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 PprType ( {- instance Outputable Type -} )
40 import PrimOp ( PrimOp(..), CCall(..), CCallTarget(..) )
42 import TysPrim ( realWorldStatePrimTy, addrPrimTy )
43 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon,
44 unboxedTupleCon, addrDataCon
47 import Maybes ( maybeToBool )
51 Desugaring of @foreign@ declarations is naturally split up into
52 parts, an @import@ and an @export@ part. A @foreign import@
55 foreign import cc nm f :: prim_args -> IO prim_res
59 f :: prim_args -> IO prim_res
60 f a1 ... an = _ccall_ nm cc a1 ... an
62 so we reuse the desugaring code in @DsCCall@ to deal with these.
66 -> [TypecheckedForeignDecl]
67 -> DsM ( [CoreBind] -- desugared foreign imports
68 , [CoreBind] -- helper functions for foreign exports
69 , SDoc -- Header file prototypes for
70 -- "foreign exported" functions.
71 , SDoc -- C stubs to use when calling
72 -- "foreign exported" functions.
74 dsForeigns mod_name fos = foldlDs combine ([],[],empty,empty) fos
76 combine (acc_fi, acc_fe, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
77 | isForeignImport = -- foreign import (dynamic)?
78 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ bs ->
79 returnDs (bs ++ acc_fi, acc_fe, acc_h, acc_c)
81 dsFLabel i ext_nm `thenDs` \ b ->
82 returnDs (b:acc_fi, acc_fe, acc_h, acc_c)
83 | isDynamicExtName ext_nm =
84 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (fi,fe,h,c) ->
85 returnDs (fi:acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
87 | otherwise = -- foreign export
88 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (fe,h,c) ->
89 returnDs (acc_fi, fe:acc_fe, h $$ acc_h, c $$ acc_c)
101 (FoImport uns) = imp_exp
105 Desugaring foreign imports is just the matter of creating a binding
106 that on its RHS unboxes its arguments, performs the external call
107 (using the @CCallOp@ primop), before boxing the result up and returning it.
109 However, we create a worker/wrapper pair, thus:
111 foreign import f :: Int -> IO Int
113 f x = IO ( \s -> case x of { I# x# ->
114 case fw s x# of { (# s1, y# #) ->
117 fw s x# = ccall f s x#
119 The strictness/CPR analyser won't do this automatically because it doesn't look
120 inside returned tuples; but inlining this wrapper is a Really Good Idea
121 because it exposes the boxing to the call site.
126 -> Type -- Type of foreign import.
127 -> Bool -- True <=> might cause Haskell GC
131 dsFImport fn_id ty may_not_gc ext_name cconv
133 (tvs, fun_ty) = splitForAllTys ty
134 (arg_tys, io_res_ty) = splitFunTys fun_ty
136 newSysLocalsDs arg_tys `thenDs` \ args ->
137 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
138 boxResult io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
141 Dynamic -> getUniqueDs `thenDs` \ u ->
142 returnDs (DynamicTarget u)
143 ExtName fs _ -> returnDs (StaticTarget fs)) `thenDs` \ lbl ->
145 getUniqueDs `thenDs` \ ccall_uniq ->
146 getUniqueDs `thenDs` \ work_uniq ->
149 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
150 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
151 the_ccall = CCall lbl False (not may_not_gc) cconv
152 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
153 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
154 work_id = mkWorkerId work_uniq fn_id worker_ty
157 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
158 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
159 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
161 returnDs [NonRec fn_id wrap_rhs, NonRec work_id work_rhs]
167 dsFLabel :: Id -> ExtName -> DsM CoreBind
168 dsFLabel nm ext_name = returnDs (NonRec nm fo_rhs)
170 fo_rhs = mkConApp addrDataCon [mkLit (MachLitLit enm addrPrimTy)]
171 enm = extNameStatic ext_name
174 The function that does most of the work for `@foreign export@' declarations.
175 (see below for the boilerplate code a `@foreign export@' declaration expands
178 For each `@foreign export foo@' in a module M we generate:
180 \item a C function `@foo@', which calls
181 \item a Haskell stub `@M.$ffoo@', which calls
183 the user-written Haskell function `@M.foo@'.
187 -> Type -- Type of foreign export.
191 -> Bool -- True => invoke IO action that's hanging off
192 -- the first argument's stable pointer
197 dsFExport fn_id ty mod_name ext_name cconv isDyn
198 = -- BUILD THE returnIO WRAPPER, if necessary
199 -- Look at the result type of the exported function, orig_res_ty
200 -- If it's IO t, return (\x.x, IO t, t)
201 -- If it's plain t, return (\x.returnIO x, IO t, t)
202 (case splitTyConApp_maybe orig_res_ty of
203 Just (ioTyCon, [res_ty])
204 -> ASSERT( getUnique ioTyCon == ioTyConKey )
205 -- The function already returns IO t
206 returnDs (\body -> body, orig_res_ty, res_ty)
208 other -> -- The function returns t, so wrap the call in returnIO
209 dsLookupGlobalValue returnIO_NAME `thenDs` \ retIOId ->
210 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
211 funResultTy (applyTy (idType retIOId) orig_res_ty),
212 -- We don't have ioTyCon conveniently to hand
215 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
220 -- BUILD THE deRefStablePtr WRAPPER, if necessary
222 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
223 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
224 dsLookupGlobalValue deRefStablePtr_NAME `thenDs` \ deRefStablePtrId ->
226 the_deref_app = mkApps (Var deRefStablePtrId)
227 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
229 dsLookupGlobalValue bindIO_NAME `thenDs` \ bindIOId ->
231 stbl_app cont = mkApps (Var bindIOId)
232 [ Type stbl_ptr_to_ty
235 , mkLams [stbl_value] cont]
237 returnDs (stbl_value, stbl_app, stbl_ptr)
241 panic "stbl_ptr" -- should never be touched.
242 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
246 getModuleDs `thenDs` \ mod ->
247 getUniqueDs `thenDs` \ uniq ->
248 getSrcLocDs `thenDs` \ src_loc ->
249 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
251 wrapper_args | isDyn = stbl_ptr:fe_args
252 | otherwise = fe_args
254 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
255 | otherwise = fe_arg_tys
257 helper_ty = mkForAllTys tvs $
258 mkFunTys wrapper_arg_tys io_res_ty
260 f_helper_glob = mkVanillaId helper_name helper_ty
264 | isLocalName name = mod_name
265 | otherwise = nameModule name
267 occ = mkForeignExportOcc (nameOccName name)
268 prov = LocalDef src_loc Exported
269 helper_name = mkGlobalName uniq mod occ prov
271 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
272 the_body = mkLams (tvs ++ wrapper_args) the_app
273 c_nm = extNameStatic ext_name
275 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
277 wrapper_arg_tys res_ty cconv isDyn
279 returnDs (NonRec f_helper_glob the_body, h_stub, c_stub)
282 (tvs,sans_foralls) = splitForAllTys ty
283 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
285 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
286 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
288 fe_arg_tys | isDyn = tail fe_arg_tys'
289 | otherwise = fe_arg_tys'
291 stbl_ptr_ty | isDyn = head fe_arg_tys'
292 | otherwise = error "stbl_ptr_ty"
295 @foreign export dynamic@ lets you dress up Haskell IO actions
296 of some fixed type behind an externally callable interface (i.e.,
297 as a C function pointer). Useful for callbacks and stuff.
300 foreign export stdcall f :: (Addr -> Int -> IO Int) -> IO Addr
302 -- Haskell-visible constructor, which is generated from the
305 f :: (Addr -> Int -> IO Int) -> IO Addr
306 f cback = IO ( \ s1# ->
307 case makeStablePtr# cback s1# of { StateAndStablePtr# s2# sp# ->
308 case _ccall_ "mkAdjustor" sp# ``f_helper'' s2# of
309 StateAndAddr# s3# a# ->
319 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
320 -- `special' foreign export that invokes the closure pointed to by the
325 dsFExportDynamic :: Id
326 -> Type -- Type of foreign export.
330 -> DsM (CoreBind, CoreBind, SDoc, SDoc)
331 dsFExportDynamic i ty mod_name ext_name cconv =
332 newSysLocalDs ty `thenDs` \ fe_id ->
334 -- hack: need to get at the name of the C stub we're about to generate.
335 fe_nm = moduleUserString mod_name ++ "_" ++ toCName fe_id
336 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
338 dsFExport i export_ty mod_name fe_ext_name cconv True
339 `thenDs` \ (fe@(NonRec fe_helper fe_expr), h_code, c_code) ->
340 newSysLocalDs arg_ty `thenDs` \ cback ->
341 dsLookupGlobalValue makeStablePtr_NAME `thenDs` \ makeStablePtrId ->
343 mk_stbl_ptr_app = mkApps (Var makeStablePtrId) [ Type arg_ty, Var cback ]
345 dsLookupGlobalValue bindIO_NAME `thenDs` \ bindIOId ->
346 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
349 = mkApps (Var bindIOId)
350 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
357 The arguments to the external function which will
358 create a little bit of (template) code on the fly
359 for allowing the (stable pointed) Haskell closure
360 to be entered using an external calling convention
363 adj_args = [ mkIntLitInt (callConvToInt cconv)
365 , mkLit (MachLitLit (_PK_ fe_nm) addrPrimTy)
367 -- name of external entry point providing these services.
368 -- (probably in the RTS.)
369 adjustor = SLIT("createAdjustor")
371 dsCCall adjustor adj_args False False ioAddrTy `thenDs` \ ccall_adj ->
372 let ccall_adj_ty = exprType ccall_adj
373 ccall_io_adj = mkLams [stbl_value] $
374 Note (Coerce io_res_ty (unUsgTy ccall_adj_ty))
377 let io_app = mkLams tvs $
379 stbl_app ccall_io_adj addrTy
381 returnDs (NonRec i io_app, fe, h_code, c_code)
384 (tvs,sans_foralls) = splitForAllTys ty
385 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
387 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
389 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
391 ioAddrTy :: Type -- IO Addr
392 ioAddrTy = mkTyConApp ioTyCon [addrTy]
394 toCName :: Id -> String
395 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
400 \subsection{Generating @foreign export@ stubs}
404 For each @foreign export@ function, a C stub function is generated.
405 The C stub constructs the application of the exported Haskell function
406 using the hugs/ghc rts invocation API.
409 fexportEntry :: String
417 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
419 -- name of the (Haskell) helper function generated by the desugarer.
420 h_nm = ppr helper <> text "_closure"
421 -- prototype for the exported function.
422 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
424 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
425 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
432 , text "SchedulerStatus rc;"
434 -- create the application + perform it.
435 , text "rc=rts_evalIO" <>
436 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
437 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
438 <> comma <> text "rc") <> semi
439 , text "return" <> return_what <> semi
444 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
446 cParamTypes = map showStgType real_args
448 res_ty_is_unit = res_ty == unitTy
450 cResType | res_ty_is_unit = text "void"
451 | otherwise = showStgType res_ty
454 | cc == cCallConv = empty
455 | otherwise = pprCallConv cc
457 declareResult = text "HaskellObj ret;"
459 externDecl = mkExtern (text "HaskellObj") h_nm
461 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
463 return_what | res_ty_is_unit = empty
464 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
466 c_args = mkCArgNames 0 args
469 If we're generating an entry point for a 'foreign export ccall dynamic',
470 then we receive the return address of the C function that wants to
471 invoke a Haskell function as any other C function, as second arg.
472 This arg is unused within the body of the generated C stub, but
473 needed by the Adjustor.c code to get the stack cleanup right.
475 (proto_args, real_args)
476 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
477 , head args : addrTy : tail args)
478 | otherwise = (mkCArgNames 0 args, args)
480 mkCArgNames :: Int -> [a] -> [SDoc]
481 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
483 mkHObj :: Type -> SDoc
484 mkHObj t = text "rts_mk" <> text (showFFIType t)
486 unpackHObj :: Type -> SDoc
487 unpackHObj t = text "rts_get" <> text (showFFIType t)
489 showStgType :: Type -> SDoc
490 showStgType t = text "Stg" <> text (showFFIType t)
492 showFFIType :: Type -> String
493 showFFIType t = getOccString (getName tc)
495 tc = case splitTyConApp_maybe t of
497 Nothing -> pprPanic "showFFIType" (ppr t)