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, mkFCall, boxResult, unboxArg, resultWrapper )
18 import HsSyn ( ExtName(..), ForeignDecl(..), isDynamicExtName, ForKind(..) )
19 import HsDecls ( extNameStatic )
20 import TcHsSyn ( TypecheckedForeignDecl )
21 import CoreUtils ( exprType, mkInlineMe )
22 import Id ( Id, idType, idName, mkVanillaGlobal, mkSysLocal,
24 import IdInfo ( neverInlinePrag, vanillaIdInfo )
25 import Literal ( Literal(..) )
26 import Module ( Module, moduleUserString )
27 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
28 mkForeignExportOcc, isLocalName,
31 import Type ( repType, splitTyConApp_maybe,
32 splitFunTys, splitForAllTys,
33 Type, mkFunTys, mkForAllTys, mkTyConApp,
34 mkFunTy, splitAppTy, applyTy, funResultTy
36 import ForeignCall ( ForeignCall(..), CCallSpec(..),
38 CCallTarget(..), dynamicTarget,
39 CCallConv(..), ccallConvToInt
41 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon )
42 import TysPrim ( addrPrimTy )
43 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
44 bindIOName, returnIOName
48 import Maybe ( fromJust )
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.
65 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
66 -- the occurrence analyser will sort it all out
69 -> [TypecheckedForeignDecl]
70 -> DsM ( [Id] -- Foreign-exported binders;
71 -- we have to generate code to register these
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_feb, acc_f, 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 (acc_feb, bs ++ acc_f, acc_h, acc_c)
85 dsFLabel i (idType i) ext_nm `thenDs` \ b ->
86 returnDs (acc_feb, b:acc_f, acc_h, acc_c)
87 | isDynamicExtName ext_nm =
88 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (feb,bs,h,c) ->
89 returnDs (feb:acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
91 | otherwise = -- foreign export
92 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (feb,fe,h,c) ->
93 returnDs (feb:acc_feb, fe:acc_f, h $$ acc_h, c $$ acc_c)
105 FoImport uns = imp_exp
108 Desugaring foreign imports is just the matter of creating a binding
109 that on its RHS unboxes its arguments, performs the external call
110 (using the @CCallOp@ primop), before boxing the result up and returning it.
112 However, we create a worker/wrapper pair, thus:
114 foreign import f :: Int -> IO Int
116 f x = IO ( \s -> case x of { I# x# ->
117 case fw s x# of { (# s1, y# #) ->
120 fw s x# = ccall f s x#
122 The strictness/CPR analyser won't do this automatically because it doesn't look
123 inside returned tuples; but inlining this wrapper is a Really Good Idea
124 because it exposes the boxing to the call site.
129 -> Type -- Type of foreign import.
130 -> Safety -- Whether can re-enter the Haskell RTS, do GC etc
134 dsFImport fn_id ty safety ext_name cconv
136 (tvs, fun_ty) = splitForAllTys ty
137 (arg_tys, io_res_ty) = splitFunTys fun_ty
139 newSysLocalsDs arg_tys `thenDs` \ args ->
140 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
143 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
145 -- These are the ids we pass to boxResult, which are used to decide
146 -- whether to touch# an argument after the call (used to keep
147 -- ForeignObj#s live across a 'safe' foreign import).
148 maybe_arg_ids | playSafe safety = work_arg_ids
151 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
153 getUniqueDs `thenDs` \ ccall_uniq ->
154 getUniqueDs `thenDs` \ work_uniq ->
156 lbl = case ext_name of
157 Dynamic -> dynamicTarget
158 ExtName fs _ -> StaticTarget fs
161 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
162 the_ccall = CCall (CCallSpec lbl cconv safety False)
163 the_ccall_app = mkFCall ccall_uniq the_ccall val_args ccall_result_ty
164 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
165 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
168 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
169 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
170 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
172 returnDs [(work_id, work_rhs), (fn_id, wrap_rhs)]
178 dsFLabel :: Id -> Type -> ExtName -> DsM Binding
179 dsFLabel nm ty ext_name =
180 ASSERT(fromJust res_ty == addrPrimTy) -- typechecker ensures this
181 returnDs (nm, fo_rhs (mkLit (MachLabel enm)))
183 (res_ty, fo_rhs) = resultWrapper ty
184 enm = extNameStatic ext_name
187 The function that does most of the work for `@foreign export@' declarations.
188 (see below for the boilerplate code a `@foreign export@' declaration expands
191 For each `@foreign export foo@' in a module M we generate:
193 \item a C function `@foo@', which calls
194 \item a Haskell stub `@M.$ffoo@', which calls
196 the user-written Haskell function `@M.foo@'.
200 -> Type -- Type of foreign export.
204 -> Bool -- True => invoke IO action that's hanging off
205 -- the first argument's stable pointer
206 -> DsM ( Id -- The foreign-exported Id
211 dsFExport fn_id ty mod_name ext_name cconv isDyn
212 = -- BUILD THE returnIO WRAPPER, if necessary
213 -- Look at the result type of the exported function, orig_res_ty
214 -- If it's IO t, return (\x.x, IO t, t)
215 -- If it's plain t, return (\x.returnIO x, IO t, t)
216 (case splitTyConApp_maybe orig_res_ty of
217 Just (ioTyCon, [res_ty])
218 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
219 -- The function already returns IO t
220 returnDs (\body -> body, orig_res_ty, res_ty)
222 other -> -- The function returns t, so wrap the call in returnIO
223 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
224 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
225 funResultTy (applyTy (idType retIOId) orig_res_ty),
226 -- We don't have ioTyCon conveniently to hand
229 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
234 -- BUILD THE deRefStablePtr WRAPPER, if necessary
236 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
237 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
238 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
239 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
241 the_deref_app = mkApps (Var deRefStablePtrId)
242 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
244 stbl_app cont = mkApps (Var bindIOId)
245 [ Type stbl_ptr_to_ty
248 , mkLams [stbl_value] cont]
250 returnDs (stbl_value, stbl_app, stbl_ptr)
254 panic "stbl_ptr" -- should never be touched.
255 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
259 getModuleDs `thenDs` \ mod ->
260 getUniqueDs `thenDs` \ uniq ->
261 getSrcLocDs `thenDs` \ src_loc ->
262 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
264 wrapper_args | isDyn = stbl_ptr:fe_args
265 | otherwise = fe_args
267 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
268 | otherwise = fe_arg_tys
270 helper_ty = mkForAllTys tvs $
271 mkFunTys wrapper_arg_tys io_res_ty
273 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
277 | isLocalName name = mod_name
278 | otherwise = nameModule name
280 occ = mkForeignExportOcc (nameOccName name)
281 helper_name = mkGlobalName uniq mod occ src_loc
283 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
284 the_body = mkLams (tvs ++ wrapper_args) the_app
285 c_nm = extNameStatic ext_name
287 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
289 wrapper_arg_tys res_ty cconv isDyn
291 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
294 (tvs,sans_foralls) = splitForAllTys ty
295 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
297 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
298 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
300 fe_arg_tys | isDyn = tail fe_arg_tys'
301 | otherwise = fe_arg_tys'
303 stbl_ptr_ty | isDyn = head fe_arg_tys'
304 | otherwise = error "stbl_ptr_ty"
307 @foreign export dynamic@ lets you dress up Haskell IO actions
308 of some fixed type behind an externally callable interface (i.e.,
309 as a C function pointer). Useful for callbacks and stuff.
312 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
314 -- Haskell-visible constructor, which is generated from the above:
315 -- SUP: No check for NULL from createAdjustor anymore???
317 f :: (Addr -> Int -> IO Int) -> IO Addr
319 bindIO (newStablePtr cback)
320 (\StablePtr sp# -> IO (\s1# ->
321 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
322 (# s2#, a# #) -> (# s2#, A# a# #)))
324 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
325 -- `special' foreign export that invokes the closure pointed to by the
330 dsFExportDynamic :: Id
331 -> Type -- Type of foreign export.
335 -> DsM (Id, [Binding], SDoc, SDoc)
336 dsFExportDynamic i ty mod_name ext_name cconv =
337 newSysLocalDs ty `thenDs` \ fe_id ->
339 -- hack: need to get at the name of the C stub we're about to generate.
340 fe_nm = moduleUserString mod_name ++ "_" ++ toCName fe_id
341 fe_ext_name = ExtName (_PK_ fe_nm) Nothing
343 dsFExport i export_ty mod_name fe_ext_name cconv True
344 `thenDs` \ (feb, fe, h_code, c_code) ->
345 newSysLocalDs arg_ty `thenDs` \ cback ->
346 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
348 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
350 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
351 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
354 = mkApps (Var bindIOId)
355 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
362 The arguments to the external function which will
363 create a little bit of (template) code on the fly
364 for allowing the (stable pointed) Haskell closure
365 to be entered using an external calling convention
368 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
370 , mkLit (MachLabel (_PK_ fe_nm))
372 -- name of external entry point providing these services.
373 -- (probably in the RTS.)
374 adjustor = SLIT("createAdjustor")
376 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
377 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
378 let ccall_adj_ty = exprType ccall_adj
379 ccall_io_adj = mkLams [stbl_value] $
380 Note (Coerce io_res_ty ccall_adj_ty)
382 io_app = mkLams tvs $
384 stbl_app ccall_io_adj res_ty
385 fed = (i `setInlinePragma` neverInlinePrag, io_app)
386 -- Never inline the f.e.d. function, because the litlit
387 -- might not be in scope in other modules.
389 returnDs (feb, [fed, fe], h_code, c_code)
392 (tvs,sans_foralls) = splitForAllTys ty
393 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
394 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
395 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
397 toCName :: Id -> String
398 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
403 \subsection{Generating @foreign export@ stubs}
407 For each @foreign export@ function, a C stub function is generated.
408 The C stub constructs the application of the exported Haskell function
409 using the hugs/ghc rts invocation API.
412 fexportEntry :: String
420 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
422 -- name of the (Haskell) helper function generated by the desugarer.
423 h_nm = ppr helper <> text "_closure"
424 -- prototype for the exported function.
425 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
427 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
428 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
435 , text "SchedulerStatus rc;"
437 -- create the application + perform it.
438 , text "rc=rts_evalIO" <>
439 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
440 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
441 <> comma <> text "rc") <> semi
442 , text "return" <> return_what <> semi
447 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
449 cParamTypes = map showStgType real_args
451 res_ty_is_unit = res_ty == unitTy
453 cResType | res_ty_is_unit = text "void"
454 | otherwise = showStgType res_ty
456 pprCconv = case cc of
458 StdCallConv -> ppr cc
460 declareResult = text "HaskellObj ret;"
462 externDecl = mkExtern (text "HaskellObj") h_nm
464 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
466 return_what | res_ty_is_unit = empty
467 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
469 c_args = mkCArgNames 0 args
472 If we're generating an entry point for a 'foreign export ccall dynamic',
473 then we receive the return address of the C function that wants to
474 invoke a Haskell function as any other C function, as second arg.
475 This arg is unused within the body of the generated C stub, but
476 needed by the Adjustor.c code to get the stack cleanup right.
478 (proto_args, real_args)
480 CCallConv | isDyn -> ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
481 , head args : addrTy : tail args)
482 other -> (mkCArgNames 0 args, args)
484 mkCArgNames :: Int -> [a] -> [SDoc]
485 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
487 mkHObj :: Type -> SDoc
488 mkHObj t = text "rts_mk" <> text (showFFIType t)
490 unpackHObj :: Type -> SDoc
491 unpackHObj t = text "rts_get" <> text (showFFIType t)
493 showStgType :: Type -> SDoc
494 showStgType t = text "Hs" <> text (showFFIType t)
496 showFFIType :: Type -> String
497 showFFIType t = getOccString (getName tc)
499 tc = case splitTyConApp_maybe (repType t) of
501 Nothing -> pprPanic "showFFIType" (ppr t)