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, mkVanillaId, mkSysLocal,
25 import IdInfo ( neverInlinePrag )
26 import Literal ( Literal(..) )
27 import Module ( Module, moduleUserString )
28 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
29 mkForeignExportOcc, isLocalName,
32 import Type ( unUsgTy, repType,
33 splitTyConApp_maybe, splitFunTys, splitForAllTys,
34 Type, mkFunTys, mkForAllTys, mkTyConApp,
35 mkTyVarTy, mkFunTy, splitAppTy, applyTy, funResultTy
37 import PrimOp ( PrimOp(..), CCall(..),
38 CCallTarget(..), dynamicTarget )
39 import TysWiredIn ( unitTy, addrTy, stablePtrTyCon,
42 import TysPrim ( addrPrimTy )
43 import PrelNames ( Uniquable(..), hasKey,
44 ioTyConKey, deRefStablePtrName, returnIOIdKey,
46 returnIOName, makeStablePtrName
50 import Maybe ( fromJust )
53 Desugaring of @foreign@ declarations is naturally split up into
54 parts, an @import@ and an @export@ part. A @foreign import@
57 foreign import cc nm f :: prim_args -> IO prim_res
61 f :: prim_args -> IO prim_res
62 f a1 ... an = _ccall_ nm cc a1 ... an
64 so we reuse the desugaring code in @DsCCall@ to deal with these.
67 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
68 -- the occurrence analyser will sort it all out
71 -> [TypecheckedForeignDecl]
72 -> DsM ( [Id] -- Foreign-exported binders;
73 -- we have to generate code to register these
75 , SDoc -- Header file prototypes for
76 -- "foreign exported" functions.
77 , SDoc -- C stubs to use when calling
78 -- "foreign exported" functions.
80 dsForeigns mod_name fos = foldlDs combine ([], [], empty, empty) fos
82 combine (acc_feb, acc_f, acc_h, acc_c) fo@(ForeignDecl i imp_exp _ ext_nm cconv _)
83 | isForeignImport = -- foreign import (dynamic)?
84 dsFImport i (idType i) uns ext_nm cconv `thenDs` \ bs ->
85 returnDs (acc_feb, bs ++ acc_f, acc_h, acc_c)
87 dsFLabel i (idType i) ext_nm `thenDs` \ b ->
88 returnDs (acc_feb, b:acc_f, acc_h, acc_c)
89 | isDynamicExtName ext_nm =
90 dsFExportDynamic i (idType i) mod_name ext_nm cconv `thenDs` \ (feb,bs,h,c) ->
91 returnDs (feb:acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
93 | otherwise = -- foreign export
94 dsFExport i (idType i) mod_name ext_nm cconv False `thenDs` \ (feb,fe,h,c) ->
95 returnDs (feb:acc_feb, fe:acc_f, h $$ acc_h, c $$ acc_c)
107 (FoImport uns) = imp_exp
111 Desugaring foreign imports is just the matter of creating a binding
112 that on its RHS unboxes its arguments, performs the external call
113 (using the @CCallOp@ primop), before boxing the result up and returning it.
115 However, we create a worker/wrapper pair, thus:
117 foreign import f :: Int -> IO Int
119 f x = IO ( \s -> case x of { I# x# ->
120 case fw s x# of { (# s1, y# #) ->
123 fw s x# = ccall f s x#
125 The strictness/CPR analyser won't do this automatically because it doesn't look
126 inside returned tuples; but inlining this wrapper is a Really Good Idea
127 because it exposes the boxing to the call site.
132 -> Type -- Type of foreign import.
133 -> Bool -- True <=> might cause Haskell GC
137 dsFImport fn_id ty may_not_gc ext_name cconv
139 (tvs, fun_ty) = splitForAllTys ty
140 (arg_tys, io_res_ty) = splitFunTys fun_ty
142 newSysLocalsDs arg_tys `thenDs` \ args ->
143 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
144 boxResult io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
146 getUniqueDs `thenDs` \ ccall_uniq ->
147 getUniqueDs `thenDs` \ work_uniq ->
149 lbl = case ext_name of
150 Dynamic -> dynamicTarget
151 ExtName fs _ -> StaticTarget fs
154 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
155 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
156 the_ccall = CCall lbl False (not may_not_gc) cconv
157 the_ccall_app = mkCCall ccall_uniq the_ccall val_args ccall_result_ty
158 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
159 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
162 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
163 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
164 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
166 returnDs [(work_id, work_rhs), (fn_id, wrap_rhs)]
172 dsFLabel :: Id -> Type -> ExtName -> DsM Binding
173 dsFLabel nm ty ext_name =
174 ASSERT(fromJust res_ty == addrPrimTy) -- typechecker ensures this
175 returnDs (nm, fo_rhs (mkLit (MachLabel enm)))
177 (res_ty, fo_rhs) = resultWrapper ty
178 enm = extNameStatic ext_name
181 The function that does most of the work for `@foreign export@' declarations.
182 (see below for the boilerplate code a `@foreign export@' declaration expands
185 For each `@foreign export foo@' in a module M we generate:
187 \item a C function `@foo@', which calls
188 \item a Haskell stub `@M.$ffoo@', which calls
190 the user-written Haskell function `@M.foo@'.
194 -> Type -- Type of foreign export.
198 -> Bool -- True => invoke IO action that's hanging off
199 -- the first argument's stable pointer
200 -> DsM ( Id -- The foreign-exported Id
205 dsFExport fn_id ty mod_name ext_name cconv isDyn
206 = -- BUILD THE returnIO WRAPPER, if necessary
207 -- Look at the result type of the exported function, orig_res_ty
208 -- If it's IO t, return (\x.x, IO t, t)
209 -- If it's plain t, return (\x.returnIO x, IO t, t)
210 (case splitTyConApp_maybe orig_res_ty of
211 Just (ioTyCon, [res_ty])
212 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
213 -- The function already returns IO t
214 returnDs (\body -> body, orig_res_ty, res_ty)
216 other -> -- The function returns t, so wrap the call in returnIO
217 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
218 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
219 funResultTy (applyTy (idType retIOId) orig_res_ty),
220 -- We don't have ioTyCon conveniently to hand
223 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
228 -- BUILD THE deRefStablePtr WRAPPER, if necessary
230 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
231 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
232 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
233 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
235 the_deref_app = mkApps (Var deRefStablePtrId)
236 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
238 stbl_app cont = mkApps (Var bindIOId)
239 [ Type stbl_ptr_to_ty
242 , mkLams [stbl_value] cont]
244 returnDs (stbl_value, stbl_app, stbl_ptr)
248 panic "stbl_ptr" -- should never be touched.
249 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
253 getModuleDs `thenDs` \ mod ->
254 getUniqueDs `thenDs` \ uniq ->
255 getSrcLocDs `thenDs` \ src_loc ->
256 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
258 wrapper_args | isDyn = stbl_ptr:fe_args
259 | otherwise = fe_args
261 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
262 | otherwise = fe_arg_tys
264 helper_ty = mkForAllTys tvs $
265 mkFunTys wrapper_arg_tys io_res_ty
267 f_helper_glob = mkVanillaId helper_name helper_ty
271 | isLocalName name = mod_name
272 | otherwise = nameModule name
274 occ = mkForeignExportOcc (nameOccName name)
275 helper_name = mkGlobalName uniq mod occ src_loc
277 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
278 the_body = mkLams (tvs ++ wrapper_args) the_app
279 c_nm = extNameStatic ext_name
281 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
283 wrapper_arg_tys res_ty cconv isDyn
285 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
288 (tvs,sans_foralls) = splitForAllTys ty
289 (fe_arg_tys', orig_res_ty) = splitFunTys sans_foralls
291 (_, stbl_ptr_ty') = splitForAllTys stbl_ptr_ty
292 (_, stbl_ptr_to_ty) = splitAppTy stbl_ptr_ty'
294 fe_arg_tys | isDyn = tail fe_arg_tys'
295 | otherwise = fe_arg_tys'
297 stbl_ptr_ty | isDyn = head fe_arg_tys'
298 | otherwise = error "stbl_ptr_ty"
301 @foreign export dynamic@ lets you dress up Haskell IO actions
302 of some fixed type behind an externally callable interface (i.e.,
303 as a C function pointer). Useful for callbacks and stuff.
306 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
308 -- Haskell-visible constructor, which is generated from the above:
309 -- SUP: No check for NULL from createAdjustor anymore???
311 f :: (Addr -> Int -> IO Int) -> IO Addr
313 bindIO (makeStablePtr cback)
314 (\StablePtr sp# -> IO (\s1# ->
315 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
316 (# s2#, a# #) -> (# s2#, A# 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 (Id, [Binding], 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 = moduleUserString mod_name ++ "_" ++ 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` \ (feb, fe, h_code, c_code) ->
339 newSysLocalDs arg_ty `thenDs` \ cback ->
340 dsLookupGlobalValue makeStablePtrName `thenDs` \ makeStablePtrId ->
342 mk_stbl_ptr_app = mkApps (Var makeStablePtrId) [ Type arg_ty, Var cback ]
344 dsLookupGlobalValue bindIOName `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 (MachLabel (_PK_ fe_nm))
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 io_res_ty `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 res_ty
379 fed = (i `setInlinePragma` neverInlinePrag, io_app)
380 -- Never inline the f.e.d. function, because the litlit
381 -- might not be in scope in other modules.
383 returnDs (feb, [fed, fe], h_code, c_code)
386 (tvs,sans_foralls) = splitForAllTys ty
387 ([arg_ty], io_res_ty) = splitFunTys sans_foralls
389 Just (ioTyCon, [res_ty]) = splitTyConApp_maybe io_res_ty
391 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
393 ioAddrTy :: Type -- IO Addr
394 ioAddrTy = mkTyConApp ioTyCon [addrTy]
396 toCName :: Id -> String
397 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
402 \subsection{Generating @foreign export@ stubs}
406 For each @foreign export@ function, a C stub function is generated.
407 The C stub constructs the application of the exported Haskell function
408 using the hugs/ghc rts invocation API.
411 fexportEntry :: String
419 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
421 -- name of the (Haskell) helper function generated by the desugarer.
422 h_nm = ppr helper <> text "_closure"
423 -- prototype for the exported function.
424 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
426 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
427 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
434 , text "SchedulerStatus rc;"
436 -- create the application + perform it.
437 , text "rc=rts_evalIO" <>
438 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
439 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
440 <> comma <> text "rc") <> semi
441 , text "return" <> return_what <> semi
446 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
448 cParamTypes = map showStgType real_args
450 res_ty_is_unit = res_ty == unitTy
452 cResType | res_ty_is_unit = text "void"
453 | otherwise = showStgType res_ty
456 | cc == cCallConv = empty
457 | otherwise = pprCallConv cc
459 declareResult = text "HaskellObj ret;"
461 externDecl = mkExtern (text "HaskellObj") h_nm
463 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
465 return_what | res_ty_is_unit = empty
466 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
468 c_args = mkCArgNames 0 args
471 If we're generating an entry point for a 'foreign export ccall dynamic',
472 then we receive the return address of the C function that wants to
473 invoke a Haskell function as any other C function, as second arg.
474 This arg is unused within the body of the generated C stub, but
475 needed by the Adjustor.c code to get the stack cleanup right.
477 (proto_args, real_args)
478 | cc == cCallConv && isDyn = ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
479 , head args : addrTy : tail args)
480 | otherwise = (mkCArgNames 0 args, args)
482 mkCArgNames :: Int -> [a] -> [SDoc]
483 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
485 mkHObj :: Type -> SDoc
486 mkHObj t = text "rts_mk" <> text (showFFIType t)
488 unpackHObj :: Type -> SDoc
489 unpackHObj t = text "rts_get" <> text (showFFIType t)
491 showStgType :: Type -> SDoc
492 showStgType t = text "Stg" <> text (showFFIType t)
494 showFFIType :: Type -> String
495 showFFIType t = getOccString (getName tc)
497 tc = case splitTyConApp_maybe (repType t) of
499 Nothing -> pprPanic "showFFIType" (ppr t)