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 ( ForeignDecl(..), FoExport(..), FoImport(..) )
19 import TcHsSyn ( TypecheckedForeignDecl )
20 import CoreUtils ( exprType, mkInlineMe )
21 import Id ( Id, idType, idName, mkVanillaGlobal, mkSysLocal,
23 import IdInfo ( neverInlinePrag, vanillaIdInfo )
24 import Literal ( Literal(..) )
25 import Module ( Module, moduleUserString )
26 import Name ( mkGlobalName, nameModule, nameOccName, getOccString,
27 mkForeignExportOcc, isLocalName,
31 -- Import Type not TcType; in this module we are generating code
32 -- to marshal representation types across to C
33 import Type ( splitTyConApp_maybe, funResultTy,
34 splitFunTys, splitForAllTys, splitAppTy,
35 Type, mkFunTys, mkForAllTys, mkTyConApp,
36 mkFunTy, applyTy, eqType, repType
38 import TcType ( tcSplitForAllTys, tcSplitFunTys,
39 tcSplitTyConApp_maybe, tcSplitAppTy,
43 import ForeignCall ( ForeignCall(..), CCallSpec(..),
46 CCallConv(..), ccallConvToInt
48 import CStrings ( CLabelString )
49 import TysWiredIn ( addrTy, unitTy, stablePtrTyCon )
50 import TysPrim ( addrPrimTy )
51 import PrelNames ( hasKey, ioTyConKey, deRefStablePtrName, newStablePtrName,
52 bindIOName, returnIOName
56 import Maybe ( fromJust )
59 Desugaring of @foreign@ declarations is naturally split up into
60 parts, an @import@ and an @export@ part. A @foreign import@
63 foreign import cc nm f :: prim_args -> IO prim_res
67 f :: prim_args -> IO prim_res
68 f a1 ... an = _ccall_ nm cc a1 ... an
70 so we reuse the desugaring code in @DsCCall@ to deal with these.
73 type Binding = (Id, CoreExpr) -- No rec/nonrec structure;
74 -- the occurrence analyser will sort it all out
77 -> [TypecheckedForeignDecl]
78 -> DsM ( [Id] -- Foreign-exported binders;
79 -- we have to generate code to register these
81 , SDoc -- Header file prototypes for
82 -- "foreign exported" functions.
83 , SDoc -- C stubs to use when calling
84 -- "foreign exported" functions.
86 dsForeigns mod_name fos
87 = foldlDs combine ([], [], empty, empty) fos
89 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignImport id _ spec _)
90 = dsFImport mod_name id spec `thenDs` \ (bs, h, c) ->
91 returnDs (acc_feb, bs ++ acc_f, h $$ acc_h, c $$ acc_c)
93 combine (acc_feb, acc_f, acc_h, acc_c) (ForeignExport id _ (CExport (CExportStatic ext_nm cconv)) _)
94 = dsFExport mod_name id (idType id) ext_nm cconv False `thenDs` \ (feb, b, h, c) ->
95 returnDs (feb:acc_feb, b : acc_f, h $$ acc_h, c $$ acc_c)
99 %************************************************************************
101 \subsection{Foreign import}
103 %************************************************************************
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.
128 -> DsM ([Binding], SDoc, SDoc)
129 dsFImport mod_name lbl_id (LblImport ext_nm)
130 = ASSERT(fromJust res_ty `eqType` addrPrimTy) -- typechecker ensures this
131 returnDs ([(lbl_id, rhs)], empty, empty)
133 (res_ty, fo_rhs) = resultWrapper (idType lbl_id)
134 rhs = fo_rhs (mkLit (MachLabel ext_nm))
136 dsFImport mod_name fn_id (CImport spec) = dsFCall mod_name fn_id (CCall spec)
137 dsFImport mod_name fn_id (DNImport spec) = dsFCall mod_name fn_id (DNCall spec)
138 dsFImport mod_name fn_id (CDynImport cconv) = dsFExportDynamic mod_name fn_id cconv
142 %************************************************************************
144 \subsection{Foreign calls}
146 %************************************************************************
149 dsFCall mod_Name fn_id fcall
152 (tvs, fun_ty) = tcSplitForAllTys ty
153 (arg_tys, io_res_ty) = tcSplitFunTys fun_ty
155 newSysLocalsDs arg_tys `thenDs` \ args ->
156 mapAndUnzipDs unboxArg (map Var args) `thenDs` \ (val_args, arg_wrappers) ->
159 work_arg_ids = [v | Var v <- val_args] -- All guaranteed to be vars
161 -- These are the ids we pass to boxResult, which are used to decide
162 -- whether to touch# an argument after the call (used to keep
163 -- ForeignObj#s live across a 'safe' foreign import).
164 maybe_arg_ids | unsafe_call fcall = work_arg_ids
167 boxResult maybe_arg_ids io_res_ty `thenDs` \ (ccall_result_ty, res_wrapper) ->
169 getUniqueDs `thenDs` \ ccall_uniq ->
170 getUniqueDs `thenDs` \ work_uniq ->
173 worker_ty = mkForAllTys tvs (mkFunTys (map idType work_arg_ids) ccall_result_ty)
174 the_ccall_app = mkFCall ccall_uniq fcall val_args ccall_result_ty
175 work_rhs = mkLams tvs (mkLams work_arg_ids the_ccall_app)
176 work_id = mkSysLocal SLIT("$wccall") work_uniq worker_ty
179 work_app = mkApps (mkVarApps (Var work_id) tvs) val_args
180 wrapper_body = foldr ($) (res_wrapper work_app) arg_wrappers
181 wrap_rhs = mkInlineMe (mkLams (tvs ++ args) wrapper_body)
183 returnDs ([(work_id, work_rhs), (fn_id, wrap_rhs)], empty, empty)
185 unsafe_call (CCall (CCallSpec _ _ safety)) = playSafe safety
186 unsafe_call (DNCall _) = False
190 %************************************************************************
192 \subsection{Foreign export}
194 %************************************************************************
196 The function that does most of the work for `@foreign export@' declarations.
197 (see below for the boilerplate code a `@foreign export@' declaration expands
200 For each `@foreign export foo@' in a module M we generate:
202 \item a C function `@foo@', which calls
203 \item a Haskell stub `@M.$ffoo@', which calls
205 the user-written Haskell function `@M.foo@'.
209 -> Id -- Either the exported Id,
210 -- or the foreign-export-dynamic constructor
211 -> Type -- The type of the thing callable from C
212 -> CLabelString -- The name to export to C land
214 -> Bool -- True => foreign export dynamic
215 -- so invoke IO action that's hanging off
216 -- the first argument's stable pointer
217 -> DsM ( Id -- The foreign-exported Id
222 dsFExport mod_name fn_id ty ext_name cconv isDyn
223 = -- BUILD THE returnIO WRAPPER, if necessary
224 -- Look at the result type of the exported function, orig_res_ty
225 -- If it's IO t, return (\x.x, IO t, t)
226 -- If it's plain t, return (\x.returnIO x, IO t, t)
227 (case tcSplitTyConApp_maybe orig_res_ty of
228 Just (ioTyCon, [res_ty])
229 -> ASSERT( ioTyCon `hasKey` ioTyConKey )
230 -- The function already returns IO t
231 returnDs (\body -> body, orig_res_ty, res_ty)
233 other -> -- The function returns t, so wrap the call in returnIO
234 dsLookupGlobalValue returnIOName `thenDs` \ retIOId ->
235 returnDs (\body -> mkApps (Var retIOId) [Type orig_res_ty, body],
236 tcFunResultTy (applyTy (idType retIOId) orig_res_ty),
237 -- We don't have ioTyCon conveniently to hand
240 ) `thenDs` \ (return_io_wrapper, -- Either identity or returnIO
245 -- BUILD THE deRefStablePtr WRAPPER, if necessary
247 newSysLocalDs stbl_ptr_ty `thenDs` \ stbl_ptr ->
248 newSysLocalDs stbl_ptr_to_ty `thenDs` \ stbl_value ->
249 dsLookupGlobalValue deRefStablePtrName `thenDs` \ deRefStablePtrId ->
250 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
252 the_deref_app = mkApps (Var deRefStablePtrId)
253 [ Type stbl_ptr_to_ty, Var stbl_ptr ]
255 stbl_app cont = mkApps (Var bindIOId)
256 [ Type stbl_ptr_to_ty
259 , mkLams [stbl_value] cont]
261 returnDs (stbl_value, stbl_app, stbl_ptr)
265 panic "stbl_ptr" -- should never be touched.
266 )) `thenDs` \ (i, getFun_wrapper, stbl_ptr) ->
270 getModuleDs `thenDs` \ mod ->
271 getUniqueDs `thenDs` \ uniq ->
272 getSrcLocDs `thenDs` \ src_loc ->
273 newSysLocalsDs fe_arg_tys `thenDs` \ fe_args ->
275 wrapper_args | isDyn = stbl_ptr:fe_args
276 | otherwise = fe_args
278 wrapper_arg_tys | isDyn = stbl_ptr_ty:fe_arg_tys
279 | otherwise = fe_arg_tys
281 helper_ty = mkForAllTys tvs $
282 mkFunTys wrapper_arg_tys io_res_ty
284 f_helper_glob = mkVanillaGlobal helper_name helper_ty vanillaIdInfo
288 | isLocalName name = mod_name
289 | otherwise = nameModule name
291 occ = mkForeignExportOcc (nameOccName name)
292 helper_name = mkGlobalName uniq mod occ src_loc
294 the_app = getFun_wrapper (return_io_wrapper (mkVarApps (Var i) (tvs ++ fe_args)))
295 the_body = mkLams (tvs ++ wrapper_args) the_app
297 (h_stub, c_stub) = fexportEntry (moduleUserString mod)
298 ext_name f_helper_glob
299 wrapper_arg_tys res_ty cconv isDyn
301 returnDs (f_helper_glob, (f_helper_glob, the_body), h_stub, c_stub)
304 (tvs,sans_foralls) = tcSplitForAllTys ty
305 (fe_arg_tys', orig_res_ty) = tcSplitFunTys sans_foralls
307 (_, stbl_ptr_ty') = tcSplitForAllTys stbl_ptr_ty
308 (_, stbl_ptr_to_ty) = tcSplitAppTy stbl_ptr_ty'
310 fe_arg_tys | isDyn = tail fe_arg_tys'
311 | otherwise = fe_arg_tys'
313 stbl_ptr_ty | isDyn = head fe_arg_tys'
314 | otherwise = error "stbl_ptr_ty"
317 @foreign export dynamic@ lets you dress up Haskell IO actions
318 of some fixed type behind an externally callable interface (i.e.,
319 as a C function pointer). Useful for callbacks and stuff.
322 foreign export dynamic f :: (Addr -> Int -> IO Int) -> IO Addr
324 -- Haskell-visible constructor, which is generated from the above:
325 -- SUP: No check for NULL from createAdjustor anymore???
327 f :: (Addr -> Int -> IO Int) -> IO Addr
329 bindIO (newStablePtr cback)
330 (\StablePtr sp# -> IO (\s1# ->
331 case _ccall_ createAdjustor cconv sp# ``f_helper'' s1# of
332 (# s2#, a# #) -> (# s2#, A# a# #)))
334 foreign export "f_helper" f_helper :: StablePtr (Addr -> Int -> IO Int) -> Addr -> Int -> IO Int
335 -- `special' foreign export that invokes the closure pointed to by the
340 dsFExportDynamic :: Module
343 -> DsM ([Binding], SDoc, SDoc)
344 dsFExportDynamic mod_name id cconv
345 = newSysLocalDs ty `thenDs` \ fe_id ->
347 -- hack: need to get at the name of the C stub we're about to generate.
348 fe_nm = _PK_ (moduleUserString mod_name ++ "_" ++ toCName fe_id)
350 dsFExport mod_name id export_ty fe_nm cconv True `thenDs` \ (feb, fe, h_code, c_code) ->
351 newSysLocalDs arg_ty `thenDs` \ cback ->
352 dsLookupGlobalValue newStablePtrName `thenDs` \ newStablePtrId ->
354 mk_stbl_ptr_app = mkApps (Var newStablePtrId) [ Type arg_ty, Var cback ]
356 dsLookupGlobalValue bindIOName `thenDs` \ bindIOId ->
357 newSysLocalDs (mkTyConApp stablePtrTyCon [arg_ty]) `thenDs` \ stbl_value ->
360 = mkApps (Var bindIOId)
361 [ Type (mkTyConApp stablePtrTyCon [arg_ty])
368 The arguments to the external function which will
369 create a little bit of (template) code on the fly
370 for allowing the (stable pointed) Haskell closure
371 to be entered using an external calling convention
374 adj_args = [ mkIntLitInt (ccallConvToInt cconv)
376 , mkLit (MachLabel fe_nm)
378 -- name of external entry point providing these services.
379 -- (probably in the RTS.)
380 adjustor = SLIT("createAdjustor")
382 dsCCall adjustor adj_args PlayRisky False io_res_ty `thenDs` \ ccall_adj ->
383 -- PlayRisky: the adjustor doesn't allocate in the Haskell heap or do a callback
384 let ccall_adj_ty = exprType ccall_adj
385 ccall_io_adj = mkLams [stbl_value] $
386 Note (Coerce io_res_ty ccall_adj_ty)
388 io_app = mkLams tvs $
390 stbl_app ccall_io_adj res_ty
391 fed = (id `setInlinePragma` neverInlinePrag, io_app)
392 -- Never inline the f.e.d. function, because the litlit
393 -- might not be in scope in other modules.
395 returnDs ([fed, fe], h_code, c_code)
399 (tvs,sans_foralls) = tcSplitForAllTys ty
400 ([arg_ty], io_res_ty) = tcSplitFunTys sans_foralls
401 Just (ioTyCon, [res_ty]) = tcSplitTyConApp_maybe io_res_ty
402 export_ty = mkFunTy (mkTyConApp stablePtrTyCon [arg_ty]) arg_ty
404 toCName :: Id -> String
405 toCName i = showSDoc (pprCode CStyle (ppr (idName i)))
410 \subsection{Generating @foreign export@ stubs}
414 For each @foreign export@ function, a C stub function is generated.
415 The C stub constructs the application of the exported Haskell function
416 using the hugs/ghc rts invocation API.
419 fexportEntry :: String
427 fexportEntry mod_nm c_nm helper args res_ty cc isDyn = (header_bits, c_bits)
429 -- name of the (Haskell) helper function generated by the desugarer.
430 h_nm = ppr helper <> text "_closure"
431 -- prototype for the exported function.
432 header_bits = ptext SLIT("extern") <+> fun_proto <> semi
434 fun_proto = cResType <+> pprCconv <+> ptext c_nm <>
435 parens (hsep (punctuate comma (zipWith (<+>) cParamTypes proto_args)))
442 , text "SchedulerStatus rc;"
444 -- create the application + perform it.
445 , text "rc=rts_evalIO" <>
446 parens (foldl appArg (text "(StgClosure*)&" <> h_nm) (zip args c_args) <> comma <> text "&ret") <> semi
447 , text "rts_checkSchedStatus" <> parens (doubleQuotes (ptext c_nm)
448 <> comma <> text "rc") <> semi
449 , text "return" <> return_what <> semi
454 text "rts_apply" <> parens (acc <> comma <> mkHObj a <> parens c_a)
456 cParamTypes = map showStgType real_args
458 res_ty_is_unit = res_ty `eqType` unitTy
460 cResType | res_ty_is_unit = text "void"
461 | otherwise = showStgType res_ty
463 pprCconv = case cc of
465 StdCallConv -> ppr cc
467 declareResult = text "HaskellObj ret;"
469 externDecl = mkExtern (text "HaskellObj") h_nm
471 mkExtern ty nm = text "extern" <+> ty <+> nm <> semi
473 return_what | res_ty_is_unit = empty
474 | otherwise = parens (unpackHObj res_ty <> parens (text "ret"))
476 c_args = mkCArgNames 0 args
479 If we're generating an entry point for a 'foreign export ccall dynamic',
480 then we receive the return address of the C function that wants to
481 invoke a Haskell function as any other C function, as second arg.
482 This arg is unused within the body of the generated C stub, but
483 needed by the Adjustor.c code to get the stack cleanup right.
485 (proto_args, real_args)
487 CCallConv | isDyn -> ( text "a0" : text "a_" : mkCArgNames 1 (tail args)
488 , head args : addrTy : tail args)
489 other -> (mkCArgNames 0 args, args)
491 mkCArgNames :: Int -> [a] -> [SDoc]
492 mkCArgNames n as = zipWith (\ _ n -> text ('a':show n)) as [n..]
494 mkHObj :: Type -> SDoc
495 mkHObj t = text "rts_mk" <> text (showFFIType t)
497 unpackHObj :: Type -> SDoc
498 unpackHObj t = text "rts_get" <> text (showFFIType t)
500 showStgType :: Type -> SDoc
501 showStgType t = text "Hs" <> text (showFFIType t)
503 showFFIType :: Type -> String
504 showFFIType t = getOccString (getName tc)
506 tc = case splitTyConApp_maybe (repType t) of
508 Nothing -> pprPanic "showFFIType" (ppr t)