May 2006 - C2hs - Haskell.org

Binding to Libdb, FunPtrs
by Udo Stenzel 22 May '06

22 May '06

Hello, I'd like to use c2hs to create a binding for Sleepy Cat's LibDB. However, some difficulties crop up: - variadic functions. I realize I can't call them anyway, and I don't need to (they are just for primitive error reporting). But there are pointers to variadic functions in some structures, and I need c2hs to parse them and correctly calculate offsets. - lots of FunPtrs. The whole API is defined as structures with FunPtrs inside. c2hs will happily create get hooks for them, but won't generate the foreign import "dynamic" declarations. - defines. Am I right in assuming that c2hs does not recognize #define'd constant and so cannot reflect them in Haskell? I'm willing to dive into the code and fix this, I just want to make sure I don't (clumsily) duplicate any effort. As for the FunPtrs inside structs, I'm thinking of a new hook that combines a get hook and a fun (or call) hook. Does anyone have a better idea? Regards, Udo. -- Manchmal stehe ich nachts auf und installier's mir einfach... -- H0arry @ IRC

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patch applied (c2hs): change handling of marshallers for dynamic function hooks
by chak＠cse.unsw.edu.au 22 May '06

22 May '06

Mon May 15 07:26:39 PDT 2006 Udo Stenzel <u.stenzel(a)web.de> * change handling of marshallers for dynamic function hooks M ./c2hs/gen/GenBind.hs -16 +30

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patch applied (c2hs): minor beautification
by chak＠cse.unsw.edu.au 22 May '06

22 May '06

Sun Apr 30 14:54:44 PDT 2006 Udo Stenzel <u.stenzel(a)web.de> * minor beautification M ./c2hs/chs/CHS.hs -2 +4 M ./c2hs/gen/GenBind.hs -4 +10

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patch applied (c2hs): support fun hooks for FunPtrs inside structs
by chak＠cse.unsw.edu.au 22 May '06

22 May '06

Sat Apr 29 16:59:56 PDT 2006 Udo Stenzel <u.stenzel(a)web.de> * support fun hooks for FunPtrs inside structs This is a bit hackish at times, as I cut-and-paste-coded a bit. Though pending cleanup, it seems to work. M ./c2hs/gen/GenBind.hs -7 +46

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patch applied (c2hs): improve translation of apath to identifier
by chak＠cse.unsw.edu.au 22 May '06

22 May '06

Sat Apr 29 16:59:00 PDT 2006 Udo Stenzel <u.stenzel(a)web.de> * improve translation of apath to identifier M ./c2hs/chs/CHS.hs -6 +9

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patch applied (c2hs): allow call hooks for FunPtrs inside structures
by chak＠cse.unsw.edu.au 22 May '06

22 May '06

Sat Apr 29 08:50:23 PDT 2006 Udo Stenzel <u.stenzel(a)web.de> * allow call hooks for FunPtrs inside structures M ./c2hs/chs/CHS.hs -15 +40 M ./c2hs/gen/GenBind.hs -4 +69

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patch applied (c2hs): Allow escape sequences in the file name part of #line directives
by Duncan Coutts 16 May '06

16 May '06

Thu Apr 6 14:47:15 PDT 2006 Duncan Coutts <duncan.coutts(a)worc.ox.ac.uk> * Allow escape sequences in the file name part of #line directives M ./c2hs/c/CLexer.x -2 +2

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Repository move and additional maintainer
by Manuel M T Chakravarty 16 May '06

16 May '06

The C->Haskell darcs repository just moved to http://darcs.haskell.org/c2hs/ Please change the file _darcs/prefs/defaultrepo in your local repositories correspondingly. Moreover, Duncan Coutts is now a second maintainer of the tool. (He's the one who heroically rewrote C->Haskell's parser.) Manuel

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darcs patch: Allow escape sequences in the file name part of #line ...
by Duncan Coutts 15 May '06

15 May '06

Here's a simple patch, just to check that "darcs send" is gettin through to the list. I'm using: darcs send --edit-description The patch fixes things for non-english locales where cpp sometimes uses escape sequences in filenames or 'virtual' file names like translations of "<interactive>". Currently the c2hs lexer doesn't accept escape sequences. This patch changes that. Thu Apr 6 22:47:15 BST 2006 Duncan Coutts <duncan.coutts(a)worc.ox.ac.uk> * Allow escape sequences in the file name part of #line directives

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{# sizeof #} hook going wrong for cases of structs with embeded arrays.
by Duncan Coutts 13 May '06

13 May '06

c2hs is calculating the sizeof glib's GValue structure incorrectly (this led to a nasty bug). GValue is defined like this: struct _GValue { /*< private >*/ GType g_type; /* public for GTypeValueTable methods */ union { gint v_int; guint v_uint; glong v_long; gulong v_ulong; gint64 v_int64; guint64 v_uint64; gfloat v_float; gdouble v_double; gpointer v_pointer; } data[2]; }; We used to use this code: allocaGValue :: (GValue -> IO b) -> IO b allocaGValue body = allocaBytes {# sizeof GValue #} $ \gvPtr -> do ... but we eventually discovered that {# sizeof GValue #} was giving us the wrong value, I think it was 8. The right value should be 8+8+4=20. Our current workaround is: allocaGValue :: (GValue -> IO b) -> IO b allocaGValue body = -- c2hs is broken in that it can't handle arrays of compound arrays in the -- sizeof hook allocaBytes ({# sizeof GType #}+ 2* {# sizeof guint64 #}) $ \gvPtr -> do Axel also added this temporary hack so that at least c2hs would report an error rather the giving the wrong answer: --- ../build/gtk2hs-0.9.10/tools/c2hs/c/CTrav.hs 2004-11-21 21:05:27.000000000 +0000 +++ ../build/gtk2hs/tools/c2hs/c/CTrav.hs 2006-04-25 18:53:10.000000000 +0100 @@ -73,7 +73,7 @@ -- isTypedef, simplifyDecl, declrFromDecl, declrNamed, declaredDeclr, declaredName, structMembers, expandDecl, - structName, enumName, tagName, isPtrDeclr, dropPtrDeclr, + structName, enumName, tagName, isArrDeclr, isPtrDeclr, dropPtrDeclr, isPtrDecl, isFunDeclr, structFromDecl, funResultAndArgs, chaseDecl, findAndChaseDecl, checkForAlias, checkForOneAliasName, lookupEnum, lookupStructUnion, @@ -537,6 +537,16 @@ isPtrDeclr (CFunDeclr declr _ _ _) = isPtrDeclr declr isPtrDeclr _ = False +-- checks whether the given declarator defines an object that is an array of +-- some other type (EXPORTED) +-- +-- * difference between arrays and pure pointers is important for size +-- calculations +-- +isArrDeclr :: CDeclr -> Bool +isArrDeclr (CArrDeclr declr _ _) = True +isArrDeclr _ = False + -- drops the first pointer level from the given declarator (EXPORTED) -- -- * the declarator must declare a pointer object --- ../build/gtk2hs-0.9.10/tools/c2hs/gen/GenBind.hs 2005-10-17 21:41:30.000000000 +0100 +++ ../build/gtk2hs/tools/c2hs/gen/GenBind.hs 2006-04-25 18:53:10.000000000 +0100 @@ -1665,6 +1667,8 @@ -- * we make use of the assertion that `extractCompType' can only return a -- `DefinedET' when the declaration is a pointer declaration -- +sizeAlignOf (CDecl specs [(Just declr, _, size)] ats) | isArrDeclr declr = + interr $ "sizeAlignOf: calculating size of constant array not supported." sizeAlignOf cdecl = do ct <- extractCompType cdecl So, that's the temporary solution. Of course it'd be better if we could actually calculate this struct size. This issue of struct sizes (and alignments) is probably an area that needs more testing (and on other arches since eg MS packs bit-fields differently). Perhaps we could write a prog that scans a header file and generates a .chs and .hsc file with {# sizeof #} hooks for every structure. Then we could compare the two (with various headers and on various platforms) and see where the remaining issues are. Using .hsc as a reference would be the right thing here because hsc2hs uses gcc to find the struct size. That same kind of test would also do for struct member offsets. Duncan

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