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, boxResult, unboxArg, wrapUnboxedValue )
19 import HsSyn ( ExtName(..), ForeignDecl(..), isDynamic, ForKind(..) )
21 import TcHsSyn ( TypecheckedForeignDecl )
22 import CoreUtils ( coreExprType )
23 import Const ( Con(..), mkMachInt )
24 import DataCon ( DataCon, dataConId )
25 import Id ( Id, idType, idName, mkWildId, mkVanillaId )
26 import Const ( Literal(..) )
27 import Module ( Module )
28 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
29 mkForeignExportOcc, isLocalName,
30 NamedThing(..), Provenance(..), ExportFlag(..)
32 import PrelInfo ( deRefStablePtr_NAME, bindIO_NAME, makeStablePtr_NAME, realWorldPrimId )
33 import Type ( splitAlgTyConApp_maybe,
34 splitTyConApp_maybe, splitFunTys, splitForAllTys,
35 Type, mkFunTys, mkForAllTys, mkTyConApp,
36 mkTyVarTy, mkFunTy, splitAppTy
38 import PrimOp ( PrimOp(..) )
40 import TysPrim ( realWorldStatePrimTy, addrPrimTy )
41 import TysWiredIn ( unitTyCon, addrTy, stablePtrTyCon,
42 unboxedTupleCon, addrDataCon
48 Desugaring of @foreign@ declarations is naturally split up into
49 parts, an @import@ and an @export@ part. A @foreign import@
52 foreign import cc nm f :: prim_args -> IO prim_res
56 f :: prim_args -> IO prim_res
57 f a1 ... an = _ccall_ nm cc a1 ... an
59 so we reuse the desugaring code in @DsCCall@ to deal with these.
63 -> [TypecheckedForeignDecl]
64 -> DsM ( [CoreBind] -- desugared foreign imports
65 , [CoreBind] -- helper functions for foreign exports
66 , SDoc -- Header file prototypes for
67 -- "foreign exported" functions.
68 , SDoc -- C stubs to use when calling
69 -- "foreign exported" functions.
71 dsForeigns mod_name fos = foldlDs combine ([],[],empty,empty) fos
73 combine (acc_fi, acc_fe, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
74 | isForeignImport = -- foreign import (dynamic)?
75 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ b ->
76 returnDs (b:acc_fi, acc_fe, acc_h, acc_c)
78 dsFLabel i ext_nm `thenDs` \ b ->
79 returnDs (b:acc_fi, acc_fe, acc_h, acc_c)
81 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (fi,fe,h,c) ->
82 returnDs (fi:acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
84 | otherwise = -- foreign export
85 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (fe,h,c) ->
86 returnDs (acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
98 (FoImport uns) = imp_exp
102 Desugaring foreign imports is just the matter of creating a binding
103 that on its RHS unboxes its arguments, performs the external call
104 (using the @CCallOp@ primop), before boxing the result up and returning it.
108 -> Type -- Type of foreign import.
109 -> Bool -- True <=> might cause Haskell GC
113 dsFImport nm ty may_not_gc ext_name cconv =
114 newSysLocalDs realWorldStatePrimTy `thenDs` \ old_s ->
115 splitForeignTyDs ty `thenDs` \ (tvs, args, mbIoDataCon, io_res_ty) ->
118 | is_io_action = old_s
119 | otherwise = realWorldPrimId
121 arg_exprs = map (Var) args
128 mapAndUnzipDs unboxArg arg_exprs `thenDs` \ (unboxed_args, arg_wrappers) ->
129 (if not is_io_action then
130 newSysLocalDs realWorldStatePrimTy `thenDs` \ state_tok ->
131 wrapUnboxedValue io_res_ty `thenDs` \ (ccall_result_ty, v, res_v) ->
132 returnDs ( ccall_result_ty
133 , \ prim_app -> Case prim_app (mkWildId ccall_result_ty)
134 [(DataCon (unboxedTupleCon 2), [state_tok, v], res_v)])
136 boxResult io_res_ty) `thenDs` \ (final_result_ty, res_wrapper) ->
138 Dynamic -> getUniqueDs `thenDs` \ u ->
140 ExtName fs _ -> returnDs (Left fs)) `thenDs` \ label ->
142 val_args = Var the_state_arg : unboxed_args
143 final_args = Type inst_ty : val_args
145 -- A CCallOp has type (forall a. a), so we must instantiate
146 -- it at the full type, including the state argument
147 inst_ty = mkFunTys (map coreExprType val_args) final_result_ty
149 the_ccall_op = CCallOp label False (not may_not_gc) cconv
151 the_prim_app = mkPrimApp the_ccall_op (final_args :: [CoreArg])
153 body = foldr ($) (res_wrapper the_prim_app) arg_wrappers
156 | not is_io_action = body
157 | otherwise = Lam old_s body
159 newSysLocalDs (coreExprType the_body) `thenDs` \ ds ->
165 mkApps (Var (dataConId ioDataCon))
166 [Type io_res_ty, Var ds]
168 fo_rhs = mkLams (tvs ++ args)
169 (mkDsLet (NonRec ds (the_body::CoreExpr)) io_app)
171 returnDs (NonRec nm fo_rhs)
174 Given the type of a foreign import declaration, split it up into
175 its constituent parts.
178 splitForeignTyDs :: Type -> DsM ([TyVar], [Id], Maybe DataCon, Type)
179 splitForeignTyDs ty =
180 newSysLocalsDs arg_tys `thenDs` \ ds_args ->
181 case splitAlgTyConApp_maybe res_ty of
182 Just (_,(io_res_ty:_),(ioCon:_)) -> -- .... -> IO t
183 returnDs (tvs, ds_args, Just ioCon, io_res_ty)
185 returnDs (tvs, ds_args, Nothing, res_ty)
187 (arg_tys, res_ty) = splitFunTys sans_foralls
188 (tvs, sans_foralls) = splitForAllTys ty
195 dsFLabel :: Id -> ExtName -> DsM CoreBind
196 dsFLabel nm ext_name = returnDs (NonRec nm fo_rhs)
198 fo_rhs = mkConApp addrDataCon [mkLit (MachLitLit enm addrPrimTy)]
202 Dynamic -> panic "dsFLabel: Dynamic - shouldn't ever happen."
206 The function that does most of the work for `@foreign export@' declarations.
207 (see below for the boilerplate code a `@foreign export@' declaration expands
210 For each `@foreign export foo@' in a module M we generate:
212 \item a C function `@foo@', which calls
213 \item a Haskell stub `@M.$ffoo@', which calls
215 the user-written Haskell function `@M.foo@'.
219 -> Type -- Type of foreign export.
223 -> Bool -- True => invoke IO action that's hanging off
224 -- the first argument's stable pointer
229 dsFExport i ty mod_name ext_name cconv isDyn =
230 getUniqueDs `thenDs` \ uniq ->
231 getSrcLocDs `thenDs` \ src_loc ->
233 f_helper_glob = mkVanillaId helper_name helper_ty
237 | isLocalName name = mod_name
238 | otherwise = nameModule name
240 occ = mkForeignExportOcc (nameOccName name)
241 prov = LocalDef src_loc Exported
242 helper_name = mkGlobalName uniq mod occ prov
244 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
246 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
247 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
248 dsLookupGlobalValue deRefStablePtr_NAME `thenDs` \ deRefStablePtrId ->
250 the_deref_app = mkApps (Var deRefStablePtrId)
251 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
253 newSysLocalDs (coreExprType the_deref_app) `thenDs` \ x_deref_app ->
254 dsLookupGlobalValue bindIO_NAME `thenDs` \ bindIOId ->
255 newSysLocalDs (mkFunTy stbl_ptr_to_ty
256 (mkTyConApp ioTyCon [res_ty])) `thenDs` \ x_cont ->
259 bindNonRec x_cont (mkLams [stbl_value] cont) $
260 bindNonRec x_deref_app the_deref_app
261 (mkApps (Var bindIOId)
262 [ Type stbl_ptr_to_ty
267 returnDs (stbl_value, stbl_app, stbl_ptr)
271 panic "stbl_ptr" -- should never be touched.
272 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
275 | isDyn = stbl_ptr:fe_args
276 | otherwise = fe_args
279 | isDyn = stbl_ptr_ty:helper_arg_tys
280 | otherwise = helper_arg_tys
284 mkApps (Var i) (map (Type . mkTyVarTy) tvs ++ map Var fe_args)
286 getModuleAndGroupDs `thenDs` \ (mod,_) ->
287 getUniqueDs `thenDs` \ uniq ->
289 the_body = mkLams (tvs ++ wrapper_args) the_app
294 Dynamic -> panic "dsFExport: Dynamic - shouldn't ever happen."
296 (h_stub, c_stub) = fexportEntry c_nm f_helper_glob
297 wrapper_arg_tys the_result_ty cconv isDyn
299 returnDs (NonRec f_helper_glob the_body, h_stub, c_stub)
303 (tvs,sans_foralls) = splitForAllTys ty
304 (fe_arg_tys', io_res) = splitFunTys sans_foralls
307 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res
309 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
310 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
313 | isDyn = tail fe_arg_tys'
314 | otherwise = fe_arg_tys'
316 (stbl_ptr_ty, helper_arg_tys) =
318 (x:xs) | isDyn -> (x,xs)
319 ls -> (error "stbl_ptr_ty", ls)
323 mkFunTys arg_tys io_res
326 | isDyn = stbl_ptr_ty : helper_arg_tys
327 | otherwise = helper_arg_tys
330 case splitTyConApp_maybe io_res of
332 case splitTyConApp_maybe res_ty of
333 Just (tc,_) | getUnique tc /= getUnique unitTyCon -> Just res_ty
339 @foreign export dynamic@ lets you dress up Haskell IO actions
340 of some fixed type behind an externally callable interface (i.e.,
341 as a C function pointer). Useful for callbacks and stuff.
344 foreign export stdcall f :: (Addr -> Int -> IO Int) -> IO Addr
346 -- Haskell-visible constructor, which is generated from the
349 f :: (Addr -> Int -> IO Int) -> IO Addr
350 f cback = IO ( \ s1# ->
351 case makeStablePtr# cback s1# of { StateAndStablePtr# s2# sp# ->
352 case _ccall_ "mkAdjustor" sp# ``f_helper'' s2# of
353 StateAndAddr# s3# a# ->
363 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
364 -- `special' foreign export that invokes the closure pointed to by the
369 dsFExportDynamic :: Id
370 -> Type -- Type of foreign export.
374 -> DsM (CoreBind, CoreBind, SDoc, SDoc)
375 dsFExportDynamic i ty mod_name ext_name cconv =
376 newSysLocalDs ty `thenDs` \ fe_id ->
378 -- hack: need to get at the name of the C stub we're about to generate.
379 fe_nm = toCName fe_id
380 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
382 dsFExport i export_ty mod_name fe_ext_name cconv True
383 `thenDs` \ (fe@(NonRec fe_helper fe_expr), h_code, c_code) ->
384 newSysLocalDs arg_ty `thenDs` \ cback ->
385 dsLookupGlobalValue makeStablePtr_NAME `thenDs` \ makeStablePtrId ->
387 mk_stbl_ptr_app = mkApps (Var makeStablePtrId) [ Type arg_ty, Var cback ]
388 mk_stbl_ptr_app_ty = coreExprType mk_stbl_ptr_app
390 newSysLocalDs mk_stbl_ptr_app_ty `thenDs` \ x_mk_stbl_ptr_app ->
391 dsLookupGlobalValue bindIO_NAME `thenDs` \ bindIOId ->
392 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
394 stbl_app = \ x_cont cont ret_ty ->
395 bindNonRec x_cont cont $
396 bindNonRec x_mk_stbl_ptr_app mk_stbl_ptr_app $
397 (mkApps (Var bindIOId)
398 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
400 , Var x_mk_stbl_ptr_app
405 The arguments to the external function which will
406 create a little bit of (template) code on the fly
407 for allowing the (stable pointed) Haskell closure
408 to be entered using an external calling convention
411 adj_args = [ mkLit (mkMachInt (fromInt (callConvToInt cconv)))
413 , mkLit (MachLitLit (_PK_ fe_nm) addrPrimTy)
415 -- name of external entry point providing these services.
416 -- (probably in the RTS.)
417 adjustor = SLIT("createAdjustor")
419 dsCCall adjustor adj_args False False addrTy `thenDs` \ ccall_adj ->
420 let ccall_adj_ty = coreExprType ccall_adj
422 newSysLocalDs ccall_adj_ty `thenDs` \ x_ccall_adj ->
424 mkLams [stbl_value] $
425 bindNonRec x_ccall_adj ccall_adj $
426 Note (Coerce (mkTyConApp ioTyCon [res_ty]) ccall_adj_ty)
429 newSysLocalDs (coreExprType ccall_io_adj) `thenDs` \ x_ccall_io_adj ->
430 let io_app = mkLams tvs $
432 stbl_app x_ccall_io_adj ccall_io_adj addrTy
434 returnDs (NonRec i io_app, fe, h_code, c_code)
437 (tvs,sans_foralls) = splitForAllTys ty
438 ([arg_ty], io_res) = splitFunTys sans_foralls
440 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res
442 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
444 toCName :: Id -> String
445 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
451 \subsection{Generating @foreign export@ stubs}
455 For each @foreign export@ function, a C stub function is generated.
456 The C stub constructs the application of the exported Haskell function
457 using the hugs/ghc rts invocation API.
460 fexportEntry :: FAST_STRING
467 fexportEntry c_nm helper args res cc isDyn = (header_bits, c_bits)
469 -- name of the (Haskell) helper function generated by the desugarer.
470 h_nm = ppr helper <> text "_closure"
471 -- prototype for the exported function.
472 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
474 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
475 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
482 , text "SchedulerStatus rc;"
484 -- create the application + perform it.
485 , text "rc=rts_evalIO" <>
486 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
492 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
494 cParamTypes = map showStgType real_args
498 Nothing -> text "void"
499 Just t -> showStgType t
502 | cc == cCallConv = empty
503 | otherwise = pprCallConv cc
505 declareResult = text "HaskellObj ret;"
507 externDecl = mkExtern (text "HaskellObj") h_nm
509 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
512 text "rts_checkSchedStatus" <>
513 parens (doubleQuotes (ptext c_nm) <> comma <> text "rc") <> semi $$
515 Nothing -> text "return"
516 Just _ -> text "return" <> parens (res_name)) <> semi
521 Just t -> unpackHObj t <> parens (text "ret")
523 c_args = mkCArgNames 0 args
526 If we're generating an entry point for a 'foreign export ccall dynamic',
527 then we receive the return address of the C function that wants to
528 invoke a Haskell function as any other C function, as second arg.
529 This arg is unused within the body of the generated C stub, but
530 needed by the Adjustor.c code to get the stack cleanup right.
532 (proto_args, real_args)
533 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
534 , head args : addrTy : tail args)
535 | otherwise = (mkCArgNames 0 args, args)
537 mkCArgNames :: Int -> [a] -> [SDoc]
538 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
540 mkHObj :: Type -> SDoc
541 mkHObj t = text "rts_mk" <> text (showFFIType t)
543 unpackHObj :: Type -> SDoc
544 unpackHObj t = text "rts_get" <> text (showFFIType t)
546 showStgType :: Type -> SDoc
547 showStgType t = text "Stg" <> text (showFFIType t)
549 showFFIType :: Type -> String
550 showFFIType t = getOccString (getName tc)
552 tc = case splitTyConApp_maybe t of
554 Nothing -> pprPanic "showFFIType" (ppr t)