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, resultWrapper )
18 import HsSyn ( ExtName(..), ForeignDecl(..), isDynamicExtName, ForKind(..) )
19 import HsDecls ( extNameStatic )
21 import TcHsSyn ( TypecheckedForeignDecl )
22 import CoreUtils ( exprType, mkInlineMe )
23 import Id ( Id, idType, idName, mkId, mkSysLocal,
25 import IdInfo ( neverInlinePrag, vanillaIdInfo, IdFlavour(..),
27 import Literal ( Literal(..) )
28 import Module ( Module, moduleUserString )
29 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
30 mkForeignExportOcc, isLocalName,
33 import Type ( repType, splitTyConApp_maybe,
34 tyConAppTyCon, splitFunTys, splitForAllTys,
35 Type, mkFunTys, mkForAllTys, mkTyConApp,
36 mkFunTy, splitAppTy, applyTy, funResultTy
38 import PrimOp ( CCall(..), CCallTarget(..), dynamicTarget )
39 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon )
40 import TysPrim ( addrPrimTy )
41 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
42 bindIOName, returnIOName
46 import Maybe ( fromJust )
49 Desugaring of @foreign@ declarations is naturally split up into
50 parts, an @import@ and an @export@ part. A @foreign import@
53 foreign import cc nm f :: prim_args -> IO prim_res
57 f :: prim_args -> IO prim_res
58 f a1 ... an = _ccall_ nm cc a1 ... an
60 so we reuse the desugaring code in @DsCCall@ to deal with these.
63 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
64 -- the occurrence analyser will sort it all out
67 -> [TypecheckedForeignDecl]
68 -> DsM ( [Id] -- Foreign-exported binders;
69 -- we have to generate code to register these
71 , SDoc -- Header file prototypes for
72 -- "foreign exported" functions.
73 , SDoc -- C stubs to use when calling
74 -- "foreign exported" functions.
76 dsForeigns mod_name fos = foldlDs combine ([], [], empty, empty) fos
78 combine (acc_feb, acc_f, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
79 | isForeignImport = -- foreign import (dynamic)?
80 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ bs ->
81 returnDs (acc_feb, bs ++ acc_f, acc_h, acc_c)
83 dsFLabel i (idType i) ext_nm `thenDs` \ b ->
84 returnDs (acc_feb, b:acc_f, acc_h, acc_c)
85 | isDynamicExtName ext_nm =
86 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (feb,bs,h,c) ->
87 returnDs (feb:acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
89 | otherwise = -- foreign export
90 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (feb,fe,h,c) ->
91 returnDs (feb:acc_feb, fe:acc_f, h $$ acc_h, c $$ acc_c)
103 (FoImport uns) = imp_exp
107 Desugaring foreign imports is just the matter of creating a binding
108 that on its RHS unboxes its arguments, performs the external call
109 (using the @CCallOp@ primop), before boxing the result up and returning it.
111 However, we create a worker/wrapper pair, thus:
113 foreign import f :: Int -> IO Int
115 f x = IO ( \s -> case x of { I# x# ->
116 case fw s x# of { (# s1, y# #) ->
119 fw s x# = ccall f s x#
121 The strictness/CPR analyser won't do this automatically because it doesn't look
122 inside returned tuples; but inlining this wrapper is a Really Good Idea
123 because it exposes the boxing to the call site.
128 -> Type -- Type of foreign import.
129 -> Bool -- True <=> might cause Haskell GC
133 dsFImport fn_id ty may_not_gc ext_name cconv
135 (tvs, fun_ty) = splitForAllTys ty
136 (arg_tys, io_res_ty) = splitFunTys fun_ty
138 newSysLocalsDs arg_tys `thenDs` \ args ->
139 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
140 boxResult io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
142 getUniqueDs `thenDs` \ ccall_uniq ->
143 getUniqueDs `thenDs` \ work_uniq ->
145 lbl = case ext_name of
146 Dynamic -> dynamicTarget
147 ExtName fs _ -> StaticTarget fs
150 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
151 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
152 the_ccall = CCall lbl False (not may_not_gc) cconv
153 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
154 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
155 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
158 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
159 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
160 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
162 returnDs [(work_id, work_rhs), (fn_id, wrap_rhs)]
168 dsFLabel :: Id -> Type -> ExtName -> DsM Binding
169 dsFLabel nm ty ext_name =
170 ASSERT(fromJust res_ty == addrPrimTy) -- typechecker ensures this
171 returnDs (nm, fo_rhs (mkLit (MachLabel enm)))
173 (res_ty, fo_rhs) = resultWrapper ty
174 enm = extNameStatic ext_name
177 The function that does most of the work for `@foreign export@' declarations.
178 (see below for the boilerplate code a `@foreign export@' declaration expands
181 For each `@foreign export foo@' in a module M we generate:
183 \item a C function `@foo@', which calls
184 \item a Haskell stub `@M.$ffoo@', which calls
186 the user-written Haskell function `@M.foo@'.
190 -> Type -- Type of foreign export.
194 -> Bool -- True => invoke IO action that's hanging off
195 -- the first argument's stable pointer
196 -> DsM ( Id -- The foreign-exported Id
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 returnIOName `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 deRefStablePtrName `thenDs` \ deRefStablePtrId ->
229 dsLookupGlobalValue bindIOName `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 = mkId helper_name helper_ty
264 (vanillaIdInfo `setFlavourInfo` ExportedId)
268 | isLocalName name = mod_name
269 | otherwise = nameModule name
271 occ = mkForeignExportOcc (nameOccName name)
272 helper_name = mkGlobalName uniq mod occ src_loc
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 (f_helper_glob, (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 (newStablePtr 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 (Id, [Binding], 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` \ (feb, fe, h_code, c_code) ->
336 newSysLocalDs arg_ty `thenDs` \ cback ->
337 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
339 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
341 dsLookupGlobalValue bindIOName `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 (MachLabel (_PK_ fe_nm))
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 io_res_ty `thenDs` \ ccall_adj ->
368 let ccall_adj_ty = exprType ccall_adj
369 ccall_io_adj = mkLams [stbl_value] $
370 Note (Coerce io_res_ty ccall_adj_ty)
373 let io_app = mkLams tvs $
375 stbl_app ccall_io_adj res_ty
376 fed = (i `setInlinePragma` neverInlinePrag, io_app)
377 -- Never inline the f.e.d. function, because the litlit
378 -- might not be in scope in other modules.
380 returnDs (feb, [fed, 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 (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 "Hs" <> text (showFFIType t)
491 showFFIType :: Type -> String
492 showFFIType t = getOccString (getName tc)
494 tc = case splitTyConApp_maybe (repType t) of
496 Nothing -> pprPanic "showFFIType" (ppr t)