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 )
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, mkSysLocal,
27 import IdInfo ( neverInlinePrag )
28 import MkId ( mkWorkerId )
29 import Literal ( Literal(..) )
30 import Module ( Module, moduleUserString )
31 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
32 mkForeignExportOcc, isLocalName,
33 NamedThing(..), Provenance(..), ExportFlag(..)
35 import Type ( unUsgTy, repType,
36 splitTyConApp_maybe, splitFunTys, splitForAllTys,
37 Type, mkFunTys, mkForAllTys, mkTyConApp,
38 mkTyVarTy, mkFunTy, splitAppTy, applyTy, funResultTy
40 import PprType ( {- instance Outputable Type -} )
41 import PrimOp ( PrimOp(..), CCall(..), CCallTarget(..) )
43 import TysPrim ( realWorldStatePrimTy, addrPrimTy )
44 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon,
47 import Unique ( Uniquable(..), hasKey,
48 ioTyConKey, deRefStablePtrIdKey, returnIOIdKey,
49 bindIOIdKey, makeStablePtrIdKey
51 import Maybes ( maybeToBool )
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, fun_ty) = splitForAllTys ty
138 (arg_tys, io_res_ty) = splitFunTys fun_ty
140 newSysLocalsDs arg_tys `thenDs` \ args ->
141 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
142 boxResult io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
145 Dynamic -> getUniqueDs `thenDs` \ u ->
146 returnDs (DynamicTarget u)
147 ExtName fs _ -> returnDs (StaticTarget fs)) `thenDs` \ lbl ->
149 getUniqueDs `thenDs` \ ccall_uniq ->
150 getUniqueDs `thenDs` \ work_uniq ->
153 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
154 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
155 the_ccall = CCall lbl False (not may_not_gc) cconv
156 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
157 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
158 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
161 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
162 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
163 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
165 returnDs [NonRec fn_id wrap_rhs, NonRec work_id work_rhs]
171 dsFLabel :: Id -> ExtName -> DsM CoreBind
172 dsFLabel nm ext_name = returnDs (NonRec nm fo_rhs)
174 fo_rhs = mkConApp addrDataCon [mkLit (MachLitLit enm addrPrimTy)]
175 enm = extNameStatic ext_name
178 The function that does most of the work for `@foreign export@' declarations.
179 (see below for the boilerplate code a `@foreign export@' declaration expands
182 For each `@foreign export foo@' in a module M we generate:
184 \item a C function `@foo@', which calls
185 \item a Haskell stub `@M.$ffoo@', which calls
187 the user-written Haskell function `@M.foo@'.
191 -> Type -- Type of foreign export.
195 -> Bool -- True => invoke IO action that's hanging off
196 -- the first argument's stable pointer
201 dsFExport fn_id ty mod_name ext_name cconv isDyn
202 = -- BUILD THE returnIO WRAPPER, if necessary
203 -- Look at the result type of the exported function, orig_res_ty
204 -- If it's IO t, return (\x.x, IO t, t)
205 -- If it's plain t, return (\x.returnIO x, IO t, t)
206 (case splitTyConApp_maybe orig_res_ty of
207 Just (ioTyCon, [res_ty])
208 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
209 -- The function already returns IO t
210 returnDs (\body -> body, orig_res_ty, res_ty)
212 other -> -- The function returns t, so wrap the call in returnIO
213 dsLookupGlobalValue returnIOIdKey `thenDs` \ retIOId ->
214 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
215 funResultTy (applyTy (idType retIOId) orig_res_ty),
216 -- We don't have ioTyCon conveniently to hand
219 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
224 -- BUILD THE deRefStablePtr WRAPPER, if necessary
226 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
227 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
228 dsLookupGlobalValue deRefStablePtrIdKey `thenDs` \ deRefStablePtrId ->
229 dsLookupGlobalValue bindIOIdKey `thenDs` \ bindIOId ->
231 the_deref_app = mkApps (Var deRefStablePtrId)
232 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
234 stbl_app cont = mkApps (Var bindIOId)
235 [ Type stbl_ptr_to_ty
238 , mkLams [stbl_value] cont]
240 returnDs (stbl_value, stbl_app, stbl_ptr)
244 panic "stbl_ptr" -- should never be touched.
245 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
249 getModuleDs `thenDs` \ mod ->
250 getUniqueDs `thenDs` \ uniq ->
251 getSrcLocDs `thenDs` \ src_loc ->
252 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
254 wrapper_args | isDyn = stbl_ptr:fe_args
255 | otherwise = fe_args
257 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
258 | otherwise = fe_arg_tys
260 helper_ty = mkForAllTys tvs $
261 mkFunTys wrapper_arg_tys io_res_ty
263 f_helper_glob = mkVanillaId helper_name helper_ty
267 | isLocalName name = mod_name
268 | otherwise = nameModule name
270 occ = mkForeignExportOcc (nameOccName name)
271 prov = LocalDef src_loc Exported
272 helper_name = mkGlobalName uniq mod occ prov
274 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
275 the_body = mkLams (tvs ++ wrapper_args) the_app
276 c_nm = extNameStatic ext_name
278 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
280 wrapper_arg_tys res_ty cconv isDyn
282 returnDs (NonRec f_helper_glob the_body, h_stub, c_stub)
285 (tvs,sans_foralls) = splitForAllTys ty
286 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
288 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
289 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
291 fe_arg_tys | isDyn = tail fe_arg_tys'
292 | otherwise = fe_arg_tys'
294 stbl_ptr_ty | isDyn = head fe_arg_tys'
295 | otherwise = error "stbl_ptr_ty"
298 @foreign export dynamic@ lets you dress up Haskell IO actions
299 of some fixed type behind an externally callable interface (i.e.,
300 as a C function pointer). Useful for callbacks and stuff.
303 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
305 -- Haskell-visible constructor, which is generated from the above:
306 -- SUP: No check for NULL from createAdjustor anymore???
308 f :: (Addr -> Int -> IO Int) -> IO Addr
310 bindIO (makeStablePtr cback)
311 (\StablePtr sp# -> IO (\s1# ->
312 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
313 (# s2#, a# #) -> (# s2#, A# a# #)))
315 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
316 -- `special' foreign export that invokes the closure pointed to by the
321 dsFExportDynamic :: Id
322 -> Type -- Type of foreign export.
326 -> DsM (CoreBind, CoreBind, SDoc, SDoc)
327 dsFExportDynamic i ty mod_name ext_name cconv =
328 newSysLocalDs ty `thenDs` \ fe_id ->
330 -- hack: need to get at the name of the C stub we're about to generate.
331 fe_nm = moduleUserString mod_name ++ "_" ++ toCName fe_id
332 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
334 dsFExport i export_ty mod_name fe_ext_name cconv True
335 `thenDs` \ (fe@(NonRec fe_helper fe_expr), h_code, c_code) ->
336 newSysLocalDs arg_ty `thenDs` \ cback ->
337 dsLookupGlobalValue makeStablePtrIdKey `thenDs` \ makeStablePtrId ->
339 mk_stbl_ptr_app = mkApps (Var makeStablePtrId) [ Type arg_ty, Var cback ]
341 dsLookupGlobalValue bindIOIdKey `thenDs` \ bindIOId ->
342 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
345 = mkApps (Var bindIOId)
346 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
353 The arguments to the external function which will
354 create a little bit of (template) code on the fly
355 for allowing the (stable pointed) Haskell closure
356 to be entered using an external calling convention
359 adj_args = [ mkIntLitInt (callConvToInt cconv)
361 , mkLit (MachLitLit (_PK_ fe_nm) addrPrimTy)
363 -- name of external entry point providing these services.
364 -- (probably in the RTS.)
365 adjustor = SLIT("createAdjustor")
367 dsCCall adjustor adj_args False False ioAddrTy `thenDs` \ ccall_adj ->
368 let ccall_adj_ty = exprType ccall_adj
369 ccall_io_adj = mkLams [stbl_value] $
370 Note (Coerce io_res_ty (unUsgTy ccall_adj_ty))
373 let io_app = mkLams tvs $
375 stbl_app ccall_io_adj addrTy
377 -- Never inline the f.e.d. function, because the litlit might not be in scope
379 returnDs (NonRec (i `setInlinePragma` neverInlinePrag) io_app, fe, h_code, c_code)
382 (tvs,sans_foralls) = splitForAllTys ty
383 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
385 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
387 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
389 ioAddrTy :: Type -- IO Addr
390 ioAddrTy = mkTyConApp ioTyCon [addrTy]
392 toCName :: Id -> String
393 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
398 \subsection{Generating @foreign export@ stubs}
402 For each @foreign export@ function, a C stub function is generated.
403 The C stub constructs the application of the exported Haskell function
404 using the hugs/ghc rts invocation API.
407 fexportEntry :: String
415 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
417 -- name of the (Haskell) helper function generated by the desugarer.
418 h_nm = ppr helper <> text "_closure"
419 -- prototype for the exported function.
420 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
422 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
423 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
430 , text "SchedulerStatus rc;"
432 -- create the application + perform it.
433 , text "rc=rts_evalIO" <>
434 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
435 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
436 <> comma <> text "rc") <> semi
437 , text "return" <> return_what <> semi
442 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
444 cParamTypes = map showStgType real_args
446 res_ty_is_unit = res_ty == unitTy
448 cResType | res_ty_is_unit = text "void"
449 | otherwise = showStgType res_ty
452 | cc == cCallConv = empty
453 | otherwise = pprCallConv cc
455 declareResult = text "HaskellObj ret;"
457 externDecl = mkExtern (text "HaskellObj") h_nm
459 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
461 return_what | res_ty_is_unit = empty
462 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
464 c_args = mkCArgNames 0 args
467 If we're generating an entry point for a 'foreign export ccall dynamic',
468 then we receive the return address of the C function that wants to
469 invoke a Haskell function as any other C function, as second arg.
470 This arg is unused within the body of the generated C stub, but
471 needed by the Adjustor.c code to get the stack cleanup right.
473 (proto_args, real_args)
474 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
475 , head args : addrTy : tail args)
476 | otherwise = (mkCArgNames 0 args, args)
478 mkCArgNames :: Int -> [a] -> [SDoc]
479 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
481 mkHObj :: Type -> SDoc
482 mkHObj t = text "rts_mk" <> text (showFFIType t)
484 unpackHObj :: Type -> SDoc
485 unpackHObj t = text "rts_get" <> text (showFFIType t)
487 showStgType :: Type -> SDoc
488 showStgType t = text "Stg" <> text (showFFIType t)
490 showFFIType :: Type -> String
491 showFFIType t = getOccString (getName tc)
493 tc = case splitTyConApp_maybe (repType t) of
495 Nothing -> pprPanic "showFFIType" (ppr t)