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, mkVanillaGlobal, mkSysLocal,
25 import IdInfo ( neverInlinePrag, vanillaIdInfo )
26 import Literal ( Literal(..) )
27 import Module ( Module, moduleUserString )
28 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
29 mkForeignExportOcc, isLocalName,
32 import Type ( repType, splitTyConApp_maybe,
33 splitFunTys, splitForAllTys,
34 Type, mkFunTys, mkForAllTys, mkTyConApp,
35 mkFunTy, splitAppTy, applyTy, funResultTy
37 import PrimOp ( CCall(..), CCallTarget(..), dynamicTarget )
38 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon )
39 import TysPrim ( addrPrimTy )
40 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
41 bindIOName, returnIOName
45 import Maybe ( fromJust )
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.
62 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
63 -- the occurrence analyser will sort it all out
66 -> [TypecheckedForeignDecl]
67 -> DsM ( [Id] -- Foreign-exported binders;
68 -- we have to generate code to register these
70 , SDoc -- Header file prototypes for
71 -- "foreign exported" functions.
72 , SDoc -- C stubs to use when calling
73 -- "foreign exported" functions.
75 dsForeigns mod_name fos = foldlDs combine ([], [], empty, empty) fos
77 combine (acc_feb, acc_f, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
78 | isForeignImport = -- foreign import (dynamic)?
79 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ bs ->
80 returnDs (acc_feb, bs ++ acc_f, acc_h, acc_c)
82 dsFLabel i (idType i) ext_nm `thenDs` \ b ->
83 returnDs (acc_feb, b:acc_f, acc_h, acc_c)
84 | isDynamicExtName ext_nm =
85 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (feb,bs,h,c) ->
86 returnDs (feb:acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
88 | otherwise = -- foreign export
89 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (feb,fe,h,c) ->
90 returnDs (feb:acc_feb, fe:acc_f, h $$ acc_h, c $$ acc_c)
102 (FoImport uns) = imp_exp
106 Desugaring foreign imports is just the matter of creating a binding
107 that on its RHS unboxes its arguments, performs the external call
108 (using the @CCallOp@ primop), before boxing the result up and returning it.
110 However, we create a worker/wrapper pair, thus:
112 foreign import f :: Int -> IO Int
114 f x = IO ( \s -> case x of { I# x# ->
115 case fw s x# of { (# s1, y# #) ->
118 fw s x# = ccall f s x#
120 The strictness/CPR analyser won't do this automatically because it doesn't look
121 inside returned tuples; but inlining this wrapper is a Really Good Idea
122 because it exposes the boxing to the call site.
127 -> Type -- Type of foreign import.
128 -> Bool -- True <=> cannot re-enter the Haskell RTS
132 dsFImport fn_id ty unsafe ext_name cconv
134 (tvs, fun_ty) = splitForAllTys ty
135 (arg_tys, io_res_ty) = splitFunTys fun_ty
137 newSysLocalsDs arg_tys `thenDs` \ args ->
138 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
141 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
143 -- these are the ids we pass to boxResult, which are used to decide
144 -- whether to touch# an argument after the call (used to keep
145 -- ForeignObj#s live across a 'safe' foreign import).
146 maybe_arg_ids | unsafe = []
147 | otherwise = work_arg_ids
149 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
151 getUniqueDs `thenDs` \ ccall_uniq ->
152 getUniqueDs `thenDs` \ work_uniq ->
154 lbl = case ext_name of
155 Dynamic -> dynamicTarget
156 ExtName fs _ -> StaticTarget fs
159 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
160 the_ccall = CCall lbl False (not unsafe) cconv
161 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
162 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
163 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
166 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
167 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
168 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
170 returnDs [(work_id, work_rhs), (fn_id, wrap_rhs)]
176 dsFLabel :: Id -> Type -> ExtName -> DsM Binding
177 dsFLabel nm ty ext_name =
178 ASSERT(fromJust res_ty == addrPrimTy) -- typechecker ensures this
179 returnDs (nm, fo_rhs (mkLit (MachLabel enm)))
181 (res_ty, fo_rhs) = resultWrapper ty
182 enm = extNameStatic ext_name
185 The function that does most of the work for `@foreign export@' declarations.
186 (see below for the boilerplate code a `@foreign export@' declaration expands
189 For each `@foreign export foo@' in a module M we generate:
191 \item a C function `@foo@', which calls
192 \item a Haskell stub `@M.$ffoo@', which calls
194 the user-written Haskell function `@M.foo@'.
198 -> Type -- Type of foreign export.
202 -> Bool -- True => invoke IO action that's hanging off
203 -- the first argument's stable pointer
204 -> DsM ( Id -- The foreign-exported Id
209 dsFExport fn_id ty mod_name ext_name cconv isDyn
210 = -- BUILD THE returnIO WRAPPER, if necessary
211 -- Look at the result type of the exported function, orig_res_ty
212 -- If it's IO t, return (\x.x, IO t, t)
213 -- If it's plain t, return (\x.returnIO x, IO t, t)
214 (case splitTyConApp_maybe orig_res_ty of
215 Just (ioTyCon, [res_ty])
216 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
217 -- The function already returns IO t
218 returnDs (\body -> body, orig_res_ty, res_ty)
220 other -> -- The function returns t, so wrap the call in returnIO
221 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
222 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
223 funResultTy (applyTy (idType retIOId) orig_res_ty),
224 -- We don't have ioTyCon conveniently to hand
227 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
232 -- BUILD THE deRefStablePtr WRAPPER, if necessary
234 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
235 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
236 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
237 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
239 the_deref_app = mkApps (Var deRefStablePtrId)
240 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
242 stbl_app cont = mkApps (Var bindIOId)
243 [ Type stbl_ptr_to_ty
246 , mkLams [stbl_value] cont]
248 returnDs (stbl_value, stbl_app, stbl_ptr)
252 panic "stbl_ptr" -- should never be touched.
253 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
257 getModuleDs `thenDs` \ mod ->
258 getUniqueDs `thenDs` \ uniq ->
259 getSrcLocDs `thenDs` \ src_loc ->
260 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
262 wrapper_args | isDyn = stbl_ptr:fe_args
263 | otherwise = fe_args
265 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
266 | otherwise = fe_arg_tys
268 helper_ty = mkForAllTys tvs $
269 mkFunTys wrapper_arg_tys io_res_ty
271 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
275 | isLocalName name = mod_name
276 | otherwise = nameModule name
278 occ = mkForeignExportOcc (nameOccName name)
279 helper_name = mkGlobalName uniq mod occ src_loc
281 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
282 the_body = mkLams (tvs ++ wrapper_args) the_app
283 c_nm = extNameStatic ext_name
285 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
287 wrapper_arg_tys res_ty cconv isDyn
289 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
292 (tvs,sans_foralls) = splitForAllTys ty
293 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
295 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
296 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
298 fe_arg_tys | isDyn = tail fe_arg_tys'
299 | otherwise = fe_arg_tys'
301 stbl_ptr_ty | isDyn = head fe_arg_tys'
302 | otherwise = error "stbl_ptr_ty"
305 @foreign export dynamic@ lets you dress up Haskell IO actions
306 of some fixed type behind an externally callable interface (i.e.,
307 as a C function pointer). Useful for callbacks and stuff.
310 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
312 -- Haskell-visible constructor, which is generated from the above:
313 -- SUP: No check for NULL from createAdjustor anymore???
315 f :: (Addr -> Int -> IO Int) -> IO Addr
317 bindIO (newStablePtr cback)
318 (\StablePtr sp# -> IO (\s1# ->
319 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
320 (# s2#, a# #) -> (# s2#, A# a# #)))
322 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
323 -- `special' foreign export that invokes the closure pointed to by the
328 dsFExportDynamic :: Id
329 -> Type -- Type of foreign export.
333 -> DsM (Id, [Binding], SDoc, SDoc)
334 dsFExportDynamic i ty mod_name ext_name cconv =
335 newSysLocalDs ty `thenDs` \ fe_id ->
337 -- hack: need to get at the name of the C stub we're about to generate.
338 fe_nm = moduleUserString mod_name ++ "_" ++ toCName fe_id
339 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
341 dsFExport i export_ty mod_name fe_ext_name cconv True
342 `thenDs` \ (feb, fe, h_code, c_code) ->
343 newSysLocalDs arg_ty `thenDs` \ cback ->
344 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
346 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
348 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
349 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
352 = mkApps (Var bindIOId)
353 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
360 The arguments to the external function which will
361 create a little bit of (template) code on the fly
362 for allowing the (stable pointed) Haskell closure
363 to be entered using an external calling convention
366 adj_args = [ mkIntLitInt (callConvToInt cconv)
368 , mkLit (MachLabel (_PK_ fe_nm))
370 -- name of external entry point providing these services.
371 -- (probably in the RTS.)
372 adjustor = SLIT("createAdjustor")
374 dsCCall adjustor adj_args False False io_res_ty `thenDs` \ ccall_adj ->
375 let ccall_adj_ty = exprType ccall_adj
376 ccall_io_adj = mkLams [stbl_value] $
377 Note (Coerce io_res_ty ccall_adj_ty)
380 let io_app = mkLams tvs $
382 stbl_app ccall_io_adj res_ty
383 fed = (i `setInlinePragma` neverInlinePrag, io_app)
384 -- Never inline the f.e.d. function, because the litlit
385 -- might not be in scope in other modules.
387 returnDs (feb, [fed, fe], h_code, c_code)
390 (tvs,sans_foralls) = splitForAllTys ty
391 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
393 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
395 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
397 ioAddrTy :: Type -- IO Addr
398 ioAddrTy = mkTyConApp ioTyCon [addrTy]
400 toCName :: Id -> String
401 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
406 \subsection{Generating @foreign export@ stubs}
410 For each @foreign export@ function, a C stub function is generated.
411 The C stub constructs the application of the exported Haskell function
412 using the hugs/ghc rts invocation API.
415 fexportEntry :: String
423 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
425 -- name of the (Haskell) helper function generated by the desugarer.
426 h_nm = ppr helper <> text "_closure"
427 -- prototype for the exported function.
428 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
430 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
431 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
438 , text "SchedulerStatus rc;"
440 -- create the application + perform it.
441 , text "rc=rts_evalIO" <>
442 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
443 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
444 <> comma <> text "rc") <> semi
445 , text "return" <> return_what <> semi
450 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
452 cParamTypes = map showStgType real_args
454 res_ty_is_unit = res_ty == unitTy
456 cResType | res_ty_is_unit = text "void"
457 | otherwise = showStgType res_ty
460 | cc == cCallConv = empty
461 | otherwise = pprCallConv cc
463 declareResult = text "HaskellObj ret;"
465 externDecl = mkExtern (text "HaskellObj") h_nm
467 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
469 return_what | res_ty_is_unit = empty
470 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
472 c_args = mkCArgNames 0 args
475 If we're generating an entry point for a 'foreign export ccall dynamic',
476 then we receive the return address of the C function that wants to
477 invoke a Haskell function as any other C function, as second arg.
478 This arg is unused within the body of the generated C stub, but
479 needed by the Adjustor.c code to get the stack cleanup right.
481 (proto_args, real_args)
482 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
483 , head args : addrTy : tail args)
484 | otherwise = (mkCArgNames 0 args, args)
486 mkCArgNames :: Int -> [a] -> [SDoc]
487 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
489 mkHObj :: Type -> SDoc
490 mkHObj t = text "rts_mk" <> text (showFFIType t)
492 unpackHObj :: Type -> SDoc
493 unpackHObj t = text "rts_get" <> text (showFFIType t)
495 showStgType :: Type -> SDoc
496 showStgType t = text "Hs" <> text (showFFIType t)
498 showFFIType :: Type -> String
499 showFFIType t = getOccString (getName tc)
501 tc = case splitTyConApp_maybe (repType t) of
503 Nothing -> pprPanic "showFFIType" (ppr t)