess, if I knew what it meant, and what to do about it? Cheers, Claus

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child process statistics
by Dean Herington 28 Feb '03

28 Feb '03

Does anyone know how to get the process statistics (cputime, page faults, etc.) for a child process? When the child process has terminated, before doing getAnyProcessStatus on it, I'd like to get its statistics. Browsing the libraries documentation didn't turn anything up. I couldn't even find what I want at the Unix level among man pages. (I'm happy to write some FFI code to access system routines if I can locate the right ones.) Dean

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