October 2001 - Glasgow-haskell-users

RE: gtk+hs and libgmp
by Simon Marlow 25 Oct '01

25 Oct '01

> On Thu, 2001-10-25 at 12:04, Simon Marlow wrote: > > > > > The version in /opt/ghc/lib/ghc-5.02 should work, as should > /usr/local/lib/libgmp.so.3.1.1. The version in /usr/lib > looks like GMP 2, so that would cause the link errors. > > > > Make sure the link command line doesn't have -L/usr/lib on > it, or at least not before -L/usr/local/lib and > -L/opt/ghc/lib/ghc-5.02. > > > > Cheers, > > Simon > I tried to remove the libgmp.so from both /usr/local/lib and /usr/lib. > ghc doesn't seem to link with the one in /opt/ghc. Also when I give > /opt/ghc/lib/ghc-5.02/libgmp.a on the command line it doesn't > work... It > only works with /usr/local/lib/libgmp.so. I guess, that gmp is always > used, so I wonder that it works apart from gtk+hs. It seems very strange that the libgmp in your GHC installation doesn't work. How did you install GHC? Do you have problems linking other programs, or just gtk+hs programs? Cheers, Simon

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RE: gtk+hs and libgmp
by Gérard Milmeister 25 Oct '01

25 Oct '01

On Thu, 2001-10-25 at 12:04, Simon Marlow wrote: > > The version in /opt/ghc/lib/ghc-5.02 should work, as should /usr/local/lib/libgmp.so.3.1.1. The version in /usr/lib looks like GMP 2, so that would cause the link errors. > > Make sure the link command line doesn't have -L/usr/lib on it, or at least not before -L/usr/local/lib and -L/opt/ghc/lib/ghc-5.02. > > Cheers, > Simon I tried to remove the libgmp.so from both /usr/local/lib and /usr/lib. ghc doesn't seem to link with the one in /opt/ghc. Also when I give /opt/ghc/lib/ghc-5.02/libgmp.a on the command line it doesn't work... It only works with /usr/local/lib/libgmp.so. I guess, that gmp is always used, so I wonder that it works apart from gtk+hs. -- Gérard Milmeister Tannenrauchstr. 35 8038 Zürich gemi(a)bluewin.ch

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RE: Thread-Safety through FFI
by Simon Marlow 25 Oct '01

25 Oct '01

> >This might work, but no guarantees. > > OK, so I'd be better off making sure all Haskell runs in one > OS-thread. My concerns still apply - non-thread-friendly library calls may mean that GHC's RTS interacts badly with the rest of your threaded program. > Although presumably I can use Haskell-threads: I can have a special > Haskell-thread that handled a queue of incoming execution requests, > firing off a new Haskell-thread for each one. And then I could have a > native-code mechanism to allow asynchronous additions to the queue. Yes, there's no restriction on using Haskell threads because they're handled internally by the RTS. Cheers, Simon

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RE: GHC Installation Location
by Simon Marlow 25 Oct '01

25 Oct '01

> At 2001-10-25 03:01, Simon Marlow wrote: > > >I've wondered at various times in the past whether there > ought to be a > >link from /usr/local/includes/ghc to > /usr/local/lib/ghc-5.02/includes. > > Won't help, my GHC is installed at /usr/lib/ghc-5.02/, > exactly where the > Debian package put it. And now that location is hard-coded in > my Makefile. > > >But the usual way around this problem is to use 'ghc' as > your C compiler > >- then the -I flag gets injected automatically. > > GHC didn't seem to want to compile my .cpp file -- instead it > quietly and > successfully did nothing. Yes, I guess GHC should really understand C++ file suffixes. > Also I had to do this: > > extern "C" { > #include "Rts.h" > } Thanks, I'll look into fixing that. Cheers, Simon

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Profiling in GHC-4.08.1
by Andre W B Furtado 25 Oct '01

25 Oct '01

I was trying to compile a .hs file with the profiling option enabled (-prof -auto-all) but I got an error message: /usr/bin/ld: cannot find -lHSstd_p_imp collect2: ld returned 1 exit status Does anyone know what is this "-lHSstd_p_imp"? I am using GHC-4.08.1 (with Cygwin) under a Windows 98 platform. Thanks, -- Andre

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RE: Thread-Safety through FFI
by Ashley Yakeley 25 Oct '01

25 Oct '01

At 2001-10-25 03:12, Simon Marlow wrote: >This might work, but no guarantees. OK, so I'd be better off making sure all Haskell runs in one OS-thread. Although presumably I can use Haskell-threads: I can have a special Haskell-thread that handled a queue of incoming execution requests, firing off a new Haskell-thread for each one. And then I could have a native-code mechanism to allow asynchronous additions to the queue. -- Ashley Yakeley, Seattle WA

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Multi-parameter OOP
by George Russell 25 Oct '01

25 Oct '01

Recently I've been experimenting with a sort of OOP with GHC, using existential types and (overlapping, undecidable) multi-parameter type classes, but it doesn't seem to work as you might expect because of the way GHC resolves overloaded functions at compile-time. For example, given class A a data WrappedA = forall a . A a => WrappedA a data A1 = A1 instance A A1 class B b data WrappedB = forall b . B b => WrappedB b data B1 = B1 instance B B1 class AB a b where toBool :: a -> b -> Bool instance (A a,B b) => AB a b where toBool _ _ = False instance AB A1 B1 where toBool _ _ = True instance AB WrappedA WrappedB where toBool (WrappedA a) (WrappedB b) = toBool a b a naive user (like me a month ago) might expect that this to work, so that toBool (WrappedA a) (WrappedB b) will return False unless a is an A1, and b a B1, in which case it returns True. In fact ghc5.02 (rightly) gives an error message with the second instance declaration: Could not unambiguously deduce (AB a b) from the context (A a, B b) The choice of (overlapping) instance declaration depends on the instantiation of `a, b' So is there any other way of doing this sort of dynamic lookup at runtime, in a reasonably neat way?

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RE: Thread-Safety through FFI
by Simon Marlow 25 Oct '01

25 Oct '01

> >It isn't safe to call foreign exported > >functions from more that one OS thread simultaneously. > > OK, can I call a foreign exported function from some other > thread while > the main thread is in 'foreign import' native code? I could > have calls to > the foreign exported function block until the main thread called a > special foreign imported 'yield' function. This might work, but no guarantees. Make sure that at least the foreign import yield doesn't have an unsafe annotation. The reason I'm slightly worried is that the RTS isn't written to be used in a threaded environment - it doesn't use thread-friendly library calls, and I don't even want to think about signal handling. Cheers, Simon

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qforeign-0.65: Bzip2: problems with [Word8]
by Michael Marte 25 Oct '01

25 Oct '01

Hello *, I am just trying to catch up with the lastest developments. >From qforeign-0.64 to qforeign-0.65, some types were changed: "Zlib and Bzip2 express byte lists as [Word8] instead of String." But I need String -> String! (Reading from a file, decompressing, and feeding it to the XML parser.) How can I do this? I found out that fromIntegral does the conversion from Word8 to Char but I do not know how to convert from Char to Word8. Since files are pretty large, the conversions should have no operational impact. Thanks, Michael

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RE: gtk+hs and libgmp
by Simon Marlow 25 Oct '01

25 Oct '01

> When trying to compile the examples in gtk+hs, I get the > following link > errors: > /opt/ghc/lib/ghc-5.02/libHSstd.a(PrelFloat__413.o): In > function `shP2_2_alt': > PrelFloat__413.o(.text+0x2b0): undefined reference to `__gmpz_cmp_si' > etc.. > When linking simple programs, this doesn't occur. > I have the following gmp's installing: > /usr/lib/libgmp.so.2.0.2 > /usr/local/lib/libgmp.so.3.1.1 > /opt/ghc/lib/ghc-5.02/libgmp.a > It seems that the programs only link with the version in > /usr/local/lib. > I tried putting this path in 'library_dirs' for package 'gmp' in > 'package.conf', but to no avail. Only when I explicitly put > '/usr/local/lib/libgmp.so' in 'extra_ld_opts' for package 'gmp' > did it work. The version in /opt/ghc/lib/ghc-5.02 should work, as should /usr/local/lib/libgmp.so.3.1.1. The version in /usr/lib looks like GMP 2, so that would cause the link errors. Make sure the link command line doesn't have -L/usr/lib on it, or at least not before -L/usr/local/lib and -L/opt/ghc/lib/ghc-5.02. Cheers, Simon

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