June 2007 - C2hs - Haskell.org

Storable (Maybe a) leaks memory?
by Bjorn Bringert 14 Jun '07

14 Jun '07

In the C2HS.hs which is generated by 'c2hs -l', I found this code: instance Storable a => Storable (Maybe a) where sizeOf _ = sizeOf (undefined :: Ptr ()) alignment _ = alignment (undefined :: Ptr ()) peek p = do ptr <- peek (castPtr p) if ptr == nullPtr then return Nothing else liftM Just $ peek ptr poke p v = do ptr <- case v of Nothing -> return nullPtr Just v' -> new v' poke (castPtr p) ptr In the poke implementation, 'Foreign.Marshal.Utils.new' is used. 'new' uses malloc, and would thus most likely lead to memory leaks, since the user of this instance probably doesn't know that he needs to free the block pointed to by the written value. Or did I miss something clever here? The best alternative I can see is to restrict it to Storable a => Storable (Maybe (Ptr a)), and skip the call to 'new', but that requires extensions. /Björn

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patch applied (c2hs): Change the interpretation of --output and --output-dir slightly
by Duncan Coutts 04 Jun '07

04 Jun '07

Mon Jun 4 07:56:52 PDT 2007 Duncan Coutts <duncan.coutts(a)worc.ox.ac.uk> * Change the interpretation of --output and --output-dir slightly To make it work better with Cabal. It's best explained by example: For --output=Foo/Bar.hs --output-dir=dist, the final file name is now dist/Foo/Bar.hs rather than dist/Bar.hs as before. Also, the .h file referred to in Bar.hs is now just "Foo/Bar.chs.h". That is, it is relative to the output file name, not with the extra output-dir prefix. This works much better with Cabal's build scheme, where generated files go into dist, and the root of the build tree is not searched for .h files instead we only have to -Idist, ie search the dir where we generated all the .chs.h files. M ./c2hs/toplevel/Main.hs -17 +10

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Feature request: #pointer should add Storable instance
by Björn Bringert 04 Jun '07

04 Jun '07

I'll just keep spamming this list with features I'm missing. I use #pointer to create newtypes, but I'm missing Storable instances for the produced newtypes. It's very nice to be able to use alloca, peek etc for passing pointers around. Even GHC can't derive Storable since the type is recursive, but it's easy to write the instance. Here's what I do now: {#pointer *SWIrecRecognizer as RecRecognizer newtype #} instance Storable RecRecognizer where sizeOf (RecRecognizer r) = sizeOf r alignment (RecRecognizer r) = alignment r peek p = fmap RecRecognizer (peek (castPtr p)) poke p (RecRecognizer r) = poke (castPtr p) r c2hs could easily produce that Storable instance, and I can't see any reason not to. /Björn

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Passing extra arguments to marshalling functions
by Björn Bringert 04 Jun '07

04 Jun '07

I have a function for checking return values of functions: checkResult :: String -> CInt -> IO () checkResult _ 0 = return () checkResult f n = fail $ f ++ " failed (" ++ show n ++ ")" Now, I want to call that on the exit value of lots of functions, like this: {#fun foo {} -> `()' `checkResult "foo"'*- #} {#fun bar {} -> `()' `checkResult "bar"'*- #} ... However, the marshallers can only be function names, not arbitrary expressions. Wouldn't it be a useful generalization to allow arbitrary expressions as marshallers? That way you could even have one-off marshallers as lambda expressions. /Björn

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Trac ticket spam
by Björn Bringert 02 Jun '07

02 Jun '07

The c2hs Trac seems to have a lot of spam in it, for example http://hackage.haskell.org/trac/c2hs/ticket/11 /Björn

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patch applied (c2hs): Simplify Ident representation and construction
by Duncan Coutts 01 Jun '07

01 Jun '07

Fri Jun 1 08:01:55 PDT 2007 Duncan Coutts <duncan.coutts(a)worc.ox.ac.uk> * Simplify Ident representation and construction The ambiguousness resolving number was not being utilised at all in c2hs so I have removed it. Similarly the parsing of lexemes was unnecessary for C identifiers and simplifying it makes the parser >10% faster. Also removed all the unused functions (of which there were many). M ./base/syms/Idents.hs -238 +18

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patch applied (c2hs): Remove CVS $Revision and $Date tags
by Duncan Coutts 01 Jun '07

01 Jun '07

Thu May 31 10:25:06 PDT 2007 Duncan Coutts <duncan.coutts(a)worc.ox.ac.uk> * Remove CVS $Revision and $Date tags they are not used by darcs so are out of date and are thus useless M ./base/errors/Errors.hs -2 M ./base/general/Position.hs -2 M ./base/general/UNames.hs -2 M ./base/state/CIO.hs -2 M ./base/state/State.hs -2 M ./base/state/StateBase.hs -2 M ./base/state/StateTrans.hs -2 M ./base/state/tests/Main.hs -2 M ./base/syms/Attributes.hs -2 M ./base/syms/Idents.hs -2 M ./base/syms/NameSpaces.hs -2 M ./base/syms/tests/Main.hs -2 M ./base/syntax/Lexers.hs -2 M ./c2hs/c/C.hs -2 M ./c2hs/c/CAST.hs -2 M ./c2hs/c/CAttrs.hs -2 M ./c2hs/c/CBuiltin.hs -2 M ./c2hs/c/CLexer.x -2 M ./c2hs/c/CNames.hs -2 M ./c2hs/c/CPretty.hs -2 M ./c2hs/c/CTokens.hs -2 M ./c2hs/c/CTrav.hs -2 M ./c2hs/chs/CHS.hs -2 M ./c2hs/chs/CHSLexer.hs -2 M ./c2hs/examples/libghttpHS/Ghttp.chs -2 M ./c2hs/examples/libghttpHS/Makefile -2 M ./c2hs/gen/CInfo.hs -2 M ./c2hs/gen/GBMonad.hs -2 M ./c2hs/gen/GenHeader.hs -2 M ./c2hs/state/C2HSState.hs -2 M ./c2hs/state/Switches.hs -2 M ./c2hs/toplevel/C2HSConfig.hs -2 M ./c2hs/toplevel/c2hs_config.c -2 M ./c2hs/toplevel/c2hs_config.h -2

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patch applied (c2hs): Don't include the CHeader in the AttrC
by Duncan Coutts 01 Jun '07

01 Jun '07

Thu May 31 10:09:38 PDT 2007 Duncan Coutts <duncan.coutts(a)worc.ox.ac.uk> * Don't include the CHeader in the AttrC AttrC should be accumulated from a sequence of external definitions rather than containing the whole CHeader from the beinning. This should make processing partial translation units easier. M ./c2hs/c/C.hs -6 +4 M ./c2hs/c/CAttrs.hs -17 +10 M ./c2hs/c/CNames.hs -9 +8 M ./c2hs/c/CTrav.hs -7 +2

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