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 )
26 import MkId ( 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, returnIO_NAME, bindIO_NAME, makeStablePtr_NAME )
34 import Type ( unUsgTy,
35 splitTyConApp_maybe, splitFunTys, splitForAllTys,
36 Type, mkFunTys, mkForAllTys, mkTyConApp,
37 mkTyVarTy, mkFunTy, splitAppTy, applyTy, funResultTy
39 import PrimOp ( PrimOp(..), CCall(..), CCallTarget(..) )
41 import TysPrim ( realWorldStatePrimTy, addrPrimTy )
42 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon,
43 unboxedTupleCon, addrDataCon
46 import Maybes ( maybeToBool )
50 Desugaring of @foreign@ declarations is naturally split up into
51 parts, an @import@ and an @export@ part. A @foreign import@
54 foreign import cc nm f :: prim_args -> IO prim_res
58 f :: prim_args -> IO prim_res
59 f a1 ... an = _ccall_ nm cc a1 ... an
61 so we reuse the desugaring code in @DsCCall@ to deal with these.
65 -> [TypecheckedForeignDecl]
66 -> DsM ( [CoreBind] -- desugared foreign imports
67 , [CoreBind] -- helper functions for foreign exports
68 , SDoc -- Header file prototypes for
69 -- "foreign exported" functions.
70 , SDoc -- C stubs to use when calling
71 -- "foreign exported" functions.
73 dsForeigns mod_name fos = foldlDs combine ([],[],empty,empty) fos
75 combine (acc_fi, acc_fe, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
76 | isForeignImport = -- foreign import (dynamic)?
77 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ bs ->
78 returnDs (bs ++ acc_fi, acc_fe, acc_h, acc_c)
80 dsFLabel i ext_nm `thenDs` \ b ->
81 returnDs (b:acc_fi, acc_fe, acc_h, acc_c)
82 | isDynamicExtName ext_nm =
83 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (fi,fe,h,c) ->
84 returnDs (fi:acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
86 | otherwise = -- foreign export
87 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (fe,h,c) ->
88 returnDs (acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
100 (FoImport uns) = imp_exp
104 Desugaring foreign imports is just the matter of creating a binding
105 that on its RHS unboxes its arguments, performs the external call
106 (using the @CCallOp@ primop), before boxing the result up and returning it.
108 However, we create a worker/wrapper pair, thus:
110 foreign import f :: Int -> IO Int
112 f x = IO ( \s -> case x of { I# x# ->
113 case fw s x# of { (# s1, y# #) ->
116 fw s x# = ccall f s x#
118 The strictness/CPR analyser won't do this automatically because it doesn't look
119 inside returned tuples; but inlining this wrapper is a Really Good Idea
120 because it exposes the boxing to the call site.
125 -> Type -- Type of foreign import.
126 -> Bool -- True <=> might cause Haskell GC
130 dsFImport fn_id ty may_not_gc ext_name cconv
132 (tvs, fun_ty) = splitForAllTys ty
133 (arg_tys, io_res_ty) = splitFunTys fun_ty
135 newSysLocalsDs arg_tys `thenDs` \ args ->
136 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
137 boxResult io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
140 Dynamic -> getUniqueDs `thenDs` \ u ->
141 returnDs (DynamicTarget u)
142 ExtName fs _ -> returnDs (StaticTarget fs)) `thenDs` \ lbl ->
144 getUniqueDs `thenDs` \ ccall_uniq ->
145 getUniqueDs `thenDs` \ work_uniq ->
148 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
149 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
150 the_ccall = CCall lbl False (not may_not_gc) cconv
151 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
152 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
153 work_id = mkWorkerId work_uniq fn_id worker_ty
156 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
157 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
158 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
160 returnDs [NonRec fn_id wrap_rhs, NonRec work_id work_rhs]
166 dsFLabel :: Id -> ExtName -> DsM CoreBind
167 dsFLabel nm ext_name = returnDs (NonRec nm fo_rhs)
169 fo_rhs = mkConApp addrDataCon [mkLit (MachLitLit enm addrPrimTy)]
170 enm = extNameStatic ext_name
173 The function that does most of the work for `@foreign export@' declarations.
174 (see below for the boilerplate code a `@foreign export@' declaration expands
177 For each `@foreign export foo@' in a module M we generate:
179 \item a C function `@foo@', which calls
180 \item a Haskell stub `@M.$ffoo@', which calls
182 the user-written Haskell function `@M.foo@'.
186 -> Type -- Type of foreign export.
190 -> Bool -- True => invoke IO action that's hanging off
191 -- the first argument's stable pointer
196 dsFExport i ty mod_name ext_name cconv isDyn
197 = -- BUILD THE returnIO WRAPPER, if necessary
198 -- Look at the result type of the exported function, orig_res_ty
199 -- If it's IO t, return (\x.x, IO t, t)
200 -- If it's plain t, return (\x.returnIO x, IO t, t)
201 (case splitTyConApp_maybe orig_res_ty of
202 Just (ioTyCon, [res_ty])
203 -> ASSERT( getUnique ioTyCon == ioTyConKey )
204 -- The function already returns IO t
205 returnDs (\body -> body, orig_res_ty, res_ty)
207 other -> -- The function returns t, so wrap the call in returnIO
208 dsLookupGlobalValue returnIO_NAME `thenDs` \ retIOId ->
209 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
210 funResultTy (applyTy (idType retIOId) orig_res_ty),
211 -- We don't have ioTyCon conveniently to hand
214 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
219 -- BUILD THE deRefStablePtr WRAPPER, if necessary
221 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
222 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
223 dsLookupGlobalValue deRefStablePtr_NAME `thenDs` \ deRefStablePtrId ->
225 the_deref_app = mkApps (Var deRefStablePtrId)
226 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
228 dsLookupGlobalValue bindIO_NAME `thenDs` \ bindIOId ->
230 stbl_app cont = mkApps (Var bindIOId)
231 [ Type stbl_ptr_to_ty
234 , mkLams [stbl_value] cont]
236 returnDs (stbl_value, stbl_app, stbl_ptr)
240 panic "stbl_ptr" -- should never be touched.
241 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
245 getModuleDs `thenDs` \ mod ->
246 getUniqueDs `thenDs` \ uniq ->
247 getSrcLocDs `thenDs` \ src_loc ->
248 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
250 wrapper_args | isDyn = stbl_ptr:fe_args
251 | otherwise = fe_args
253 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
254 | otherwise = fe_arg_tys
256 helper_ty = mkForAllTys tvs $
257 mkFunTys wrapper_arg_tys io_res_ty
259 f_helper_glob = mkVanillaId helper_name helper_ty
263 | isLocalName name = mod_name
264 | otherwise = nameModule name
266 occ = mkForeignExportOcc (nameOccName name)
267 prov = LocalDef src_loc Exported
268 helper_name = mkGlobalName uniq mod occ prov
270 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
271 the_body = mkLams (tvs ++ wrapper_args) the_app
272 c_nm = extNameStatic ext_name
274 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
276 wrapper_arg_tys res_ty cconv isDyn
278 returnDs (NonRec f_helper_glob the_body, h_stub, c_stub)
281 (tvs,sans_foralls) = splitForAllTys ty
282 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
284 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
285 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
287 fe_arg_tys | isDyn = tail fe_arg_tys'
288 | otherwise = fe_arg_tys'
290 stbl_ptr_ty | isDyn = head fe_arg_tys'
291 | otherwise = error "stbl_ptr_ty"
294 @foreign export dynamic@ lets you dress up Haskell IO actions
295 of some fixed type behind an externally callable interface (i.e.,
296 as a C function pointer). Useful for callbacks and stuff.
299 foreign export stdcall f :: (Addr -> Int -> IO Int) -> IO Addr
301 -- Haskell-visible constructor, which is generated from the
304 f :: (Addr -> Int -> IO Int) -> IO Addr
305 f cback = IO ( \ s1# ->
306 case makeStablePtr# cback s1# of { StateAndStablePtr# s2# sp# ->
307 case _ccall_ "mkAdjustor" sp# ``f_helper'' s2# of
308 StateAndAddr# s3# a# ->
318 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
319 -- `special' foreign export that invokes the closure pointed to by the
324 dsFExportDynamic :: Id
325 -> Type -- Type of foreign export.
329 -> DsM (CoreBind, CoreBind, SDoc, SDoc)
330 dsFExportDynamic i ty mod_name ext_name cconv =
331 newSysLocalDs ty `thenDs` \ fe_id ->
333 -- hack: need to get at the name of the C stub we're about to generate.
334 fe_nm = toCName fe_id
335 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
337 dsFExport i export_ty mod_name fe_ext_name cconv True
338 `thenDs` \ (fe@(NonRec fe_helper fe_expr), h_code, c_code) ->
339 newSysLocalDs arg_ty `thenDs` \ cback ->
340 dsLookupGlobalValue makeStablePtr_NAME `thenDs` \ makeStablePtrId ->
342 mk_stbl_ptr_app = mkApps (Var makeStablePtrId) [ Type arg_ty, Var cback ]
344 dsLookupGlobalValue bindIO_NAME `thenDs` \ bindIOId ->
345 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
348 = mkApps (Var bindIOId)
349 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
356 The arguments to the external function which will
357 create a little bit of (template) code on the fly
358 for allowing the (stable pointed) Haskell closure
359 to be entered using an external calling convention
362 adj_args = [ mkIntLitInt (callConvToInt cconv)
364 , mkLit (MachLitLit (_PK_ fe_nm) addrPrimTy)
366 -- name of external entry point providing these services.
367 -- (probably in the RTS.)
368 adjustor = SLIT("createAdjustor")
370 dsCCall adjustor adj_args False False ioAddrTy `thenDs` \ ccall_adj ->
371 let ccall_adj_ty = exprType ccall_adj
372 ccall_io_adj = mkLams [stbl_value] $
373 Note (Coerce io_res_ty (unUsgTy ccall_adj_ty))
376 let io_app = mkLams tvs $
378 stbl_app ccall_io_adj addrTy
380 returnDs (NonRec i io_app, fe, h_code, c_code)
383 (tvs,sans_foralls) = splitForAllTys ty
384 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
386 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
388 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
390 ioAddrTy :: Type -- IO Addr
391 ioAddrTy = mkTyConApp ioTyCon [addrTy]
393 toCName :: Id -> String
394 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
399 \subsection{Generating @foreign export@ stubs}
403 For each @foreign export@ function, a C stub function is generated.
404 The C stub constructs the application of the exported Haskell function
405 using the hugs/ghc rts invocation API.
408 fexportEntry :: String
416 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
418 -- name of the (Haskell) helper function generated by the desugarer.
419 h_nm = ppr helper <> text "_closure"
420 -- prototype for the exported function.
421 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
423 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
424 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
431 , text "SchedulerStatus rc;"
433 -- create the application + perform it.
434 , text "rc=rts_evalIO" <>
435 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
436 , text "rts_checkSchedStatus" <> parens (doubleQuotes (text mod_nm <> char '.' <> ptext c_nm)
437 <> comma <> text "rc") <> semi
438 , text "return" <> return_what <> semi
443 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
445 cParamTypes = map showStgType real_args
447 res_ty_is_unit = res_ty == unitTy
449 cResType | res_ty_is_unit = text "void"
450 | otherwise = showStgType res_ty
453 | cc == cCallConv = empty
454 | otherwise = pprCallConv cc
456 declareResult = text "HaskellObj ret;"
458 externDecl = mkExtern (text "HaskellObj") h_nm
460 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
462 return_what | res_ty_is_unit = empty
463 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
465 c_args = mkCArgNames 0 args
468 If we're generating an entry point for a 'foreign export ccall dynamic',
469 then we receive the return address of the C function that wants to
470 invoke a Haskell function as any other C function, as second arg.
471 This arg is unused within the body of the generated C stub, but
472 needed by the Adjustor.c code to get the stack cleanup right.
474 (proto_args, real_args)
475 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
476 , head args : addrTy : tail args)
477 | otherwise = (mkCArgNames 0 args, args)
479 mkCArgNames :: Int -> [a] -> [SDoc]
480 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
482 mkHObj :: Type -> SDoc
483 mkHObj t = text "rts_mk" <> text (showFFIType t)
485 unpackHObj :: Type -> SDoc
486 unpackHObj t = text "rts_get" <> text (showFFIType t)
488 showStgType :: Type -> SDoc
489 showStgType t = text "Stg" <> text (showFFIType t)
491 showFFIType :: Type -> String
492 showFFIType t = getOccString (getName tc)
494 tc = case splitTyConApp_maybe t of
496 Nothing -> pprPanic "showFFIType" (ppr t)