2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1998
6 Desugaring foreign declarations (see also DsCCall).
10 -- The above warning supression flag is a temporary kludge.
11 -- While working on this module you are encouraged to remove it and fix
12 -- any warnings in the module. See
13 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
16 module DsForeign ( dsForeigns ) where
18 #include "HsVersions.h"
19 import TcRnMonad -- temp
55 Desugaring of @foreign@ declarations is naturally split up into
56 parts, an @import@ and an @export@ part. A @foreign import@
59 foreign import cc nm f :: prim_args -> IO prim_res
63 f :: prim_args -> IO prim_res
64 f a1 ... an = _ccall_ nm cc a1 ... an
66 so we reuse the desugaring code in @DsCCall@ to deal with these.
69 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
70 -- the occurrence analyser will sort it all out
72 dsForeigns :: [LForeignDecl Id]
73 -> DsM (ForeignStubs, [Binding])
75 = returnDs (NoStubs, [])
78 fives <- mapM do_ldecl fos
80 (hs, cs, hdrs, idss, bindss) = unzip5 fives
82 fe_init_code = map foreignExportInitialiser fe_ids
86 (vcat cs $$ vcat fe_init_code)
90 do_ldecl (L loc decl) = putSrcSpanDs loc (do_decl decl)
92 do_decl (ForeignImport id _ spec)
93 = traceIf (text "fi start" <+> ppr id) `thenDs` \ _ ->
94 dsFImport (unLoc id) spec `thenDs` \ (bs, h, c, mbhd) ->
95 traceIf (text "fi end" <+> ppr id) `thenDs` \ _ ->
96 returnDs (h, c, maybeToList mbhd, [], bs)
98 do_decl (ForeignExport (L _ id) _ (CExport (CExportStatic ext_nm cconv)))
99 = dsFExport id (idType id)
100 ext_nm cconv False `thenDs` \(h, c, _, _) ->
101 returnDs (h, c, [], [id], [])
105 %************************************************************************
107 \subsection{Foreign import}
109 %************************************************************************
111 Desugaring foreign imports is just the matter of creating a binding
112 that on its RHS unboxes its arguments, performs the external call
113 (using the @CCallOp@ primop), before boxing the result up and returning it.
115 However, we create a worker/wrapper pair, thus:
117 foreign import f :: Int -> IO Int
119 f x = IO ( \s -> case x of { I# x# ->
120 case fw s x# of { (# s1, y# #) ->
123 fw s x# = ccall f s x#
125 The strictness/CPR analyser won't do this automatically because it doesn't look
126 inside returned tuples; but inlining this wrapper is a Really Good Idea
127 because it exposes the boxing to the call site.
132 -> DsM ([Binding], SDoc, SDoc, Maybe FastString)
133 dsFImport id (CImport cconv safety header lib spec)
134 = dsCImport id spec cconv safety no_hdrs `thenDs` \(ids, h, c) ->
135 returnDs (ids, h, c, if no_hdrs then Nothing else Just header)
137 no_hdrs = nullFS header
139 -- FIXME: the `lib' field is needed for .NET ILX generation when invoking
140 -- routines that are external to the .NET runtime, but GHC doesn't
141 -- support such calls yet; if `nullFastString lib', the value was not given
142 dsFImport id (DNImport spec)
143 = dsFCall id (DNCall spec) True {- No headers -} `thenDs` \(ids, h, c) ->
144 returnDs (ids, h, c, Nothing)
150 -> Bool -- True <=> no headers in the f.i decl
151 -> DsM ([Binding], SDoc, SDoc)
152 dsCImport id (CLabel cid) _ _ no_hdrs
153 = resultWrapper (idType id) `thenDs` \ (resTy, foRhs) ->
154 ASSERT(fromJust resTy `coreEqType` addrPrimTy) -- typechecker ensures this
155 let rhs = foRhs (mkLit (MachLabel cid Nothing)) in
156 returnDs ([(setImpInline no_hdrs id, rhs)], empty, empty)
157 dsCImport id (CFunction target) cconv safety no_hdrs
158 = dsFCall id (CCall (CCallSpec target cconv safety)) no_hdrs
159 dsCImport id CWrapper cconv _ _
160 = dsFExportDynamic id cconv
162 setImpInline :: Bool -- True <=> No #include headers
163 -- in the foreign import declaration
165 -- If there is a #include header in the foreign import
166 -- we make the worker non-inlinable, because we currently
167 -- don't keep the #include stuff in the CCallId, and hence
168 -- it won't be visible in the importing module, which can be
170 -- (The #include stuff is just collected from the foreign import
171 -- decls in a module.)
172 -- If you want to do cross-module inlining of the c-calls themselves,
173 -- put the #include stuff in the package spec, not the foreign
175 setImpInline True id = id
176 setImpInline False id = id `setInlinePragma` NeverActive
180 %************************************************************************
182 \subsection{Foreign calls}
184 %************************************************************************
187 dsFCall fn_id fcall no_hdrs
190 (tvs, fun_ty) = tcSplitForAllTys ty
191 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
192 -- Must use tcSplit* functions because we want to
193 -- see that (IO t) in the corner
195 newSysLocalsDs arg_tys `thenDs` \ args ->
196 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
199 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
208 dsLookupGlobalId checkDotnetResName `thenDs` \ check_id ->
209 return (Just check_id)
210 | otherwise = return Nothing
214 newSysLocalDs addrPrimTy `thenDs` \ err_res ->
215 returnDs (\ (mb_res_ty, resWrap) ->
217 Nothing -> (Just (mkTyConApp (tupleTyCon Unboxed 1)
220 Just x -> (Just (mkTyConApp (tupleTyCon Unboxed 2)
223 | otherwise = returnDs id
225 augmentResultDs `thenDs` \ augment ->
226 topConDs `thenDs` \ topCon ->
227 boxResult augment topCon io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
229 newUnique `thenDs` \ ccall_uniq ->
230 newUnique `thenDs` \ work_uniq ->
233 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
234 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
235 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
236 work_id = setImpInline no_hdrs $ -- See comments with setImpInline
237 mkSysLocal FSLIT("$wccall") work_uniq worker_ty
240 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
241 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
242 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
244 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
248 %************************************************************************
250 \subsection{Foreign export}
252 %************************************************************************
254 The function that does most of the work for `@foreign export@' declarations.
255 (see below for the boilerplate code a `@foreign export@' declaration expands
258 For each `@foreign export foo@' in a module M we generate:
260 \item a C function `@foo@', which calls
261 \item a Haskell stub `@M.$ffoo@', which calls
263 the user-written Haskell function `@M.foo@'.
266 dsFExport :: Id -- Either the exported Id,
267 -- or the foreign-export-dynamic constructor
268 -> Type -- The type of the thing callable from C
269 -> CLabelString -- The name to export to C land
271 -> Bool -- True => foreign export dynamic
272 -- so invoke IO action that's hanging off
273 -- the first argument's stable pointer
274 -> DsM ( SDoc -- contents of Module_stub.h
275 , SDoc -- contents of Module_stub.c
276 , String -- string describing type to pass to createAdj.
277 , Int -- size of args to stub function
280 dsFExport fn_id ty ext_name cconv isDyn
283 (_tvs,sans_foralls) = tcSplitForAllTys ty
284 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
285 -- We must use tcSplits here, because we want to see
286 -- the (IO t) in the corner of the type!
287 fe_arg_tys | isDyn = tail fe_arg_tys'
288 | otherwise = fe_arg_tys'
290 -- Look at the result type of the exported function, orig_res_ty
291 -- If it's IO t, return (t, True)
292 -- If it's plain t, return (t, False)
293 (case tcSplitIOType_maybe orig_res_ty of
294 Just (ioTyCon, res_ty, co) -> returnDs (res_ty, True)
295 -- The function already returns IO t
296 -- ToDo: what about the coercion?
297 Nothing -> returnDs (orig_res_ty, False)
298 -- The function returns t
299 ) `thenDs` \ (res_ty, -- t
300 is_IO_res_ty) -> -- Bool
302 mkFExportCBits ext_name
303 (if isDyn then Nothing else Just fn_id)
304 fe_arg_tys res_ty is_IO_res_ty cconv
307 @foreign import "wrapper"@ (previously "foreign export dynamic") lets
308 you dress up Haskell IO actions of some fixed type behind an
309 externally callable interface (i.e., as a C function pointer). Useful
310 for callbacks and stuff.
313 type Fun = Bool -> Int -> IO Int
314 foreign import "wrapper" f :: Fun -> IO (FunPtr Fun)
316 -- Haskell-visible constructor, which is generated from the above:
317 -- SUP: No check for NULL from createAdjustor anymore???
319 f :: Fun -> IO (FunPtr Fun)
321 bindIO (newStablePtr cback)
322 (\StablePtr sp# -> IO (\s1# ->
323 case _ccall_ createAdjustor cconv sp# ``f_helper'' <arg info> s1# of
324 (# s2#, a# #) -> (# s2#, A# a# #)))
326 foreign import "&f_helper" f_helper :: FunPtr (StablePtr Fun -> Fun)
328 -- and the helper in C:
330 f_helper(StablePtr s, HsBool b, HsInt i)
332 rts_evalIO(rts_apply(rts_apply(deRefStablePtr(s),
333 rts_mkBool(b)), rts_mkInt(i)));
338 dsFExportDynamic :: Id
340 -> DsM ([Binding], SDoc, SDoc)
341 dsFExportDynamic id cconv
342 = newSysLocalDs ty `thenDs` \ fe_id ->
343 getModuleDs `thenDs` \ mod ->
345 -- hack: need to get at the name of the C stub we're about to generate.
346 fe_nm = mkFastString (unpackFS (zEncodeFS (moduleNameFS (moduleName mod))) ++ "_" ++ toCName fe_id)
348 newSysLocalDs arg_ty `thenDs` \ cback ->
349 dsLookupGlobalId newStablePtrName `thenDs` \ newStablePtrId ->
350 dsLookupTyCon stablePtrTyConName `thenDs` \ stable_ptr_tycon ->
352 stable_ptr_ty = mkTyConApp stable_ptr_tycon [arg_ty]
353 export_ty = mkFunTy stable_ptr_ty arg_ty
355 dsLookupGlobalId bindIOName `thenDs` \ bindIOId ->
356 newSysLocalDs stable_ptr_ty `thenDs` \ stbl_value ->
357 dsFExport id export_ty fe_nm cconv True
358 `thenDs` \ (h_code, c_code, typestring, args_size) ->
361 The arguments to the external function which will
362 create a little bit of (template) code on the fly
363 for allowing the (stable pointed) Haskell closure
364 to be entered using an external calling convention
367 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
369 , mkLit (MachLabel fe_nm mb_sz_args)
370 , mkLit (mkStringLit typestring)
372 -- name of external entry point providing these services.
373 -- (probably in the RTS.)
374 adjustor = FSLIT("createAdjustor")
376 -- Determine the number of bytes of arguments to the stub function,
377 -- so that we can attach the '@N' suffix to its label if it is a
378 -- stdcall on Windows.
379 mb_sz_args = case cconv of
380 StdCallConv -> Just args_size
384 dsCCall adjustor adj_args PlayRisky (mkTyConApp io_tc [res_ty]) `thenDs` \ ccall_adj ->
385 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
387 let io_app = mkLams tvs $
389 mkCoerceI (mkSymCoI co) $
390 mkApps (Var bindIOId)
393 , mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
394 , Lam stbl_value ccall_adj
397 fed = (id `setInlinePragma` NeverActive, io_app)
398 -- Never inline the f.e.d. function, because the litlit
399 -- might not be in scope in other modules.
401 returnDs ([fed], h_code, c_code)
405 (tvs,sans_foralls) = tcSplitForAllTys ty
406 ([arg_ty], fn_res_ty) = tcSplitFunTys sans_foralls
407 Just (io_tc, res_ty, co) = tcSplitIOType_maybe fn_res_ty
408 -- Must have an IO type; hence Just
409 -- co : fn_res_ty ~ IO res_ty
411 toCName :: Id -> String
412 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
417 \subsection{Generating @foreign export@ stubs}
421 For each @foreign export@ function, a C stub function is generated.
422 The C stub constructs the application of the exported Haskell function
423 using the hugs/ghc rts invocation API.
426 mkFExportCBits :: FastString
427 -> Maybe Id -- Just==static, Nothing==dynamic
430 -> Bool -- True <=> returns an IO type
434 String, -- the argument reps
435 Int -- total size of arguments
437 mkFExportCBits c_nm maybe_target arg_htys res_hty is_IO_res_ty cc
438 = (header_bits, c_bits, type_string,
439 sum [ machRepByteWidth rep | (_,_,_,rep) <- aug_arg_info] -- all the args
442 -- list the arguments to the C function
443 arg_info :: [(SDoc, -- arg name
445 Type, -- Haskell type
446 MachRep)] -- the MachRep
447 arg_info = [ let stg_type = showStgType ty in
448 (arg_cname n stg_type,
451 typeMachRep (getPrimTyOf ty))
452 | (ty,n) <- zip arg_htys [1::Int ..] ]
455 | libffi = char '*' <> parens (stg_ty <> char '*') <>
456 ptext SLIT("args") <> brackets (int (n-1))
457 | otherwise = text ('a':show n)
459 -- generate a libffi-style stub if this is a "wrapper" and libffi is enabled
460 libffi = cLibFFI && isNothing maybe_target
463 -- libffi needs to know the result type too:
464 | libffi = primTyDescChar res_hty : arg_type_string
465 | otherwise = arg_type_string
467 arg_type_string = [primTyDescChar ty | (_,_,ty,_) <- arg_info]
468 -- just the real args
470 -- add some auxiliary args; the stable ptr in the wrapper case, and
471 -- a slot for the dummy return address in the wrapper + ccall case
473 | isNothing maybe_target = stable_ptr_arg : insertRetAddr cc arg_info
474 | otherwise = arg_info
477 (text "the_stableptr", text "StgStablePtr", undefined,
478 typeMachRep (mkStablePtrPrimTy alphaTy))
480 -- stuff to do with the return type of the C function
481 res_hty_is_unit = res_hty `coreEqType` unitTy -- Look through any newtypes
483 cResType | res_hty_is_unit = text "void"
484 | otherwise = showStgType res_hty
486 -- Now we can cook up the prototype for the exported function.
487 pprCconv = case cc of
489 StdCallConv -> text (ccallConvAttribute cc)
491 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
495 = ptext SLIT("void") <+> ftext c_nm <>
496 parens (ptext SLIT("void *cif STG_UNUSED, void* resp, void** args, void* the_stableptr"))
498 = cResType <+> pprCconv <+> ftext c_nm <>
499 parens (hsep (punctuate comma (map (\(nm,ty,_,_) -> ty <+> nm)
502 -- the target which will form the root of what we ask rts_evalIO to run
504 = case maybe_target of
505 Nothing -> text "(StgClosure*)deRefStablePtr(the_stableptr)"
506 Just hs_fn -> char '&' <> ppr hs_fn <> text "_closure"
508 cap = text "cap" <> comma
510 -- the expression we give to rts_evalIO
512 = foldl appArg the_cfun arg_info -- NOT aug_arg_info
514 appArg acc (arg_cname, _, arg_hty, _)
516 <> parens (cap <> acc <> comma <> mkHObj arg_hty <> parens (cap <> arg_cname))
518 -- various other bits for inside the fn
519 declareResult = text "HaskellObj ret;"
520 declareCResult | res_hty_is_unit = empty
521 | otherwise = cResType <+> text "cret;"
523 assignCResult | res_hty_is_unit = empty
525 text "cret=" <> unpackHObj res_hty <> parens (text "ret") <> semi
527 -- an extern decl for the fn being called
529 = case maybe_target of
531 Just hs_fn -> text "extern StgClosure " <> ppr hs_fn <> text "_closure" <> semi
534 -- finally, the whole darn thing
541 , ptext SLIT("Capability *cap;")
544 , text "cap = rts_lock();"
545 -- create the application + perform it.
546 , ptext SLIT("cap=rts_evalIO") <> parens (
548 ptext SLIT("rts_apply") <> parens (
551 <> ptext (if is_IO_res_ty
552 then SLIT("runIO_closure")
553 else SLIT("runNonIO_closure"))
559 , ptext SLIT("rts_checkSchedStatus") <> parens (doubleQuotes (ftext c_nm)
560 <> comma <> text "cap") <> semi
562 , ptext SLIT("rts_unlock(cap);")
563 , if res_hty_is_unit then empty
565 then char '*' <> parens (cResType <> char '*') <>
566 ptext SLIT("resp = cret;")
567 else ptext SLIT("return cret;")
572 foreignExportInitialiser :: Id -> SDoc
573 foreignExportInitialiser hs_fn =
574 -- Initialise foreign exports by registering a stable pointer from an
575 -- __attribute__((constructor)) function.
576 -- The alternative is to do this from stginit functions generated in
577 -- codeGen/CodeGen.lhs; however, stginit functions have a negative impact
578 -- on binary sizes and link times because the static linker will think that
579 -- all modules that are imported directly or indirectly are actually used by
581 -- (this is bad for big umbrella modules like Graphics.Rendering.OpenGL)
583 [ text "static void stginit_export_" <> ppr hs_fn
584 <> text "() __attribute__((constructor));"
585 , text "static void stginit_export_" <> ppr hs_fn <> text "()"
586 , braces (text "getStablePtr"
587 <> parens (text "(StgPtr) &" <> ppr hs_fn <> text "_closure")
592 -- NB. the calculation here isn't strictly speaking correct.
593 -- We have a primitive Haskell type (eg. Int#, Double#), and
594 -- we want to know the size, when passed on the C stack, of
595 -- the associated C type (eg. HsInt, HsDouble). We don't have
596 -- this information to hand, but we know what GHC's conventions
597 -- are for passing around the primitive Haskell types, so we
598 -- use that instead. I hope the two coincide --SDM
599 typeMachRep ty = argMachRep (typeCgRep ty)
601 mkHObj :: Type -> SDoc
602 mkHObj t = text "rts_mk" <> text (showFFIType t)
604 unpackHObj :: Type -> SDoc
605 unpackHObj t = text "rts_get" <> text (showFFIType t)
607 showStgType :: Type -> SDoc
608 showStgType t = text "Hs" <> text (showFFIType t)
610 showFFIType :: Type -> String
611 showFFIType t = getOccString (getName tc)
613 tc = case tcSplitTyConApp_maybe (repType t) of
615 Nothing -> pprPanic "showFFIType" (ppr t)
617 #if !defined(x86_64_TARGET_ARCH)
618 insertRetAddr CCallConv args = ret_addr_arg : args
619 insertRetAddr _ args = args
621 -- On x86_64 we insert the return address after the 6th
622 -- integer argument, because this is the point at which we
623 -- need to flush a register argument to the stack (See rts/Adjustor.c for
625 insertRetAddr CCallConv args = go 0 args
626 where go 6 args = ret_addr_arg : args
627 go n (arg@(_,_,_,rep):args)
628 | I64 <- rep = arg : go (n+1) args
629 | otherwise = arg : go n args
631 insertRetAddr _ args = args
634 ret_addr_arg = (text "original_return_addr", text "void*", undefined,
635 typeMachRep addrPrimTy)
637 -- This function returns the primitive type associated with the boxed
638 -- type argument to a foreign export (eg. Int ==> Int#).
639 getPrimTyOf :: Type -> Type
641 | isBoolTy rep_ty = intPrimTy
642 -- Except for Bool, the types we are interested in have a single constructor
643 -- with a single primitive-typed argument (see TcType.legalFEArgTyCon).
645 case splitProductType_maybe rep_ty of
646 Just (_, _, data_con, [prim_ty]) ->
647 ASSERT(dataConSourceArity data_con == 1)
648 ASSERT2(isUnLiftedType prim_ty, ppr prim_ty)
650 _other -> pprPanic "DsForeign.getPrimTyOf" (ppr ty)
654 -- represent a primitive type as a Char, for building a string that
655 -- described the foreign function type. The types are size-dependent,
656 -- e.g. 'W' is a signed 32-bit integer.
657 primTyDescChar :: Type -> Char
659 | ty `coreEqType` unitTy = 'v'
661 = case typePrimRep (getPrimTyOf ty) of
662 IntRep -> signed_word
663 WordRep -> unsigned_word
666 AddrRep -> unsigned_word
669 _ -> pprPanic "primTyDescChar" (ppr ty)
671 (signed_word, unsigned_word)
672 | wORD_SIZE == 4 = ('W','w')
673 | wORD_SIZE == 8 = ('L','l')
674 | otherwise = panic "primTyDescChar"