2 % (c) The AQUA Project, Glasgow University, 1998
4 \section[DsCCall]{Desugaring \tr{foreign} declarations}
6 Expanding out @foreign import@ and @foreign export@ declarations.
9 module DsForeign ( dsForeigns ) where
11 #include "HsVersions.h"
15 import DsCCall ( dsCCall, mkCCall, boxResult, unboxArg, wrapUnboxedValue )
19 import HsSyn ( ExtName(..), ForeignDecl(..), isDynamicExtName, ForKind(..) )
20 import HsDecls ( extNameStatic )
22 import TcHsSyn ( TypecheckedForeignDecl )
23 import CoreUtils ( exprType, mkInlineMe )
24 import DataCon ( DataCon, dataConWrapId )
25 import Id ( Id, idType, idName, mkWildId, mkVanillaId )
26 import MkId ( mkCCallOpId, mkWorkerId )
27 import Literal ( Literal(..) )
28 import Module ( Module, moduleUserString )
29 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
30 mkForeignExportOcc, isLocalName,
31 NamedThing(..), Provenance(..), ExportFlag(..)
33 import PrelInfo ( deRefStablePtr_NAME, bindIO_NAME, makeStablePtr_NAME, realWorldPrimId )
34 import Type ( splitAlgTyConApp_maybe, unUsgTy,
35 splitTyConApp_maybe, splitFunTys, splitForAllTys,
36 Type, mkFunTys, mkForAllTys, mkTyConApp,
37 mkTyVarTy, mkFunTy, splitAppTy
39 import PprType ( {- instance Outputable Type -} )
40 import PrimOp ( PrimOp(..), CCall(..), CCallTarget(..) )
42 import TysPrim ( realWorldStatePrimTy, addrPrimTy )
43 import TysWiredIn ( unitTyCon, addrTy, stablePtrTyCon,
44 unboxedTupleCon, addrDataCon
47 import Maybes ( maybeToBool )
50 #if __GLASGOW_HASKELL__ >= 404
51 import GlaExts ( fromInt )
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.
70 -> [TypecheckedForeignDecl]
71 -> DsM ( [CoreBind] -- desugared foreign imports
72 , [CoreBind] -- helper functions for foreign exports
73 , SDoc -- Header file prototypes for
74 -- "foreign exported" functions.
75 , SDoc -- C stubs to use when calling
76 -- "foreign exported" functions.
78 dsForeigns mod_name fos = foldlDs combine ([],[],empty,empty) fos
80 combine (acc_fi, acc_fe, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
81 | isForeignImport = -- foreign import (dynamic)?
82 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ bs ->
83 returnDs (bs ++ acc_fi, acc_fe, acc_h, acc_c)
85 dsFLabel i ext_nm `thenDs` \ b ->
86 returnDs (b:acc_fi, acc_fe, acc_h, acc_c)
87 | isDynamicExtName ext_nm =
88 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (fi,fe,h,c) ->
89 returnDs (fi:acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
91 | otherwise = -- foreign export
92 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (fe,h,c) ->
93 returnDs (acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
105 (FoImport uns) = imp_exp
109 Desugaring foreign imports is just the matter of creating a binding
110 that on its RHS unboxes its arguments, performs the external call
111 (using the @CCallOp@ primop), before boxing the result up and returning it.
113 However, we create a worker/wrapper pair, thus:
115 foreign import f :: Int -> IO Int
117 f x = IO ( \s -> case x of { I# x# ->
118 case fw s x# of { (# s1, y# #) ->
121 fw s x# = ccall f s x#
123 The strictness/CPR analyser won't do this automatically because it doesn't look
124 inside returned tuples; but inlining this wrapper is a Really Good Idea
125 because it exposes the boxing to the call site.
130 -> Type -- Type of foreign import.
131 -> Bool -- True <=> might cause Haskell GC
135 dsFImport fn_id ty may_not_gc ext_name cconv
137 (tvs, arg_tys, mbIoDataCon, io_res_ty) = splitForeignTyDs ty
138 is_io_action = maybeToBool mbIoDataCon
140 newSysLocalsDs arg_tys `thenDs` \ args ->
141 newSysLocalDs realWorldStatePrimTy `thenDs` \ old_s ->
142 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (unboxed_args, arg_wrappers) ->
144 (if not is_io_action then
145 newSysLocalDs realWorldStatePrimTy `thenDs` \ state_tok ->
146 wrapUnboxedValue io_res_ty `thenDs` \ (ccall_result_ty, v, res_v) ->
147 returnDs ( ccall_result_ty
148 , \ prim_app -> Case prim_app (mkWildId ccall_result_ty)
149 [(DataAlt (unboxedTupleCon 2), [state_tok, v], res_v)])
151 boxResult io_res_ty) `thenDs` \ (ccall_result_ty, res_wrapper) ->
154 Dynamic -> getUniqueDs `thenDs` \ u ->
155 returnDs (DynamicTarget u)
156 ExtName fs _ -> returnDs (StaticTarget fs)) `thenDs` \ lbl ->
158 getUniqueDs `thenDs` \ ccall_uniq ->
159 getUniqueDs `thenDs` \ work_uniq ->
161 the_state_arg | is_io_action = old_s
162 | otherwise = realWorldPrimId
165 val_args = Var the_state_arg : unboxed_args
166 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
167 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
168 the_ccall = CCall lbl False (not may_not_gc) cconv
169 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
170 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
171 work_id = mkWorkerId work_uniq fn_id worker_ty
174 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
175 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
176 io_app = case mbIoDataCon of
177 Nothing -> wrapper_body
178 Just ioDataCon -> mkApps (Var (dataConWrapId ioDataCon))
179 [Type io_res_ty, Lam old_s wrapper_body]
180 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) io_app)
182 returnDs [NonRec fn_id wrap_rhs, NonRec work_id work_rhs]
185 Given the type of a foreign import declaration, split it up into
186 its constituent parts.
189 splitForeignTyDs :: Type -> ([TyVar], [Type], Maybe DataCon, Type)
191 = case splitAlgTyConApp_maybe res_ty of
192 Just (_,(io_res_ty:_),(ioCon:_)) -> -- .... -> IO t
193 (tvs, arg_tys, Just ioCon, io_res_ty)
195 (tvs, arg_tys, Nothing, res_ty)
197 (arg_tys, res_ty) = splitFunTys sans_foralls
198 (tvs, sans_foralls) = splitForAllTys ty
204 dsFLabel :: Id -> ExtName -> DsM CoreBind
205 dsFLabel nm ext_name = returnDs (NonRec nm fo_rhs)
207 fo_rhs = mkConApp addrDataCon [mkLit (MachLitLit enm addrPrimTy)]
208 enm = extNameStatic ext_name
211 The function that does most of the work for `@foreign export@' declarations.
212 (see below for the boilerplate code a `@foreign export@' declaration expands
215 For each `@foreign export foo@' in a module M we generate:
217 \item a C function `@foo@', which calls
218 \item a Haskell stub `@M.$ffoo@', which calls
220 the user-written Haskell function `@M.foo@'.
224 -> Type -- Type of foreign export.
228 -> Bool -- True => invoke IO action that's hanging off
229 -- the first argument's stable pointer
234 dsFExport i ty mod_name ext_name cconv isDyn =
235 getUniqueDs `thenDs` \ uniq ->
236 getSrcLocDs `thenDs` \ src_loc ->
238 f_helper_glob = mkVanillaId helper_name helper_ty
242 | isLocalName name = mod_name
243 | otherwise = nameModule name
245 occ = mkForeignExportOcc (nameOccName name)
246 prov = LocalDef src_loc Exported
247 helper_name = mkGlobalName uniq mod occ prov
249 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
251 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
252 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
253 dsLookupGlobalValue deRefStablePtr_NAME `thenDs` \ deRefStablePtrId ->
255 the_deref_app = mkApps (Var deRefStablePtrId)
256 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
258 newSysLocalDs (exprType the_deref_app) `thenDs` \ x_deref_app ->
259 dsLookupGlobalValue bindIO_NAME `thenDs` \ bindIOId ->
260 newSysLocalDs (mkFunTy stbl_ptr_to_ty
261 (mkTyConApp ioTyCon [res_ty])) `thenDs` \ x_cont ->
264 bindNonRec x_cont (mkLams [stbl_value] cont) $
265 bindNonRec x_deref_app the_deref_app
266 (mkApps (Var bindIOId)
267 [ Type stbl_ptr_to_ty
272 returnDs (stbl_value, stbl_app, stbl_ptr)
276 panic "stbl_ptr" -- should never be touched.
277 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
280 | isDyn = stbl_ptr:fe_args
281 | otherwise = fe_args
284 | isDyn = stbl_ptr_ty:helper_arg_tys
285 | otherwise = helper_arg_tys
289 mkApps (Var i) (map (Type . mkTyVarTy) tvs ++ map Var fe_args)
291 getModuleDs `thenDs` \ mod ->
292 getUniqueDs `thenDs` \ uniq ->
294 the_body = mkLams (tvs ++ wrapper_args) the_app
295 c_nm = extNameStatic ext_name
297 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
299 wrapper_arg_tys the_result_ty cconv isDyn
301 returnDs (NonRec f_helper_glob the_body, h_stub, c_stub)
305 (tvs,sans_foralls) = splitForAllTys ty
306 (fe_arg_tys', io_res) = splitFunTys sans_foralls
309 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res
311 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
312 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
315 | isDyn = tail fe_arg_tys'
316 | otherwise = fe_arg_tys'
318 (stbl_ptr_ty, helper_arg_tys) =
320 (x:xs) | isDyn -> (x,xs)
321 ls -> (error "stbl_ptr_ty", ls)
325 mkFunTys arg_tys io_res
328 | isDyn = stbl_ptr_ty : helper_arg_tys
329 | otherwise = helper_arg_tys
332 case splitTyConApp_maybe io_res of
334 case splitTyConApp_maybe res_ty of
335 Just (tc,_) | getUnique tc /= getUnique unitTyCon -> Just res_ty
341 @foreign export dynamic@ lets you dress up Haskell IO actions
342 of some fixed type behind an externally callable interface (i.e.,
343 as a C function pointer). Useful for callbacks and stuff.
346 foreign export stdcall f :: (Addr -> Int -> IO Int) -> IO Addr
348 -- Haskell-visible constructor, which is generated from the
351 f :: (Addr -> Int -> IO Int) -> IO Addr
352 f cback = IO ( \ s1# ->
353 case makeStablePtr# cback s1# of { StateAndStablePtr# s2# sp# ->
354 case _ccall_ "mkAdjustor" sp# ``f_helper'' s2# of
355 StateAndAddr# s3# a# ->
365 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
366 -- `special' foreign export that invokes the closure pointed to by the
371 dsFExportDynamic :: Id
372 -> Type -- Type of foreign export.
376 -> DsM (CoreBind, CoreBind, SDoc, SDoc)
377 dsFExportDynamic i ty mod_name ext_name cconv =
378 newSysLocalDs ty `thenDs` \ fe_id ->
380 -- hack: need to get at the name of the C stub we're about to generate.
381 fe_nm = toCName fe_id
382 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
384 dsFExport i export_ty mod_name fe_ext_name cconv True
385 `thenDs` \ (fe@(NonRec fe_helper fe_expr), h_code, c_code) ->
386 newSysLocalDs arg_ty `thenDs` \ cback ->
387 dsLookupGlobalValue makeStablePtr_NAME `thenDs` \ makeStablePtrId ->
389 mk_stbl_ptr_app = mkApps (Var makeStablePtrId) [ Type arg_ty, Var cback ]
390 mk_stbl_ptr_app_ty = exprType mk_stbl_ptr_app
392 newSysLocalDs mk_stbl_ptr_app_ty `thenDs` \ x_mk_stbl_ptr_app ->
393 dsLookupGlobalValue bindIO_NAME `thenDs` \ bindIOId ->
394 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
396 stbl_app = \ x_cont cont ret_ty ->
397 bindNonRec x_cont cont $
398 bindNonRec x_mk_stbl_ptr_app mk_stbl_ptr_app $
399 (mkApps (Var bindIOId)
400 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
402 , Var x_mk_stbl_ptr_app
407 The arguments to the external function which will
408 create a little bit of (template) code on the fly
409 for allowing the (stable pointed) Haskell closure
410 to be entered using an external calling convention
413 adj_args = [ mkIntLitInt (callConvToInt cconv)
415 , mkLit (MachLitLit (_PK_ fe_nm) addrPrimTy)
417 -- name of external entry point providing these services.
418 -- (probably in the RTS.)
419 adjustor = SLIT("createAdjustor")
421 dsCCall adjustor adj_args False False addrTy `thenDs` \ ccall_adj ->
422 let ccall_adj_ty = exprType ccall_adj
424 newSysLocalDs ccall_adj_ty `thenDs` \ x_ccall_adj ->
426 mkLams [stbl_value] $
427 bindNonRec x_ccall_adj ccall_adj $
428 Note (Coerce (mkTyConApp ioTyCon [res_ty]) (unUsgTy ccall_adj_ty))
431 newSysLocalDs (exprType ccall_io_adj) `thenDs` \ x_ccall_io_adj ->
432 let io_app = mkLams tvs $
434 stbl_app x_ccall_io_adj ccall_io_adj addrTy
436 returnDs (NonRec i io_app, fe, h_code, c_code)
439 (tvs,sans_foralls) = splitForAllTys ty
440 ([arg_ty], io_res) = splitFunTys sans_foralls
442 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res
444 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
446 toCName :: Id -> String
447 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
453 \subsection{Generating @foreign export@ stubs}
457 For each @foreign export@ function, a C stub function is generated.
458 The C stub constructs the application of the exported Haskell function
459 using the hugs/ghc rts invocation API.
462 fexportEntry :: String
470 fexportEntry mod_nm c_nm helper args res cc isDyn = (header_bits, c_bits)
472 -- name of the (Haskell) helper function generated by the desugarer.
473 h_nm = ppr helper <> text "_closure"
474 -- prototype for the exported function.
475 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
477 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
478 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
485 , text "SchedulerStatus rc;"
487 -- create the application + perform it.
488 , text "rc=rts_evalIO" <>
489 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
495 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
497 cParamTypes = map showStgType real_args
501 Nothing -> text "void"
502 Just t -> showStgType t
505 | cc == cCallConv = empty
506 | otherwise = pprCallConv cc
508 declareResult = text "HaskellObj ret;"
510 externDecl = mkExtern (text "HaskellObj") h_nm
512 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
515 text "rts_checkSchedStatus" <>
516 parens (doubleQuotes (text mod_nm <> char '.' <> ptext c_nm) <> comma <> text "rc") <> semi $$
518 Nothing -> text "return"
519 Just _ -> text "return" <> parens (res_name)) <> semi
524 Just t -> unpackHObj t <> parens (text "ret")
526 c_args = mkCArgNames 0 args
529 If we're generating an entry point for a 'foreign export ccall dynamic',
530 then we receive the return address of the C function that wants to
531 invoke a Haskell function as any other C function, as second arg.
532 This arg is unused within the body of the generated C stub, but
533 needed by the Adjustor.c code to get the stack cleanup right.
535 (proto_args, real_args)
536 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
537 , head args : addrTy : tail args)
538 | otherwise = (mkCArgNames 0 args, args)
540 mkCArgNames :: Int -> [a] -> [SDoc]
541 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
543 mkHObj :: Type -> SDoc
544 mkHObj t = text "rts_mk" <> text (showFFIType t)
546 unpackHObj :: Type -> SDoc
547 unpackHObj t = text "rts_get" <> text (showFFIType t)
549 showStgType :: Type -> SDoc
550 showStgType t = text "Stg" <> text (showFFIType t)
552 showFFIType :: Type -> String
553 showFFIType t = getOccString (getName tc)
555 tc = case splitTyConApp_maybe t of
557 Nothing -> pprPanic "showFFIType" (ppr t)