FIXED IT!!! The problem with charm.hs and its FFI dependency charm.c is that both want to produce an intermediary charm.o file. Solution: rename charm.hs to hscharm.hs.
Would you (or anyone else) care to update the tutorials on the Haskell Wiki? As someone wrote below:
While the tutorials at HaskellWikihttp://www.haskell.org/haskellwiki/FFI_complete_examples are helpful, they're outdated. Argh!
It would be great if someone was public-spirited enough to fix this. The root page is here
http://haskell.org/haskellwiki/GHC/Using_the_FFI
which in turn links to the "complete examples" page mentioned above.
The docshttp://www.haskell.org/ghc/docs/latest/html/users_guide/ffi-ghc.html#glasgow... say that -#include pragmas no longer work, but fail to explain how to load code without them. Suffice to say I have no recourse but trial and error."
Ah, now that is a GHC documentation question. Can you tell us what should the docs should say instead? Then we can fix the docs.
Simon
From: haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of Andrew Pennebaker
Sent: 14 July 2011 07:57
To: Jason Dagit
Cc: Haskell Cafe
Subject: Re: [Haskell-cafe] FFI for a beginner
FIXED IT!!!
The problem with charm.hs and its FFI dependency charm.c is that both want to produce an intermediary charm.o file.
Solution: rename charm.hs to hscharm.hs.
Cheers,
Andrew Pennebaker
www.yellosoft.ushttp://www.yellosoft.us
On Tue, Apr 12, 2011 at 5:55 PM, Andrew Pennebaker mailto:andrew.pennebaker@gmail.com> wrote:
hsc2hs and c2hs are good suggestions, and some of the tutorials I'm following use them.
But 1) Many Haskell FFI tutorials don't require them, so they only seem to help, or only help in older versions of GHC.
And 2) When I did compile using c2hs, it just produced the same file, but with filler comments like {#- LINE 13 #-}. And they still refused to compile for the same reason:
ld: duplicate symbol _Charm_getWidth_info in charm.o and charm.o
Cheers,
Andrew Pennebaker
www.yellosoft.ushttp://www.yellosoft.us
On Sat, Apr 9, 2011 at 9:50 PM, Jason Dagit mailto:dagitj@gmail.com> wrote:
I don't know how to make ghc load them without using either hsc2hs or c2hs. I've had better experiences with hsc, but your mileage may vary.
On Apr 8, 2011 3:34 AM, "Andrew Pennebaker" mailto:andrew.pennebaker@gmail.com> wrote:
ncurses is proving too difficult to setup, so I'm working on a new library called charm. The C code works by itself, but I can't compile a Haskell wrapper for it. While the tutorials at HaskellWikihttp://www.haskell.org/haskellwiki/FFI_complete_examples are helpful, they're outdated. Argh! The docshttp://www.haskell.org/ghc/docs/latest/html/users_guide/ffi-ghc.html#glasgow... say that -#include pragmas no longer work, but fail to explain how to load code without them. Suffice to say I have no recourse but trial and error.
GitHub: charmhttps://github.com/mcandre/charm and hscharmhttps://github.com/mcandre/hscharm
$ make
cp /usr/include/charm.c .
ghc --make -fforce-recomp -o hellocharm hellocharm.hs charm.hs charm.c -I/usr/include -dylib-install-name /usr/lib/libcharm.dynlib
[1 of 2] Compiling Charm ( charm.hs, charm.o )
[2 of 2] Compiling Main ( hellocharm.hs, hellocharm.o )
Linking hellocharm ...
ld: duplicate symbol _Charm_getWidth_info in charm.o and charm.o
collect2: ld returned 1 exit status
make: *** [hellocharm] Error 1
Cheers,
Andrew Pennebaker
www.yellosoft.ushttp://www.yellosoft.us
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