- Glasgow-haskell-users

RE: Uninitialized UArray - feature or bug?
by Simon Marlow 13 Jan '03

13 Jan '03

> This is a little weird: > > Prelude> :m + Data.Array.Unboxed > Prelude Data.Array.Unboxed> let f () = array (1, 5) [] :: > UArray Int Int > Prelude Data.Array.Unboxed> f () == f () > False > > Are we giving away purity for efficiency? ;) > If this behaviour is intended, maybe it should be documented? > > Maybe it would be a good idea to define default values for types which > can be unboxed? That's a very good point :) Fixed now, thanks. Cheers, Simon

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RE: FFI & C++ & Cygwin
by Simon Peyton-Jones 13 Jan '03

13 Jan '03

| It is possible to trick ghc into using cygwin's gcc in mingw-mode, | the following steps works for me to do that: Interesting. The only worry is that the run-time system and libraries are all pre-compiled with the mingw gcc. So it's not clear to me that the process Peter outlines will always work. Or, if it does, why doesn't it work using the mingw gcc all the time for Haskell files? Here's a guess: use g++ -mno-cygwin for the C++ files and ordinary ghc for the Haskell files. Then, linking with ghc will give linking errors, as Koen found, only because the g++ files expect to be linked with some g++ runtime system code. If that is the only problem, it can be solved by doing g++ -v to link, seeing what extra link libraries are given to ld, and giving those same libraries to the ghc link step. Or, dually, see what libraries ghc passes to ld, and give those to g++. If this works, and someone will write it up, I'll add it to the users guide. Incidentally, on the subject of building GHC to target Cygwin (rather than Mingw), I'm sure it's possible, because Sigbjorn has done it, although it's not a route we support, and I just don't know understand all the differences well enough to know what the problems are. But, if someone makes it work (which I'm sure is possible) I'd gladly apply make-system patches, and add guidance notes to the building guide, in here: http://haskell.cs.yale.edu/ghc/docs/latest/html/building/winbuild.html Simon | * compile the c++-stuff with g++ -mno-cygwin | * copy /usr/bin/gcc.exe to c:/ghc/ghc-5.04.2/gcc.exe | * rename c:/ghc/ghc-5.04.2/gcc-lib to something else | (ghc feeds a -B option to gcc, which we cannot(?) override) | * compile with "ghc -optl -mno-cygwin -lstdc++" | (add -optc -mno-cygwin if -fvia-C is used) | | (i.e. we would like to use /usr/bin/gcc -mno-cygwin as the linker) | | I think it should be possible to use -pgml instead of replacing | the binary, but that didn't work for me.. | | > However, I have tried to recompile the C++ libraries using | > the Mingwin C++ compiler but it starts throwing pages of | > error messages at me. | | However, the method above doesn't help if you really need cygwin | for your c++-library, which you seem to do? | | | /Peter | | _______________________________________________ | Glasgow-haskell-users mailing list | Glasgow-haskell-users(a)haskell.org | http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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System.CPUTime
by Koen Claessen 13 Jan '03

13 Jan '03

Dear all, I have a question about the semantics of the function 'getCPUTime' in the module 'System.CPUTime'. Does it ever reset itself? I.e. is there a guarantee that if t1 is the result of a call to getCPUTime, any other call to getCPUTime will produce a result that is greater? It seems not to reset itself on Solaris and Linux GHC (or it has a very long period), but it seems to reset itself within 5 minutes or so on Windows GHC (version 5.04.2, binary downloaded from GHC's homepage, running Windows 2000). Regards, /Koen.

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Another question regarding Template Haskell
by Sean Seefried 13 Jan '03

13 Jan '03

Would it be possible to write a function "showFun" such that one could write a program f x y = x +y -- say main = putStrLn (show $(showFun f)) and the result of this program would be "f" I don't think it's possible at the moment because one can't reify expressions. Sean Seefried p.s. If I'm posting to the wrong group, I apologise, it's just that template-haskell doesn't seem to be a mail group just yet. I've posted to it and haven't seen any of my postings appear yet.

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Why doesn't this Template Haskell program work?
by Sean Seefried 13 Jan '03

13 Jan '03

I compiled the following program with ghc-5.05.20030109 ---------- import Language.Haskell.THSyntax main = putStrLn (show $(lift ('a', 'b'))) instance (Lift a, Lift b) => Lift (a,b) where lift (a,b) = tup [lift a, lift b] ----- and received the following error message ------- ghc --make -fglasgow-exts -package haskell-src -package haskell98 Main.hs -o test Chasing modules from: Main.hs Compiling Main ( Main.hs, ./Main.o ) Loading package base ... linking ... done. Loading package haskell98 ... linking ... done. Loading package haskell-src ... linking ... done. ghc-5.05.20030109: panic! (the `impossible' happened, GHC version 5.05.20030109): nameModule zdfLiftZ2T{-a1dB-} Please report it as a compiler bug to glasgow-haskell-bugs(a)haskell.org, or http://sourceforge.net/projects/ghc/. ------ Why? Because if I compile the following program, -------- import Language.Haskell.THSyntax main = putStrLn (show $(tup [lift 'a', lift 'b'])) -------- it works just fine. Also, is the template-haskell mailing list active? Sean Seefried

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Uninitialized UArray - feature or bug?
by Tomasz Zielonka 13 Jan '03

13 Jan '03

Hello! This is a little weird: Prelude> :m + Data.Array.Unboxed Prelude Data.Array.Unboxed> let f () = array (1, 5) [] :: UArray Int Int Prelude Data.Array.Unboxed> f () == f () False Are we giving away purity for efficiency? ;) If this behaviour is intended, maybe it should be documented? Maybe it would be a good idea to define default values for types which can be unboxed? Regards, Tom -- .signature: Too many levels of symbolic links

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Shutting Down the RTS
by Wolfgang Thaller 12 Jan '03

12 Jan '03

I'm almost ready to send in a patch that should fix most of the current issues with the threaded RTS. But.... I'm stuck at the problem of terminating the RTS in a proper way. According to the GHC manual, a concurrent Haskell program should terminate when the main action terminates. This sounds reasonable and matches the behaviour of C programs on most platforms. In the threaded RTS, this behaviour has never been implemented. We can't simply return from schedule(), because we might no longer be running in the thread of the RTS main() routine. The thread where rts_mainEvalIO was called might be busy executing some foreign code that we know nothing about. (Im)possible solution #1: As soon as the main action terminates, call shutdownHaskellAndExit(). At first, this seems to work fine. But then, shutdownHaskellAndExit() comes along and tries to run finalizers. For every finalizer, the RTS is started back up again using rts_mainEvalIO(), and this time, we really have to exit by returning from rts_mainEvalIO(). Possible solution #2: Forget about running finalizers at program termination and just exit(). In most of the situations where I'd use finalizers, I don't need to run them upon program termination, the OS cleans up after me. Also, the finalizers are not run in the correct order anyway, and there are situations where running them in the wrong order might be worse than not running them at all. And, most of all, solution #2 is easy to implement. Can somebody suggest a third solution, or shall I go for #2 for the time being? Cheers, Wolfgang

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FFI & C++ & Cygwin
by Koen Claessen 11 Jan '03

11 Jan '03

Dear GHC users, I have the following problem and I wonder if anyone can help. I am using the FFI to talk to a library of functions written in C++. On Unixes (Solaris, Linux) this works just fine if one adds the right -ldstdc++ here and there. However, I am using Cygwin now and that is where all the problems start. The C++ stuff compiles fine (using Cygwin's g++). The Haskell stuff compiles just fine (using Win Ghc). However, at linking time I get the following error: - undefined reference to '_impure_ptr' - undefined reference to 'operator delete(void*)' - undefined reference to 'vtable for ___cxxabiv1::__blahblah' These are all things that C++ uses internally. I think the problem is that I used Cygwin's g++ compiler and that Ghc uses Mingwin's gcc compiler to compile and link. However, I have tried to recompile the C++ libraries using the Mingwin C++ compiler but it starts throwing pages of error messages at me. The other way around: using a Cygwin specific GHC, seems more appropriate, but where does one get one of those? (I have never managed to compile one myself.) Any ideas? /Koen.

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Re: signal masks and garbage collection.
by Wolfgang Thaller 10 Jan '03

10 Jan '03

Keean Schupke wrote: > I am trying to block the SIGPIPE signal, I have used the Posix > sigprocmask > call to set the signal to blocked. However the program sill bails out > if the > client closes its socket. The exception handler appears to be called > then > the program terminates. When I run the program in gdb, it gives a > SIGPIPE > signal just after the thread swap happens... Heres the report from gdb: I think I know what's going on: The runtime system is using sigprocmask for it's own purposes and accidentally overwrites your signal mask. In short: stay away from sigProcMask and friends, they don't work. Instead, try to use: installHandler sigPIPE Ignore Nothing I hope that works, I haven't tried it. Cheers, Wolfgang Thaller

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RE: openFile and threads
by Peter Thiemann 10 Jan '03

10 Jan '03

Hi, one thing that I gleaned from Matthias's strace output is the fcntl system calls to obtain the locks. They are not really needed for my application and could be avoided using the POSIX library. However, this does not seem to be a big issue just from the cost of the system calls, because there is no noticeable difference between Matthias's C programs. > > But it sounds like in your case you need to open lots of (small?) files. > What do you do with the contents of the files? Yes, the files are small. They typically contain less than 10 words. These words are key words and the Select program selects file names based on boolean expressions formed from the key words. What I'm actually doing is implementing a data base for email messages, where these file names are the primary keys for the messages. Each message is represented by two files of the same name (but in different directories), the data file containing the raw message, and the meta data file that just contains a list of key words. Keeping the meta data in this way allows for smooth interaction with file synchronization across several computers. So it's necessary that each set of key words resides in its own file. I have created a web page with a little more argumentation about it: http://www.informatik.uni-freiburg.de/~thiemann/MailStore The downloadables may be a bit out of date, but you get the idea. Hope that helps. -Peter

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